From 741b38017c03e0877d5aa3f26fb2fe1bf6081e65 Mon Sep 17 00:00:00 2001
From: Nick Martin <nim@meteor.com>
Date: Tue, 12 Jan 2016 16:17:35 -0800
Subject: [PATCH] Expose options `disableOplog`, `pollingInterval`, and
 `pollingThrottle` to `Cursor.find`

These can be useful to tune performance for application specific data patterns.
---
 History.md                               |  2 ++
 packages/mongo/collection.js             |  3 +++
 packages/mongo/oplog_observe_driver.js   |  3 ++-
 packages/mongo/polling_observe_driver.js | 10 +++++++---
 4 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/History.md b/History.md
index 9b12d41a34..b32e7edbfe 100644
--- a/History.md
+++ b/History.md
@@ -15,6 +15,8 @@
 
 * Allow `git+` URL schemes for npm dependencies #844
 
+* Expose options `disableOplog`, `pollingInterval`, and `pollingThrottle` to `Cursor.find` for tuning observe parameters on the server.
+
 Patches contributed by GitHub users vereed, devgrok, ...
 
 
diff --git a/packages/mongo/collection.js b/packages/mongo/collection.js
index 3154c27d39..f7b5f7c2e0 100644
--- a/packages/mongo/collection.js
+++ b/packages/mongo/collection.js
@@ -280,6 +280,9 @@ _.extend(Mongo.Collection.prototype, {
    * @param {MongoFieldSpecifier} options.fields Dictionary of fields to return or exclude.
    * @param {Boolean} options.reactive (Client only) Default `true`; pass `false` to disable reactivity
    * @param {Function} options.transform Overrides `transform` on the  [`Collection`](#collections) for this cursor.  Pass `null` to disable transformation.
+   * @param {Boolean} options.disableOplog (Server only) Pass true to disable oplog-tailing on this query. This affects the way server processes calls to `observe` on this query. Disabling the oplog can be useful when working with data that updates in large batches.
+   * @param {Number} options.pollingInterval (Server only) How often to poll this query when observing on the server. In milliseconds. Defaults to 10 seconds.
+   * @param {Number} options.pollingThrottle (Server only) Minimum time to allow between re-polling. Increasing this will save CPU and mongo load at the expense of slower updates to users. Decreasing this is not recommended. In milliseconds. Defaults to 50 milliseconds.
    * @returns {Mongo.Cursor}
    */
   find: function (/* selector, options */) {
diff --git a/packages/mongo/oplog_observe_driver.js b/packages/mongo/oplog_observe_driver.js
index e52b9960ec..024e0a817a 100644
--- a/packages/mongo/oplog_observe_driver.js
+++ b/packages/mongo/oplog_observe_driver.js
@@ -959,7 +959,8 @@ OplogObserveDriver.cursorSupported = function (cursorDescription, matcher) {
   var options = cursorDescription.options;
 
   // Did the user say no explicitly?
-  if (options._disableOplog)
+  // underscored version of the option is COMPAT with 1.2
+  if (options.disableOplog || options._disableOplog)
     return false;
 
   // skip is not supported: to support it we would need to keep track of all
diff --git a/packages/mongo/polling_observe_driver.js b/packages/mongo/polling_observe_driver.js
index 5d111a1b11..feb2f85aba 100644
--- a/packages/mongo/polling_observe_driver.js
+++ b/packages/mongo/polling_observe_driver.js
@@ -28,7 +28,8 @@ PollingObserveDriver = function (options) {
   // Make sure to create a separately throttled function for each
   // PollingObserveDriver object.
   self._ensurePollIsScheduled = _.throttle(
-    self._unthrottledEnsurePollIsScheduled, 50 /* ms */);
+    self._unthrottledEnsurePollIsScheduled,
+    self._cursorDescription.options.pollingThrottle || 50 /* ms */);
 
   // XXX figure out if we still need a queue
   self._taskQueue = new Meteor._SynchronousQueue();
@@ -43,7 +44,7 @@ PollingObserveDriver = function (options) {
         self._pendingWrites.push(fence.beginWrite());
       // Ensure a poll is scheduled... but if we already know that one is,
       // don't hit the throttled _ensurePollIsScheduled function (which might
-      // lead to us calling it unnecessarily in 50ms).
+      // lead to us calling it unnecessarily in <pollingThrottle> ms).
       if (self._pollsScheduledButNotStarted === 0)
         self._ensurePollIsScheduled();
     }
@@ -60,7 +61,10 @@ PollingObserveDriver = function (options) {
   if (options._testOnlyPollCallback) {
     self._testOnlyPollCallback = options._testOnlyPollCallback;
   } else {
-    var pollingInterval = self._cursorDescription.options._pollingInterval || 10 * 1000;
+    var pollingInterval =
+          self._cursorDescription.options.pollingInterval ||
+          self._cursorDescription.options._pollingInterval || // COMPAT with 1.2
+          10 * 1000;
     var intervalHandle = Meteor.setInterval(
       _.bind(self._ensurePollIsScheduled, self), pollingInterval);
     self._stopCallbacks.push(function () {