SERVER-32876 Don't stall ftdc due to WT cache full

7 files changed, 32 insertions, 7 deletions

diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
index 4d1d0a8faab..7761857bf90 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
@@ -909,7 +909,7 @@ int64_t WiredTigerRecordStore::storageSize(OperationContext* txn,
     if (_isEphemeral) {
         return dataSize(txn);
     }
-    WiredTigerSession* session = WiredTigerRecoveryUnit::get(txn)->getSession(txn);
+    WiredTigerSession* session = WiredTigerRecoveryUnit::get(txn)->getSessionNoTxn(txn);
     StatusWith<int64_t> result =
         WiredTigerUtil::getStatisticsValueAs<int64_t>(session->getSession(),
                                                       "statistics:" + getURI(),
@@ -1628,7 +1628,7 @@ void WiredTigerRecordStore::appendCustomStats(OperationContext* txn,
         result->appendIntOrLL("sleepCount", _cappedSleep.load());
         result->appendIntOrLL("sleepMS", _cappedSleepMS.load());
     }
-    WiredTigerSession* session = WiredTigerRecoveryUnit::get(txn)->getSession(txn);
+    WiredTigerSession* session = WiredTigerRecoveryUnit::get(txn)->getSessionNoTxn(txn);
     WT_SESSION* s = session->getSession();
     BSONObjBuilder bob(result->subobjStart(_engineName));
     {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
index 1296bb3d84e..fe35bd07651 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
@@ -43,6 +43,7 @@
 #include "mongo/util/concurrency/ticketholder.h"
 #include "mongo/util/log.h"
 #include "mongo/util/mongoutils/str.h"
+#include "mongo/util/scopeguard.h"
 #include "mongo/util/stacktrace.h"
 
 namespace mongo {
@@ -172,7 +173,12 @@ WiredTigerSession* WiredTigerRecoveryUnit::getSession(OperationContext* opCtx) {
 
 WiredTigerSession* WiredTigerRecoveryUnit::getSessionNoTxn(OperationContext* opCtx) {
     _ensureSession();
-    return _session.get();
+    WiredTigerSession* session = _session.get();
+
+    // Dropping the queued idents might block session, which is not desired for fastpath workflow
+    // like FTDC thread. Disable dropping of queued idents for such sessions.
+    session->dropQueuedIdentsAtSessionEndAllowed(false);
+    return session;
 }
 
 void WiredTigerRecoveryUnit::abandonSnapshot() {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
index d29186db578..9df6ba94651 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
@@ -357,6 +357,11 @@ void WiredTigerSessionCache::releaseSession(WiredTigerSession* session) {
 
     bool returnedToCache = false;
     uint64_t currentEpoch = _epoch.load();
+    bool dropQueuedIdentsAtSessionEnd = session->isDropQueuedIdentsAtSessionEndAllowed();
+
+    // Reset this session's flag for dropping queued idents to default, before returning it to
+    // session cache.
+    session->dropQueuedIdentsAtSessionEndAllowed(true);
 
     if (session->_getEpoch() == currentEpoch) {  // check outside of lock to reduce contention
         stdx::lock_guard<stdx::mutex> lock(_cacheLock);
@@ -370,7 +375,7 @@ void WiredTigerSessionCache::releaseSession(WiredTigerSession* session) {
     if (!returnedToCache)
         delete session;
 
-    if (_engine && _engine->haveDropsQueued())
+    if (dropQueuedIdentsAtSessionEnd && _engine && _engine->haveDropsQueued())
         _engine->dropSomeQueuedIdents();
 }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h
index 26ec9934fcf..34c05a3304b 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h
@@ -109,6 +109,14 @@ public:
         return _cursorsOut;
     }
 
+    bool isDropQueuedIdentsAtSessionEndAllowed() const {
+        return _dropQueuedIdentsAtSessionEnd;
+    }
+
+    void dropQueuedIdentsAtSessionEndAllowed(bool dropQueuedIdentsAtSessionEnd) {
+        _dropQueuedIdentsAtSessionEnd = dropQueuedIdentsAtSessionEnd;
+    }
+
     static uint64_t genTableId();
 
     /**
@@ -139,6 +147,7 @@ private:
     CursorCache _cursors;            // owned
     uint64_t _cursorGen;
     int _cursorsOut;
+    bool _dropQueuedIdentsAtSessionEnd = true;
 };
 
 /**
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp
index 7783cea4cbf..bab41079a9b 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp
@@ -202,7 +202,7 @@ void WiredTigerSizeStorer::syncCache(bool syncToDisk) {
 
     WT_SESSION* session = _session.getSession();
     invariantWTOK(session->begin_transaction(session, syncToDisk ? "sync=true" : ""));
-    ScopeGuard rollbacker = MakeGuard(session->rollback_transaction, session, "");
+    auto rollbacker = MakeGuard(session->rollback_transaction, session, "");
 
     for (Map::iterator it = myMap.begin(); it != myMap.end(); ++it) {
         string uriKey = it->first;
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_snapshot_manager.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_snapshot_manager.cpp
index da0f618f1bd..e6000e62604 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_snapshot_manager.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_snapshot_manager.cpp
@@ -38,6 +38,7 @@
 #include "mongo/db/storage/wiredtiger/wiredtiger_snapshot_manager.h"
 #include "mongo/util/log.h"
 #include "mongo/util/mongoutils/str.h"
+#include "mongo/util/scopeguard.h"
 
 namespace mongo {
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
index f00b4a33804..c0f0907f8da 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
@@ -103,9 +103,13 @@ void WiredTigerUtil::fetchTypeAndSourceURI(OperationContext* opCtx,
 
 StatusWith<std::string> WiredTigerUtil::getMetadata(OperationContext* opCtx, StringData uri) {
     invariant(opCtx);
-    WiredTigerCursor curwrap("metadata:create", WiredTigerSession::kMetadataTableId, false, opCtx);
-    WT_CURSOR* cursor = curwrap.get();
+
+    auto session = WiredTigerRecoveryUnit::get(opCtx)->getSessionNoTxn(opCtx);
+    WT_CURSOR* cursor =
+        session->getCursor("metadata:create", WiredTigerSession::kMetadataTableId, false);
     invariant(cursor);
+    ON_BLOCK_EXIT([&] { session->releaseCursor(WiredTigerSession::kMetadataTableId, cursor); });
+
     std::string strUri = uri.toString();
     cursor->set_key(cursor, strUri.c_str());
     int ret = cursor->search(cursor);