NAME
    Log::Log4perl::Layout::JSON

VERSION
    version 0.001001

SYNOPSIS
    Example configuration:

        log4perl.rootLogger = INFO, Test
        log4perl.appender.Test = Log::Log4perl::Appender::String
        log4perl.appender.Test.layout = Log::Log4perl::Layout::JSON


        # Specify which fields to include in the JSON hash:
        # (using PatternLayout placeholders)

        log4perl.appender.Test.layout.field.message = %m
        log4perl.appender.Test.layout.field.category = %c
        log4perl.appender.Test.layout.field.class = %C
        log4perl.appender.Test.layout.field.file = %F{1}
        log4perl.appender.Test.layout.field.sub = %M{1}


        # Specify a prefix string for the JSON (optional)
        # http://blog.gerhards.net/2012/03/cee-enhanced-syslog-defined.html

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


        # Include the data in the Log::Log4perl::MDC hash (optional)
        log4perl.appender.Test.layout.include_mdc = 1

        # Use this field name for MDC data (else MDC data is placed at top level)
        log4perl.appender.Test.layout.name_for_mdc = mdc


        # Use canonical order for hash keys (optional)

        log4perl.appender.Test.layout.canonical = 1

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 can be included.

  EXAMPLE
        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 '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.)

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

AUTHOR
    Tim Bunce <Tim.Bunce@pobox.com>

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.