SERVER-44522 serverStatus metrics for awaitable isMaster

1 files changed, 15 insertions, 0 deletions

diff --git a/src/mongo/s/commands/cluster_is_master_cmd.cpp b/src/mongo/s/commands/cluster_is_master_cmd.cpp
index 203f5e2e3df..084e9ef7488 100644
--- a/src/mongo/s/commands/cluster_is_master_cmd.cpp
+++ b/src/mongo/s/commands/cluster_is_master_cmd.cpp
@@ -42,6 +42,7 @@
 #include "mongo/rpc/metadata/client_metadata.h"
 #include "mongo/rpc/metadata/client_metadata_ismaster.h"
 #include "mongo/rpc/topology_version_gen.h"
+#include "mongo/transport/ismaster_metrics.h"
 #include "mongo/transport/message_compressor_manager.h"
 #include "mongo/util/map_util.h"
 #include "mongo/util/net/socket_utils.h"
@@ -49,7 +50,11 @@
 
 namespace mongo {
 
+// Hangs in the beginning of each isMaster command when set.
 MONGO_FAIL_POINT_DEFINE(waitInIsMaster);
+// Awaitable isMaster requests with the proper topologyVersions are expected to sleep for
+// maxAwaitTimeMS on mongos. This failpoint will hang right before doing this sleep when set.
+MONGO_FAIL_POINT_DEFINE(hangWhileWaitingForIsMasterResponse);
 
 TopologyVersion mongosTopologyVersion;
 
@@ -152,6 +157,13 @@ public:
 
                 // The topologyVersion never changes on a running mongos process, so just sleep for
                 // maxAwaitTimeMS.
+                IsMasterMetrics::get(opCtx)->incrementNumAwaitingTopologyChanges();
+                ON_BLOCK_EXIT(
+                    [&] { IsMasterMetrics::get(opCtx)->decrementNumAwaitingTopologyChanges(); });
+                if (MONGO_unlikely(hangWhileWaitingForIsMasterResponse.shouldFail())) {
+                    LOGV2(31463, "hangWhileWaitingForIsMasterResponse failpoint enabled.");
+                    hangWhileWaitingForIsMasterResponse.pauseWhileSet(opCtx);
+                }
                 opCtx->sleepFor(Milliseconds(maxAwaitTimeMS));
             }
         } else {
@@ -200,6 +212,9 @@ public:
                     maxAwaitTimeMSField);
             invariant(clientTopologyVersion);
 
+            InExhaustIsMaster::get(opCtx->getClient()->session().get())
+                ->setInExhaustIsMaster(true /* inExhaustIsMaster */);
+
             if (clientTopologyVersion->getProcessId() == mongosTopologyVersion.getProcessId() &&
                 clientTopologyVersion->getCounter() == mongosTopologyVersion.getCounter()) {
                 // Indicate that an exhaust message should be generated and the previous BSONObj