How can I disable logging of specific library?

Questions / Help
1

I’m using GitHub - larskrantz/logger_papertrail_backend: A Papertrail backend for Elixir Logger.

From Elixir v1.15.0, it shows warnings like below.

warning: the log level :warn is deprecated, use :warning instead
  (logger 1.15.0) lib/logger.ex:1137: Logger.elixir_level_to_erlang_level/1
  (logger 1.15.0) lib/logger.ex:591: Logger.compare_levels/2
  (logger_papertrail_backend 1.1.0) lib/logger_papertrail_backend/logger.ex:60: LoggerPapertrailBackend.Logger.meet_level?/2
  (logger_papertrail_backend 1.1.0) lib/logger_papertrail_backend/logger.ex:33: LoggerPapertrailBackend.Logger.handle_event/2
  (stdlib 5.0.1) gen_event.erl:802: :gen_event.server_update/4
  (stdlib 5.0.1) gen_event.erl:784: :gen_event.server_notify/4
  (stdlib 5.0.1) gen_event.erl:786: :gen_event.server_notify/4
  (stdlib 5.0.1) gen_event.erl:526: :gen_event.handle_msg/6
  (stdlib 5.0.1) proc_lib.erl:241: :proc_lib.init_p_do_apply/3

Logger send :warn to logger backends instead of :warning.

This is reported as “warn” in Elixir’s logger backends for backwards compatibility reasons.

logger_papertrail_backend uses Logger.compare_level/2, so it inputs :warn to Logger.compare_level/2.

I want to disable that warning from logger_papertrail_backend.

How can I do that?

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2

Per the Logger docs:

If you want to purge all log calls from an application named :foo and only keep errors from Bar.foo/3, you can set up two different matches:

config :logger,
  compile_time_purge_matching: [
    [application: :foo],
    [module: Bar, function: "foo/3", level_lower_than: :error]
  ]

So I assume for your purposes you could write something like:

config :logger, compile_time_purge_matching: [
  [application: :logger_papertrail_backend, level_lower_than: :error
]
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3

Thank you!

1 Like
4

This does not work for me for some reason, any ideas why?

config :logger, :console,
  format: "[$level] $message\n",
  compile_time_purge_matching: [
    [module: ExMQTT, level_lower_than: :error]
  ]

Even with this I still see ExMQTT debug logs

5

The docs for ExMQTT state:

An Elixir wrapper around the Erlang emqtt library.

It’s possible that logs from the ExMQTT module itself are being purged, but logs from modules in the wrapped :emqtt library are still being emitted.

What specific messages are you seeing? You could use that to triangulate the emitting module by grepping around the source code for the log text in both respective libraries.

6

Another thing to be aware is that you need recompile the deps after setting up the config.
Example

# since tesla and ecto_sql are deps don't forget to recompile them if you want to turn on / off their logs
# mix deps.compile --force tesla ecto_sql
config :logger,
  backends: [:console],
  compile_time_purge_matching: [
    [application: :ecto_sql],
    [application: :tesla],
    [module: Lor.Lol.Replays.Worker, level_lower_than: :info]
  ]
7

Good idea, but no, I see ExMQTT logs:
they are all prefixed with [ExMQTT]

[debug] [ExMQTT] Connecting to localhost:1883
....
[debug] [ExMQTT] Connected #PID<0.711.0>

Another thing to be aware is that you need recompile the deps after setting up the config.

Yeah, I’ve tried it:

rm -rf _build
rm -rf deps
mix deps.get
mix deps.compile
mix phx.server

I’m starting to think maybe there is something specific to running the app with mix phx.server that is breaking this for me

UPD:
I fixed it with this:

# Do not include metadata nor timestamps in development logs
config :logger, :console, format: "[$level] $message\n"

Logger.put_module_level(ExMQTT, :error)
Logger.put_module_level(:emqtt, :error)

I don’t really like that those put_module_level are not part of config :logger section, but I was not able to figure out how to do it otherwise (and compile_time_purge_matching also did not work, not sure why - don’t really care in this case)

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