err, @ayhan.rashidov I am wrong, this is not a bug. Actually, the data you see is 100% correct. When you mention logging level info all the logs that are less or equal to the verbosity will be logged regardless of the backend.

Verbosity levels:
debug > info > warn > error

so “info” level will log all info, warn and error logs and “warn” will log all warn & error logs ., etc.

if you really want only error logs to a file and only info logs in one log ( I would advice against it) . you can use metadata.

config :logger,
  backends: [{LoggerFileBackend, :info},
             {LoggerFileBackend, :error}]

config :logger, :info,
  path: "/path/to/info.log",
  level: :info,
  metadata_filter: [level: :info]

config :logger, :error,
  path: "/path/to/error.log",
  level: :error,
  metadata_filter: [level: :error]

and you may use like –

Logger.info("This is info log",level: :info)
Logger.error("This is info log",level: :error)

@ayhan.rashidov looks like you caught a bug.

your config is from their github.