Keep receiving messages even after recieveing SIGTERM and lost data

[snowhork]

Even after fluentd receives SIGTERM and closes, fluentd seems to keep recieving messages for a while.
So, even if flush_at_shutdown is true,

• buffer remains after shutdown
• some messages seem to be lost

---

Environment:

commit 9738a421c2fe9f001b723ce86e4a6e47412c4baf
ruby 2.3.1p112
Mac OS 10.13.4

Preparation:

gem install fluent-logger

vi fluentd.conf
vi post.rb  # source is as follows

fluentd.conf is

<source>
  @type forward
</source>

<match debug.**>
  @type file
  path tmp/file
  flush_at_shutdown true
</match>

post.rb is

require 'fluent-logger'
log = Fluent::Logger::FluentLogger.new

cnt = 0
while log.post('debug', { message: cnt+1 })
  cnt += 1
  sleep 0.00001
end
puts "finished at #{Time.now}, post-count: #{cnt}"

Run commands below:

bundle exec ./bin/fluentd -c ./fluent.conf &
# => [1] 61688
ruby post.rb &
kill 61688
# => ....
# => finished at 2018-05-16 13:39:10 +0900, post-count: 111296

After that, you can find a buffer file.

tail -n 1 tmp/file.20180516_0.log
# => 2018-05-16T13:39:07+09:00	debug	{"message":79760}
tail -n 1 tmp/file/buffer.b56c4b4cd48555a7da3dd7abe659bf157.log
# => 2018-05-16T13:39:07+09:00	debug	{"message":79763}

In this case, messages between 79763 and 111296 seem to be lost.

[repeatedly]

Will check with fluent-logger.

[abicky]

I've investigated the cause before. I think socketry/cool.io#61 is related although I familiar with neither cool.io nor socket programming.