protect ReplicaSet watcher with a lock

1 files changed, 17 insertions, 3 deletions

diff --git a/client/dbclient_rs.cpp b/client/dbclient_rs.cpp
index f844cd0d3b4..76ed1992f41 100644
--- a/client/dbclient_rs.cpp
+++ b/client/dbclient_rs.cpp
@@ -34,8 +34,21 @@ namespace mongo {
     // global background job responsible for checking every X amount of time
     class ReplicaSetMonitorWatcher : public BackgroundJob {
     public:
-        virtual string name() const { return "ReplicaSetMonitorWatcher"; }
+        ReplicaSetMonitorWatcher() : _safego("ReplicaSetMonitorWatcher::_safego") {}
 
+        virtual string name() const { return "ReplicaSetMonitorWatcher"; }
+        
+        void safeGo() {
+            // check outside of lock for speed
+            if ( getState() == BackgroundJob::Running )
+                return;
+            
+            scoped_lock lk( _safego );
+            if ( getState() == BackgroundJob::Running )
+                return;
+            
+            go();
+        }
     protected:
         void run() {
             while ( ! inShutdown() ) {
@@ -49,6 +62,8 @@ namespace mongo {
             }
         }
 
+        mongo::mutex _safego;
+
     } replicaSetMonitorWatcher;
 
 
@@ -93,8 +108,7 @@ namespace mongo {
         if ( ! m )
             m.reset( new ReplicaSetMonitor( name , servers ) );
 
-        if ( replicaSetMonitorWatcher.getState() == BackgroundJob::NotStarted )
-            replicaSetMonitorWatcher.go();
+        replicaSetMonitorWatcher.safeGo();
 
         return m;
     }