Error in oplog callback

[cscott]

@glasser running on the oplog-with-operators release:

Error in oplog callback TypeError: Cannot call method 'has' of null
I20140117-21:50:13.826(-5)?     at _.extend._handleOplogEntrySteadyOrFetching (packages/mongo-livedata/oplog_observe_driver.js:256)
I20140117-21:50:13.827(-5)?     at packages/mongo-livedata/oplog_observe_driver.js:65
I20140117-21:50:13.827(-5)?     at packages/mongo-livedata/oplog_tailing.js:88
I20140117-21:50:13.827(-5)?     at runWithEnvironment (packages/meteor/dynamics_nodejs.js:88)
I20140117-21:50:13.828(-5)?     at packages/meteor/dynamics_nodejs.js:98
I20140117-21:50:13.828(-5)?     at packages/livedata/crossbar.js:77
I20140117-21:50:13.829(-5)?     at Array.forEach (native)
I20140117-21:50:13.829(-5)?     at Function._.each._.forEach (packages/underscore/underscore.js:89)
I20140117-21:50:13.830(-5)?     at _.extend.fire (packages/livedata/crossbar.js:76)
I20140117-21:50:13.830(-5)?     at packages/mongo-livedata/oplog_tailing.js:212

[Slava]

Looks like the update event from oplog triggered a callback after the query was stopped.

[glasser]

Thanks! Analyzing the code, it seems most likely that this is the bug fixed by d30bb79. (This commit was able to be so simple because of fca2966, a refactoring inspired by this issue.) It's the only way I can see that that callback could have been called after the observe driver got stopped. (d868325 adds another assertion that makes it more clear that there's no other concurrency going on here.)