Elixir 1.19: Refactor Logger configuration to what Elixir 1.15+ expects

Elixir 1.19 started emitting warnings about our use of:
config :logger, :console and
config :logger, backends: []
which got split in 1.15 to :default_handler, :default_formatter, and
LoggerBackends.add(backend) respectively.

On Pleroma startup it is now necessary to add the additional logger
backends at runtime (done with configure_logger() in application.ex).
New config key :pleroma, :logger_backends: [] has replaced the older
backends array. The logger_backends package is now used to facilitate
usage of other logger backends besides the default one (:logger_std_h
from OTP).

Warnings were added to Pleroma startup to warn about the usage of
:logger, backends and additional logic was introduced to make addition
of ExSyslogger to admin's configuration less dumb.

Ref: https://hexdocs.pm/logger/1.15.0/Logger.html#module-backends-and-backwards-compatibility

config/config.exs

@@ -132,11 +132,12 @@ config :pleroma, Pleroma.Web.Endpoint,
     "SameSite=Lax"
   ]
 
-# Configures Elixir's Logger
-config :logger, backends: [:console]
+# config :logger, :console has been changed in 1.15+ and split into
+# :default_handler and :default_formatter. It started emitting warnings in 1.19.
+# See https://hexdocs.pm/logger/1.19.0/Logger.html#module-backends-and-backwards-compatibility
+config :logger, :default_handler, level: :debug
 
-config :logger, :console,
-  level: :debug,
+config :logger, :default_formatter,
   format: "\n$time $metadata[$level] $message\n",
   metadata: [:actor, :path, :type, :user]
 

config/dev.exs

@@ -36,7 +36,7 @@ config :pleroma, Pleroma.Emails.Mailer, adapter: Swoosh.Adapters.Local
 # different ports.
 
 # Do not include timestamps in development logs
-config :logger, Logger.Backends.Console, format: "$metadata[$level] $message\n"
+config :logger, :default_formatter, format: "$metadata[$level] $message\n"
 
 # Set a higher stacktrace during development. Avoid configuring such
 # in production as building large stacktraces may be expensive.

config/prod.exs

@@ -20,8 +20,7 @@ config :pleroma, Pleroma.Web.Endpoint,
 config :phoenix, serve_endpoints: true
 
 # Do not print debug messages in production
-config :logger, Logger.Backends.Console, level: :info
-config :logger, :console, level: :info
+config :logger, :default_handler, level: :info
 config :logger, :ex_syslogger, level: :info
 
 # ## SSL Support

config/test.exs

@@ -15,9 +15,9 @@ config :pleroma, Pleroma.Captcha,
   method: Pleroma.Captcha.Mock
 
 # Print only warnings and errors during test
-config :logger, :console,
-  level: :warning,
-  format: "\n[$level] $message\n"
+config :logger, :default_handler, level: :warning
+
+config :logger, :default_formatter, format: "\n[$level] $message\n"
 
 config :pleroma, :auth, oauth_consumer_strategies: []
 

docs/configuration/cheatsheet.md

@@ -858,12 +858,14 @@ Web Push Notifications configuration. You can use the mix task `mix web_push.gen
 * ``private_key``: VAPID private key
 
 ## :logger
-* `backends`: `:console` is used to send logs to stdout, `{ExSyslogger, :ex_syslogger}` to log to syslog
+* Logging to console/stdout is done by default, use `{ExSyslogger, :ex_syslogger}` to log to syslog
 
 An example to enable ONLY ExSyslogger (f/ex in ``prod.secret.exs``) with info and debug suppressed:
 ```elixir
-config :logger,
-  backends: [{ExSyslogger, :ex_syslogger}]
+config :pleroma,
+  logger_backends: [{ExSyslogger, :ex_syslogger}]
+
+config :logger, default_handler: false
 
 config :logger, :ex_syslogger,
   level: :warning
@@ -871,8 +873,8 @@ config :logger, :ex_syslogger,
 
 Another example, keeping console output and adding the pid to syslog output:
 ```elixir
-config :logger,
-  backends: [:console, {ExSyslogger, :ex_syslogger}]
+config :pleroma,
+  logger_backends: [{ExSyslogger, :ex_syslogger}]
 
 config :logger, :ex_syslogger,
   level: :warning,
@@ -883,23 +885,22 @@ See: [logger’s documentation](https://hexdocs.pm/logger/Logger.html) and [ex_s
 
 An example of logging info to local syslog, but debug to console:
 ```elixir
-config :logger,
-  backends: [ {ExSyslogger, :ex_syslogger}, :console ],
-  level: :info
+config :pleroma,
+  logger_backends: [ {ExSyslogger, :ex_syslogger}]
 
 config :logger, :ex_syslogger,
   level: :info,
   ident: "pleroma",
   format: "$metadata[$level] $message"
 
-config :logger, :console,
-  level: :debug,
+config :logger, :default_handler,
+  level: :debug
+
+config :logger, :default_formatter,
   format: "\n$time $metadata[$level] $message\n",
   metadata: [:request_id]
 ```
 
-
-
 ## Database options
 
 ### RUM indexing for full text search

lib/pleroma/application.ex

@@ -43,6 +43,7 @@ defmodule Pleroma.Application do
     # every time the application is restarted, so we disable module
     # conflicts at runtime
     Code.compiler_options(ignore_module_conflict: true)
+    configure_logger()
     Pleroma.Telemetry.Logger.attach()
     Config.Holder.save_default()
     Pleroma.HTML.compile_scrubbers()
@@ -113,6 +114,37 @@ defmodule Pleroma.Application do
     Supervisor.start_link(children, opts)
   end
 
+  def configure_logger do
+    if Application.get_env(:logger, :backends) do
+      Logger.warning(
+        "'config :logger, backends: [...]' is deprecated syntax due to changes in Elixir. Use 'config :pleroma, :logger_backends: [...]' instead."
+      )
+    end
+
+    Config.get([:logger_backends], [])
+    |> Enum.each(fn backend ->
+      backend = backend_to_logger(backend)
+
+      case LoggerBackends.add(backend) do
+        {:ok, _} ->
+          Logger.debug("Successfully added logger backend: #{inspect(backend)}")
+
+        {:error, reason} ->
+          Logger.error("Failed to add logger backend #{inspect(backend)}: #{inspect(reason)}")
+      end
+    end)
+  end
+
+  defp backend_to_logger({:ex_syslogger = backend, name}) do
+    Logger.warning(
+      "Configuration {:#{backend}, :#{name}} is incorrect. Use {ExSyslogger, :#{name}} instead!"
+    )
+
+    {ExSyslogger, name}
+  end
+
+  defp backend_to_logger(backend), do: backend
+
   def load_custom_modules do
     dir = Config.get([:modules, :runtime_dir])