SERVER-63759 First implementation of the Router API

7 files changed, 353 insertions, 67 deletions

diff --git a/src/mongo/db/pipeline/dispatch_shard_pipeline_test.cpp b/src/mongo/db/pipeline/dispatch_shard_pipeline_test.cpp
index 8c9528e0e09..ebf3d147c8f 100644
--- a/src/mongo/db/pipeline/dispatch_shard_pipeline_test.cpp
+++ b/src/mongo/db/pipeline/dispatch_shard_pipeline_test.cpp
@@ -27,12 +27,10 @@
  *    it in the license file.
  */
 
-#include "mongo/platform/basic.h"
-
 #include "mongo/db/pipeline/aggregation_request_helper.h"
 #include "mongo/db/pipeline/sharded_agg_helpers.h"
 #include "mongo/s/query/sharded_agg_test_fixture.h"
-#include "mongo/s/stale_shard_version_helpers.h"
+#include "mongo/s/router.h"
 
 namespace mongo {
 namespace {
@@ -196,15 +194,13 @@ TEST_F(DispatchShardPipelineTest, WrappedDispatchDoesRetryOnStaleConfigError) {
     const bool hasChangeStream = false;
     auto future = launchAsync([&] {
         // Shouldn't throw.
-        auto results =
-            shardVersionRetry(operationContext(),
-                              Grid::get(getServiceContext())->catalogCache(),
-                              kTestAggregateNss,
-                              "dispatch shard pipeline"_sd,
-                              [&]() {
-                                  return sharded_agg_helpers::dispatchShardPipeline(
-                                      serializedCommand, hasChangeStream, pipeline->clone());
-                              });
+        sharding::router::CollectionRouter router(getServiceContext(), kTestAggregateNss);
+        auto results = router.route(operationContext(),
+                                    "dispatch shard pipeline"_sd,
+                                    [&](OperationContext* opCtx, const ChunkManager& cm) {
+                                        return sharded_agg_helpers::dispatchShardPipeline(
+                                            serializedCommand, hasChangeStream, pipeline->clone());
+                                    });
         ASSERT_EQ(results.remoteCursors.size(), 1UL);
         ASSERT(!bool(results.splitPipeline));
     });
@@ -213,7 +209,7 @@ TEST_F(DispatchShardPipelineTest, WrappedDispatchDoesRetryOnStaleConfigError) {
     // namespace, then mock out a successful response.
     onCommand([&](const executor::RemoteCommandRequest& request) {
         return createErrorCursorResponse(
-            Status{ErrorCodes::StaleShardVersion, "Mock error: shard version mismatch"});
+            {ErrorCodes::StaleShardVersion, "Mock error: shard version mismatch"});
     });
 
     // Mock the expected config server queries.
diff --git a/src/mongo/db/pipeline/process_interface/shardsvr_process_interface.cpp b/src/mongo/db/pipeline/process_interface/shardsvr_process_interface.cpp
index 2d51dc92697..204806d839a 100644
--- a/src/mongo/db/pipeline/process_interface/shardsvr_process_interface.cpp
+++ b/src/mongo/db/pipeline/process_interface/shardsvr_process_interface.cpp
@@ -50,8 +50,8 @@
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/cluster_commands_helpers.h"
 #include "mongo/s/cluster_write.h"
-#include "mongo/s/grid.h"
 #include "mongo/s/query/document_source_merge_cursors.h"
+#include "mongo/s/router.h"
 #include "mongo/s/stale_shard_version_helpers.h"
 
 namespace mongo {
@@ -311,37 +311,40 @@ void ShardServerProcessInterface::createCollection(OperationContext* opCtx,
 
 void ShardServerProcessInterface::createIndexesOnEmptyCollection(
     OperationContext* opCtx, const NamespaceString& ns, const std::vector<BSONObj>& indexSpecs) {
-    auto cachedDbInfo =
-        uassertStatusOK(Grid::get(opCtx)->catalogCache()->getDatabase(opCtx, ns.db()));
-    BSONObjBuilder newCmdBuilder;
-    newCmdBuilder.append("createIndexes", ns.coll());
-    newCmdBuilder.append("indexes", indexSpecs);
-    newCmdBuilder.append(WriteConcernOptions::kWriteConcernField,
-                         opCtx->getWriteConcern().toBSON());
-    auto cmdObj = newCmdBuilder.done();
-
-    shardVersionRetry(
+    sharding::router::DBPrimaryRouter router(opCtx->getServiceContext(), ns.db());
+    router.route(
         opCtx,
-        Grid::get(opCtx)->catalogCache(),
-        ns,
         "copying index for empty collection {}"_format(ns.ns()),
-        [&] {
-            auto response = executeCommandAgainstDatabasePrimary(
-                opCtx,
-                ns.db(),
-                std::move(cachedDbInfo),
-                cmdObj,
-                ReadPreferenceSetting(ReadPreference::PrimaryOnly),
-                Shard::RetryPolicy::kIdempotent);
+        [&](OperationContext* opCtx, const CachedDatabaseInfo& cdb) {
+            BSONObjBuilder cmdBuilder;
+            cmdBuilder.append("createIndexes", ns.coll());
+            cmdBuilder.append("indexes", indexSpecs);
+            cmdBuilder.append(WriteConcernOptions::kWriteConcernField,
+                              opCtx->getWriteConcern().toBSON());
+            sharding::router::DBPrimaryRouter::appendCRUDUnshardedRoutingTokenToCommand(
+                cdb->getPrimary(), cdb->getVersion(), &cmdBuilder);
+
+            auto cmdObj = cmdBuilder.obj();
+
+            auto response = std::move(
+                gatherResponses(opCtx,
+                                ns.db(),
+                                ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+                                Shard::RetryPolicy::kIdempotent,
+                                std::vector<AsyncRequestsSender::Request>{
+                                    AsyncRequestsSender::Request(cdb->getPrimary(), cmdObj)})
+                    .front());
 
             uassertStatusOKWithContext(response.swResponse,
-                                       str::stream() << "failed to run command " << cmdObj);
-            auto result = response.swResponse.getValue().data;
+                                       str::stream() << "command was not sent " << cmdObj);
+            const auto& result = response.swResponse.getValue().data;
             uassertStatusOKWithContext(getStatusFromCommandResult(result),
-                                       str::stream() << "failed while running command " << cmdObj);
+                                       str::stream() << "command was sent but failed " << cmdObj);
             uassertStatusOKWithContext(
                 getWriteConcernStatusFromCommandResult(result),
-                str::stream() << "write concern failed while running command " << cmdObj);
+                str::stream()
+                    << "command was sent and succeeded, but failed waiting for write concern "
+                    << cmdObj);
         });
 }
 
diff --git a/src/mongo/db/pipeline/sharded_agg_helpers.cpp b/src/mongo/db/pipeline/sharded_agg_helpers.cpp
index 9c5ea37cbcb..3eaeb1666c8 100644
--- a/src/mongo/db/pipeline/sharded_agg_helpers.cpp
+++ b/src/mongo/db/pipeline/sharded_agg_helpers.cpp
@@ -26,11 +26,12 @@
  *    exception statement from all source files in the program, then also delete
  *    it in the license file.
  */
+
 #define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kQuery
 
 #include "mongo/platform/basic.h"
 
-#include "sharded_agg_helpers.h"
+#include "mongo/db/pipeline/sharded_agg_helpers.h"
 
 #include "mongo/db/curop.h"
 #include "mongo/db/pipeline/aggregate_command_gen.h"
@@ -58,11 +59,13 @@
 #include "mongo/s/query/cluster_query_knobs_gen.h"
 #include "mongo/s/query/document_source_merge_cursors.h"
 #include "mongo/s/query/establish_cursors.h"
+#include "mongo/s/router.h"
 #include "mongo/s/transaction_router.h"
 #include "mongo/util/fail_point.h"
 #include "mongo/util/visit_helper.h"
 
-namespace mongo::sharded_agg_helpers {
+namespace mongo {
+namespace sharded_agg_helpers {
 
 MONGO_FAIL_POINT_DEFINE(shardedAggregateHangBeforeEstablishingShardCursors);
 
@@ -613,7 +616,6 @@ void abandonCacheIfSentToShards(Pipeline* shardsPipeline) {
     }
 }
 
-
 }  // namespace
 
 std::unique_ptr<Pipeline, PipelineDeleter> targetShardsAndAddMergeCursors(
@@ -1349,19 +1351,22 @@ std::unique_ptr<Pipeline, PipelineDeleter> attachCursorToPipeline(
                 ns == NamespaceString::kChangeStreamPreImagesNamespace);
     };
 
-    auto catalogCache = Grid::get(expCtx->opCtx)->catalogCache();
-    return shardVersionRetry(
-        expCtx->opCtx, catalogCache, expCtx->ns, "targeting pipeline to attach cursors"_sd, [&]() {
-            auto pipelineToTarget = pipeline->clone();
+    if (shardTargetingPolicy == ShardTargetingPolicy::kNotAllowed ||
+        shouldAlwaysAttachLocalCursorForNamespace(expCtx->ns)) {
+        auto pipelineToTarget = pipeline->clone();
 
-            if (shardTargetingPolicy == ShardTargetingPolicy::kNotAllowed ||
-                shouldAlwaysAttachLocalCursorForNamespace(expCtx->ns)) {
-                return expCtx->mongoProcessInterface->attachCursorSourceToPipelineForLocalRead(
-                    pipelineToTarget.release());
-            }
+        return expCtx->mongoProcessInterface->attachCursorSourceToPipelineForLocalRead(
+            pipelineToTarget.release());
+    }
+
+    sharding::router::CollectionRouter router(expCtx->opCtx->getServiceContext(), expCtx->ns);
+    return router.route(
+        expCtx->opCtx,
+        "targeting pipeline to attach cursors"_sd,
+        [&](OperationContext* opCtx, const ChunkManager& cm) {
+            auto pipelineToTarget = pipeline->clone();
 
-            auto cm = catalogCache->getCollectionRoutingInfo(expCtx->opCtx, expCtx->ns);
-            if (cm.isOK() && !cm.getValue().isSharded()) {
+            if (!cm.isSharded()) {
                 // If the collection is unsharded and we are on the primary, we should be able to
                 // do a local read. The primary may be moved right after the primary shard check,
                 // but the local read path will do a db version check before it establishes a cursor
@@ -1371,7 +1376,7 @@ std::unique_ptr<Pipeline, PipelineDeleter> attachCursorToPipeline(
                     expCtx->mongoProcessInterface->setExpectedShardVersion(
                         expCtx->opCtx, expCtx->ns, ChunkVersion::UNSHARDED());
                     setDbVersion = expCtx->mongoProcessInterface->setExpectedDbVersion(
-                        expCtx->opCtx, expCtx->ns, cm.getValue().dbVersion());
+                        expCtx->opCtx, expCtx->ns, cm.dbVersion());
 
                     // During 'attachCursorSourceToPipelineForLocalRead', the expected db version
                     // must be set. Whether or not that call is succesful, to avoid affecting later
@@ -1424,4 +1429,5 @@ std::unique_ptr<Pipeline, PipelineDeleter> attachCursorToPipeline(
         });
 }
 
-}  // namespace mongo::sharded_agg_helpers
+}  // namespace sharded_agg_helpers
+}  // namespace mongo
diff --git a/src/mongo/s/SConscript b/src/mongo/s/SConscript
index c312f01776f..867de0bdedf 100644
--- a/src/mongo/s/SConscript
+++ b/src/mongo/s/SConscript
@@ -48,12 +48,13 @@ env.Library(
     source=[
         'cluster_commands_helpers.cpp',
         'multi_statement_transaction_requests_sender.cpp',
-        'transaction_router.cpp',
         'router_transactions_metrics.cpp',
         'router_transactions_stats.idl',
+        'router.cpp',
         'session_catalog_router.cpp',
         'stale_shard_version_helpers.cpp',
         'transaction_router_resource_yielder.cpp',
+        'transaction_router.cpp',
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/db/commands/txn_cmd_request',
diff --git a/src/mongo/s/query/SConscript b/src/mongo/s/query/SConscript
index 3e78801e64f..e0e72ae107f 100644
--- a/src/mongo/s/query/SConscript
+++ b/src/mongo/s/query/SConscript
@@ -92,17 +92,6 @@ env.Library(
 )
 
 env.Library(
-    target="cluster_client_cursor_mock",
-    source=[
-        "cluster_client_cursor_mock.cpp",
-    ],
-    LIBDEPS=[
-        '$BUILD_DIR/mongo/base',
-        '$BUILD_DIR/mongo/db/shared_request_handling',
-    ],
-)
-
-env.Library(
     target="store_possible_cursor",
     source=[
         "store_possible_cursor.cpp"
@@ -152,6 +141,7 @@ env.CppUnitTest(
         "async_results_merger_test.cpp",
         "blocking_results_merger_test.cpp",
         "cluster_client_cursor_impl_test.cpp",
+        "cluster_client_cursor_mock.cpp",
         "cluster_cursor_manager_test.cpp",
         "cluster_exchange_test.cpp",
         "establish_cursors_test.cpp",
@@ -167,6 +157,7 @@ env.CppUnitTest(
         "$BUILD_DIR/mongo/db/logical_session_id",
         "$BUILD_DIR/mongo/db/query/query_request",
         "$BUILD_DIR/mongo/db/query/query_test_service_context",
+        "$BUILD_DIR/mongo/db/shared_request_handling",
         "$BUILD_DIR/mongo/executor/thread_pool_task_executor_test_fixture",
         "$BUILD_DIR/mongo/s/sharding_router_test_fixture",
         "$BUILD_DIR/mongo/s/vector_clock_mongos",
@@ -174,7 +165,6 @@ env.CppUnitTest(
         "async_results_merger",
         "cluster_aggregate",
         "cluster_client_cursor",
-        "cluster_client_cursor_mock",
         "cluster_cursor_manager",
         "router_exec_stage",
         "store_possible_cursor",
diff --git a/src/mongo/s/router.cpp b/src/mongo/s/router.cpp
new file mode 100644
index 00000000000..dba40ad1137
--- /dev/null
+++ b/src/mongo/s/router.cpp
@@ -0,0 +1,165 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    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
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    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 Server Side 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_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kSharding
+
+#include "mongo/s/router.h"
+
+#include "mongo/logv2/log.h"
+#include "mongo/s/grid.h"
+#include "mongo/s/stale_exception.h"
+
+namespace mongo {
+namespace sharding {
+namespace router {
+
+RouterBase::RouterBase(ServiceContext* service) : _service(service) {}
+
+DBPrimaryRouter::DBPrimaryRouter(ServiceContext* service, StringData db)
+    : RouterBase(service), _db(db.toString()) {}
+
+void DBPrimaryRouter::appendDDLRoutingTokenToCommand(const DatabaseType& dbt,
+                                                     BSONObjBuilder* builder) {
+    const auto& dbVersion = dbt.getVersion();
+    if (!dbVersion.isFixed()) {
+        BSONObjBuilder dbvBuilder(builder->subobjStart(DatabaseVersion::kDatabaseVersionField));
+        dbVersion.serialize(&dbvBuilder);
+    }
+}
+
+void DBPrimaryRouter::appendCRUDUnshardedRoutingTokenToCommand(const ShardId& shardId,
+                                                               const DatabaseVersion& dbVersion,
+                                                               BSONObjBuilder* builder) {
+    if (!dbVersion.isFixed()) {
+        BSONObjBuilder dbvBuilder(builder->subobjStart(DatabaseVersion::kDatabaseVersionField));
+        dbVersion.serialize(&dbvBuilder);
+    }
+    ChunkVersion::UNSHARDED().serializeToBSON(ChunkVersion::kShardVersionField, builder);
+}
+
+CachedDatabaseInfo DBPrimaryRouter::_getRoutingInfo(OperationContext* opCtx) const {
+    auto catalogCache = Grid::get(_service)->catalogCache();
+    return uassertStatusOK(catalogCache->getDatabase(opCtx, _db));
+}
+
+void DBPrimaryRouter::_onException(RouteContext* context, Status s) {
+    if (++context->numAttempts > kMaxNumStaleVersionRetries) {
+        uassertStatusOKWithContext(
+            s,
+            str::stream() << "Exceeded maximum number of " << kMaxNumStaleVersionRetries
+                          << " retries attempting \'" << context->comment << "\'");
+    } else {
+        LOGV2_DEBUG(637590,
+                    3,
+                    "Retrying {description}. Got error: {status}",
+                    "description"_attr = context->comment,
+                    "status"_attr = s);
+    }
+
+    auto catalogCache = Grid::get(_service)->catalogCache();
+
+    if (s == ErrorCodes::StaleDbVersion) {
+        auto si = s.extraInfo<StaleDbRoutingVersion>();
+        invariant(si);
+        invariant(si->getDb() == _db,
+                  str::stream() << "StaleDbVersion on unexpected database. Expected " << _db
+                                << ", received " << si->getDb());
+
+        catalogCache->onStaleDatabaseVersion(si->getDb(), si->getVersionWanted());
+    } else {
+        uassertStatusOK(s);
+    }
+}
+
+CollectionRouter::CollectionRouter(ServiceContext* service, NamespaceString nss)
+    : RouterBase(service), _nss(std::move(nss)) {}
+
+void CollectionRouter::appendCRUDRoutingTokenToCommand(const ShardId& shardId,
+                                                       const ChunkManager& cm,
+                                                       BSONObjBuilder* builder) {
+    auto chunkVersion(cm.getVersion(shardId));
+
+    if (chunkVersion == ChunkVersion::UNSHARDED()) {
+        // Need to add the database version as well
+        const auto& dbVersion = cm.dbVersion();
+        if (!dbVersion.isFixed()) {
+            BSONObjBuilder dbvBuilder(builder->subobjStart(DatabaseVersion::kDatabaseVersionField));
+            dbVersion.serialize(&dbvBuilder);
+        }
+    }
+    chunkVersion.serializeToBSON(ChunkVersion::kShardVersionField, builder);
+}
+
+ChunkManager CollectionRouter::_getRoutingInfo(OperationContext* opCtx) const {
+    auto catalogCache = Grid::get(_service)->catalogCache();
+    return uassertStatusOK(catalogCache->getCollectionRoutingInfo(opCtx, _nss));
+}
+
+void CollectionRouter::_onException(RouteContext* context, Status s) {
+    if (++context->numAttempts > kMaxNumStaleVersionRetries) {
+        uassertStatusOKWithContext(
+            s,
+            str::stream() << "Exceeded maximum number of " << kMaxNumStaleVersionRetries
+                          << " retries attempting \'" << context->comment << "\'");
+    } else {
+        LOGV2_DEBUG(637591,
+                    3,
+                    "Retrying {description}. Got error: {status}",
+                    "description"_attr = context->comment,
+                    "status"_attr = s);
+    }
+
+    auto catalogCache = Grid::get(_service)->catalogCache();
+
+    if (s.isA<ErrorCategory::StaleShardVersionError>()) {
+        if (auto si = s.extraInfo<StaleConfigInfo>()) {
+            invariant(si->getNss() == _nss,
+                      str::stream() << "StaleConfig on unexpected namespace. Expected " << _nss
+                                    << ", received " << si->getNss());
+            catalogCache->invalidateShardOrEntireCollectionEntryForShardedCollection(
+                _nss, si->getVersionWanted(), si->getShardId());
+        } else {
+            catalogCache->invalidateCollectionEntry_LINEARIZABLE(_nss);
+        }
+    } else if (s == ErrorCodes::StaleDbVersion) {
+        auto si = s.extraInfo<StaleDbRoutingVersion>();
+        invariant(si);
+        invariant(si->getDb() == _nss.db(),
+                  str::stream() << "StaleDbVersion on unexpected database. Expected " << _nss.db()
+                                << ", received " << si->getDb());
+
+        catalogCache->onStaleDatabaseVersion(si->getDb(), si->getVersionWanted());
+    } else {
+        uassertStatusOK(s);
+    }
+}
+
+}  // namespace router
+}  // namespace sharding
+}  // namespace mongo
diff --git a/src/mongo/s/router.h b/src/mongo/s/router.h
new file mode 100644
index 00000000000..6cfd1d9e546
--- /dev/null
+++ b/src/mongo/s/router.h
@@ -0,0 +1,125 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    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
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    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 Server Side 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.
+ */
+
+#pragma once
+
+#include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/db/namespace_string.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/s/catalog_cache.h"
+
+namespace mongo {
+namespace sharding {
+namespace router {
+
+class RouterBase {
+protected:
+    RouterBase(ServiceContext* service);
+
+    struct RouteContext {
+        const std::string comment;
+        int numAttempts{0};
+    };
+
+    ServiceContext* const _service;
+};
+
+// Both the router classes below declare the scope in which their 'route' method is executed as a
+// router for the relevant database or collection. These classes are the only way to obtain routing
+// information for a given entry.
+
+/**
+ * This class should mostly be used for routing of DDL operations which need to be coordinated from
+ * the primary shard of the database.
+ */
+class DBPrimaryRouter : public RouterBase {
+public:
+    DBPrimaryRouter(ServiceContext* service, StringData db);
+
+    template <typename F>
+    auto route(OperationContext* opCtx, StringData comment, F&& callbackFn) {
+        RouteContext context{comment.toString()};
+        while (true) {
+            auto cdb = _getRoutingInfo(opCtx);
+            try {
+                return callbackFn(opCtx, cdb);
+            } catch (const DBException& ex) {
+                _onException(&context, ex.toStatus());
+            }
+        }
+    }
+
+    static void appendDDLRoutingTokenToCommand(const DatabaseType& dbt, BSONObjBuilder* builder);
+
+    static void appendCRUDUnshardedRoutingTokenToCommand(const ShardId& shardId,
+                                                         const DatabaseVersion& dbVersion,
+                                                         BSONObjBuilder* builder);
+
+private:
+    CachedDatabaseInfo _getRoutingInfo(OperationContext* opCtx) const;
+    void _onException(RouteContext* context, Status s);
+
+    std::string _db;
+};
+
+/**
+ * This class should mostly be used for routing CRUD operations which need to have a view of the
+ * entire routing table for a collection.
+ */
+class CollectionRouter : public RouterBase {
+public:
+    CollectionRouter(ServiceContext* service, NamespaceString nss);
+
+    template <typename F>
+    auto route(OperationContext* opCtx, StringData comment, F&& callbackFn) {
+        RouteContext context{comment.toString()};
+        while (true) {
+            auto cm = _getRoutingInfo(opCtx);
+            try {
+                return callbackFn(opCtx, cm);
+            } catch (const DBException& ex) {
+                _onException(&context, ex.toStatus());
+            }
+        }
+    }
+
+    static void appendCRUDRoutingTokenToCommand(const ShardId& shardId,
+                                                const ChunkManager& cm,
+                                                BSONObjBuilder* builder);
+
+private:
+    ChunkManager _getRoutingInfo(OperationContext* opCtx) const;
+    void _onException(RouteContext* context, Status s);
+
+    NamespaceString _nss;
+};
+
+}  // namespace router
+}  // namespace sharding
+}  // namespace mongo