Mike Wallace created COUCHDB-2968:
-------------------------------------
Summary: 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
dist}} 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 dist}} 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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