Add ServerEngine

[naritta]

https://github.com/fluent/fluentd/wiki/Fluentd-running-on-ServerEngine

implement
・Logging
・Signal handler
・Daemonize
・Worker processes

[repeatedly]

Could you add remaining list on the description?

[naritta]

I got it.

[naritta]

remaining is:
・create cache for loading config
・fix rpc_server signal handler
・add tests

[cosmo0920]

Here is GitHub.
We can use task list in descriptions with GFM: https://github.com/blog/1375-task-lists-in-gfm-issues-pulls-comments

[naritta]

Now, the main signal handler in fluentd and serverengine is like below.

	fluentd	serverengine(default)
INT/TERM	graceful shutdown	graceful shutdown
HUP	graceful restart	graceful restart(not when worker_type is "process")
USR1	flush buffer	graceful restart

Then I fixed
・to use INT/TERM and HUP handler on serverengine for graceful shutdown and restart.
・let USR1 handler on fluentd as it is for flush buffer.

As a result, the signal handler will be same as ordinal fluentd like below.

	fluentd
INT/TERM	graceful shutdown
HUP	graceful restart
USR1	flush buffer

[naritta]

@repeatedly
fluentd signal handler(here USR1) is prior to serverengine signal handler, so we need to concern about USR1 restarting function. flush buffer is executed if it got USR1.
But if you concern about it and we should set other signal (like WINCH?) as restarting function on serverengine just in case, please let me know.

[naritta]

[MEMO] The remaining problem is
・cause error in binding UDP handle after closing and creating again.
・can't use fiddle in Ruby21-x64 and Ruby22-x64.

[tagomoris]

Fluent::Test::DummyLogDevice is just for tests. Use STDERR as before.

[tagomoris]

This looks ready to merge.

[tagomoris]

Done!

[naritta]

Thank you!