Stop flush timer before closing queue

[abicky]

As Datadog::Sender#flush adds :flush command to the queue, the flush timer should be closed before the sender closes the queue to avoid ClosedQueueError.

[abicky]

Without this change, the test fails as follows:

% bundle exec rspec spec/statsd/sender_spec.rb:116
Run options: include {:locations=>{"./spec/statsd/sender_spec.rb"=>[116]}}

Datadog::Statsd::Sender
  #stop
    when flush_interval is set
#<Thread:0x00007ff6e711b4e0@Statsd Timer /Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/timer.rb:18 run> terminated with exception (report_on_exception is true):
/Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/sender.rb:43:in `push': queue closed (ClosedQueueError)
        from /Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/sender.rb:43:in `flush'
        from /Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/sender.rb:24:in `block in initialize'
        from /Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/timer.rb:25:in `block (2 levels) in start'
        from /Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/timer.rb:20:in `synchronize'
        from /Users/arabiki/ghq/src/github.com/DataDog/dogstatsd-ruby/lib/datadog/statsd/timer.rb:20:in `block in start'
      stops the worker thread and the flush timer thread (FAILED - 1)

Failures:

  1) Datadog::Statsd::Sender#stop when flush_interval is set stops the worker thread and the flush timer thread
     Failure/Error: current_message_queue.push(:flush)

     ClosedQueueError:
       queue closed
     # ./lib/datadog/statsd/sender.rb:43:in `push'
     # ./lib/datadog/statsd/sender.rb:43:in `flush'
     # ./lib/datadog/statsd/sender.rb:24:in `block in initialize'
     # ./lib/datadog/statsd/timer.rb:25:in `block (2 levels) in start'
     # ./lib/datadog/statsd/timer.rb:20:in `synchronize'
     # ./lib/datadog/statsd/timer.rb:20:in `block in start'

Finished in 0.01402 seconds (files took 0.4371 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/statsd/sender_spec.rb:117 # Datadog::Statsd::Sender#stop when flush_interval is set stops the worker thread and the flush timer thread

[remeh]

Makes total sense, thanks for your contribution!

[abicky]

@remeh Thank you for merging the PR, and I'm sorry I didn't notice the bug when I implemented #231.
Do you have any plan to release a new version? I'd like to use the version including this bug fix.

[aniruddhb]

Echo'oing @abicky , it would be awesome to get this fix released as part of the gem 😃 Appreciate all the work that goes into this piece of software.

[remeh]

@abicky @aniruddhb I'll work on a new release this week 👍