VERSION

version 1.09

NAME

Log::Any::Adapter::JSON - One-line JSON logging of arbitrary structured data

SYNOPSIS

Get a logger and specify the output destination:

  use Log::Any '$log';
  use Log::Any::Adapter ('JSON', '/path/to/file.log');

  # or

  use Log::Any '$log';
  use Log::Any::Adapter;

  my $handle = ...; # FH, pipe, etc

  Log::Any::Adapter->set('JSON', $handle);

Log some data:

  $log->info('Hello, world');
  $log->info('Hello, %s', $name);
  $log->debug('Blabla', { tracking_id => 42 });
  $log->debug('Blorgle', { foo => 'bar' }, [qw/a b c/], 'last thing');

DESCRIPTION

This Log::Any adapter logs formatted messages and arbitrary structured data in a single line of JSON per entry. You must pass a filename or an open handle to which the entries will be printed.

Optionally you may pass an encoding argument which will be used to apply a binmode layer to the output handle. The default encoding is UTF-8.

Optionally you may turn off string formatting, see below.

PARAMETERS

log_level

Set the minimum logging level to output. Any messages lower than this level will be discarded. Default is trace.

    use Log::Any::Adapter ('JSON', \*STDERR, log_level => 'info');

encoding

Defaults to UTF-8. Pass a different encoding to change the bindmode applied to the log output.

localtime

By default the message time will be in UTC. If you wish to log using your system's localtime instead, set this parameter to a true value. Output will look something like:

  2021-05-01T10:01:37.482042-04:00

versus, by default, always something like:

  2021-05-01T10:01:37.482042Z

without_formatting

By default the message will be formatted using sprintf if it contains formatting codes such as '%s'. This will cause the program to die if a message does not contain enough arguments to process all the formatting codes in a message. If your logs will contain the format codes and should not be formatted, or to prevent log messages from dependencies or untrusted sources from accidentally crashing the program, you can disable message formatting by setting this parameter to a true value:

    use Log::Any::Adapter ('JSON', \*STDERR, without_formatting => 1);

OUTPUT

Logged data fields

The adapter expects a string and an optional list @items.

If the string has no formatting tokens, it is included in the log entry in the message field as-is.

If the string has formatting tokens, @items is checked to verify that the next N values are scalars, where N is the number of tokens in the string. If the number is the same, the string and tokens are combined using sprintf() and the resulting string is included in the log entry in the message field. If the token and value counts don't match, the adapter croaks.

After the format processing, the remainder of the items array is processed. It may hold arrayrefs, which are included in a top- level key named list_data; additional scalars, which are pushed into the additional_messages key; and hashrefs. The first hashref encountered has its keys promoted to top-level keys in the log entry, while additional hashrefs are included in a top-level key named hash_data.

Other fields

In addition, the log entry will have the following fields:

time
level
category

EXAMPLES

Plain text message

  $log->debug('a simple message');

Output is a single line with JSON like:

  {
    "category":"main",
    "level":"debug",
    "message":"hello, world",
    "time":"2021-03-03T17:23:25.731243Z"
  }

Formatted message

  my $val = "string";
  my $num = 2;

  $log->debug('a formatted %s with %d tokens', $val, $num);

Output is a single line with JSON like:

  {
    "category":"main",
    "level":"debug",
    "message":"a formatted string with 2 tokens",
    "time":"2021-03-03T17:23:25.731243Z"
  }

Single hashref

The first hashref encountered has its keys elevated to the top level.

  $log->debug('the message', { tracker => 42 });

Output is a single line with JSON like:

    {
      "category":"main",
      "level":"debug",
      "message":"the message",
      "time":"2021-03-03T17:23:25.731243Z",
      "tracker":42
    }

Reserved key names that may not be used in the first hashref include:

  * category
  * context
  * level
  * message
  * time

Additional hashrefs and arrayrefs

  $log->debug('the message', { tracker => 42 }, { foo => 'bar'});

Output is a single line with JSON like:

  {
    "category":"main",
    "hash_data":{
      "foo":"bar"
    },
    "level":"debug",
    "message":"the message",
    "time":"2021-03-03T17:23:25.731243Z",
    "tracker":42
  }

Another example:

  $log->debug('the message', { tracker => 42 }, {foo => 'bar'}, [1..3]);

Output is a single line with JSON like:

  {
    "category":"main",
    "hash_data":[
      {"foo":"bar"}
    ],
    "level":"debug",
    "list_data":[
      [1,2,3]
    ],
    "message":"the message",
    "time":"2021-03-03T17:23:25.731243Z",
    "tracker":42
}

Additional messages

Any scalars that are passed that are not consumed as the values of formatting tokens will be included in an additional_messages key.

  $log->debug('a simple message', 'foo', 'bar');

Output is a single line with JSON like:

  {
    "additional_messages":[
      'foo',
      'bar'
    ],
    "category":"main",
    "level":"debug",
    "message":"hello, world",
    "time":"2021-03-03T17:23:25.731243Z"
  }

SEE ALSO

Log::Any

Log::Any::Adapter

AUTHOR

Nick Tonkin <tonkin@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2021 by Nick Tonkin.

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