Logger dumps error with classname

[tagomoris]

In these days, many plugin authors (and core developers) writes logging code like below many times.

log.error "my message", error_class: e.class, error: e.to_s, other: attributes

Fairly speaking, this is waste of time and key typing.

Fluentd will log errors like below with this change by just specifying error: e:

log.error "my message", error: e
# [error]: my message error=MyErrorClass[message of e]

[tagomoris]

@repeatedly @sonots How do you think about this change?

[sonots]

I am positive for specifying only an error object, but somebody might be watching logs of fluentd by a log monitoring system for alerting. Changing log format would break compatibilities for their system, so I think we should keep compatibilities of log format.

[tagomoris]

@sonots Do you mean that we should print errors in format below?

error_class=MyErrorClass error="message of e"

[sonots]

@tagomoris yes!

[tagomoris]

@sonots Hmm, it looks a bit verbose for me, and v0.14 may be a good time to do that kind of change.
@repeatedly How do you think?

[repeatedly]

Keeping compatibility is good for existing users. Maybe, asking it on mailing list is better.

v0.14 may be a good time to do that kind of change.

This change affects v0.12 because we will backport several changes to v0.12 and skipping this patch is hard...
If you want to change error message format, we should suspend this patch until just before v0.14 release.

[tagomoris]

Okay, I'll change format of errors.

[tagomoris]

Done.

[sonots]

v would be a string like

fluentd/lib/fluent/output.rb

Line 127 in 88054a0

$log.error "error on output thread", error: $!.to_s

, so need to add and v.is_a?(Exception).

[sonots]

Need to add another condition !map.has_key?('error_class'), otherwirse, error_class= appears twice for old codes such as:

log.error 'message', error_class: e.class, error: e

[tagomoris]

That's right. I fixed so.

[sonots]

LGTM!

[tagomoris]

Merged.