NAME
    Juno - Asynchronous event-driven checking mechanism

VERSION
    version 0.009

SYNOPSIS
    This runs an asynchronous checker on two servers (*jack* and *jill*),
    running an HTTP test every 10 seconds with an additional *Host* header.

        my $juno = Juno->new(
            hosts    => [ 'jack', 'jill' ],
            interval => 10,
            checks   => {
                HTTP => {
                    headers => {
                        { 'Host', 'example.com' },
                    },

                    on_result => sub {
                        my $result = shift;
                        ...
                    },
                },
            },
        );

        # makes juno run in the background
        $juno->run;

DESCRIPTION
    Juno is a hub of checking methods (HTTP, Ping, SNMP, etc.) meant to
    provide developers with an asynchronous event-based checking agent that
    has callable events for the each check's result. You can then use this
    probed data for whatever it is you want. This helps you write stuff like
    monitoring services, amongst other things.

    Juno is flexible, introspective and composable but still very
    straight-forward. To use Juno, you simply need to create a new object,
    give it all the information needed (such as the test you want to run)
    and the optional (and possibly required) additional check-specific
    arguments, and then just let it run in the background, working for you.

    Each check Juno runs can have multiple events launched for it. The
    events will only be called if you ask them to be called. This means that
    if you do not want a certain event to run for a specific check, just
    don't provide it.

EVENTS
    Let's go over the events you can run. Each check should provide all of
    these events unless specified otherwise in the check's documentation.

    Also, note that each check tried to decide if a result has been
    successful or not. This could be decided using return codes, response
    headers, failed results, etc. You have callbacks for successful results
    or not, but they do not prevent you from using the other callbacks
    provided. They will still work seamlessly if you provide all of them.

    *   on_before

        This event gets called before the check is actually called.

        One thing you can do with it is to check how long a request takes.
        You can timestamp before a check is done, and once a check has a
        result, you can timestamp that again. The diff between those
        timestamps is how long it took to run the check.

    *   on_result

        This event gets called as soon as a check result has come in. It
        might have failed, it might have been successful. It doesn't matter.

        One usage for it is to timestamp the result to correspond to the
        "before" callback explained above.

        Another usage for it is in case you want to check for yourself if
        the result has been successful or not. Perhaps you have your own API
        you're testing against and you (and only *you*) can decide if it was
        successful.

        You will receive the entire result and can make any decision you
        want.

    *   on_success

        This callback is called when the check decides the result has
        succeeded.

    *   on_fail

        This callback is called when the check decides the result has
        failed.

    Hopefully by now you understand the basic concepts of Juno. The
    following documentation will help you get started on how to use Juno
    exactly, creating a new object and providing it with all the information
    required.

ATTRIBUTES
  checks
    The checks you want to run.

    This is a hashref of the checks. The key is the check itself (correlates
    to the class in "Juno::Check::") and the values are the attributes to
    that check.

        my $juno = Juno->new(
            hosts  => [ '10.0.0.2', '10.0.0.3' ],
            checks => {
                HTTP => {
                    path => '/test',
                },
            },
        );

    The "checks" argument is the most important one, and it is mandatory.
    This defines what will be checked, and adds additional parameters. Some
    might be optional, some might be mandatory. You should read each check's
    documentation to know what options are available and which are required.

    If you need to run multiple checks of the same type, such as two
    different HTTP tests, you will need to run two Juno instances. It's
    perfectly fine, because Juno has no global variables and works
    seamlessly with multiple instances.

    Hopefully this will change in the future, providing more advanced
    options to have multiple checks of the same type.

  hosts
    An arrayref of hosts you want all checks to monitor.

        my $juno = Juno->new(
            hosts => [ '10.0.1.100', 'sub.domain.com' ],
            ...
        );

  interval
    The interval for every check.

        my $juno = Juno->new(
            interval => 5.6,
            ...
        );

    This sets every check to be run every 5.6 seconds.

    Default: 10 seconds.

  after
    Delay seconds for first check.

        my $juno = Juno->new(
            after => 10,
            ...
        );

    This will force all checks to only begin after 10 seconds. It will
    basically rest for 10 seconds and then start the checks. We can't really
    think of many reasons why you would need this (perhaps waiting for a
    database connection?), but nonetheless it is an optional feature and you
    should have control over it if you want to change it.

    If this is set to zero (the default), it will not delay the execution of
    the checks.

    Default: 0 seconds

  prop_attributes
    The "prop_attributes" are an arrayref of attributes that are propagated
    from the main Juno object to each check object. This could be a
    hard-coded list, but it's cleaner to put it in an attribute. This means
    it's available for you to change. There really is no need for you to do
    that.

        my $juno = Juno->new(
            prop_attributes => [ 'hosts', 'interval' ],
            ...
        );

    Default: hosts, interval, after.

METHODS
  run
    Run Juno.

        use Juno;
        use AnyEvent;

        my $cv   = AnyEvent->condvar;
        my $juno = Juno->new(...);

        $juno->run;
        $cv->recv;

    When you call Juno's "run" method, it will begin running the checks.
    Separating the running to a method allows you to set up a Juno object
    (or several Juno objects) in advance and calling them later on when
    you're ready for them to start working.

    However, note that running Juno will not keep the program running by
    itself. You will need some condition to keep the program running, as
    demonstrated above.

AUTHORS
    *   Sawyer X <xsawyerx@cpan.org>

    *   Adam Balali <adamba@cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2012 by Sawyer X.

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

