SERVER-3528: memory footprint of JS context keeps increasing as it is used, delete every 100 use

2 files changed, 15 insertions, 2 deletions

diff --git a/scripting/engine.cpp b/scripting/engine.cpp
index 1982940327c..7d13cb764fc 100644
--- a/scripting/engine.cpp
+++ b/scripting/engine.cpp
@@ -26,7 +26,7 @@ namespace mongo {
 
     int Scope::_numScopes = 0;
 
-    Scope::Scope() : _localDBName("") , _loadedVersion(0) {
+    Scope::Scope() : _localDBName("") , _loadedVersion(0), _numTimeUsed(0) {
         _numScopes++;
     }
 
@@ -284,7 +284,8 @@ namespace mongo {
         void done( const string& pool , Scope * s ) {
             scoped_lock lk( _mutex );
             list<Scope*> & l = _pools[pool];
-            if ( l.size() > 10 ) {
+            // make we dont keep to many contexts, or use them for too long
+            if ( l.size() > 10 || s->getTimeUsed() > 100 ) {
                 delete s;
             }
             else {
@@ -302,6 +303,7 @@ namespace mongo {
             Scope * s = l.back();
             l.pop_back();
             s->reset();
+            s->incTimeUsed();
             return s;
         }
 
diff --git a/scripting/engine.h b/scripting/engine.h
index 1f9f1f52e2e..9dd5f1d322c 100644
--- a/scripting/engine.h
+++ b/scripting/engine.h
@@ -132,6 +132,11 @@ namespace mongo {
 
         static void validateObjectIdString( const string &str );
 
+        /** increments the number of times a scope was used */
+        void incTimeUsed() { ++_numTimeUsed; }
+        /** gets the number of times a scope was used */
+        int getTimeUsed() { return _numTimeUsed; }
+
     protected:
 
         virtual ScriptingFunction _createFunction( const char * code ) = 0;
@@ -141,6 +146,7 @@ namespace mongo {
         set<string> _storedNames;
         static long long _lastVersion;
         map<string,ScriptingFunction> _cachedFunctions;
+        int _numTimeUsed;
 
         static int _numScopes;
     };
@@ -168,7 +174,12 @@ namespace mongo {
 
         static void setup();
 
+        /** gets a scope from the pool or a new one if pool is empty
+         * @param pool An identifier for the pool, usually the db name
+         * @return the scope */
         auto_ptr<Scope> getPooledScope( const string& pool );
+
+        /** call this method to release some JS resources when a thread is done */
         void threadDone();
 
         struct Unlocker { virtual ~Unlocker() {} };