NAME
   Log::Log4perl::Layout::JSON

VERSION
   version 0.002003

SYNOPSIS
   Example configuration:

       log4perl.appender.Example.layout = Log::Log4perl::Layout::JSON
       log4perl.appender.Example.layout.field.message = %m{chomp}
       log4perl.appender.Example.layout.field.category = %c
       log4perl.appender.Example.layout.field.class = %C
       log4perl.appender.Example.layout.field.file = %F{1}
       log4perl.appender.Example.layout.field.sub = %M{1}
       log4perl.appender.Example.layout.include_mdc = 1

   See below for more configuration options.

DESCRIPTION
   This class implements a "Log::Log4perl" layout format, similar to
   Log::Log4perl::Layout::PatternLayout except that the output is a JSON
   hash.

   The JSON hash is ASCII encoded, with no newlines or other whitespace,
   and is suitable for output, via Log::Log4perl appenders, to files and
   syslog etc.

   Contextual data in the Log::Log4perl::MDC hash will be included if
   "include_mdc" is true.

NAME
   Log::Log4perl::Layout::JSON - Layout a log message as a JSON hash,
   including MDC data

LAYOUT CONFIGURATION
 field
   Specify one or more fields to include in the JSON hash. The value is a
   string containing one of more Log::Log4perl::Layout::PatternLayout
   placeholders. For example:

       log4perl.appender.Example.layout.field.message = %m{chomp}
       log4perl.appender.Example.layout.field.category = %c
       log4perl.appender.Example.layout.field.where = %F{1}:%L

   If no fields are specified, the default is "message = %m{chomp}". It is
   recommended that "message" be the first field.

 prefix
   Specify a prefix string for the JSON. For example:

       log4perl.appender.Example.layout.prefix = @cee:

   See http://blog.gerhards.net/2012/03/cee-enhanced-syslog-defined.html

 include_mdc
   Include the data in the Log::Log4perl::MDC hash.

       log4perl.appender.Example.layout.include_mdc = 1

   See also "name_for_mdc".

 name_for_mdc
   Use this name as the key in the JSON hash for the contents of MDC data

       log4perl.appender.Example.layout.name_for_mdc = mdc

   If not set then MDC data is placed at top level of the hash.

   Where MDC field names match the names of fields defined by the Log4perl
   configuration then the MDC values take precedence. This is currently
   construde as a feature.

 canonical
   If true then use canonical order for hash keys when encoding the JSON.

       log4perl.appender.Example.layout.canonical = 1

   This is mainly intended for testing.

 max_json_length_kb
   Set the maximum JSON length in kilobytes. The default is 20KB.

       log4perl.appender.Example.layout.max_json_length_kb = 3.8

   This is useful where some downstream system has a limit on the maximum
   size of a message.

   For example, rsyslog has a "maxMessageSize" configuration parameter with
   a default of 4KB. Longer messages are simply truncated (which would
   corrupt the JSON). We use rsyslog with maxMessageSize set to 128KB.

   If the JSON is larger than the specified size (not including "prefix")
   then some action is performed to reduce the size of the JSON.

   Currently fields are simply removed until the JSON is within the size.
   The MDC field/fields are removed first and then the fields specified in
   the Log4perl config, in reverse order. A message is printed on "STDERR"
   for each field removed.

   In future this rather dumb logic will be replaced by something smarter.

 EXAMPLE USING Log::Log4perl::MDC
       local Log::Log4perl::MDC->get_context->{request} = {
           request_uri => $req->request_uri,
           query_parameters => $req->query_parameters
       };

       # ...

       for my $id (@list_of_ids) {

           local Log::Log4perl::MDC->get_context->{id} = $id;

           do_something_useful($id);

       }

   Using code like that shown above, any log messages produced by
   do_something_useful() will automatically include the 'contextual data',
   showing the request URI, the hash of decoded query parameters, and the
   current value of $id.

   If there's a $SIG{__WARN__} handler setup to log warnings via
   "Log::Log4perl" then any warnings from perl, such as uninitialized
   values, will also be logged with this context data included.

   The use of "local" ensures that contextual data doesn't stay in the MDC
   beyond the relevant scope. (For more complex cases you could use
   something like Scope::Guard or simply take care to delete old data.)

AUTHOR
   Tim Bunce <[email protected]>

COPYRIGHT AND LICENSE
   This software is copyright (c) 2014 by Tim Bunce.

   This is free software; you can redistribute it and/or modify it under
   the same terms as the Perl 5 programming language system itself.

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.