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https://issues.apache.org/jira/browse/COUCHDB-2968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15190899#comment-15190899
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ASF GitHub Bot commented on COUCHDB-2968:
-----------------------------------------
Github user asfgit closed the pull request at:
https://github.com/apache/couchdb-couch-log/pull/11
> couch_log doesn't use the configured backend in the couchdb OTP release
> -----------------------------------------------------------------------
>
> Key: COUCHDB-2968
> URL: https://issues.apache.org/jira/browse/COUCHDB-2968
> Project: CouchDB
> Issue Type: Bug
> Components: Logging
> Reporter: Mike Wallace
>
> When testing the couch_log backends with the OTP release generated by {{make
> install}} I found couch_log wasn't using the couch_log_lager backend, however
> when testing with a dev/run cluster it works as expected.
> To test I used the following for rel/files/sys.config:
> {code}
> [
> {lager, [
> {error_logger_hwm, 1000},
> {error_logger_redirect, true},
> {handlers, [
> {lager_file_backend,
> [{file,"/tmp/allthelogs.log"},
> {level,debug},
> {size,10485760},
> {date,"$D0"},
> {count,5}]},
> {lager_console_backend, [error, {
> lager_default_formatter,
> [
> date, " ", time,
> " [", severity, "] ",
> node, " ", pid, " ",
> message,
> "\n"
> ]
> }]}
> ]}
> ]}
> ].
> {code}
> In a dev/run node I can do the following in a remsh:
> {code}
> $ erl -name [email protected] -remsh [email protected] -setcookie monster
> -hidden
> ([email protected])1> couch_log:info("A log statement", []).
> ok
> {code}
> Then I can verify the log statement appears in the expected location:
> {code}
> $ tail -n 5 /tmp/allthelogs.log
> 2016-03-10 13:40:54.353 [notice] <0.711.0>@couch_log_lager:notice:43
> Setup: [{<<"action">>,<<"receive_cookie">>},{<<"cookie">>,<<"monster">>}]
> 2016-03-10 13:40:54.353 [notice] <0.711.0>@couch_log_lager:notice:43
> receive_cookie:
> [{<<"action">>,<<"receive_cookie">>},{<<"cookie">>,<<"monster">>}]
> 2016-03-10 13:40:54.354 [notice] <0.711.0>@couch_log_lager:notice:43
> 37ad126c7d 127.0.0.1 127.0.0.1:35984 POST /_cluster_setup 201 ok 1
> 2016-03-10 13:40:55.172 [notice] <0.844.0>@couch_log_lager:notice:43
> 7f57dc0474 127.0.0.1 127.0.0.1:15984 POST /_cluster_setup 400 ok 673
> 2016-03-10 13:43:44.887 [info] <0.3844.0>@couch_log_lager:info:39 A log
> statement
> {code}
> But for a node running from the OTP release created by {{make install}}
> nothing
> appears in the log until I have explictly called couch_log_lager:
> {code}
> $ erl -name [email protected] -remsh [email protected] -setcookie monster
> -hidden
> ([email protected])1> couch_log:info("A log statement", []).
> ok
> ([email protected])2> module_loaded(couch_log_lager).
> false
> ([email protected])3> couch_log_lager:info("Another log statement", []).
> ok
> ([email protected])4> couch_log:info("One more log statement", []).
> ok
> {code}
> {code}
> $ tail -n 5 /tmp/allthelogs.log
> 2016-03-10 13:14:37.507 [info] <0.7.0> Application setup started on node
> '[email protected]'
> 2016-03-10 13:14:37.507 [info] <0.7.0> Application snappy started on node
> '[email protected]'
> 2016-03-10 13:14:37.855 [debug] <0.374.0>@lager_handler_watcher:94 Lager
> installed handler lager_backend_throttle into lager_event
> 2016-03-10 13:18:52.264 [info] <0.3927.0>@couch_log_lager:info:39 Another
> log statement
> 2016-03-10 13:19:00.521 [info] <0.3927.0>@couch_log_lager:info:39 One
> more log statement
> {code}
> Note the first log statement does not appear in /tmp/allthelogs.
> I think this is a result of testing for whether the backend module is loaded
> before we use it in couch_log *(1). With a dev/run node,
> {{module_loaded(couch_log_lager).}} returns {{true}} whereas with a built
> node it returns {{false}} until called explicitly.
> I read up on Erlang's code server and thought I understood why - when running
> in {{interactive}} mode, the code server will load modules dynamically so if
> nothing calls couch_log_lager, it will never get loaded and couch_log will
> never use it. However what I don't understand is why it works with a dev/run
> node since that is also running in {{interactive}} mode - yet couch_log_lager
> is
> automatically loaded.
> The fix would appear to be to remove the test for module_loaded however we
> should verify whether there are any negative implications if we do that.
> (1)
> https://github.com/apache/couchdb-couch-log/blob/master/src/couch_log.erl#L116
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