Message::Passing(3pm)

NAME
Message::Passing - a simple way of doing messaging.

SYNOPSIS
    message-pass --input STDIN --output STDOUT
    {"foo": "bar"}
    {"foo":"bar"}

DESCRIPTION
A library for building high performance, loosely coupled and reliable/resilient applications, structured as small services which communicate over the network by passing messages.

  BASIC PREMISE
You have data for discrete events, represented by a hash (and serialized as JSON).

This could be a text log line, an audit record of an API event, a metric emitted from your application that you wish to aggregate and process - anything that can be a simple hash really..

You want to be able to shove these events over the network easily, and aggregate them / filter and rewrite them / split them into worker queues.

This module is designed as a simple framework for writing components that let you do all of these things, in a simple and easily extensible manor.

For a practical example, You generate events from a source (e.g. ZeroMQ output of logs and performance metrics from your Catalyst FCGI or Starman workers) and run one script that will give you a central application log file, or push the logs into Elasticsearch.

There are a growing set of components you can plug together to make your solution.

Getting started is really easy - you can just use the "message-pass" command installed by the distribution. If you have a common config that you want to repeat, or you want to write your own server which does something more flexible than the normal script allows, then see Message::Passing::DSL.

To dive straight in, see the documentation for the command line utility message-pass, and see the examples in Message::Passing::Manual::Cookbook.

For more about how the system works, see Message::Passing::Manual::Concepts.

COMPONENTS
Below is a non-exhaustive list of components available.

  INPUTS
Inputs receive data from a source (usually a network protocol).

They are responsible for decoding the data into a hash before passing it onto the next stage.

Inputs include:

Message::Passing::Input::STDIN
Message::Passing::Input::ZeroMQ
Message::Passing::Input::STOMP
Message::Passing::Input::AMQP
Message::Passing::Input::Syslog
Message::Passing::Input::Redis
Message::Passing::Input::Test

You can easily write your own input, just use AnyEvent, and consume Message::Passing::Role::Input.

  FILTER
Filters can transform a message in any way.

Examples include:

Message::Passing::Filter::Null - Returns the input unchanged.
Message::Passing::Filter::All - Stops any messages it receives from being passed to the output. I.e. literally filters all input out.
Message::Passing::Filter::T - Splits the incoming message to multiple outputs.

You can easily write your own filter, just consume Message::Passing::Role::Filter.

Note that filters can be chained, and a filter can return undef to stop a message being passed to the output.

  OUTPUTS
Outputs send data to somewhere, i.e. they consume messages.

Message::Passing::Output::STDOUT
Message::Passing::Output::AMQP
Message::Passing::Output::STOMP
Message::Passing::Output::ZeroMQ
Message::Passing::Output::WebHooks
Message::Passing::Output::Search::Elasticsearch
Message::Passing::Output::Redis
Message::Passing::Output::Test

SEE ALSO

Message::Passing::Manual - The manual (contributions cherished).
<http://www.slideshare.net/bobtfish/messaging-interoperability-and-log-aggregation-a-new-framework> - Slide deck!
Log::Message::Structured - For creating your log messages.
Log::Dispatch::Message::Passing - use Message::Passing outputs from Log::Dispatch.

THIS MODULE
This is a simple MooX::Options script, with one input, one filter and one output. To build your own similar scripts, see:

Message::Passing::DSL - To declare your message chains.
Message::Passing::Role::CLIComponent - To provide "foo" and "foo_options" attribute pairs.
Message::Passing::Role::Script - To provide daemonization features.

  METHODS
build_chain

Builds and returns the configured chain of input => filter => output.

start

Class method to call the run_message_server function with the results of having constructed an instance of this class, parsed command line options and constructed a chain.

This is the entry point for the script.

AUTHOR
Tomas (t0m) Doran <bobtfish@bobtfish.net>

SUPPORT

  Bugs
Please log bugs at rt.cpan.org. Each distribution has a bug tracker link in its metacpan.org page.

  Discussion
#message-passing on irc.perl.org.

  Source code
Source code for all modules is available at <http://github.com/suretec> and forks/patches are very welcome.

SPONSORSHIP
This module exists due to the wonderful people at Suretec Systems Ltd. <http://www.suretecsystems.com/> who sponsored its development for its VoIP division called SureVoIP <http://www.surevoip.co.uk/> for use with the SureVoIP API - <http://www.surevoip.co.uk/support/wiki/api_documentation>

COPYRIGHT
Copyright Suretec Systems Ltd. 2012.

Logstash (upon which many ideas for this project are based, but from which we do not reuse any code) is copyright 2010 Jorden Sissel.

LICENSE
GNU Library General Public License, Version 2.1