Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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None
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None
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None
Description
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:
[
{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"
]
}]}
]}
]}
].
In a dev/run node I can do the following in a remsh:
$ erl -name ohai@127.0.0.1 -remsh node1@127.0.0.1 -setcookie monster -hidden
(node1@127.0.0.1)1> couch_log:info("A log statement", []).
ok
Then I can verify the log statement appears in the expected location:
$ 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
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:
$ erl -name ohai@127.0.0.1 -remsh couchdb@127.0.0.1 -setcookie monster -hidden
(couchdb@127.0.0.1)1> couch_log:info("A log statement", []).
ok
(couchdb@127.0.0.1)2> module_loaded(couch_log_lager).
false
(couchdb@127.0.0.1)3> couch_log_lager:info("Another log statement", []).
ok
(couchdb@127.0.0.1)4> couch_log:info("One more log statement", []).
ok
$ tail -n 5 /tmp/allthelogs.log
2016-03-10 13:14:37.507 [info] <0.7.0> Application setup started on node 'couchdb@127.0.0.1'
2016-03-10 13:14:37.507 [info] <0.7.0> Application snappy started on node 'couchdb@127.0.0.1'
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
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