NAME
Juno - Asynchronous event-driven checking mechanism
VERSION
version 0.010
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.