Morpheus is a very flexible and powerful configuration module.

1. Morpheus
Ultimate configuration engine
http://github.com/druxa/morpheus

2. Evolution
my $xml = $ua->get(“http://api.example.com/get”);
This is trivial. And bad if your program is large enough.

3. Evolution
our $API_HOST = “api.example.com”;
...
my $xml = $ua->get(“http://$API_HOST/get”);
This is a little bit better, but still bad.

4. Evolution
my $conf = Config::General->new(“config_file”);
my $API_HOST = $conf->getall->{API_HOST};
...
my $xml = $ua->get(“http://$API_HOST/get”);
This version is as far as most coders would go.

5. The end?
Who needs “ultimate configuration engine”, really...

6. Only just beginning
$conf = Config::General->new(“config_file”);
Where is this file located?

7. Which one to choose?
$config_file = “./config”;
$config_file = “/etc/my-app/config”;
$config_file = “$ENV{CONFIG_PATH}/config”;
Who configurates the configurator? And is one config file really enough?

8. Real-world examples
Everyone reinvents configuration from scratch.

9. Example: git
• ~/.gitconfig + .git/config
• ini-style configs
• git config --list
• GIT_CONFIG env variable

10. Example: lighttpd
• /etc/lighttpd/conf-enabled/*
• include “config_file”
• include_shell “config_generator.sh”

11. Example: syslog-ng
• one monolythic file
Our system administrators had to write config generation scripts to deal
with this.

12. Enough!
We want to:
• separate config providers from consumers
completely
• fill config values from any sources we like
• make this mechanism extensible

13. Layers
Your code
Consumer APIs
Morpheus
Provider APIs
Users

14. Layers
Consumer APIs
Morpheus
Provider APIs

15. Configuration tree
All configuration values for every program live in
one global and dynamic configuration tree.
You can think of this tree as:
• file system
• hashref with lots of nested hashrefs inside
• Windows registry (but not really)

16. Configuration tree
• dynamic - can return different results from
different points of view
• assembled from various sources
• can contain any scalars as values: coderefs,
objects, etc.

17. Layers
Consumer APIs
Morpheus
Provider APIs
“Consumer” is a code which needs some configuration values.
It should never care where these values come from.

18. Consumers
Consumer APIs
/usr/bin/morph use Morpheus defaults
Morpheus
Provider APIs
There are many ways to obtain configuration.

19. use Morpheus
use Morpheus;
$API_HOST = morph(“/MyApp/api_host”);
We’ll explain later how Morpheus can be configured to return the right value.

20. Imports
use Morpheus “/MyApp” => [
‘$api_host’
];

21. Imports
use Morpheus “/MyApp” => [
api_host => ‘$API_HOST’,
];

22. Complex imports
use Morpheus "/foo/bar" => [
qw($V1 $V2 $V3),
"v5" => '$V5', "v6/a" => '$A',
"v7" => [ '$C', '$D', "e" => '$E' ],
];

23. /usr/bin/morph
$ morph /MyApp
{
"api_host" : "api.example.com",
"rate_limit" : 1000
}
If you didn’t recognize, this is JSON.

24. /usr/bin/morph
$ morph --format=xml /MyApp
<opt>
<api_host>api.example.com</api_host>
<rate_limit>1000</rate_limit>
</opt>

25. /usr/bin/morph
$ morph --format=tt2 --template=my.tt /MyApp
< ... any config format you like ... >
There is also --format=dumper, but I won’t waste another slide on it.

26. Setting defaults
use Morpheus -defaults => {
‘/MyApp’ => {
api_host => ‘api.example.com’,
},
};
This is the first example of *providing* config values.
Now you can use Morpheus instead of ‘use constant’ everywhere!

27. Layers
Consumer APIs
Morpheus
Provider APIs
All values are provided by plugins.

28. Providers
Consumer APIs
Morpheus
Provider APIs
Bootstrap plugins
Runtime plugins
User APIs
Don’t panic!

29. Providers
You’ll only need these 99% of the time
Provider APIs
Bootstrap plugins
Runtime plugins
User APIs
At least this will be the case when Morpheus will be mature enough...

30. Plugins
• API: ‘list’ and ‘get’
• but not as trivial as you expect
• we need more plugins for more config formats

31. Bootstrap
Bootstrap is a technique for configuring Morpheus
using Morpheus itself.
Bootstrap plugins fill /morpheus/plugins
namespace with runtime plugins.
Bootstrap sets plugin priority order.

32. Our setup
These are plugins we currently use:
Env > DB > File > Defaults

33. Morpheus::Plugin::Env
$ MORPHEUS=‘foo => { bar => 5 }’ morph /foo
{
"bar" : 5
}
Yes, $ENV{MORPHEUS} contains perl code.

34. Morpheus::Plugin::DB
mysql> SELECT * FROM Morpheus;
+----------------------+-----------+
| Name | Config |
+----------------------+-----------+
| /foo/bar |5 |
+----------------------+-----------+
Config column contains perl code too!

35. Morpheus::Plugin::File
$ cat /etc/foo.cfg
$bar = 5;
We load configs from [qw( ./etc /etc )].
This path is configurable via /morpheus/plugin/file/options/path

36. Perl configs
$ cat /etc/MyApp.cfg
$API = {
host => ‘api.example.com’,
};
$ cat /etc/MyApp/API.cfg
$host = ‘api.example.com’;
$ cat /etc/MyApp/API/host.cfg
‘api.example.com’
These are all the same.

37. Perl configs
$ cat /etc/foo.cfg
use Morpheus;
$bar = morph(‘/foo/bar’) + 1;
Recursive morph calls work. Unless you’ll introduce dependency loop, of course.

38. Perl configs
$ cat /etc/MyApp.cfg
use Morpheus;
my $environment = morph(“/environment”);
if ($environment eq ‘development’) {
$api_host = “api-dev.example.com”;
}
else {
$api_host = “api.example.com”;
}
Don’t be alarmed. Having this feature available doesn’t mean you have to use it.

39. Perl configs
$ cat /etc/MyApp.cfg
$API = {
host => ‘api.example.com’,
port => 1234,
rate_limit => 100,
};
$ cat /etc/MyApp.99.cfg
use Morpheus;
$API = { rate_limit =>
morph(“/MyApp/API/rate_limit”) * 10 };
‘99’ is a priority. Default priority is zero.

40. Perl configs
$ morph /MyApp
{
"API" : {
"rate_limit" : 1000,
"port" : 1234,
"host" : "api.example.com"
}
}
Morphed!

41. Future directions
• MooseX::Morpheus
• customizible merging policies
• customazible caching policies
• meta-information layer

42. Future directions
But most important, we need community help.
Because we need tons of plugins for compatibility
with existing modules:
Config::General, Config::INI, Config::JSON, etc.

43. Contacts
http://search.cpan.org/dist/Morpheus
http://github.com/druxa/morpheus
morpheus-perl@googlegroups.com
irc://irc.perl.org#morpheus