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From "Adam Kocoloski (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COUCHDB-761) Timeouts in couch_log are masked, crashes callers
Date Mon, 17 May 2010 11:02:42 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12868165#action_12868165
] 

Adam Kocoloski commented on COUCHDB-761:
----------------------------------------

I haven't tested it, but the patch looks correct.

Since we're moving away from the *_report functions we could also simplify the messages a
bit.  For example, instead of

gen_event:sync_notify(error_logger, {info_report, group_leader(), {self(), couch_info, {Format,
Args}}});

we could do

gen_event:sync_notify(error_logger, {couch, info, self(), Format, Args});

or, since we're doing sync logging, we might even partially format the message in the sending
process and make it a little simpler to copy:

gen_event:sync_notify(error_logger, {couch, info, self(), io_lib:format(Format, Args)});

Randall, what do you think?



> Timeouts in couch_log are masked, crashes callers
> -------------------------------------------------
>
>                 Key: COUCHDB-761
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-761
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Database Core
>    Affects Versions: 0.10.1, 0.10.2, 0.11
>            Reporter: Randall Leeds
>            Priority: Blocker
>             Fix For: 0.10.3, 0.11.1, 1.0
>
>         Attachments: improved-sync-logging.patch
>
>
> Several users have reported seeing crash reports stemming from a function_clause match
on handle_info in various gen_servers. The offending message looks like {#Ref<>, <integer>}.
> After months of banter and sleuthing, I determined that the likely cause was a late reply
to a gen_server:call that timed out, with the #Ref being the tag on the response. After it
came up again today in IRC, kocolosk quickly discovered that the problem appears to be in
couch_log.erl.
> The logging macros (?LOG_*)  call couch_log/*_on which calls get_level_integer/0. When
this call times out the timeout is eaten and a late reply arrives to the calling process later,
triggering the crash.
> Suggestions on how to fix this welcome. Ideas so far are async logging or infinite timeout.

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