Added encoding and from_encoding parameters

[yoheimuta]

In our production environment, to_json errors have occurred after updating td-agent v2.3.5.

fluentd.warn.internal.message.ip-10-0-1-218
----------------
[15:30:56] Slack Error: /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/activesupport-4.2.8/lib/active_support/core_ext/object/json.rb:34:in `encode' / "\xE4" from ASCII-8BIT to UTF-8

This error is when fluent-plugin-slack to_json the output of fluent-plugin-rds-slowlog.
Specifically, in-rds-slowlog outputs ASCII-8BIT encoded character string, but out_slack's to_json expects UTF-8 encoded character string, so it is an error.

• ref.

  fluent-plugin-rds-slowlog/lib/fluent/plugin/in_rds_slowlog.rb

  Line 71 in d2f1d6c

  row.each_key {|key| row[key].force_encoding(Encoding::ASCII_8BIT) if row[key].is_a?(String)}

• ref. https://github.com/sowawa/fluent-plugin-slack/blob/c423f539985c9f401736f4b814a5cec68a5a5f9b/lib/fluent/plugin/slack_client.rb#L118

The direct cause is that the emitted ASCII-8BIT string is not implicitly converted to UTF-8 by current msgpack-ruby, since msgpack-ruby v0.6.0~ is now internally used by updating td-agent (fluentd)

• ref. https://github.com/msgpack/msgpack-ruby/blob/master/ChangeLog#L71

Since we confirmed that this problem will be solved by passing UTF-8 to encoding parameter, we made PR.

• ref. Add "encoding" parameter to in_tail plugin fluent/fluentd#889
• ref. https://gist.github.com/tamtam180/29028c011abdd36ae0ef#comment-1466407

[yoheimuta]

continuous-integration/travis-ci/pr

There is no point to think about, is it caused by the correction contents here?

https://travis-ci.org/kenjiskywalker/fluent-plugin-rds-slowlog/jobs/233084029 -- failed
https://travis-ci.org/yoheimuta/fluent-plugin-rds-slowlog/jobs/233084021 -- passed

[cosmo0920]

This PR seems to be useful.
Could you rebase at current master, @yoheimuta ?

@kenjiskywalker How do you think about this PR?

[kenjiskywalker]

@cosmo0920
thanks notification and advice 👍

@yoheimuta
sorry for my late reply .
Plz rebase , I'll check it again 🙏

[yoheimuta]

Thanks! I'll rebase.

[cosmo0920]

This is just a my thought. Feel free to ignore it.
We can describe parameters how to work with desc method which can display usage with fluent-plugin-config-format.
So, we might have to add parameter descriptions with desc method.
But this is not issue, just a suggestion.

[yoheimuta]

Thanks !
It is desirable to add the desc method, so I added a fdf2ad4.

[cosmo0920]

Very Good. Thank you!

[yoheimuta]

Thanks! I'll rebase.

@kenjiskywalker @cosmo0920 I rebased, so please confirm.

[kenjiskywalker]

@yoheimuta @cosmo0920

Thank you 🙏

[yoheimuta]

Thanks!