Revert "SERVER-26791 Shard metadata commands should perform partial refresh as much as possible"

This reverts commit 6add2c82bacecd5f54613ebf4be1553f3b046cbc.

4 files changed, 78 insertions, 411 deletions

diff --git a/buildscripts/resmokeconfig/suites/sharding_continuous_config_stepdown.yml b/buildscripts/resmokeconfig/suites/sharding_continuous_config_stepdown.yml
index 9213045e0e6..462d8cff458 100644
--- a/buildscripts/resmokeconfig/suites/sharding_continuous_config_stepdown.yml
+++ b/buildscripts/resmokeconfig/suites/sharding_continuous_config_stepdown.yml
@@ -66,7 +66,6 @@ selector:
     - jstests/sharding/listDatabases.js
     - jstests/sharding/bulk_insert.js
     - jstests/sharding/printShardingStatus.js
-    - jstests/sharding/cmds_epoch_mismatch.js
     # Balancer writes (direct write to config database with no retries)
     - jstests/sharding/convert_to_and_from_sharded.js
     - jstests/sharding/remove2.js
diff --git a/src/mongo/db/s/SConscript b/src/mongo/db/s/SConscript
index c82b0701de3..eac2ad60283 100644
--- a/src/mongo/db/s/SConscript
+++ b/src/mongo/db/s/SConscript
@@ -226,9 +226,6 @@ env.CppUnitTest(
         'sharding_state_test.cpp',
     ],
     LIBDEPS=[
-        '$BUILD_DIR/mongo/db/query/query_request',
-        '$BUILD_DIR/mongo/s/catalog/dist_lock_manager_mock',
-        '$BUILD_DIR/mongo/s/catalog/sharding_catalog_client_impl',
         '$BUILD_DIR/mongo/s/catalog/sharding_catalog_mock',
         '$BUILD_DIR/mongo/s/sharding_mongod_test_fixture',
     ],
diff --git a/src/mongo/db/s/sharding_state.cpp b/src/mongo/db/s/sharding_state.cpp
index 258f5191b9f..ab9ca2c7dd7 100644
--- a/src/mongo/db/s/sharding_state.cpp
+++ b/src/mongo/db/s/sharding_state.cpp
@@ -273,24 +273,41 @@ Status ShardingState::onStaleShardVersion(OperationContext* txn,
         }
     }
 
-    auto refreshStatusAndVersion =
-        _refreshMetadata(txn, nss, (currentMetadata ? currentMetadata.getMetadata() : nullptr));
-    return refreshStatusAndVersion.getStatus();
-}
+    // At the first attempt try to use the currently loaded metadata and on subsequent attempts use
+    // the complete metadata
+    int numRefreshAttempts = 0;
+
+    while (true) {
+        numRefreshAttempts++;
+
+        auto refreshStatusAndVersion =
+            _refreshMetadata(txn, nss, (currentMetadata ? currentMetadata.getMetadata() : nullptr));
+        if (refreshStatusAndVersion.isOK()) {
+            LOG(1) << "Successfully refreshed metadata for " << nss.ns() << " to "
+                   << refreshStatusAndVersion.getValue();
+            return Status::OK();
+        }
 
-Status ShardingState::refreshMetadataNow(OperationContext* txn,
-                                         const NamespaceString& nss,
-                                         ChunkVersion* latestShardVersion) {
-    ScopedCollectionMetadata currentMetadata;
+        if (refreshStatusAndVersion == ErrorCodes::RemoteChangeDetected &&
+            numRefreshAttempts < kMaxNumMetadataRefreshAttempts) {
+            currentMetadata = ScopedCollectionMetadata();
 
-    {
-        AutoGetCollection autoColl(txn, nss, MODE_IS);
+            log() << "Refresh failed and will be retried as full reload "
+                  << refreshStatusAndVersion.getStatus();
+            continue;
+        }
 
-        currentMetadata = CollectionShardingState::get(txn, nss)->getMetadata();
+        return refreshStatusAndVersion.getStatus();
     }
 
-    auto refreshLatestShardVersionStatus =
-        _refreshMetadata(txn, nss, currentMetadata.getMetadata());
+
+    MONGO_UNREACHABLE;
+}
+
+Status ShardingState::refreshMetadataNow(OperationContext* txn,
+                                         const NamespaceString& nss,
+                                         ChunkVersion* latestShardVersion) {
+    auto refreshLatestShardVersionStatus = _refreshMetadata(txn, nss, nullptr);
     if (!refreshLatestShardVersionStatus.isOK()) {
         return refreshLatestShardVersionStatus.getStatus();
     }
@@ -651,34 +668,24 @@ StatusWith<ChunkVersion> ShardingState::_refreshMetadata(
         }
     }
 
-    Status status = {ErrorCodes::InternalError, "metadata refresh not performed"};
+    // The _configServerTickets serializes this process such that only a small number of threads can
+    // try to refresh at the same time in order to avoid overloading the config server
+    _configServerTickets.waitForTicket();
+    TicketHolderReleaser needTicketFrom(&_configServerTickets);
+
     Timer t;
-    int numAttempts = 0;
-    std::unique_ptr<CollectionMetadata> remoteMetadata;
-
-    do {
-        // The _configServerTickets serializes this process such that only a small number of threads
-        // can try to refresh at the same time in order to avoid overloading the config server.
-        _configServerTickets.waitForTicket();
-        TicketHolderReleaser needTicketFrom(&_configServerTickets);
-
-        if (status == ErrorCodes::RemoteChangeDetected) {
-            metadataForDiff = nullptr;
-            log() << "Refresh failed and will be retried as full reload " << status;
-        }
 
-        log() << "MetadataLoader loading chunks for " << nss.ns() << " based on: "
-              << (metadataForDiff ? metadataForDiff->getCollVersion().toString() : "(empty)");
+    log() << "MetadataLoader loading chunks for " << nss.ns() << " based on: "
+          << (metadataForDiff ? metadataForDiff->getCollVersion().toString() : "(empty)");
+
+    std::unique_ptr<CollectionMetadata> remoteMetadata(stdx::make_unique<CollectionMetadata>());
 
-        remoteMetadata = stdx::make_unique<CollectionMetadata>();
-        status = MetadataLoader::makeCollectionMetadata(txn,
-                                                        grid.catalogClient(txn),
-                                                        nss.ns(),
-                                                        getShardName(),
-                                                        metadataForDiff,
-                                                        remoteMetadata.get());
-    } while (status == ErrorCodes::RemoteChangeDetected &&
-             ++numAttempts < kMaxNumMetadataRefreshAttempts);
+    Status status = MetadataLoader::makeCollectionMetadata(txn,
+                                                           grid.catalogClient(txn),
+                                                           nss.ns(),
+                                                           getShardName(),
+                                                           metadataForDiff,
+                                                           remoteMetadata.get());
 
     if (!status.isOK() && status != ErrorCodes::NamespaceNotFound) {
         warning() << "MetadataLoader failed after " << t.millis() << " ms"
@@ -693,23 +700,24 @@ StatusWith<ChunkVersion> ShardingState::_refreshMetadata(
 
     auto css = CollectionShardingState::get(txn, nss);
 
-    if (!status.isOK()) {
-        invariant(status == ErrorCodes::NamespaceNotFound);
-        css->refreshMetadata(txn, nullptr);
+    if (status.isOK()) {
+        css->refreshMetadata(txn, std::move(remoteMetadata));
+
+        auto metadata = css->getMetadata();
 
-        log() << "MetadataLoader took " << t.millis() << " ms and did not find the namespace";
+        log() << "MetadataLoader took " << t.millis() << " ms and found version "
+              << metadata->getCollVersion();
 
-        return ChunkVersion::UNSHARDED();
+        return metadata->getShardVersion();
     }
 
-    css->refreshMetadata(txn, std::move(remoteMetadata));
+    invariant(status == ErrorCodes::NamespaceNotFound);
 
-    auto metadata = css->getMetadata();
+    css->refreshMetadata(txn, nullptr);
 
-    log() << "MetadataLoader took " << t.millis() << " ms and found version "
-          << metadata->getCollVersion();
+    log() << "MetadataLoader took " << t.millis() << " ms and did not find the namespace";
 
-    return metadata->getShardVersion();
+    return ChunkVersion::UNSHARDED();
 }
 
 StatusWith<ScopedRegisterDonateChunk> ShardingState::registerDonateChunk(
diff --git a/src/mongo/db/s/sharding_state_test.cpp b/src/mongo/db/s/sharding_state_test.cpp
index e4953f3488c..0156058676d 100644
--- a/src/mongo/db/s/sharding_state_test.cpp
+++ b/src/mongo/db/s/sharding_state_test.cpp
@@ -33,17 +33,12 @@
 #include "mongo/db/dbdirectclient.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/namespace_string.h"
-#include "mongo/db/query/query_request.h"
 #include "mongo/db/repl/replication_coordinator_mock.h"
 #include "mongo/db/s/sharding_state.h"
 #include "mongo/db/s/type_shard_identity.h"
 #include "mongo/db/server_options.h"
 #include "mongo/db/service_context_noop.h"
 #include "mongo/db/storage/storage_options.h"
-#include "mongo/s/catalog/dist_lock_manager_mock.h"
-#include "mongo/s/catalog/sharding_catalog_client_impl.h"
-#include "mongo/s/catalog/type_chunk.h"
-#include "mongo/s/catalog/type_collection.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/sharding_mongod_test_fixture.h"
 
@@ -59,42 +54,11 @@ public:
         return &_shardingState;
     }
 
-    std::string shardName() const {
-        return _shardName.toString();
-    }
-
-    void setupCollectionMetadata(const NamespaceString& nss,
-                                 const OID& epoch,
-                                 const std::vector<BSONObj>& initChunks) {
-        auto future = launchAsync([this, &nss] {
-            ChunkVersion latestShardVersion;
-            Client::initThreadIfNotAlready();
-            ASSERT_OK(
-                shardingState()->refreshMetadataNow(operationContext(), nss, &latestShardVersion));
-        });
-
-        ChunkVersion initVersion(1, 0, epoch);
-        onFindCommand([&nss, &initVersion](const RemoteCommandRequest&) {
-            CollectionType coll;
-            coll.setNs(nss);
-            coll.setUpdatedAt(Date_t());
-            coll.setEpoch(initVersion.epoch());
-            coll.setKeyPattern(BSON("x" << 1));
-            return std::vector<BSONObj>{coll.toBSON()};
-        });
-
-        onFindCommand([&initChunks](const RemoteCommandRequest&) { return initChunks; });
-
-        future.timed_get(kFutureTimeout);
-    }
-
 protected:
     // Used to write to set up local collections before exercising server logic.
     std::unique_ptr<DBDirectClient> _dbDirectClient;
 
     void setUp() override {
-        _shardName = ShardId("a");
-
         serverGlobalParams.clusterRole = ClusterRole::None;
         ShardingMongodTestFixture::setUp();
 
@@ -112,7 +76,6 @@ protected:
             auto configTargeter =
                 RemoteCommandTargeterMock::get(shardRegistry()->getConfigShard()->getTargeter());
             configTargeter->setConnectionStringReturnValue(configConnStr);
-            configTargeter->setFindHostReturnValue(configConnStr.getServers()[0]);
 
             return Status::OK();
         });
@@ -133,32 +96,20 @@ protected:
         ShardingMongodTestFixture::tearDown();
     }
 
-    std::unique_ptr<DistLockManager> makeDistLockManager(
-        std::unique_ptr<DistLockCatalog> distLockCatalog) override {
-        return stdx::make_unique<DistLockManagerMock>(nullptr);
-    }
-
-    std::unique_ptr<ShardingCatalogClient> makeShardingCatalogClient(
-        std::unique_ptr<DistLockManager> distLockManager) override {
-        invariant(distLockManager);
-        return stdx::make_unique<ShardingCatalogClientImpl>(std::move(distLockManager));
-    }
-
 private:
     ShardingState _shardingState;
-    ShardId _shardName;
 };
 
 TEST_F(ShardingStateTest, ValidShardIdentitySucceeds) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
 
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
     ASSERT_TRUE(shardingState()->enabled());
-    ASSERT_EQ(shardName(), shardingState()->getShardName());
+    ASSERT_EQ("a", shardingState()->getShardName());
     ASSERT_EQ("config/a:1,b:2", shardingState()->getConfigServer(operationContext()).toString());
 }
 
@@ -166,7 +117,7 @@ TEST_F(ShardingStateTest, InitWhilePreviouslyInErrorStateWillStayInErrorState) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
 
     shardingState()->setGlobalInitMethodForTest(
@@ -201,7 +152,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithMatchingShardIdentitySucceeds) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(clusterID);
 
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
@@ -209,7 +160,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithMatchingShardIdentitySucceeds) {
     ShardIdentityType shardIdentity2;
     shardIdentity2.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity2.setShardName(shardName());
+    shardIdentity2.setShardName("a");
     shardIdentity2.setClusterId(clusterID);
 
     shardingState()->setGlobalInitMethodForTest(
@@ -220,7 +171,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithMatchingShardIdentitySucceeds) {
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity2));
 
     ASSERT_TRUE(shardingState()->enabled());
-    ASSERT_EQ(shardName(), shardingState()->getShardName());
+    ASSERT_EQ("a", shardingState()->getShardName());
     ASSERT_EQ("config/a:1,b:2", shardingState()->getConfigServer(operationContext()).toString());
 }
 
@@ -229,7 +180,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithSameReplSetNameSucceeds) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(clusterID);
 
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
@@ -237,7 +188,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithSameReplSetNameSucceeds) {
     ShardIdentityType shardIdentity2;
     shardIdentity2.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "b:2,c:3", "config"));
-    shardIdentity2.setShardName(shardName());
+    shardIdentity2.setShardName("a");
     shardIdentity2.setClusterId(clusterID);
 
     shardingState()->setGlobalInitMethodForTest(
@@ -248,7 +199,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithSameReplSetNameSucceeds) {
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity2));
 
     ASSERT_TRUE(shardingState()->enabled());
-    ASSERT_EQ(shardName(), shardingState()->getShardName());
+    ASSERT_EQ("a", shardingState()->getShardName());
     ASSERT_EQ("config/a:1,b:2", shardingState()->getConfigServer(operationContext()).toString());
 }
 
@@ -257,7 +208,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentReplSetNameFails) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(clusterID);
 
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
@@ -265,7 +216,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentReplSetNameFails) {
     ShardIdentityType shardIdentity2;
     shardIdentity2.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "configRS"));
-    shardIdentity2.setShardName(shardName());
+    shardIdentity2.setShardName("a");
     shardIdentity2.setClusterId(clusterID);
 
     shardingState()->setGlobalInitMethodForTest(
@@ -277,7 +228,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentReplSetNameFails) {
     ASSERT_EQ(ErrorCodes::InconsistentShardIdentity, status);
 
     ASSERT_TRUE(shardingState()->enabled());
-    ASSERT_EQ(shardName(), shardingState()->getShardName());
+    ASSERT_EQ("a", shardingState()->getShardName());
     ASSERT_EQ("config/a:1,b:2", shardingState()->getConfigServer(operationContext()).toString());
 }
 
@@ -286,7 +237,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentShardNameFails) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(clusterID);
 
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
@@ -306,7 +257,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentShardNameFails) {
     ASSERT_EQ(ErrorCodes::InconsistentShardIdentity, status);
 
     ASSERT_TRUE(shardingState()->enabled());
-    ASSERT_EQ(shardName(), shardingState()->getShardName());
+    ASSERT_EQ("a", shardingState()->getShardName());
     ASSERT_EQ("config/a:1,b:2", shardingState()->getConfigServer(operationContext()).toString());
 }
 
@@ -314,7 +265,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentClusterIdFails) {
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
 
     ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
@@ -322,7 +273,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentClusterIdFails) {
     ShardIdentityType shardIdentity2;
     shardIdentity2.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity2.setShardName(shardName());
+    shardIdentity2.setShardName("a");
     shardIdentity2.setClusterId(OID::gen());
 
     shardingState()->setGlobalInitMethodForTest(
@@ -334,7 +285,7 @@ TEST_F(ShardingStateTest, InitializeAgainWithDifferentClusterIdFails) {
     ASSERT_EQ(ErrorCodes::InconsistentShardIdentity, status);
 
     ASSERT_TRUE(shardingState()->enabled());
-    ASSERT_EQ(shardName(), shardingState()->getShardName());
+    ASSERT_EQ("a", shardingState()->getShardName());
     ASSERT_EQ("config/a:1,b:2", shardingState()->getConfigServer(operationContext()).toString());
 }
 
@@ -376,7 +327,7 @@ TEST_F(ShardingStateTest,
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
     ASSERT_OK(shardIdentity.validate());
     serverGlobalParams.overrideShardIdentity = shardIdentity.toBSON();
@@ -424,7 +375,7 @@ TEST_F(ShardingStateTest,
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
     ASSERT_OK(shardIdentity.validate());
     serverGlobalParams.overrideShardIdentity = shardIdentity.toBSON();
@@ -464,7 +415,7 @@ TEST_F(ShardingStateTest,
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
     ASSERT_OK(shardIdentity.validate());
     serverGlobalParams.overrideShardIdentity = shardIdentity.toBSON();
@@ -534,7 +485,7 @@ TEST_F(ShardingStateTest,
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
     ASSERT_OK(shardIdentity.validate());
     BSONObj validShardIdentity = shardIdentity.toBSON();
@@ -594,7 +545,7 @@ TEST_F(ShardingStateTest,
     ShardIdentityType shardIdentity;
     shardIdentity.setConfigsvrConnString(
         ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
+    shardIdentity.setShardName("a");
     shardIdentity.setClusterId(OID::gen());
     ASSERT_OK(shardIdentity.validate());
     BSONObj validShardIdentity = shardIdentity.toBSON();
@@ -609,293 +560,5 @@ TEST_F(ShardingStateTest,
     ASSERT_FALSE(swShardingInitialized.getValue());
 }
 
-TEST_F(ShardingStateTest, MetadataRefreshShouldUseDiffQuery) {
-    ShardIdentityType shardIdentity;
-    shardIdentity.setConfigsvrConnString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
-    shardIdentity.setClusterId(OID::gen());
-
-    ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
-
-    const NamespaceString nss("test.user");
-    const OID initEpoch(OID::gen());
-
-    {
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 0));
-        chunk.setMax(BSON("x" << 10));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(2, 0, initEpoch));
-        setupCollectionMetadata(nss, initEpoch, std::vector<BSONObj>{chunk.toBSON()});
-    }
-
-    const ChunkVersion newVersion(3, 0, initEpoch);
-    auto future = launchAsync([&] {
-        Client::initThreadIfNotAlready();
-        ASSERT_OK(shardingState()->onStaleShardVersion(operationContext(), nss, newVersion));
-    });
-
-    onFindCommand([&nss, &initEpoch](const RemoteCommandRequest&) {
-        CollectionType coll;
-        coll.setNs(nss);
-        coll.setUpdatedAt(Date_t());
-        coll.setEpoch(initEpoch);
-        coll.setKeyPattern(BSON("x" << 1));
-        return std::vector<BSONObj>{coll.toBSON()};
-    });
-
-    onFindCommand([this, &nss, &initEpoch](const RemoteCommandRequest& request) {
-        auto diffQueryStatus = QueryRequest::makeFromFindCommand(nss, request.cmdObj, false);
-        ASSERT_OK(diffQueryStatus.getStatus());
-
-        auto diffQuery = std::move(diffQueryStatus.getValue());
-        ASSERT_BSONOBJ_EQ(BSON("ns" << nss.ns() << "lastmod" << BSON("$gte" << Timestamp(2, 0))),
-                          diffQuery->getFilter());
-
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 10));
-        chunk.setMax(BSON("x" << 20));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(3, 10, initEpoch));
-        return std::vector<BSONObj>{chunk.toBSON()};
-    });
-
-    future.timed_get(kFutureTimeout);
-}
-
-/**
- * Test where the epoch changed right before the chunk diff query.
- */
-TEST_F(ShardingStateTest, MetadataRefreshShouldUseFullQueryOnEpochMismatch) {
-    ShardIdentityType shardIdentity;
-    shardIdentity.setConfigsvrConnString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
-    shardIdentity.setClusterId(OID::gen());
-
-    ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
-
-    const NamespaceString nss("test.user");
-    const OID initEpoch(OID::gen());
-
-    {
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 0));
-        chunk.setMax(BSON("x" << 10));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(2, 0, initEpoch));
-        setupCollectionMetadata(nss, initEpoch, std::vector<BSONObj>{chunk.toBSON()});
-    }
-
-
-    auto future = launchAsync([&] {
-        Client::initThreadIfNotAlready();
-        ASSERT_OK(shardingState()->onStaleShardVersion(
-            operationContext(), nss, ChunkVersion(3, 0, initEpoch)));
-    });
-
-    onFindCommand([&nss, &initEpoch](const RemoteCommandRequest&) {
-        CollectionType coll;
-        coll.setNs(nss);
-        coll.setUpdatedAt(Date_t());
-        coll.setEpoch(initEpoch);
-        coll.setKeyPattern(BSON("x" << 1));
-        return std::vector<BSONObj>{coll.toBSON()};
-    });
-
-    // Now when the diff query is performed, it will get chunks with a different epoch.
-    const ChunkVersion newVersion(3, 0, OID::gen());
-    onFindCommand([this, &nss, &newVersion](const RemoteCommandRequest& request) {
-        auto diffQueryStatus = QueryRequest::makeFromFindCommand(nss, request.cmdObj, false);
-        ASSERT_OK(diffQueryStatus.getStatus());
-
-        auto diffQuery = std::move(diffQueryStatus.getValue());
-        ASSERT_BSONOBJ_EQ(BSON("ns" << nss.ns() << "lastmod" << BSON("$gte" << Timestamp(2, 0))),
-                          diffQuery->getFilter());
-
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 10));
-        chunk.setMax(BSON("x" << 20));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(3, 10, newVersion.epoch()));
-        return std::vector<BSONObj>{chunk.toBSON()};
-    });
-
-    // Retry the refresh again. Now doing a full reload.
-
-    onFindCommand([&nss, &newVersion](const RemoteCommandRequest&) {
-        CollectionType coll;
-        coll.setNs(nss);
-        coll.setUpdatedAt(Date_t());
-        coll.setEpoch(newVersion.epoch());
-        coll.setKeyPattern(BSON("x" << 1));
-        return std::vector<BSONObj>{coll.toBSON()};
-    });
-
-    onFindCommand([this, &nss, &newVersion](const RemoteCommandRequest& request) {
-        auto diffQueryStatus = QueryRequest::makeFromFindCommand(nss, request.cmdObj, false);
-        ASSERT_OK(diffQueryStatus.getStatus());
-
-        auto diffQuery = std::move(diffQueryStatus.getValue());
-        ASSERT_BSONOBJ_EQ(BSON("ns" << nss.ns() << "lastmod" << BSON("$gte" << Timestamp(0, 0))),
-                          diffQuery->getFilter());
-
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 10));
-        chunk.setMax(BSON("x" << 20));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(3, 10, newVersion.epoch()));
-        return std::vector<BSONObj>{chunk.toBSON()};
-    });
-
-    future.timed_get(kFutureTimeout);
-}
-
-TEST_F(ShardingStateTest, FullMetadataOnEpochMismatchShouldStopAfterMaxRetries) {
-    ShardIdentityType shardIdentity;
-    shardIdentity.setConfigsvrConnString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
-    shardIdentity.setClusterId(OID::gen());
-
-    ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
-
-    const NamespaceString nss("test.user");
-    const OID initEpoch(OID::gen());
-
-    {
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 0));
-        chunk.setMax(BSON("x" << 10));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(2, 0, initEpoch));
-        setupCollectionMetadata(nss, initEpoch, std::vector<BSONObj>{chunk.toBSON()});
-    }
-
-
-    auto future = launchAsync([&] {
-        Client::initThreadIfNotAlready();
-        auto status = shardingState()->onStaleShardVersion(
-            operationContext(), nss, ChunkVersion(3, 0, initEpoch));
-        ASSERT_EQ(ErrorCodes::RemoteChangeDetected, status);
-    });
-
-    OID lastEpoch(initEpoch);
-    OID nextEpoch(OID::gen());
-    for (int tries = 0; tries < 3; tries++) {
-        onFindCommand([&nss, &lastEpoch](const RemoteCommandRequest&) {
-            CollectionType coll;
-            coll.setNs(nss);
-            coll.setUpdatedAt(Date_t());
-            coll.setEpoch(lastEpoch);
-            coll.setKeyPattern(BSON("x" << 1));
-            return std::vector<BSONObj>{coll.toBSON()};
-        });
-
-        onFindCommand([this, &nss, &nextEpoch, tries](const RemoteCommandRequest& request) {
-            auto diffQueryStatus = QueryRequest::makeFromFindCommand(nss, request.cmdObj, false);
-            ASSERT_OK(diffQueryStatus.getStatus());
-
-            auto diffQuery = std::move(diffQueryStatus.getValue());
-            Timestamp expectedLastMod = (tries == 0) ? Timestamp(2, 0) : Timestamp(0, 0);
-            ASSERT_BSONOBJ_EQ(
-                BSON("ns" << nss.ns() << "lastmod" << BSON("$gte" << expectedLastMod)),
-                diffQuery->getFilter());
-
-            ChunkType chunk;
-            chunk.setNS(nss.ns());
-            chunk.setMin(BSON("x" << 10));
-            chunk.setMax(BSON("x" << 20));
-            chunk.setShard(ShardId(shardName()));
-            chunk.setVersion(ChunkVersion(3, 10, nextEpoch));
-            return std::vector<BSONObj>{chunk.toBSON()};
-        });
-
-        lastEpoch = nextEpoch;
-        nextEpoch = OID::gen();
-    }
-
-    future.timed_get(kFutureTimeout);
-}
-
-TEST_F(ShardingStateTest, MetadataRefreshShouldBeOkWhenCollectionWasDropped) {
-    ShardIdentityType shardIdentity;
-    shardIdentity.setConfigsvrConnString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
-    shardIdentity.setClusterId(OID::gen());
-
-    ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
-
-    const NamespaceString nss("test.user");
-    const OID initEpoch(OID::gen());
-
-    {
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 0));
-        chunk.setMax(BSON("x" << 10));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(2, 0, initEpoch));
-        setupCollectionMetadata(nss, initEpoch, std::vector<BSONObj>{chunk.toBSON()});
-    }
-
-    const ChunkVersion newVersion(3, 0, initEpoch);
-    auto future = launchAsync([&] {
-        Client::initThreadIfNotAlready();
-        ASSERT_OK(shardingState()->onStaleShardVersion(operationContext(), nss, newVersion));
-    });
-
-    onFindCommand([&nss, &initEpoch](const RemoteCommandRequest&) {
-        CollectionType coll;
-        coll.setNs(nss);
-        coll.setUpdatedAt(Date_t());
-        coll.setEpoch(initEpoch);
-        coll.setKeyPattern(BSON("x" << 1));
-        coll.setDropped(true);
-        return std::vector<BSONObj>{coll.toBSON()};
-    });
-
-    future.timed_get(kFutureTimeout);
-}
-
-TEST_F(ShardingStateTest, MetadataRefreshShouldNotRetryOtherTypesOfError) {
-    ShardIdentityType shardIdentity;
-    shardIdentity.setConfigsvrConnString(
-        ConnectionString(ConnectionString::SET, "a:1,b:2", "config"));
-    shardIdentity.setShardName(shardName());
-    shardIdentity.setClusterId(OID::gen());
-
-    ASSERT_OK(shardingState()->initializeFromShardIdentity(operationContext(), shardIdentity));
-
-    const NamespaceString nss("test.user");
-    const OID initEpoch(OID::gen());
-
-    {
-        ChunkType chunk;
-        chunk.setNS(nss.ns());
-        chunk.setMin(BSON("x" << 0));
-        chunk.setMax(BSON("x" << 10));
-        chunk.setShard(ShardId(shardName()));
-        chunk.setVersion(ChunkVersion(2, 0, initEpoch));
-        setupCollectionMetadata(nss, initEpoch, std::vector<BSONObj>{chunk.toBSON()});
-    }
-
-    auto configTargeter =
-        RemoteCommandTargeterMock::get(shardRegistry()->getConfigShard()->getTargeter());
-    configTargeter->setFindHostReturnValue({ErrorCodes::HostNotFound, "host erased by test"});
-
-    auto status = shardingState()->onStaleShardVersion(
-        operationContext(), nss, ChunkVersion(3, 0, initEpoch));
-    ASSERT_EQ(ErrorCodes::HostNotFound, status);
-}
-
 }  // namespace
 }  // namespace mongo