Description

A wrapper around Erlang system logger to simply configuration.

Configuration

• dir: path to the directory where log files will be created (all.log and error.log). The default is current directory.
• level: log level. See Erlang's logger:level() type description. The default is notice.
• rotate_size: a size of a log file to trigger rotation. The default is 1024*1024*10 (10 mb).
• rotate_count: a maximum number of rotated files. The default is 5.
• logging_mode: avail type: [single, separate, debug_and_error]. Filter events in separate file by level or in single. The default is debug_and_error.
• single_line: whether to flatten log message into single line or not. The default is false.
• max_line_size: truncate log message at this size. The default is 1024*100 (100 kb).
• filesync_repeat_interval, sync_mode_qlen, drop_mode_qlen, flush_qlen: Same as in logger_std_h(erl) module. The defaults are correspondingly: no_repeat, 1000, 1000 and 5000.
• console: Whether to log into console or not. The default is false.
• formatter: formatter type: either plain or json. The default is plain. JSON formatter formats log message into JSON Lines. The log can be viewed using jq for example. Note that the option doesn't affect console formatter (i.e. the default logger handler) -- plain messages are always logged into console. In other words, JSON formatter is only used for log files.
• exclude_meta: only makes sense when formatter is set to json. In this case keys listed in this option are excluded from resulting meta field of the logged JSON message. The default is [domain, report_cb, gl, error_logger, logger_formatter].
• print_gun_shutdown_errors: enables logging gun noproc and {shutdown, normal} error reports in shutdown_error context from gun supervisor. Such reports occur when calling process finishes earlier than gun's connection process. This situation does not affect application therefore such reports are supressed by default. true enables logging of these reports. Default is false.

Configuration example

[
  ...
  {log, [{dir, "/path/to/log/dir"},
         {level, warning},
         {rotate_size, 1024},
         {rotate_count, 5}]}
  ...
]

Log message formatting examples

When logged as ?LOG_DEBUG("Hello, world", [], #{msisdn => 7923423444}) the corresponding log message for:

• JSON:

{
  "timestamp": "2020-10-15T10:26:15.704095+03:00",
  "severity": "debug",
  "message": "Hello, world",
  "line": 1929,
  "file": "hello.erl",
  "meta": {
    "msisdn": "7923423444"
  },
  "erlang": {
    "pid": "<0.44.0>",
    "mfa": "hello:world/0"
  }
}

• Plain text:

2020-10-15T10:26:15.704095+03:00 [debug] [<0.44.0> hello:world/0] [msisdn=7923423444] [hello.erl:1929] Hello, world