Formats the given message.
The template is a list of atoms, tuples and strings. Atoms
can be level or msg, which are placeholders
for the severity level and the log message,
repectively. Tuples are interpreted as placeholders for
metadata. Each element in the tuple must be an atom which
matches a key in the nested metadata map, e.g. the
tuple {key1,key2} will be replaced by the value of
the key2 field in this nested map (the value vill be
converted to a string):
#{key1=>#{key2=>my_value,
...},
...}
Strings are printed literally.
depth is 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.
chars_limit is a positive integer representing the
value of the option with the same name to be used when calling
io:format/3. This
value limits the total number of characters printed bu the
formatter. Notes that this is a soft limit. For a hard
truncation limit, see option max_size.
max_size is a positive integer representing the
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.
utc is a boolean. If set to true, all dates are
displayed in Universal Coordinated Time. Default
is false.
report_cb must be a function with arity 1,
returning {Format,Args}. This function will replace
any report_cb found in metadata.
If single_line=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.
If legacy_header=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.
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"