From b4e02f345a40db826ceae9da318f5532e8d6714e Mon Sep 17 00:00:00 2001
From: David Glasser <glasser@meteor.com>
Date: Tue, 29 Jul 2014 10:18:40 -0700
Subject: [PATCH] Fix a few exceptions in the oplog observe driver

First exception: _runQuery didn't check to see if it was stopped after
running the query, which could lead to this harmless error:

Exception in defer callback: TypeError: Cannot call method 'clear' of null
    at _.extend._publishNewResults (packages/mongo-livedata/oplog_observe_driver.js:749)
    at _.extend._runQuery (packages/mongo-livedata/oplog_observe_driver.js:657)
    at packages/mongo-livedata/oplog_observe_driver.js:615
    at _.extend.withValue (packages/meteor/dynamics_nodejs.js:56)
    at packages/meteor/timers.js:6
    at runWithEnvironment (packages/meteor/dynamics_nodejs.js:108)

Second exception: _fetchModifiedDocuments thought that it should only be
in FETCHING in a certain case, but QUERYING is also OK. This is also
harmless since the correct behavior is to end the deferred routine.

Exception in defer callback: Error: phase in fetchModifiedDocuments: QUERYING
    at packages/mongo-livedata/oplog_observe_driver.js:435
    at packages/mongo-livedata/oplog_observe_driver.js:16
    at _.extend.withValue (packages/meteor/dynamics_nodejs.js:56)
    at packages/meteor/timers.js:6
    at runWithEnvironment (packages/meteor/dynamics_nodejs.js:108)
---
 packages/mongo-livedata/oplog_observe_driver.js | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/packages/mongo-livedata/oplog_observe_driver.js b/packages/mongo-livedata/oplog_observe_driver.js
index ac03d24cb0..d9348a62b1 100644
--- a/packages/mongo-livedata/oplog_observe_driver.js
+++ b/packages/mongo-livedata/oplog_observe_driver.js
@@ -431,6 +431,14 @@ _.extend(OplogObserveDriver.prototype, {
     // fetch() yields.
     Meteor.defer(finishIfNeedToPollQuery(function () {
       while (!self._stopped && !self._needToFetch.empty()) {
+        if (self._phase === PHASE.QUERYING) {
+          // While fetching, we decided to go into QUERYING mode, and then we
+          // saw another oplog entry, so _needToFetch is not empty. But we
+          // shouldn't fetch these documents until AFTER the query is done.
+          break;
+        }
+
+        // Being in steady phase here would be surprising.
         if (self._phase !== PHASE.FETCHING)
           throw new Error("phase in fetchModifiedDocuments: " + self._phase);
 
@@ -654,6 +662,9 @@ _.extend(OplogObserveDriver.prototype, {
       }
     }
 
+    if (self._stopped)
+      return;
+
     self._publishNewResults(newResults, newBuffer);
   },
 
@@ -789,6 +800,9 @@ _.extend(OplogObserveDriver.prototype, {
   // This stop function is invoked from the onStop of the ObserveMultiplexer, so
   // it shouldn't actually be possible to call it until the multiplexer is
   // ready.
+  //
+  // It's important to check self._stopped after every call in this file that
+  // can yield!
   stop: function () {
     var self = this;
     if (self._stopped)