SERVER-41006 Make replBatchLimitBytes configurable

5 files changed, 18 insertions, 10 deletions

diff --git a/src/mongo/db/repl/initial_syncer.cpp b/src/mongo/db/repl/initial_syncer.cpp
index 4733e69ea10..335411ca1ba 100644
--- a/src/mongo/db/repl/initial_syncer.cpp
+++ b/src/mongo/db/repl/initial_syncer.cpp
@@ -1685,7 +1685,7 @@ StatusWith<Operations> InitialSyncer::_getNextApplierBatch_inlock() {
     // Obtain next batch of operations from OplogApplier.
     auto opCtx = makeOpCtx();
     OplogApplier::BatchLimits batchLimits;
-    batchLimits.bytes = OplogApplier::replBatchLimitBytes;
+    batchLimits.bytes = replBatchLimitBytes.load();
     batchLimits.ops = OplogApplier::getBatchLimitOperations();
     return _oplogApplier->getNextApplierBatch(opCtx.get(), batchLimits);
 }
diff --git a/src/mongo/db/repl/oplog_applier.cpp b/src/mongo/db/repl/oplog_applier.cpp
index 7e6010aa77c..a44cb2ab410 100644
--- a/src/mongo/db/repl/oplog_applier.cpp
+++ b/src/mongo/db/repl/oplog_applier.cpp
@@ -77,7 +77,7 @@ std::size_t OplogApplier::calculateBatchLimitBytes(OperationContext* opCtx,
     auto oplogMaxSizeResult =
         storageInterface->getOplogMaxSize(opCtx, NamespaceString::kRsOplogNamespace);
     auto oplogMaxSize = fassert(40301, oplogMaxSizeResult);
-    return std::min(oplogMaxSize / 10, std::size_t(replBatchLimitBytes));
+    return std::min(oplogMaxSize / 10, std::size_t(replBatchLimitBytes.load()));
 }
 
 OplogApplier::OplogApplier(executor::TaskExecutor* executor,
diff --git a/src/mongo/db/repl/oplog_applier.h b/src/mongo/db/repl/oplog_applier.h
index 49477ac03ec..0966ec3b960 100644
--- a/src/mongo/db/repl/oplog_applier.h
+++ b/src/mongo/db/repl/oplog_applier.h
@@ -104,11 +104,6 @@ public:
         OperationContext* opCtx, const BatchLimits& batchLimits)>;
 
     /**
-     * Lower bound of batch limit size (in bytes) returned by calculateBatchLimitBytes().
-     */
-    static const unsigned int replBatchLimitBytes = 100 * 1024 * 1024;
-
-    /**
      * Creates thread pool for writer tasks.
      */
     static std::unique_ptr<ThreadPool> makeWriterPool();
diff --git a/src/mongo/db/repl/repl_server_parameters.idl b/src/mongo/db/repl/repl_server_parameters.idl
index b7b2447649a..ba56ea21c4d 100644
--- a/src/mongo/db/repl/repl_server_parameters.idl
+++ b/src/mongo/db/repl/repl_server_parameters.idl
@@ -237,3 +237,16 @@ server_parameters:
             lte:
                 expr: 1000 * 1000
 
+    replBatchLimitBytes:
+        description: The maximum oplog application batch size in bytes
+        set_at: [ startup, runtime ]
+        cpp_vartype: AtomicWord<int>
+        cpp_varname: replBatchLimitBytes
+        default:
+            expr: 100 * 1024 * 1024
+        validator:
+            gte:
+                expr: 16 * 1024 * 1024
+            lte:
+                expr: 100 * 1024 * 1024
+
diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index a3dcb97e410..0b93b7d373b 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -633,16 +633,16 @@ private:
         Client::initThread("ReplBatcher");
 
         BatchLimits batchLimits;
-        batchLimits.bytes = OplogApplier::calculateBatchLimitBytes(
-            cc().makeOperationContext().get(), _storageInterface);
 
         while (true) {
             MONGO_FAIL_POINT_PAUSE_WHILE_SET(rsSyncApplyStop);
 
             batchLimits.slaveDelayLatestTimestamp = _calculateSlaveDelayLatestTimestamp();
 
-            // Check this once per batch since users can change it at runtime.
+            // Check the limits once per batch since users can change them at runtime.
             batchLimits.ops = OplogApplier::getBatchLimitOperations();
+            batchLimits.bytes = OplogApplier::calculateBatchLimitBytes(
+                cc().makeOperationContext().get(), _storageInterface);
 
             OpQueue ops(batchLimits.ops);
             {