1 files changed, 22 insertions, 24 deletions

diff --git a/src/mongo/db/s/shardsvr_move_range_command.cpp b/src/mongo/db/s/shardsvr_move_range_command.cpp
index dab2d3ab073..df6d900aa3c 100644
--- a/src/mongo/db/s/shardsvr_move_range_command.cpp
+++ b/src/mongo/db/s/shardsvr_move_range_command.cpp
@@ -97,7 +97,7 @@ public:
             // Check if there is an existing migration running and if so, join it
             if (scopedMigration.mustExecute()) {
                 auto moveChunkComplete =
-                    ExecutorFuture<void>(Grid::get(opCtx)->getExecutorPool()->getFixedExecutor())
+                    ExecutorFuture<void>(_getExecutor())
                         .then([req = request(),
                                writeConcern = opCtx->getWriteConcern(),
                                scopedMigration = std::move(scopedMigration),
@@ -215,13 +215,6 @@ public:
                     opCtx, ReadPreferenceSetting{ReadPreference::PrimaryOnly});
             }());
 
-            long long totalDocsCloned =
-                ShardingStatistics::get(opCtx).countDocsClonedOnDonor.load();
-            long long totalBytesCloned =
-                ShardingStatistics::get(opCtx).countBytesClonedOnDonor.load();
-            long long totalCloneTime =
-                ShardingStatistics::get(opCtx).totalDonorChunkCloneTimeMillis.load();
-
             MigrationSourceManager migrationSourceManager(
                 opCtx, std::move(request), std::move(writeConcern), donorConnStr, recipientHost);
 
@@ -230,23 +223,28 @@ public:
             migrationSourceManager.enterCriticalSection();
             migrationSourceManager.commitChunkOnRecipient();
             migrationSourceManager.commitChunkMetadataOnConfig();
+        }
+
+        // Returns a single-threaded executor to be used to run moveChunk commands. The executor is
+        // initialized on the first call to this function. Uses a shared_ptr because a shared_ptr is
+        // required to work with ExecutorFutures.
+        static std::shared_ptr<ThreadPool> _getExecutor() {
+            static Mutex mutex = MONGO_MAKE_LATCH("MoveChunkExecutor::_mutex");
+            static std::shared_ptr<ThreadPool> executor;
+
+            stdx::lock_guard<Latch> lg(mutex);
+            if (!executor) {
+                ThreadPool::Options options;
+                options.poolName = "MoveChunk";
+                options.minThreads = 0;
+                // We limit the size of the thread pool to a single thread because currently there
+                // can only be one moveRange operation on a shard at a time.
+                options.maxThreads = 1;
+                executor = std::make_shared<ThreadPool>(std::move(options));
+                executor->startup();
+            }
 
-            long long docsCloned =
-                ShardingStatistics::get(opCtx).countDocsClonedOnDonor.load() - totalDocsCloned;
-            long long bytesCloned =
-                ShardingStatistics::get(opCtx).countBytesClonedOnDonor.load() - totalBytesCloned;
-            long long cloneTime =
-                ShardingStatistics::get(opCtx).totalDonorChunkCloneTimeMillis.load() -
-                totalCloneTime;
-            auto migrationId = migrationSourceManager.getMigrationId();
-
-            LOGV2(7627801,
-                  "Migration finished",
-                  "migrationId"_attr = migrationId ? migrationId->toString() : "",
-                  "totalTimeMillis"_attr = migrationSourceManager.getOpTimeMillis(),
-                  "docsCloned"_attr = docsCloned,
-                  "bytesCloned"_attr = bytesCloned,
-                  "cloneTime"_attr = cloneTime);
+            return executor;
         }
     };