pretouch experiment

Author: erh

db/db.cpp

@@ -661,6 +661,7 @@ int main(int argc, char* argv[], char *envp[] )
         ("slavedelay", po::value<int>(), "specify delay (in seconds) to be used when applying master ops to slave")
         ("fastsync", "indicate that this instance is starting from a dbpath snapshot of the repl peer")
         ("autoresync", "automatically resync if slave data is stale")
+        ("pretouch", "turn on pretouch experiment TESTING ONLY")
         ("oplogSize", po::value<int>(), "size limit (in MB) for op log")
         ("opIdMem", po::value<long>(), "size limit (in bytes) for in memory storage of op ids")
         ;
@@ -832,6 +833,11 @@ int main(int argc, char* argv[], char *envp[] )
         if (params.count("autoresync")) {
             replSettings.autoresync = true;
         }
+        
+        if (params.count("pretouch")) {
+            replSettings.pretouch = true;
+        }
+
         if (params.count("source")) {
             /* specifies what the source in local.sources should be */
             cmdLine.source = params["source"].as<string>().c_str();

db/repl.cpp

@@ -895,6 +895,36 @@ namespace mongo {
             log() << "sync: caught db exception " << e << " while applying op: " << op << endl;;            
         }
     }
+
+    void pretouchOperation(const BSONObj& op) {
+        const char *which = "o";
+        const char *opType = op.getStringField("op");
+        if ( *opType == 'i' )
+            ;
+        else if( *opType == 'u' )
+            which = "o2";
+        else
+            return;
+        /* todo : other operations */
+
+        try { 
+            BSONObj o = op.getObjectField(which);
+            BSONElement _id;
+            if( o.getObjectID(_id) ) {
+                const char *ns = op.getStringField("ns");
+                BSONObjBuilder b;
+                b.append(_id);
+                BSONObj result;
+                readlock lk(ns);
+                Client::Context ctx( ns );
+                Helpers::findById(cc(), ns, b.done(), result);
+            }
+        }
+        catch( DBException& ) { 
+            log() << "ignoring assertion in pretouchOperation()" << endl;
+        }
+    }
+
 
     /* local.$oplog.main is of the form:
          { ts: ..., op: <optype>, ns: ..., o: <obj> , o2: <extraobj>, b: <boolflag> }
@@ -924,6 +954,9 @@ namespace mongo {
         if ( !only.empty() && only != clientName )
             return;
 
+        if ( replSettings.pretouch )
+            pretouchOperation(op);
+
         dblock lk;
 
         if ( localLogTail && replPair && replPair->state == ReplPair::State_Master ) {

db/repl.h

@@ -64,9 +64,11 @@ namespace mongo {
         bool autoresync;
 
         int slavedelay;
+        
+        bool pretouch;
 
         ReplSettings()
-            : slave(NotSlave) , master(false) , opIdMem(100000000) , fastsync() , autoresync(false), slavedelay() {
+            : slave(NotSlave) , master(false) , opIdMem(100000000) , fastsync() , autoresync(false), slavedelay(), pretouch(false) {
         }
 
     };