SERVER-28030 Remove writes from ChunkManager

Also moves the 'chunks' tests from dbtests into the ChunkManager
unit-tests.

(cherry picked from commit 585ade2ae5f776effa2c63c2221a4639f8545bc2)

10 files changed, 674 insertions, 956 deletions

diff --git a/src/mongo/db/s/SConscript b/src/mongo/db/s/SConscript
index cafeabe4537..dcb179b846c 100644
--- a/src/mongo/db/s/SConscript
+++ b/src/mongo/db/s/SConscript
@@ -97,6 +97,7 @@ env.Library(
         '$BUILD_DIR/mongo/base',
         '$BUILD_DIR/mongo/bson/util/bson_extract',
         '$BUILD_DIR/mongo/db/common',
+        '$BUILD_DIR/mongo/s/catalog/dist_lock_manager',
         '$BUILD_DIR/mongo/s/coreshard',
     ],
 )
diff --git a/src/mongo/dbtests/SConscript b/src/mongo/dbtests/SConscript
index b82f16fdb15..9037b0a883d 100644
--- a/src/mongo/dbtests/SConscript
+++ b/src/mongo/dbtests/SConscript
@@ -53,7 +53,6 @@ dbtest = env.Program(
     target="dbtest",
     source=[
         'basictests.cpp',
-        'chunktests.cpp',
         'clienttests.cpp',
         'commandtests.cpp',
         'counttests.cpp',
diff --git a/src/mongo/dbtests/chunktests.cpp b/src/mongo/dbtests/chunktests.cpp
deleted file mode 100644
index 047d765e431..00000000000
--- a/src/mongo/dbtests/chunktests.cpp
+++ /dev/null
@@ -1,503 +0,0 @@
-/**
- *    Copyright (C) 2012 10gen Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects
- *    for all of the code used other than as permitted herein. If you modify
- *    file(s) with this exception, you may extend this exception to your
- *    version of the file(s), but you are not obligated to do so. If you do not
- *    wish to do so, delete this exception statement from your version. If you
- *    delete this exception statement from all source files in the program,
- *    then also delete it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-
-#include "mongo/db/json.h"
-#include "mongo/db/query/collation/collator_interface_mock.h"
-#include "mongo/db/query/query_test_service_context.h"
-#include "mongo/dbtests/dbtests.h"
-#include "mongo/s/chunk_manager.h"
-#include "mongo/stdx/memory.h"
-
-namespace mongo {
-
-using std::set;
-using std::string;
-using std::vector;
-
-class TestableChunkManager : public ChunkManager {
-public:
-    TestableChunkManager(const string& ns,
-                         const ShardKeyPattern& keyPattern,
-                         std::unique_ptr<CollatorInterface> defaultCollator,
-                         bool unique)
-        : ChunkManager(ns, keyPattern, std::move(defaultCollator), unique) {}
-
-    void setSingleChunkForShards(const vector<BSONObj>& splitPoints) {
-        vector<BSONObj> mySplitPoints(splitPoints);
-        mySplitPoints.insert(mySplitPoints.begin(), _keyPattern.getKeyPattern().globalMin());
-        mySplitPoints.push_back(_keyPattern.getKeyPattern().globalMax());
-
-        for (unsigned i = 1; i < mySplitPoints.size(); ++i) {
-            const string shardId = str::stream() << (i - 1);
-            _shardIds.insert(shardId);
-
-            ChunkType chunk;
-            chunk.setNS(getns());
-            chunk.setMin(mySplitPoints[i - 1]);
-            chunk.setMax(mySplitPoints[i]);
-            chunk.setShard(shardId);
-            chunk.setVersion(ChunkVersion(0, 0, OID()));
-
-            _chunkMap[mySplitPoints[i]] = std::make_shared<Chunk>(chunk);
-        }
-
-        _chunkRangeMap = _constructRanges(_chunkMap);
-    }
-};
-
-namespace {
-
-class Base {
-public:
-    Base() = default;
-
-    virtual ~Base() = default;
-
-    void run() {
-        QueryTestServiceContext serviceContext;
-        auto opCtx = serviceContext.makeOperationContext();
-
-        ShardKeyPattern shardKeyPattern(shardKey());
-        TestableChunkManager chunkManager(
-            "TestDB.TestColl", shardKeyPattern, defaultCollator(), false);
-        chunkManager.setSingleChunkForShards(splitPoints());
-
-        set<ShardId> shardIds;
-        chunkManager.getShardIdsForQuery(opCtx.get(), query(), queryCollation(), &shardIds);
-
-        BSONArrayBuilder b;
-        for (const ShardId& shardId : shardIds) {
-            b << shardId;
-        }
-        ASSERT_BSONOBJ_EQ(expectedShardNames(), b.arr());
-    }
-
-protected:
-    virtual BSONObj shardKey() const {
-        return BSON("a" << 1);
-    }
-
-    virtual std::unique_ptr<CollatorInterface> defaultCollator() const {
-        return {nullptr};
-    }
-
-    virtual std::vector<BSONObj> splitPoints() const {
-        return {};
-    }
-
-    virtual BSONObj query() const {
-        return BSONObj();
-    }
-
-    virtual BSONObj queryCollation() const {
-        return BSONObj();
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0");
-    }
-};
-
-class EmptyQuerySingleShard : public Base {};
-
-class MultiShardBase : public Base {
-    virtual std::vector<BSONObj> splitPoints() const {
-        return {BSON("a"
-                     << "x"),
-                BSON("a"
-                     << "y"),
-                BSON("a"
-                     << "z")};
-    }
-};
-
-class EmptyQueryMultiShard : public MultiShardBase {
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2"
-                          << "3");
-    }
-};
-
-class UniversalRangeMultiShard : public EmptyQueryMultiShard {
-    virtual BSONObj query() const {
-        return BSON("b" << 1);
-    }
-};
-
-class EqualityRangeSingleShard : public EmptyQuerySingleShard {
-    virtual BSONObj query() const {
-        return BSON("a"
-                    << "x");
-    }
-};
-
-class EqualityRangeMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a"
-                    << "y");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("2");
-    }
-};
-
-class SetRangeMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return fromjson("{a:{$in:['u','y']}}");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "2");
-    }
-};
-
-class GTRangeMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << GT << "x");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("1"
-                          << "2"
-                          << "3");
-    }
-};
-
-class GTERangeMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << GTE << "x");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("1"
-                          << "2"
-                          << "3");
-    }
-};
-
-class LTRangeMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << LT << "y");
-    }
-
-    /**
-     * It isn't actually necessary to return shard 2 because its lowest key is "y", which
-     * is excluded from the query.  SERVER-4791
-     */
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2");
-    }
-};
-
-class LTERangeMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << LTE << "y");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2");
-    }
-};
-
-class OrEqualities : public MultiShardBase {
-    virtual BSONObj query() const {
-        return fromjson("{$or:[{a:'u'},{a:'y'}]}");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "2");
-    }
-};
-
-class OrEqualityInequality : public MultiShardBase {
-    virtual BSONObj query() const {
-        return fromjson("{$or:[{a:'u'},{a:{$gte:'y'}}]}");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "2"
-                          << "3");
-    }
-};
-
-class OrEqualityInequalityUnhelpful : public MultiShardBase {
-    virtual BSONObj query() const {
-        return fromjson("{$or:[{a:'u'},{a:{$gte:'zz'}},{}]}");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2"
-                          << "3");
-    }
-};
-
-template <class BASE>
-class Unsatisfiable : public BASE {
-    /**
-     * SERVER-4914 For now the first shard is returned for unsatisfiable queries, as some
-     * clients of getShardIdsForQuery() expect at least one shard.
-     */
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0");
-    }
-};
-
-class UnsatisfiableRangeSingleShard : public Unsatisfiable<Base> {
-    virtual BSONObj query() const {
-        return BSON("a" << GT << "x" << LT << "x");
-    }
-};
-
-class UnsatisfiableRangeMultiShard : public Unsatisfiable<MultiShardBase> {
-    virtual BSONObj query() const {
-        return BSON("a" << GT << "x" << LT << "x");
-    }
-};
-
-class EqualityThenUnsatisfiable : public Unsatisfiable<Base> {
-    virtual BSONObj shardKey() const {
-        return BSON("a" << 1 << "b" << 1);
-    }
-
-    virtual BSONObj query() const {
-        return BSON("a" << 1 << "b" << GT << 4 << LT << 4);
-    }
-};
-
-class InequalityThenUnsatisfiable : public Unsatisfiable<Base> {
-    virtual BSONObj shardKey() const {
-        return BSON("a" << 1 << "b" << 1);
-    }
-
-    virtual BSONObj query() const {
-        return BSON("a" << GT << 1 << "b" << GT << 4 << LT << 4);
-    }
-};
-
-class OrEqualityUnsatisfiableInequality : public MultiShardBase {
-    virtual BSONObj query() const {
-        return fromjson("{$or:[{a:'x'},{a:{$gt:'u',$lt:'u'}},{a:{$gte:'y'}}]}");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("1"
-                          << "2"
-                          << "3");
-    }
-};
-
-class CompoundKeyBase : public Base {
-    virtual BSONObj shardKey() const {
-        return BSON("a" << 1 << "b" << 1);
-    }
-
-    virtual std::vector<BSONObj> splitPoints() const {
-        return {BSON("a" << 5 << "b" << 10), BSON("a" << 5 << "b" << 20)};
-    }
-};
-
-class InMultiShard : public CompoundKeyBase {
-    virtual BSONObj query() const {
-        return BSON("a" << BSON("$in" << BSON_ARRAY(0 << 5 << 10)) << "b"
-                        << BSON("$in" << BSON_ARRAY(0 << 5 << 25)));
-    }
-
-    // If we were to send this query to just the shards it actually needed to hit, it would
-    // only hit shards 0 and 2. Because of the optimization from SERVER-4745, however, we'll
-    // also hit shard 1.
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2");
-    }
-};
-
-class CollationStringsMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a"
-                    << "y");
-    }
-
-    virtual BSONObj queryCollation() const {
-        return BSON("locale"
-                    << "mock_reverse_string");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2"
-                          << "3");
-    }
-};
-
-class DefaultCollationStringsMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a"
-                    << "y");
-    }
-
-    virtual std::unique_ptr<CollatorInterface> defaultCollator() const {
-        auto collator = stdx::make_unique<CollatorInterfaceMock>(
-            CollatorInterfaceMock::MockType::kReverseString);
-        return {std::move(collator)};
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0"
-                          << "1"
-                          << "2"
-                          << "3");
-    }
-};
-
-class SimpleCollationStringsMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a"
-                    << "y");
-    }
-
-    virtual std::unique_ptr<CollatorInterface> defaultCollator() const {
-        auto collator = stdx::make_unique<CollatorInterfaceMock>(
-            CollatorInterfaceMock::MockType::kReverseString);
-        return {std::move(collator)};
-    }
-
-    virtual BSONObj queryCollation() const {
-        return BSON("locale"
-                    << "simple");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("2");
-    }
-};
-
-class CollationNumbersMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << 5);
-    }
-
-    virtual BSONObj queryCollation() const {
-        return BSON("locale"
-                    << "mock_reverse_string");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0");
-    }
-};
-
-class DefaultCollationNumbersMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << 5);
-    }
-
-    virtual std::unique_ptr<CollatorInterface> defaultCollator() const {
-        auto collator = stdx::make_unique<CollatorInterfaceMock>(
-            CollatorInterfaceMock::MockType::kReverseString);
-        return {std::move(collator)};
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0");
-    }
-};
-
-class SimpleCollationNumbersMultiShard : public MultiShardBase {
-    virtual BSONObj query() const {
-        return BSON("a" << 5);
-    }
-
-    virtual std::unique_ptr<CollatorInterface> defaultCollator() const {
-        auto collator = stdx::make_unique<CollatorInterfaceMock>(
-            CollatorInterfaceMock::MockType::kReverseString);
-        return {std::move(collator)};
-    }
-
-    virtual BSONObj queryCollation() const {
-        return BSON("locale"
-                    << "simple");
-    }
-
-    virtual BSONArray expectedShardNames() const {
-        return BSON_ARRAY("0");
-    }
-};
-
-class All : public Suite {
-public:
-    All() : Suite("chunk") {}
-
-    void setupTests() {
-        add<EmptyQuerySingleShard>();
-        add<EmptyQueryMultiShard>();
-        add<UniversalRangeMultiShard>();
-        add<EqualityRangeSingleShard>();
-        add<EqualityRangeMultiShard>();
-        add<SetRangeMultiShard>();
-        add<GTRangeMultiShard>();
-        add<GTERangeMultiShard>();
-        add<LTRangeMultiShard>();
-        add<LTERangeMultiShard>();
-        add<OrEqualities>();
-        add<OrEqualityInequality>();
-        add<OrEqualityInequalityUnhelpful>();
-        add<UnsatisfiableRangeSingleShard>();
-        add<UnsatisfiableRangeMultiShard>();
-        add<EqualityThenUnsatisfiable>();
-        add<InequalityThenUnsatisfiable>();
-        add<OrEqualityUnsatisfiableInequality>();
-        add<InMultiShard>();
-        add<CollationStringsMultiShard>();
-        add<DefaultCollationStringsMultiShard>();
-        add<SimpleCollationStringsMultiShard>();
-        add<CollationNumbersMultiShard>();
-        add<DefaultCollationNumbersMultiShard>();
-        add<SimpleCollationNumbersMultiShard>();
-    }
-};
-
-SuiteInstance<All> myAll;
-
-}  // namespace
-}  // namespace mongo
diff --git a/src/mongo/s/SConscript b/src/mongo/s/SConscript
index ed7574032d7..225a49ccb02 100644
--- a/src/mongo/s/SConscript
+++ b/src/mongo/s/SConscript
@@ -239,6 +239,7 @@ env.Library(
         '$BUILD_DIR/mongo/db/lasterror',
         '$BUILD_DIR/mongo/db/repl/repl_coordinator_global',
         '$BUILD_DIR/mongo/executor/task_executor_pool',
+        '$BUILD_DIR/mongo/s/catalog/sharding_catalog_client',
         '$BUILD_DIR/mongo/s/query/cluster_cursor_manager',
         'client/sharding_client',
         'common',
diff --git a/src/mongo/s/catalog/sharding_catalog_client_impl.cpp b/src/mongo/s/catalog/sharding_catalog_client_impl.cpp
index 01bb420f49a..2c75c95b488 100644
--- a/src/mongo/s/catalog/sharding_catalog_client_impl.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_client_impl.cpp
@@ -55,6 +55,7 @@
 #include "mongo/executor/task_executor.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/s/balancer_configuration.h"
 #include "mongo/s/catalog/config_server_version.h"
 #include "mongo/s/catalog/dist_lock_manager.h"
 #include "mongo/s/catalog/type_changelog.h"
@@ -64,7 +65,6 @@
 #include "mongo/s/catalog/type_database.h"
 #include "mongo/s/catalog/type_shard.h"
 #include "mongo/s/catalog/type_tags.h"
-#include "mongo/s/chunk_manager.h"
 #include "mongo/s/client/shard.h"
 #include "mongo/s/client/shard_connection.h"
 #include "mongo/s/client/shard_registry.h"
@@ -117,6 +117,108 @@ void toBatchError(const Status& status, BatchedCommandResponse* response) {
     response->setOk(false);
 }
 
+/**
+ * Creates and writes to the config server the first chunks for a newly sharded collection. Returns
+ * the version generated for the collection.
+ */
+StatusWith<ChunkVersion> createFirstChunks(OperationContext* txn,
+                                           const NamespaceString& nss,
+                                           const ShardKeyPattern& shardKeyPattern,
+                                           const ShardId& primaryShardId,
+                                           const std::vector<BSONObj>& initPoints,
+                                           const std::set<ShardId>& initShardIds) {
+
+    const KeyPattern keyPattern = shardKeyPattern.getKeyPattern();
+
+    vector<BSONObj> splitPoints;
+    vector<ShardId> shardIds;
+
+    if (initPoints.empty()) {
+        // If no split points were specified use the shard's data distribution to determine them
+        auto primaryShard =
+            uassertStatusOK(Grid::get(txn)->shardRegistry()->getShard(txn, primaryShardId));
+
+        auto result = uassertStatusOK(primaryShard->runCommandWithFixedRetryAttempts(
+            txn,
+            ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
+            nss.db().toString(),
+            BSON("count" << nss.coll()),
+            Shard::RetryPolicy::kIdempotent));
+
+        long long numObjects = 0;
+        uassertStatusOK(result.commandStatus);
+        uassertStatusOK(bsonExtractIntegerField(result.response, "n", &numObjects));
+
+        if (numObjects > 0) {
+            splitPoints = uassertStatusOK(shardutil::selectChunkSplitPoints(
+                txn,
+                primaryShardId,
+                nss,
+                shardKeyPattern,
+                ChunkRange(keyPattern.globalMin(), keyPattern.globalMax()),
+                Grid::get(txn)->getBalancerConfiguration()->getMaxChunkSizeBytes(),
+                0));
+        }
+
+        // Since docs already exist for the collection, must use primary shard
+        shardIds.push_back(primaryShardId);
+    } else {
+        // Make sure points are unique and ordered
+        auto orderedPts = SimpleBSONObjComparator::kInstance.makeBSONObjSet();
+
+        for (const auto& initPoint : initPoints) {
+            orderedPts.insert(initPoint);
+        }
+
+        for (const auto& initPoint : orderedPts) {
+            splitPoints.push_back(initPoint);
+        }
+
+        if (initShardIds.empty()) {
+            // If not specified, only use the primary shard (note that it's not safe for mongos to
+            // put initial chunks on other shards without the primary mongod knowing)
+            shardIds.push_back(primaryShardId);
+        } else {
+            std::copy(initShardIds.begin(), initShardIds.end(), std::back_inserter(shardIds));
+        }
+    }
+
+    // This is the first chunk; start the versioning from scratch
+    const OID epoch = OID::gen();
+    ChunkVersion version(1, 0, epoch);
+
+    log() << "going to create " << splitPoints.size() + 1 << " chunk(s) for: " << nss
+          << " using new epoch " << version.epoch();
+
+    for (unsigned i = 0; i <= splitPoints.size(); i++) {
+        const BSONObj min = (i == 0) ? keyPattern.globalMin() : splitPoints[i - 1];
+        const BSONObj max = (i < splitPoints.size()) ? splitPoints[i] : keyPattern.globalMax();
+
+        // The correct version must be returned as part of this call so only increment for versions,
+        // which get written
+        if (i > 0) {
+            version.incMinor();
+        }
+
+        ChunkType chunk;
+        chunk.setNS(nss.ns());
+        chunk.setMin(min);
+        chunk.setMax(max);
+        chunk.setShard(shardIds[i % shardIds.size()]);
+        chunk.setVersion(version);
+
+        Status status = Grid::get(txn)->catalogClient(txn)->insertConfigDocument(
+            txn, ChunkType::ConfigNS, chunk.toBSON(), ShardingCatalogClient::kMajorityWriteConcern);
+        if (!status.isOK()) {
+            return {status.code(),
+                    str::stream() << "Creating first chunks failed due to "
+                                  << redact(status.reason())};
+        }
+    }
+
+    return version;
+}
+
 }  // namespace
 
 ShardingCatalogClientImpl::ShardingCatalogClientImpl(
@@ -421,29 +523,28 @@ Status ShardingCatalogClientImpl::shardCollection(OperationContext* txn,
         return getDBStatus.getStatus();
     }
 
+    auto const shardRegistry = Grid::get(txn)->shardRegistry();
+
     ShardId dbPrimaryShardId = getDBStatus.getValue().value.getPrimary();
-    const auto primaryShardStatus = grid.shardRegistry()->getShard(txn, dbPrimaryShardId);
+    const auto primaryShardStatus = shardRegistry->getShard(txn, dbPrimaryShardId);
     if (!primaryShardStatus.isOK()) {
         return primaryShardStatus.getStatus();
     }
 
     {
-        // In 3.0 and prior we include this extra safety check that the collection is not getting
-        // sharded concurrently by two different mongos instances. It is not 100%-proof, but it
-        // reduces the chance that two invocations of shard collection will step on each other's
-        // toes.  Now we take the distributed lock so going forward this check won't be necessary
-        // but we leave it around for compatibility with other mongoses from 3.0.
-        // TODO(spencer): Remove this after 3.2 ships.
+        // This is an extra safety check that there aren't any partially written chunks from a
+        // previous failed invocation of 'shardCollection'
         auto countStatus = _runCountCommandOnConfig(
             txn, NamespaceString(ChunkType::ConfigNS), BSON(ChunkType::ns(ns)));
         if (!countStatus.isOK()) {
             return countStatus.getStatus();
         }
+
         if (countStatus.getValue() > 0) {
-            return Status(ErrorCodes::AlreadyInitialized,
-                          str::stream() << "collection " << ns << " already sharded with "
-                                        << countStatus.getValue()
-                                        << " chunks.");
+            return {ErrorCodes::AlreadyInitialized,
+                    str::stream() << "collection " << ns << " already sharded with "
+                                  << countStatus.getValue()
+                                  << " chunks."};
         }
     }
 
@@ -470,6 +571,8 @@ Status ShardingCatalogClientImpl::shardCollection(OperationContext* txn,
                   ShardingCatalogClientImpl::kMajorityWriteConcern);
     }
 
+    const NamespaceString nss(ns);
+
     // Construct the collection default collator.
     std::unique_ptr<CollatorInterface> defaultCollator;
     if (!defaultCollation.isEmpty()) {
@@ -481,28 +584,25 @@ Status ShardingCatalogClientImpl::shardCollection(OperationContext* txn,
         defaultCollator = std::move(statusWithCollator.getValue());
     }
 
-    shared_ptr<ChunkManager> manager(
-        new ChunkManager(ns, fieldsAndOrder, std::move(defaultCollator), unique));
-    Status createFirstChunksStatus =
-        manager->createFirstChunks(txn, dbPrimaryShardId, &initPoints, &initShardIds);
+    auto createFirstChunksStatus =
+        createFirstChunks(txn, nss, fieldsAndOrder, dbPrimaryShardId, initPoints, initShardIds);
     if (!createFirstChunksStatus.isOK()) {
-        return createFirstChunksStatus;
+        return createFirstChunksStatus.getStatus();
     }
-    manager->loadExistingRanges(txn, nullptr);
+
+    const auto& collVersion = createFirstChunksStatus.getValue();
 
     {
         CollectionType coll;
-        coll.setNs(NamespaceString(manager->getns()));
-        coll.setEpoch(manager->getVersion().epoch());
+        coll.setNs(nss);
+        coll.setEpoch(collVersion.epoch());
 
         // TODO(schwerin): The following isn't really a date, but is stored as one in-memory and in
         // config.collections, as a historical oddity.
-        coll.setUpdatedAt(Date_t::fromMillisSinceEpoch(manager->getVersion().toLong()));
-        coll.setKeyPattern(manager->getShardKeyPattern().toBSON());
-        coll.setDefaultCollation(manager->getDefaultCollator()
-                                     ? manager->getDefaultCollator()->getSpec().toBSON()
-                                     : BSONObj());
-        coll.setUnique(manager->isUnique());
+        coll.setUpdatedAt(Date_t::fromMillisSinceEpoch(collVersion.toLong()));
+        coll.setKeyPattern(fieldsAndOrder.toBSON());
+        coll.setDefaultCollation(defaultCollator ? defaultCollator->getSpec().toBSON() : BSONObj());
+        coll.setUnique(unique);
 
         Status updateCollStatus = updateCollection(txn, ns, coll);
         if (!updateCollStatus.isOK()) {
@@ -514,14 +614,14 @@ Status ShardingCatalogClientImpl::shardCollection(OperationContext* txn,
     // TODO:  Think the real fix here is for mongos to just
     //        assume that all collections are sharded, when we get there
     SetShardVersionRequest ssv = SetShardVersionRequest::makeForVersioningNoPersist(
-        grid.shardRegistry()->getConfigServerConnectionString(),
+        shardRegistry->getConfigServerConnectionString(),
         dbPrimaryShardId,
         primaryShardStatus.getValue()->getConnString(),
         NamespaceString(ns),
-        manager->getVersion(),
+        collVersion,
         true);
 
-    auto shardStatus = Grid::get(txn)->shardRegistry()->getShard(txn, dbPrimaryShardId);
+    auto shardStatus = shardRegistry->getShard(txn, dbPrimaryShardId);
     if (!shardStatus.isOK()) {
         return shardStatus.getStatus();
     }
@@ -543,7 +643,7 @@ Status ShardingCatalogClientImpl::shardCollection(OperationContext* txn,
     logChange(txn,
               "shardCollection.end",
               ns,
-              BSON("version" << manager->getVersion().toString()),
+              BSON("version" << collVersion.toString()),
               ShardingCatalogClientImpl::kMajorityWriteConcern);
 
     return Status::OK();
diff --git a/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp b/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp
index 920714e4ad3..74006f5de6a 100644
--- a/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp
+++ b/src/mongo/s/catalog/sharding_catalog_shard_collection_test.cpp
@@ -154,37 +154,6 @@ public:
         return actualVersion;
     }
 
-    void expectReloadChunks(const std::string& ns, const vector<ChunkType>& chunks) {
-        onFindCommand([&](const RemoteCommandRequest& request) {
-            ASSERT_EQUALS(configHost, request.target);
-            ASSERT_BSONOBJ_EQ(kReplSecondaryOkMetadata,
-                              rpc::TrackingMetadata::removeTrackingData(request.metadata));
-
-            const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-            ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
-
-            auto query = assertGet(QueryRequest::makeFromFindCommand(nss, request.cmdObj, false));
-            BSONObj expectedQuery =
-                BSON(ChunkType::ns(ns) << ChunkType::DEPRECATED_lastmod << GTE << Timestamp());
-            BSONObj expectedSort = BSON(ChunkType::DEPRECATED_lastmod() << 1);
-
-            ASSERT_EQ(ChunkType::ConfigNS, query->ns());
-            ASSERT_BSONOBJ_EQ(expectedQuery, query->getFilter());
-            ASSERT_BSONOBJ_EQ(expectedSort, query->getSort());
-            ASSERT_FALSE(query->getLimit().is_initialized());
-
-            checkReadConcern(request.cmdObj, Timestamp(0, 0), repl::OpTime::kUninitializedTerm);
-
-            vector<BSONObj> chunksToReturn;
-
-            std::transform(chunks.begin(),
-                           chunks.end(),
-                           std::back_inserter(chunksToReturn),
-                           [](const ChunkType& chunk) { return chunk.toBSON(); });
-            return chunksToReturn;
-        });
-    }
-
     void expectUpdateCollection(const CollectionType& expectedCollection) {
         onCommand([&](const RemoteCommandRequest& request) {
             ASSERT_EQUALS(configHost, request.target);
@@ -387,9 +356,6 @@ TEST_F(ShardCollectionTest, noInitialChunksOrData) {
     // written, to avoid problems relating to non-matching epochs down the road.
     expectedChunk.setVersion(actualVersion);
 
-    // Handle the query to load the newly created chunk
-    expectReloadChunks(ns, {expectedChunk});
-
     CollectionType expectedCollection;
     expectedCollection.setNs(NamespaceString(ns));
     expectedCollection.setEpoch(expectedChunk.getVersion().epoch());
@@ -580,9 +546,6 @@ TEST_F(ShardCollectionTest, withInitialChunks) {
         expectedChunk.setVersion(actualVersion);
     }
 
-    // Handle the query to load the newly created chunk
-    expectReloadChunks(ns, expectedChunks);
-
     CollectionType expectedCollection;
     expectedCollection.setNs(NamespaceString(ns));
     expectedCollection.setEpoch(expectedChunks[4].getVersion().epoch());
@@ -776,9 +739,6 @@ TEST_F(ShardCollectionTest, withInitialData) {
         expectedChunk.setVersion(actualVersion);
     }
 
-    // Handle the query to load the newly created chunk
-    expectReloadChunks(ns, expectedChunks);
-
     CollectionType expectedCollection;
     expectedCollection.setNs(NamespaceString(ns));
     expectedCollection.setEpoch(expectedChunks[4].getVersion().epoch());
diff --git a/src/mongo/s/chunk_manager.cpp b/src/mongo/s/chunk_manager.cpp
index 8c8a03bccbc..afddc3158d5 100644
--- a/src/mongo/s/chunk_manager.cpp
+++ b/src/mongo/s/chunk_manager.cpp
@@ -35,6 +35,7 @@
 #include <boost/next_prior.hpp>
 #include <map>
 #include <set>
+#include <vector>
 
 #include "mongo/bson/simple_bsonobj_comparator.h"
 #include "mongo/bson/util/bson_extract.h"
@@ -42,16 +43,13 @@
 #include "mongo/client/remote_command_targeter.h"
 #include "mongo/db/matcher/extensions_callback_noop.h"
 #include "mongo/db/namespace_string.h"
-#include "mongo/db/operation_context.h"
 #include "mongo/db/query/collation/collation_index_key.h"
-#include "mongo/db/query/collation/collator_factory_interface.h"
 #include "mongo/db/query/index_bounds_builder.h"
 #include "mongo/db/query/query_planner.h"
 #include "mongo/db/query/query_planner_common.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/balancer_configuration.h"
 #include "mongo/s/catalog/sharding_catalog_client.h"
-#include "mongo/s/catalog/type_collection.h"
 #include "mongo/s/catalog_cache.h"
 #include "mongo/s/chunk_diff.h"
 #include "mongo/s/client/shard_registry.h"
@@ -69,7 +67,6 @@ using std::set;
 using std::shared_ptr;
 using std::string;
 using std::unique_ptr;
-using std::vector;
 
 namespace {
 
@@ -166,41 +163,20 @@ bool isChunkMapValid(const ChunkMap& chunkMap) {
 
 }  // namespace
 
-ChunkManager::ChunkManager(const string& ns,
-                           const ShardKeyPattern& pattern,
+ChunkManager::ChunkManager(const NamespaceString& nss,
+                           const OID& epoch,
+                           const ShardKeyPattern& shardKeyPattern,
                            std::unique_ptr<CollatorInterface> defaultCollator,
                            bool unique)
     : _sequenceNumber(nextCMSequenceNumber.addAndFetch(1)),
-      _ns(ns),
-      _keyPattern(pattern.getKeyPattern()),
+      _ns(nss.ns()),
+      _keyPattern(shardKeyPattern.getKeyPattern()),
       _defaultCollator(std::move(defaultCollator)),
       _unique(unique),
       _chunkMap(SimpleBSONObjComparator::kInstance.makeBSONObjIndexedMap<std::shared_ptr<Chunk>>()),
       _chunkRangeMap(
-          SimpleBSONObjComparator::kInstance.makeBSONObjIndexedMap<ShardAndChunkRange>()) {}
-
-ChunkManager::ChunkManager(OperationContext* txn, const CollectionType& coll)
-    : _sequenceNumber(nextCMSequenceNumber.addAndFetch(1)),
-      _ns(coll.getNs().ns()),
-      _keyPattern(coll.getKeyPattern()),
-      _unique(coll.getUnique()),
-
-      _chunkMap(SimpleBSONObjComparator::kInstance.makeBSONObjIndexedMap<std::shared_ptr<Chunk>>()),
-      _chunkRangeMap(
-          SimpleBSONObjComparator::kInstance.makeBSONObjIndexedMap<ShardAndChunkRange>()) {
-    // coll does not have correct version. Use same initial version as _load and createFirstChunks.
-    _version = ChunkVersion(0, 0, coll.getEpoch());
-
-    if (!coll.getDefaultCollation().isEmpty()) {
-        auto statusWithCollator = CollatorFactoryInterface::get(txn->getServiceContext())
-                                      ->makeFromBSON(coll.getDefaultCollation());
-
-        // The collation was validated upon collection creation.
-        invariantOK(statusWithCollator.getStatus());
-
-        _defaultCollator = std::move(statusWithCollator.getValue());
-    }
-}
+          SimpleBSONObjComparator::kInstance.makeBSONObjIndexedMap<ShardAndChunkRange>()),
+      _version(0, 0, epoch) {}
 
 ChunkManager::~ChunkManager() = default;
 
@@ -286,14 +262,14 @@ bool ChunkManager::_load(OperationContext* txn,
 
     repl::OpTime opTime;
     std::vector<ChunkType> chunks;
-    uassertStatusOK(
-        grid.catalogClient(txn)->getChunks(txn,
-                                           diffQuery.query,
-                                           diffQuery.sort,
-                                           boost::none,
-                                           &chunks,
-                                           &opTime,
-                                           repl::ReadConcernLevel::kMajorityReadConcern));
+    uassertStatusOK(Grid::get(txn)->catalogClient(txn)->getChunks(
+        txn,
+        diffQuery.query,
+        diffQuery.sort,
+        boost::none,
+        &chunks,
+        &opTime,
+        repl::ReadConcernLevel::kMajorityReadConcern));
 
     invariant(opTime >= _configOpTime);
     _configOpTime = opTime;
@@ -305,7 +281,7 @@ bool ChunkManager::_load(OperationContext* txn,
 
         // Add all existing shards we find to the shards set
         for (ShardVersionMap::iterator it = shardVersions->begin(); it != shardVersions->end();) {
-            auto shardStatus = grid.shardRegistry()->getShard(txn, it->first);
+            auto shardStatus = Grid::get(txn)->shardRegistry()->getShard(txn, it->first);
             if (shardStatus.isOK()) {
                 shardIds.insert(it->first);
                 ++it;
@@ -355,112 +331,6 @@ bool ChunkManager::_load(OperationContext* txn,
     }
 }
 
-void ChunkManager::calcInitSplitsAndShards(OperationContext* txn,
-                                           const ShardId& primaryShardId,
-                                           const vector<BSONObj>* initPoints,
-                                           const set<ShardId>* initShardIds,
-                                           vector<BSONObj>* splitPoints,
-                                           vector<ShardId>* shardIds) const {
-    invariant(_chunkMap.empty());
-
-    if (!initPoints || initPoints->empty()) {
-        // discover split points
-        auto primaryShard = uassertStatusOK(grid.shardRegistry()->getShard(txn, primaryShardId));
-        const NamespaceString nss{getns()};
-
-        auto result = uassertStatusOK(primaryShard->runCommandWithFixedRetryAttempts(
-            txn,
-            ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
-            nss.db().toString(),
-            BSON("count" << nss.coll()),
-            Shard::RetryPolicy::kIdempotent));
-
-        long long numObjects = 0;
-        uassertStatusOK(result.commandStatus);
-        uassertStatusOK(bsonExtractIntegerField(result.response, "n", &numObjects));
-
-        if (numObjects > 0) {
-            *splitPoints = uassertStatusOK(shardutil::selectChunkSplitPoints(
-                txn,
-                primaryShardId,
-                NamespaceString(_ns),
-                _keyPattern,
-                ChunkRange(_keyPattern.getKeyPattern().globalMin(),
-                           _keyPattern.getKeyPattern().globalMax()),
-                Grid::get(txn)->getBalancerConfiguration()->getMaxChunkSizeBytes(),
-                0));
-        }
-
-        // since docs already exists, must use primary shard
-        shardIds->push_back(primaryShardId);
-    } else {
-        // make sure points are unique and ordered
-        auto orderedPts = SimpleBSONObjComparator::kInstance.makeBSONObjSet();
-        for (unsigned i = 0; i < initPoints->size(); ++i) {
-            BSONObj pt = (*initPoints)[i];
-            orderedPts.insert(pt);
-        }
-        for (auto it = orderedPts.begin(); it != orderedPts.end(); ++it) {
-            splitPoints->push_back(*it);
-        }
-
-        if (!initShardIds || !initShardIds->size()) {
-            // If not specified, only use the primary shard (note that it's not safe for mongos
-            // to put initial chunks on other shards without the primary mongod knowing).
-            shardIds->push_back(primaryShardId);
-        } else {
-            std::copy(initShardIds->begin(), initShardIds->end(), std::back_inserter(*shardIds));
-        }
-    }
-}
-
-Status ChunkManager::createFirstChunks(OperationContext* txn,
-                                       const ShardId& primaryShardId,
-                                       const vector<BSONObj>* initPoints,
-                                       const set<ShardId>* initShardIds) {
-    // TODO distlock?
-    // TODO: Race condition if we shard the collection and insert data while we split across
-    // the non-primary shard.
-
-    vector<BSONObj> splitPoints;
-    vector<ShardId> shardIds;
-    calcInitSplitsAndShards(txn, primaryShardId, initPoints, initShardIds, &splitPoints, &shardIds);
-
-    // this is the first chunk; start the versioning from scratch
-    ChunkVersion version(1, 0, OID::gen());
-
-    log() << "going to create " << splitPoints.size() + 1 << " chunk(s) for: " << _ns
-          << " using new epoch " << version.epoch();
-
-    for (unsigned i = 0; i <= splitPoints.size(); i++) {
-        BSONObj min = i == 0 ? _keyPattern.getKeyPattern().globalMin() : splitPoints[i - 1];
-        BSONObj max =
-            i < splitPoints.size() ? splitPoints[i] : _keyPattern.getKeyPattern().globalMax();
-
-        ChunkType chunk;
-        chunk.setNS(_ns);
-        chunk.setMin(min);
-        chunk.setMax(max);
-        chunk.setShard(shardIds[i % shardIds.size()]);
-        chunk.setVersion(version);
-
-        Status status = grid.catalogClient(txn)->insertConfigDocument(
-            txn, ChunkType::ConfigNS, chunk.toBSON(), ShardingCatalogClient::kMajorityWriteConcern);
-        if (!status.isOK()) {
-            const string errMsg = str::stream() << "Creating first chunks failed: "
-                                                << redact(status.reason());
-            error() << errMsg;
-            return Status(status.code(), errMsg);
-        }
-
-        version.incMinor();
-    }
-
-    _version = ChunkVersion(0, 0, version.epoch());
-
-    return Status::OK();
-}
-
 StatusWith<shared_ptr<Chunk>> ChunkManager::findIntersectingChunk(OperationContext* txn,
                                                                   const BSONObj& shardKey,
                                                                   const BSONObj& collation) const {
@@ -654,7 +524,7 @@ IndexBounds ChunkManager::getIndexBoundsForQuery(const BSONObj& key,
 
     IndexBounds bounds;
 
-    for (vector<QuerySolution*>::const_iterator it = solutions.begin();
+    for (std::vector<QuerySolution*>::const_iterator it = solutions.begin();
          bounds.size() == 0 && it != solutions.end();
          it++) {
         // Try next solution if we failed to generate index bounds, i.e. bounds.size() == 0
@@ -693,7 +563,7 @@ IndexBounds ChunkManager::collapseQuerySolution(const QuerySolutionNode* node) {
     }
 
     IndexBounds bounds;
-    for (vector<QuerySolutionNode*>::const_iterator it = node->children.begin();
+    for (std::vector<QuerySolutionNode*>::const_iterator it = node->children.begin();
          it != node->children.end();
          it++) {
         // The first branch under OR
diff --git a/src/mongo/s/chunk_manager.h b/src/mongo/s/chunk_manager.h
index 4cd6700cacf..f2d75fdb0b0 100644
--- a/src/mongo/s/chunk_manager.h
+++ b/src/mongo/s/chunk_manager.h
@@ -31,7 +31,6 @@
 #include <map>
 #include <set>
 #include <string>
-#include <vector>
 
 #include "mongo/base/disallow_copying.h"
 #include "mongo/db/query/collation/collator_interface.h"
@@ -46,8 +45,8 @@
 namespace mongo {
 
 class CanonicalQuery;
-class CollectionType;
 struct QuerySolutionNode;
+class NamespaceString;
 class OperationContext;
 
 // The key for the map is max for each Chunk or ChunkRange
@@ -57,11 +56,9 @@ class ChunkManager {
     MONGO_DISALLOW_COPYING(ChunkManager);
 
 public:
-    ChunkManager(OperationContext* txn, const CollectionType& coll);
-
-    // Creates an empty chunk manager for the namespace
-    ChunkManager(const std::string& ns,
-                 const ShardKeyPattern& pattern,
+    ChunkManager(const NamespaceString& nss,
+                 const OID& epoch,
+                 const ShardKeyPattern& shardKeyPattern,
                  std::unique_ptr<CollatorInterface> defaultCollator,
                  bool unique);
 
@@ -91,29 +88,9 @@ public:
         return _sequenceNumber;
     }
 
-    //
-    // After constructor is invoked, we need to call loadExistingRanges.  If this is a new
-    // sharded collection, we can call createFirstChunks first.
-    //
-
-    // Creates new chunks based on info in chunk manager
-    Status createFirstChunks(OperationContext* txn,
-                             const ShardId& primaryShardId,
-                             const std::vector<BSONObj>* initPoints,
-                             const std::set<ShardId>* initShardIds);
-
     // Loads existing ranges based on info in chunk manager
     void loadExistingRanges(OperationContext* txn, const ChunkManager* oldManager);
 
-
-    // Helpers for load
-    void calcInitSplitsAndShards(OperationContext* txn,
-                                 const ShardId& primaryShardId,
-                                 const std::vector<BSONObj>* initPoints,
-                                 const std::set<ShardId>* initShardIds,
-                                 std::vector<BSONObj>* splitPoints,
-                                 std::vector<ShardId>* shardIds) const;
-
     //
     // Methods to use once loaded / created
     //
diff --git a/src/mongo/s/chunk_manager_test.cpp b/src/mongo/s/chunk_manager_test.cpp
index 4f3e3e87524..b0599fcf690 100644
--- a/src/mongo/s/chunk_manager_test.cpp
+++ b/src/mongo/s/chunk_manager_test.cpp
@@ -1,5 +1,5 @@
 /**
- *    Copyright (C) 2009 10gen Inc.
+ *    Copyright (C) 2017 MongoDB Inc.
  *
  *    This program is free software: you can redistribute it and/or  modify
  *    it under the terms of the GNU Affero General Public License, version 3,
@@ -17,260 +17,553 @@
  *    code of portions of this program with the OpenSSL library under certain
  *    conditions as described in each individual source file and distribute
  *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects
- *    for all of the code used other than as permitted herein. If you modify
- *    file(s) with this exception, you may extend this exception to your
- *    version of the file(s), but you are not obligated to do so. If you do not
- *    wish to do so, delete this exception statement from your version. If you
- *    delete this exception statement from all source files in the program,
- *    then also delete it in the license file.
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
  */
 
 #define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kDefault
 
 #include "mongo/platform/basic.h"
 
+#include <set>
+
 #include "mongo/client/remote_command_targeter_mock.h"
-#include "mongo/db/operation_context_noop.h"
+#include "mongo/db/client.h"
+#include "mongo/db/query/collation/collator_interface_mock.h"
 #include "mongo/s/catalog/sharding_catalog_test_fixture.h"
 #include "mongo/s/catalog/type_chunk.h"
 #include "mongo/s/catalog/type_collection.h"
 #include "mongo/s/catalog/type_shard.h"
 #include "mongo/s/chunk_manager.h"
-#include "mongo/s/write_ops/batched_command_request.h"
-#include "mongo/s/write_ops/batched_command_response.h"
+#include "mongo/stdx/memory.h"
+#include "mongo/util/scopeguard.h"
 
 namespace mongo {
-
-using std::unique_ptr;
-using std::set;
-using std::string;
-using std::vector;
+namespace {
 
 using executor::RemoteCommandResponse;
 using executor::RemoteCommandRequest;
 
-namespace {
-
-static int rand(int max = -1) {
-    static unsigned seed = 1337;
-
-#if !defined(_WIN32)
-    int r = rand_r(&seed);
-#else
-    int r = ::rand();  // seed not used in this case
-#endif
+const NamespaceString kNss("TestDB", "TestColl");
 
-    // Modding is bad, but don't really care in this case
-    return max > 0 ? r % max : r;
-}
-
-class ChunkManagerFixture : public ShardingCatalogTestFixture {
-public:
+class ChunkManagerTestFixture : public ShardingCatalogTestFixture {
+protected:
     void setUp() override {
         ShardingCatalogTestFixture::setUp();
         setRemote(HostAndPort("FakeRemoteClient:34567"));
-        configTargeter()->setFindHostReturnValue(configHost);
+        configTargeter()->setFindHostReturnValue(HostAndPort{CONFIG_HOST_PORT});
     }
 
-protected:
-    const HostAndPort configHost{HostAndPort(CONFIG_HOST_PORT)};
-    static const ShardId _shardId;
-    static const string _collName;
-    static const string _dbName;
-
-    static const int numSplitPoints = 100;
-
-    void genUniqueRandomSplitKeys(const string& keyName, vector<BSONObj>* splitKeys) {
-        stdx::unordered_set<int> uniquePoints;
-        while (static_cast<int>(uniquePoints.size()) < numSplitPoints) {
-            uniquePoints.insert(rand(numSplitPoints * 10));
+    /**
+     * Returns a chunk manager with chunks at the specified split points. Each individual chunk is
+     * placed on a separate shard with id ranging from "0" to the number of chunks.
+     */
+    std::unique_ptr<ChunkManager> makeChunkManager(
+        const ShardKeyPattern& shardKeyPattern,
+        std::unique_ptr<CollatorInterface> defaultCollator,
+        bool unique,
+        const std::vector<BSONObj>& splitPoints) {
+        ChunkVersion version(1, 0, OID::gen());
+
+        std::vector<BSONObj> shards;
+        std::vector<BSONObj> initialChunks;
+
+        auto splitPointsIncludingEnds(splitPoints);
+        splitPointsIncludingEnds.insert(splitPointsIncludingEnds.begin(),
+                                        shardKeyPattern.getKeyPattern().globalMin());
+        splitPointsIncludingEnds.push_back(shardKeyPattern.getKeyPattern().globalMax());
+
+        for (size_t i = 1; i < splitPointsIncludingEnds.size(); ++i) {
+            ShardType shard;
+            shard.setName(str::stream() << (i - 1));
+            shard.setHost(str::stream() << "Host" << (i - 1) << ":12345");
+
+            shards.push_back(shard.toBSON());
+
+            ChunkType chunk;
+            chunk.setNS(kNss.ns());
+            chunk.setMin(shardKeyPattern.getKeyPattern().extendRangeBound(
+                splitPointsIncludingEnds[i - 1], false));
+            chunk.setMax(shardKeyPattern.getKeyPattern().extendRangeBound(
+                splitPointsIncludingEnds[i], false));
+            chunk.setShard(shard.getName());
+            chunk.setVersion(version);
+
+            initialChunks.push_back(chunk.toBSON());
+
+            version.incMajor();
         }
-        for (auto it = uniquePoints.begin(); it != uniquePoints.end(); ++it) {
-            splitKeys->push_back(BSON(keyName << *it));
-        }
-    }
 
-    void expectInsertOnConfigSaveChunkAndReturnOk(std::vector<BSONObj>& chunks) {
-        onCommandWithMetadata([&](const RemoteCommandRequest& request) mutable {
-            ASSERT_EQ(request.target, HostAndPort(CONFIG_HOST_PORT));
-            ASSERT_EQ(request.dbname, "config");
+        // Load the initial manager
+        auto manager = stdx::make_unique<ChunkManager>(
+            kNss, version.epoch(), shardKeyPattern, std::move(defaultCollator), unique);
+
+        auto future = launchAsync([&manager] {
+            ON_BLOCK_EXIT([&] { Client::destroy(); });
+            Client::initThread("Test");
+            auto opCtx = cc().makeOperationContext();
+            manager->loadExistingRanges(opCtx.get(), nullptr);
+        });
 
-            // Get "inserted" chunk doc from RemoteCommandRequest.
-            BatchedCommandRequest batchedCommandRequest(BatchedCommandRequest::BatchType_Insert);
-            string errmsg;
-            batchedCommandRequest.parseBSON(_dbName, request.cmdObj, &errmsg);
-            vector<BSONObj> docs = batchedCommandRequest.getInsertRequest()->getDocuments();
-            BSONObj chunk = docs.front();
+        expectFindOnConfigSendBSONObjVector(initialChunks);
+        expectFindOnConfigSendBSONObjVector(shards);
 
-            // Save chunk (mimic "insertion").
-            chunks.push_back(chunk);
+        future.timed_get(kFutureTimeout);
 
-            return RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(1));
-        });
+        return manager;
     }
+};
 
-    void expectInsertOnConfigCheckMetadataAndReturnOk(set<int>& minorVersions, OID& epoch) {
-        onCommandWithMetadata([&](const RemoteCommandRequest& request) mutable {
-            ASSERT_EQ(request.target, HostAndPort(CONFIG_HOST_PORT));
-            ASSERT_EQ(request.dbname, "config");
+using ChunkManagerLoadTest = ChunkManagerTestFixture;
 
-            // Get "inserted" chunk doc from RemoteCommandRequest.
-            BatchedCommandRequest batchedCommandRequest(BatchedCommandRequest::BatchType_Insert);
-            string errmsg;
-            batchedCommandRequest.parseBSON(_dbName, request.cmdObj, &errmsg);
-            vector<BSONObj> docs = batchedCommandRequest.getInsertRequest()->getDocuments();
-            BSONObj chunk = docs.front();
+TEST_F(ChunkManagerLoadTest, IncrementalLoadAfterSplit) {
+    const ShardKeyPattern shardKeyPattern(BSON("_id" << 1));
 
-            ChunkVersion version = ChunkVersion::fromBSON(chunk, ChunkType::DEPRECATED_lastmod());
+    auto initialManager(makeChunkManager(shardKeyPattern, nullptr, true, {}));
 
-            // Check chunk's major version.
-            ASSERT(version.majorVersion() == 1);
+    ChunkVersion version = initialManager->getVersion();
 
-            // Check chunk's minor version is unique.
-            ASSERT(minorVersions.find(version.minorVersion()) == minorVersions.end());
-            minorVersions.insert(version.minorVersion());
+    CollectionType collType;
+    collType.setNs(kNss);
+    collType.setEpoch(version.epoch());
+    collType.setUpdatedAt(jsTime());
+    collType.setKeyPattern(shardKeyPattern.toBSON());
+    collType.setUnique(false);
 
-            // Check chunk's epoch is consistent.
-            ASSERT(version.epoch().isSet());
-            if (!epoch.isSet()) {
-                epoch = version.epoch();
-            }
-            ASSERT(version.epoch() == epoch);
+    ChunkManager manager(kNss, version.epoch(), shardKeyPattern, nullptr, true);
 
-            // Check chunk's shard id.
-            ASSERT(chunk[ChunkType::shard()].String() == _shardId.toString());
+    auto future =
+        launchAsync([&] { manager.loadExistingRanges(operationContext(), initialManager.get()); });
 
-            return RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(1));
-        });
-    }
-};
+    // Return set of chunks, which represent a split
+    expectFindOnConfigSendBSONObjVector([&]() {
+        version.incMajor();
+
+        ChunkType chunk1;
+        chunk1.setNS(kNss.ns());
+        chunk1.setMin(shardKeyPattern.getKeyPattern().globalMin());
+        chunk1.setMax(BSON("_id" << 0));
+        chunk1.setShard({"0"});
+        chunk1.setVersion(version);
 
-const ShardId ChunkManagerFixture::_shardId{"shard0000"};
-const string ChunkManagerFixture::_collName{"foo.bar"};
-const string ChunkManagerFixture::_dbName{"foo"};
+        version.incMinor();
 
-// Rename the fixture so that our tests have a useful name in the executable
-typedef ChunkManagerFixture ChunkManagerTests;
+        ChunkType chunk2;
+        chunk2.setNS(kNss.ns());
+        chunk2.setMin(BSON("_id" << 0));
+        chunk2.setMax(shardKeyPattern.getKeyPattern().globalMax());
+        chunk2.setShard({"0"});
+        chunk2.setVersion(version);
+
+        return std::vector<BSONObj>{chunk1.toBSON(), chunk2.toBSON()};
+    }());
+
+    future.timed_get(kFutureTimeout);
+}
 
 /**
- * Tests loading chunks into a ChunkManager with or without an old ChunkManager.
+ * Fixture to be used as a shortcut for tests which exercise the getShardIdsForQuery routing logic
  */
-TEST_F(ChunkManagerTests, Basic) {
-    OperationContextNoop txn;
-    string keyName = "_id";
-    vector<BSONObj> splitKeys;
-    genUniqueRandomSplitKeys(keyName, &splitKeys);
-    ShardKeyPattern shardKeyPattern(BSON(keyName << 1));
-    std::unique_ptr<CollatorInterface> defaultCollator;
-
-    std::vector<BSONObj> shards{
-        BSON(ShardType::name() << _shardId << ShardType::host()
-                               << ConnectionString(HostAndPort("hostFooBar:27017")).toString())};
-
-    // Generate and save a set of chunks with metadata using a temporary ChunkManager.
-
-    std::vector<BSONObj> chunks;
-    auto future = launchAsync([&] {
-        ChunkManager manager(_collName, shardKeyPattern, std::move(defaultCollator), false);
-        auto status = manager.createFirstChunks(operationContext(), _shardId, &splitKeys, NULL);
-        ASSERT_OK(status);
-    });
-
-    // Call the expect() one extra time since numChunks = numSplits + 1.
-    for (int i = 0; i < static_cast<int>(splitKeys.size()) + 1; i++) {
-        expectInsertOnConfigSaveChunkAndReturnOk(chunks);
+class ChunkManagerQueryTest : public ChunkManagerTestFixture {
+protected:
+    void runQueryTest(const BSONObj& shardKey,
+                      std::unique_ptr<CollatorInterface> defaultCollator,
+                      bool unique,
+                      const std::vector<BSONObj>& splitPoints,
+                      const BSONObj& query,
+                      const BSONObj& queryCollation,
+                      const std::set<ShardId> expectedShardIds) {
+        const ShardKeyPattern shardKeyPattern(shardKey);
+        auto chunkManager =
+            makeChunkManager(shardKeyPattern, std::move(defaultCollator), false, splitPoints);
+
+        std::set<ShardId> shardIds;
+        chunkManager->getShardIdsForQuery(operationContext(), query, queryCollation, &shardIds);
+
+        BSONArrayBuilder expectedBuilder;
+        for (const auto& shardId : expectedShardIds) {
+            expectedBuilder << shardId;
+        }
+
+        BSONArrayBuilder actualBuilder;
+        for (const auto& shardId : shardIds) {
+            actualBuilder << shardId;
+        }
+
+        ASSERT_BSONOBJ_EQ(expectedBuilder.arr(), actualBuilder.arr());
     }
+};
 
-    future.timed_get(kFutureTimeout);
+TEST_F(ChunkManagerQueryTest, EmptyQuerySingleShard) {
+    runQueryTest(BSON("a" << 1), nullptr, false, {}, BSONObj(), BSONObj(), {ShardId("0")});
+}
 
-    // Test that a *new* ChunkManager correctly loads the chunks with *no prior info*.
+TEST_F(ChunkManagerQueryTest, EmptyQueryMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSONObj(),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("1"), ShardId("2"), ShardId("3")});
+}
 
-    int numChunks = static_cast<int>(chunks.size());
-    BSONObj firstChunk = chunks.back();
-    ChunkVersion version = ChunkVersion::fromBSON(firstChunk, ChunkType::DEPRECATED_lastmod());
+TEST_F(ChunkManagerQueryTest, UniversalRangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("b" << 1),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("1"), ShardId("2"), ShardId("3")});
+}
 
-    CollectionType collType;
-    collType.setNs(NamespaceString{_collName});
-    collType.setEpoch(version.epoch());
-    collType.setUpdatedAt(jsTime());
-    collType.setKeyPattern(BSON(keyName << 1));
-    collType.setUnique(false);
-    collType.setDropped(false);
-
-    ChunkManager manager(&txn, collType);
-    future = launchAsync([&] {
-        manager.loadExistingRanges(operationContext(), nullptr);
-
-        ASSERT_EQ(version.epoch(), manager.getVersion().epoch());
-        ASSERT_EQ(numChunks - 1, manager.getVersion().minorVersion());
-        ASSERT_EQ(numChunks, static_cast<int>(manager.getChunkMap().size()));
-    });
-    expectFindOnConfigSendBSONObjVector(chunks);
-    expectFindOnConfigSendBSONObjVector(shards);
-    future.timed_get(kFutureTimeout);
+TEST_F(ChunkManagerQueryTest, EqualityRangeSingleShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {},
+                 BSON("a"
+                      << "x"),
+                 BSONObj(),
+                 {ShardId("0")});
+}
 
-    // Test that a *new* ChunkManager correctly loads modified chunks *given an old ChunkManager*.
-
-    // Simulate modified chunks collection
-    ChunkVersion laterVersion = ChunkVersion(2, 1, version.epoch());
-    BSONObj oldChunk = chunks.front();
-    BSONObjBuilder newChunk;
-    newChunk.append("_id", oldChunk.getStringField("_id"));
-    newChunk.append("ns", oldChunk.getStringField("ns"));
-    newChunk.append("min", oldChunk.getObjectField("min"));
-    newChunk.append("max", oldChunk.getObjectField("max"));
-    newChunk.append("shard", oldChunk.getStringField("shard"));
-    laterVersion.addToBSON(newChunk, ChunkType::DEPRECATED_lastmod());
-    newChunk.append("lastmodEpoch", oldChunk.getField("lastmodEpoch").OID());
-
-    // Make new manager load chunk diff
-    future = launchAsync([&] {
-        ChunkManager newManager(manager.getns(),
-                                manager.getShardKeyPattern(),
-                                manager.getDefaultCollator() ? manager.getDefaultCollator()->clone()
-                                                             : nullptr,
-                                manager.isUnique());
-        newManager.loadExistingRanges(operationContext(), &manager);
-
-        ASSERT_EQ(numChunks, static_cast<int>(manager.getChunkMap().size()));
-        ASSERT_EQ(laterVersion.toString(), newManager.getVersion().toString());
-    });
-    expectFindOnConfigSendBSONObjVector(std::vector<BSONObj>{chunks.back(), newChunk.obj()});
-
-    std::cout << "done";
-    future.timed_get(kFutureTimeout);
-    std::cout << "completely done";
+TEST_F(ChunkManagerQueryTest, EqualityRangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a"
+                      << "y"),
+                 BSONObj(),
+                 {ShardId("2")});
 }
 
-/**
- * Tests that chunk metadata is created correctly when using ChunkManager to create chunks for the
- * first time. Creating chunks on multiple shards is not tested here since there are unresolved
- * race conditions there and probably should be avoided if at all possible.
- */
-TEST_F(ChunkManagerTests, FullTest) {
-    string keyName = "_id";
-    vector<BSONObj> splitKeys;
-    genUniqueRandomSplitKeys(keyName, &splitKeys);
-    ShardKeyPattern shardKeyPattern(BSON(keyName << 1));
-    std::unique_ptr<CollatorInterface> defaultCollator;
-
-    auto future = launchAsync([&] {
-        ChunkManager manager(_collName, shardKeyPattern, std::move(defaultCollator), false);
-        auto status = manager.createFirstChunks(operationContext(), _shardId, &splitKeys, NULL);
-        ASSERT_OK(status);
-    });
-
-    // Check that config server receives chunks with the expected metadata.
-    // Call expectInsertOnConfigCheckMetadataAndReturnOk one extra time since numChunks = numSplits
-    // + 1
-    set<int> minorVersions;
-    OID epoch;
-    for (auto it = splitKeys.begin(); it != splitKeys.end(); ++it) {
-        expectInsertOnConfigCheckMetadataAndReturnOk(minorVersions, epoch);
-    }
-    expectInsertOnConfigCheckMetadataAndReturnOk(minorVersions, epoch);
-    future.timed_get(kFutureTimeout);
+TEST_F(ChunkManagerQueryTest, SetRangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 fromjson("{a:{$in:['u','y']}}"),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("2")});
+}
+
+TEST_F(ChunkManagerQueryTest, GTRangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << GT << "x"),
+                 BSONObj(),
+                 {ShardId("1"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, GTERangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << GTE << "x"),
+                 BSONObj(),
+                 {ShardId("1"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, LTRangeMultiShard) {
+    // NOTE (SERVER-4791): It isn't actually necessary to return shard 2 because its lowest key is
+    // "y", which is excluded from the query
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << LT << "y"),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("1"), ShardId("2")});
+}
+
+TEST_F(ChunkManagerQueryTest, LTERangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << LTE << "y"),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("1"), ShardId("2")});
+}
+
+TEST_F(ChunkManagerQueryTest, OrEqualities) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 fromjson("{$or:[{a:'u'},{a:'y'}]}"),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("2")});
+}
+
+TEST_F(ChunkManagerQueryTest, OrEqualityInequality) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 fromjson("{$or:[{a:'u'},{a:{$gte:'y'}}]}"),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, OrEqualityInequalityUnhelpful) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 fromjson("{$or:[{a:'u'},{a:{$gte:'zz'}},{}]}"),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("1"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, UnsatisfiableRangeSingleShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {},
+                 BSON("a" << GT << "x" << LT << "x"),
+                 BSONObj(),
+                 {ShardId("0")});
+}
+
+TEST_F(ChunkManagerQueryTest, UnsatisfiableRangeMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << GT << "x" << LT << "x"),
+                 BSONObj(),
+                 {ShardId("0")});
+}
+
+TEST_F(ChunkManagerQueryTest, EqualityThenUnsatisfiable) {
+    runQueryTest(BSON("a" << 1 << "b" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << 1 << "b" << GT << 4 << LT << 4),
+                 BSONObj(),
+                 {ShardId("0")});
+}
+
+TEST_F(ChunkManagerQueryTest, InequalityThenUnsatisfiable) {
+    runQueryTest(BSON("a" << 1 << "b" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a" << GT << 1 << "b" << GT << 4 << LT << 4),
+                 BSONObj(),
+                 {ShardId("0")});
+}
+
+TEST_F(ChunkManagerQueryTest, OrEqualityUnsatisfiableInequality) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 fromjson("{$or:[{a:'x'},{a:{$gt:'u',$lt:'u'}},{a:{$gte:'y'}}]}"),
+                 BSONObj(),
+                 {ShardId("1"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, InMultiShard) {
+    runQueryTest(BSON("a" << 1 << "b" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a" << 5 << "b" << 10), BSON("a" << 5 << "b" << 20)},
+                 BSON("a" << BSON("$in" << BSON_ARRAY(0 << 5 << 10)) << "b"
+                          << BSON("$in" << BSON_ARRAY(0 << 5 << 25))),
+                 BSONObj(),
+                 {ShardId("0"), ShardId("1"), ShardId("2")});
+}
+
+TEST_F(ChunkManagerQueryTest, CollationStringsMultiShard) {
+    runQueryTest(BSON("a" << 1),
+                 nullptr,
+                 false,
+                 {BSON("a"
+                       << "x"),
+                  BSON("a"
+                       << "y"),
+                  BSON("a"
+                       << "z")},
+                 BSON("a"
+                      << "y"),
+                 BSON("locale"
+                      << "mock_reverse_string"),
+                 {ShardId("0"), ShardId("1"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, DefaultCollationStringsMultiShard) {
+    runQueryTest(
+        BSON("a" << 1),
+        stdx::make_unique<CollatorInterfaceMock>(CollatorInterfaceMock::MockType::kReverseString),
+        false,
+        {BSON("a"
+              << "x"),
+         BSON("a"
+              << "y"),
+         BSON("a"
+              << "z")},
+        BSON("a"
+             << "y"),
+        BSON("locale"
+             << "mock_reverse_string"),
+        {ShardId("0"), ShardId("1"), ShardId("2"), ShardId("3")});
+}
+
+TEST_F(ChunkManagerQueryTest, SimpleCollationStringsMultiShard) {
+    runQueryTest(
+        BSON("a" << 1),
+        stdx::make_unique<CollatorInterfaceMock>(CollatorInterfaceMock::MockType::kReverseString),
+        false,
+        {BSON("a"
+              << "x"),
+         BSON("a"
+              << "y"),
+         BSON("a"
+              << "z")},
+        BSON("a"
+             << "y"),
+        BSON("locale"
+             << "simple"),
+        {ShardId("2")});
+}
+
+TEST_F(ChunkManagerQueryTest, CollationNumbersMultiShard) {
+    runQueryTest(
+        BSON("a" << 1),
+        stdx::make_unique<CollatorInterfaceMock>(CollatorInterfaceMock::MockType::kReverseString),
+        false,
+        {BSON("a"
+              << "x"),
+         BSON("a"
+              << "y"),
+         BSON("a"
+              << "z")},
+        BSON("a" << 5),
+        BSON("locale"
+             << "mock_reverse_string"),
+        {ShardId("0")});
+}
+
+TEST_F(ChunkManagerQueryTest, DefaultCollationNumbersMultiShard) {
+    runQueryTest(
+        BSON("a" << 1),
+        stdx::make_unique<CollatorInterfaceMock>(CollatorInterfaceMock::MockType::kReverseString),
+        false,
+        {BSON("a"
+              << "x"),
+         BSON("a"
+              << "y"),
+         BSON("a"
+              << "z")},
+        BSON("a" << 5),
+        BSONObj(),
+        {ShardId("0")});
+}
+
+TEST_F(ChunkManagerQueryTest, SimpleCollationNumbersMultiShard) {
+    runQueryTest(
+        BSON("a" << 1),
+        stdx::make_unique<CollatorInterfaceMock>(CollatorInterfaceMock::MockType::kReverseString),
+        false,
+        {BSON("a"
+              << "x"),
+         BSON("a"
+              << "y"),
+         BSON("a"
+              << "z")},
+        BSON("a" << 5),
+        BSON("locale"
+             << "simple"),
+        {ShardId("0")});
 }
 
 }  // namespace
diff --git a/src/mongo/s/config.cpp b/src/mongo/s/config.cpp
index c9a7bbaea0b..1f6323a891d 100644
--- a/src/mongo/s/config.cpp
+++ b/src/mongo/s/config.cpp
@@ -35,6 +35,8 @@
 #include <vector>
 
 #include "mongo/db/lasterror.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/db/query/collation/collator_factory_interface.h"
 #include "mongo/s/catalog/sharding_catalog_client.h"
 #include "mongo/s/catalog/type_chunk.h"
 #include "mongo/s/catalog/type_collection.h"
@@ -194,7 +196,8 @@ std::shared_ptr<ChunkManager> DBConfig::getChunkManager(OperationContext* txn,
         // Reload the chunk manager outside of the DBConfig's mutex so as to not block operations
         // for different collections on the same database
         tempChunkManager.reset(new ChunkManager(
-            oldManager->getns(),
+            NamespaceString(oldManager->getns()),
+            oldManager->getVersion().epoch(),
             oldManager->getShardKeyPattern(),
             oldManager->getDefaultCollator() ? oldManager->getDefaultCollator()->clone() : nullptr,
             oldManager->isUnique()));
@@ -321,8 +324,25 @@ bool DBConfig::_loadIfNeeded(OperationContext* txn, Counter reloadIteration) {
         _collections.erase(coll.getNs().ns());
 
         if (!coll.getDropped()) {
+            std::unique_ptr<CollatorInterface> defaultCollator;
+            if (!coll.getDefaultCollation().isEmpty()) {
+                auto statusWithCollator = CollatorFactoryInterface::get(txn->getServiceContext())
+                                              ->makeFromBSON(coll.getDefaultCollation());
+
+                // The collation was validated upon collection creation.
+                invariantOK(statusWithCollator.getStatus());
+
+                defaultCollator = std::move(statusWithCollator.getValue());
+            }
+
+            std::unique_ptr<ChunkManager> manager(
+                stdx::make_unique<ChunkManager>(coll.getNs(),
+                                                coll.getEpoch(),
+                                                ShardKeyPattern(coll.getKeyPattern()),
+                                                std::move(defaultCollator),
+                                                coll.getUnique()));
+
             // Do the blocking collection load
-            std::unique_ptr<ChunkManager> manager(stdx::make_unique<ChunkManager>(txn, coll));
             manager->loadExistingRanges(txn, nullptr);
 
             // Collections with no chunks are unsharded, no matter what the collections entry says