mongo_runner: Don't send rs.initiate too early

Fixes #1696. Thanks to @Maxpain177 for reporting and providing access to
a machine where this was easily reproducible.

tools/mongo_runner.js

@@ -234,36 +234,63 @@ exports.launchMongo = function (options) {
       proc.stdout.setEncoding('utf8');
       var listening = false;
       var replSetReady = false;
+      var replSetReadyToBeInitiated = false;
+      var alreadyInitiatedReplSet = false;
       var maybeCallOnListen = function () {
         if (listening && replSetReady) {
           if (createReplSet)
             fs.writeFileSync(portFile, options.port);
           onListen();
         }
       };
+
+      var maybeInitiateReplset = function () {
+        // We need to want to create a replset, be confident that the server is
+        // listening, be confident that the server's replset implementation is
+        // ready to be initiated, and have not already done it.
+        if (!(createReplSet && listening && replSetReadyToBeInitiated
+              && !alreadyInitiatedReplSet)) {
+          return;
+        }
+
+        alreadyInitiatedReplSet = true;
+
+        // Connect to it and start a replset.
+        var db = new mongoNpmModule.Db(
+          'meteor', new mongoNpmModule.Server('127.0.0.1', options.port),
+          {safe: true});
+        db.open(function(err, db) {
+          if (err)
+            throw err;
+          db.admin().command({
+            replSetInitiate: {
+              _id: replSetName,
+              members: [{_id : 0, host: '127.0.0.1:' + options.port}]
+            }
+          }, function (err, result) {
+            if (err)
+              throw err;
+            // why this isn't in the error is unclear.
+            if (result && result.documents && result.documents[0]
+                && result.documents[0].errmsg) {
+              throw result.document[0].errmsg;
+            }
+            db.close(true);
+          });
+        });
+      };
+
       proc.stdout.on('data', function (data) {
+        // note: don't use "else ifs" in this, because 'data' can have multiple
+        // lines
+        if (/config from self or any seed \(EMPTYCONFIG\)/.test(data)) {
+          replSetReadyToBeInitiated = true;
+          maybeInitiateReplset();
+        }
+
         if (/ \[initandlisten\] waiting for connections on port/.test(data)) {
-          if (createReplSet) {
-            // Connect to it and start a replset.
-            var db = new mongoNpmModule.Db(
-              'meteor', new mongoNpmModule.Server('127.0.0.1', options.port),
-              {safe: true});
-            db.open(function(err, db) {
-              if (err)
-                throw err;
-              db.admin().command({
-                replSetInitiate: {
-                  _id: replSetName,
-                  members: [{_id : 0, host: '127.0.0.1:' + options.port}]
-                }
-              }, function (err, result) {
-                if (err)
-                  throw err;
-                db.close(true);
-              });
-            });
-          }
           listening = true;
+          maybeInitiateReplset();
           maybeCallOnListen();
         }