Chokecherry

Wrapper around lager logger which limits the volume of info messages irrespectively of the lager's backend.

The calls chokecherry:info, chokecherry:warning, chokecherry:error are getting translated into the lager:info, lager:warning, lager:error, retaining the proper arity.

There are two ways to log out the original module's name and the invocation process' Pid:

1. Use the compiler option right inside the file which uses the chockecherry:

   -compile([{parse_transform, chokecherry_transform}]).
   

   Important: that line should precede this one:

   -compile([{parse_transform, lager_transform}]).
   

2. Use that compiler option in the global rebar.config for the project:

   {erl_opts, [
       % ...
       {parse_transform, chokecherry_transform},
       {parse_transform, lager_transform}
       % ...
   }.
   

   Important: the chokecherry_transform should precede the lager_transform.

Configuration

This application can be somewhat customized by redefining the following settings:

• the queue length for the shaper;
• timeout for the shaper.

Default settings are as follows:

[
    {chokecherry, [
        {shaper, [
            {timeout, 1000},
            {log_queue_capacity, 10000}
        ]}
    ]}
].

How it works

+------------+     +------------+     +------------+     +------------+
|            |     |            |     |            |     |            |
|    app     +----->   shaper   +----->   writer   +----->   lager    |
|            |     |            |     |            |     |            |
+------------+     +------------+     +------------+     +------------+

shaper accumulates incoming messages in the queue. If the queue size exceeds log_queue_capacity within a certain time period (1 second), it sends an error_report “chokecherry dropped N messages in the last second”, and drops messages from the end of the queue, while receiving new ones and maintaining the maximum size of the queue.

writer pulls messages from shaper and transmits them to lager.

Changelog

0.2.8

1. Simplify logic in chokecherry_shaper and chokecherry_writer.
2. Configuration parameter {writer, [{timeout, 200}] doesn't need anymore.

0.2.7

1. Added chokecherry_shaper_logger shaped messages gen_event manager.