Error: Cannot find wait timer

[isaacs]

Occasionally this happens:

Error: Cannot find wait timer
    at Feed.got_activity (/home/node/node_modules/npm-fullfat-registry/node_mo
dules/follow/lib/feed.js:355:21)
    at Feed.on_couch_data (/home/node/node_modules/npm-fullfat-registry/node_m
odules/follow/lib/feed.js:412:8)
    at Changes.handle_confirmed_req_event (/home/node/node_modules/npm-fullfat-registry/node_modules/follow/lib/feed.js:308:30)
    at Changes.EventEmitter.emit (events.js:95:17)
    at Changes.emit_changes (/home/node/node_modules/npm-fullfat-registry/node_modules/follow/lib/stream.js:223:12)
    at Changes.write_continuous (/home/node/node_modules/npm-fullfat-registry/node_modules/follow/lib/stream.js:176:8)
    at Changes.write (/home/node/node_modules/npm-fullfat-registry/node_modules/follow/lib/stream.js:124:17)
    at Request.ondata (stream.js:51:26)
    at Request.EventEmitter.emit (events.js:95:17)
    at IncomingMessage.<anonymous> (/home/node/node_modules/npm-fullfat registry/node_modules/follow/node_modules/request/request.js:840:12)

??

[davglass]

We are seeing this too while trying to replicate the npm registry.

Why is this a fatal error?
https://github.com/iriscouch/follow/blob/master/lib/feed.js#L354-L355

  if(! self.pending.wait_timer)
    return self.die(new Error('Cannot find wait timer'))

  clearTimeout(self.pending.wait_timer)
  self.pending.wait_timer = null

Since you are clearing the timeout directly after checking if it's there, shouldn't this be:

  if(! self.pending.wait_timer)
    clearTimeout(self.pending.wait_timer)

  self.pending.wait_timer = null

Doesn't make a lot of sense to me to die if it's not there just before you are going to clear it anyway.

[jcrugzz]

@davglass im guessing the assumption is that there is something wrong if that timer has already been cleared or does not exist.

Regardless this module will be refactored as a wrapper around my changes-strem module once i get some better test coverage. You can checkout the current wip in the refactor branch. This will solve some of the inconsistencies.

[isaacs]

We still see this pretty often in our production followers. It doesn't happen often enough to throw the worker into a tailspin, and we use seq-file to restart right where we left off. But still, kinda annoying.

[jcrugzz]

ok so the root of this problem is actually due to a new request being created while the feed is paused because the wait_timer expires and triggers an on_timeout() -> retry() in terms of function calls. This causes the resume to cause this particular failure in got_activity().

@davglass removing that line does seem reasonable as a stop gap so I will do some testing and publish a new version.

[jcrugzz]

this is fixed in v0.11.1. Removing that actually worked.

[davglass]

👍