logger_formatter

Configuration

The following configuration parameters can be set for logger_formatter:

single_line = boolean()

If set to true, all newlines in the message are replaced with ", ", and whitespaces following directly after newlines are removed. Note that newlines added by the formatter template are not replaced.

Default is true.

legacy_header = boolen()

If set to true a header field is added to logger_formatter's part of Metadata. The value of this field is a string similar to the header created by the old error_logger event handlers. It can be included in the log event by adding the tuple {logger_formatter,header} to the template. See Default Templates for more information

Default is false.

report_cb = fun((logger:report()) -> {io:format(),[term()]})

A function with arity 1, returning {Format,Args}. This function will replace any report_cb found in metadata.

depth = pos_integer() | unlimited

A positive integer representing the maximum depth to which terms shall be printed by this formatter. Format strings passed to this formatter are rewritten. The format controls ~p and ~w are replaced with ~P and ~W, respectively, and the value is used as the depth parameter. For details, see io:format/2,3 in STDLIB.

Default is unlimited.

chars_limit = pos_integer() | unlimited

A positive integer representing the value of the option with the same name to be used when calling io_lib:format/3. This value limits the total number of characters printed for each log event. Note that this is a soft limit. For a hard truncation limit, see option max_size.

Default is unlimited.

max_size = pos_integer() | unlimited

A positive integer representing the absolute maximum size a string returned from this formatter can have. If the formatted string is longer, after possibly being limited by depth and/or chars_limit, it will be truncated.

Default is unlimited.

template = template()

The template is a list of atoms, tuples and strings. The atoms level or msg, are treated as placeholders for the severity level and the log message, repectively. Other atoms or tuples are interpreted as placeholders for metadata, where atoms are expected to match top level keys, and tuples represent paths to sub keys in a nested map. For example the tuple {key1,key2} will be replaced by the value of the key2 field in the nested map below. The atom key1 on its own would be replaced by the complete value of the key1 field. The values are converted to strings.


#{key1=>#{key2=>my_value,
          ...}
  ...}

Strings are printed literally.

The default template differs depending on the values of legacy_header and single_line. See Default Templates for more information

utc = boolean()

If set to true, all dates are displayed in Universal Coordinated Time. Default is false.

Default templates

The default template when legacy_header=true is

[{logger_formatter,header},"\n",msg,"\n"]

which will cause log entries like this:

=ERROR REPORT==== 29-Dec-2017::13:30:51.245123 ===
    process: <0.74.0>
    exit_reason: "Something went wrong"

Note that all eight levels might occur here, not only ERROR, WARNING or INFO. And also that micro seconds are added at the end of the timestamp.

The default template when single_line=true is

[time," ",level,": ",msg,"\n"]

which will cause log entries like this:

2017-12-29 13:31:49.640317 error: process: <0.74.0>, exit_reason: "Something went wrong"

The default template when both legacy_header and single_line are set to false is:

[time," ",level,":\n",msg,"\n"]

which will cause log entries like this:

2017-12-29 13:32:25.191925 error:
    process: <0.74.0>
    exit_reason: "Something went wrong"