a systemd-journald compatible log output on stderr (#1912)
* a systemd-journald compatible log output on stderr
based on the stderr logger but changed:
- doesn't output the timestamp, the journal already has a timestamp
- output the log level as <num> where num is defined as in `sd-daemon(3)`
https://www.freedesktop.org/software/systemd/man/sd-daemon.html
diff --git a/rel/overlay/etc/default.ini b/rel/overlay/etc/default.ini
index d8476f3..9a8c70b 100644
--- a/rel/overlay/etc/default.ini
+++ b/rel/overlay/etc/default.ini
@@ -449,16 +449,25 @@
; max_message_size = 16000
;
;
-; There are three different log writers that can be configured
+; There are four different log writers that can be configured
; to write log messages. The default writes to stderr of the
; Erlang VM which is useful for debugging/development as well
; as a lot of container deployments.
;
-; There's also a file writer that works with logrotate and an
+; There's also a file writer that works with logrotate, a
; rsyslog writer for deployments that need to have logs sent
-; over the network.
+; over the network, and a journald writer that's more suitable
+; when using systemd journald.
;
writer = stderr
+; Journald Writer notes:
+;
+; The journald writer doesn't have any options. It still writes
+; the logs to stderr, but without the timestamp prepended, since
+; the journal will add it automatically, and with the log level
+; formated as per
+; https://www.freedesktop.org/software/systemd/man/sd-daemon.html
+;
;
; File Writer Options:
;
@@ -525,4 +534,4 @@
; value will be rejected. If this config setting is not defined,
; CouchDB will use the value of `max_limit` instead. If neither is
; defined, the default is 2000 as stated here.
-; max_limit_partitions = 2000
\ No newline at end of file
+; max_limit_partitions = 2000
diff --git a/src/couch_log/src/couch_log_writer_journald.erl b/src/couch_log/src/couch_log_writer_journald.erl
new file mode 100644
index 0000000..02a9c69
--- /dev/null
+++ b/src/couch_log/src/couch_log_writer_journald.erl
@@ -0,0 +1,69 @@
+% Licensed under the Apache License, Version 2.0 (the "License"); you may not
+% use this file except in compliance with the License. You may obtain a copy of
+% the License at
+%
+% http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+% License for the specific language governing permissions and limitations under
+% the License.
+
+-module(couch_log_writer_journald).
+-behaviour(couch_log_writer).
+
+
+-export([
+ init/0,
+ terminate/2,
+ write/2
+]).
+
+
+-include("couch_log.hrl").
+
+
+init() ->
+ {ok, nil}.
+
+
+terminate(_, _St) ->
+ ok.
+
+
+write(Entry, St) ->
+ #log_entry{
+ level = Level,
+ pid = Pid,
+ msg = Msg,
+ msg_id = MsgId
+ } = Entry,
+ Fmt = "<~B>~s ~p ~s ",
+ Args = [
+ level_for_journald(Level),
+ node(),
+ Pid,
+ MsgId
+ ],
+ MsgSize = couch_log_config:get(max_message_size),
+ Data = couch_log_trunc_io:format(Fmt, Args, MsgSize),
+ io:format(standard_error, [Data, Msg, "\n"], []),
+ {ok, St}.
+
+
+% log level mapping from sd-daemon(3)
+% https://www.freedesktop.org/software/systemd/man/sd-daemon.html
+-spec level_for_journald(atom()) -> integer().
+level_for_journald(Level) when is_atom(Level) ->
+ case Level of
+ debug -> 7;
+ info -> 6;
+ notice -> 5;
+ warning -> 4;
+ error -> 3;
+ critical -> 2;
+ alert -> 1;
+ emergency -> 0;
+ _ -> 3
+ end.
