Support for Heroku style REDIS_URL env variables

[iKlaus]

Being affected by the issue described in #302 I looked into what needs to be done to support Heroku's REDIS_URL environment variables. In short, they provide the credentials to a booked Redis addon via an environment variable which might change anytime at their discretion:

In order for Heroku to manage this add-on for you and respond to a variety of operational situations, the REDIS config vars may change at any time. Relying on the config var outside of your Heroku app may result in you having to re-copy the value if it changes.
-- https://devcenter.heroku.com/articles/heroku-redis#create-a-new-instance

Therefor I just wanted to be able to make use of the env() dynamic parameter notation as in

snc_redis:
    session:
        client: session
    clients:
        session:
            type:  predis
            alias: session
            dsn:  "%env(REDIS_URL)%"

I came up with a rather simple approach which basically boils down to:

• detect the specific syntax while the container compiles and bypass the validation on compilation
• assemble the service with the help of a Factory which parsed the url at runtime
• merge parsed url fragments with the rest of the connection options and then instantiates the Predis client as usual

[iKlaus]

So, fixed the tests and the code to comply with the projects extreme BC support :)

[pamil]

Just a friendly ping :)

[snc]

Merged this great PR, thanks for your work @iKlaus!

[nicholasruunu]

@snc Did you forget to tag this merge?

[snc]

@nicholasruunu No, I silently hope for some more feedback from successful uses ;-)

[nicholasruunu]

@snc We're currently using this in two apps now, although both are still on stage. Both using redis for sessions and nothing else.

[aurimasniekis]

This does not support phpredis

PHP Fatal error:  Uncaught Symfony\Component\Debug\Exception\UndefinedMethodException: Attempted to call an undefined method named "getSocket" of class "Snc\RedisBundle\DependencyInjection\Configuration\RedisEnvDsn". in /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/snc/redis-bundle/DependencyInjection/SncRedisExtension.php:277
Stack trace:
#0 /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/snc/redis-bundle/DependencyInjection/SncRedisExtension.php(108): Snc\RedisBundle\DependencyInjection\SncRedisExtension->loadPhpredisClient(Array, Object(Symfony\Component\DependencyInjection\ContainerBuilder))
#1 /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/snc/redis-bundle/DependencyInjection/SncRedisExtension.php(52): Snc\RedisBundle\DependencyInjection\SncRedisExtension->loadClient(Array, Object(Symfony\Component\DependencyInjection\ContainerBuilder))
#2 /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/symfony/dependency-injection/Compiler/MergeExtensionConfigurationPass.php(59): Snc\RedisBundle\DependencyInjection in /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/snc/redis-bundle/DependencyInjection/SncRedisExtension.php on line 277

Fatal error: Uncaught Symfony\Component\Debug\Exception\UndefinedMethodException: Attempted to call an undefined method named "getSocket" of class "Snc\RedisBundle\DependencyInjection\Configuration\RedisEnvDsn". in /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/snc/redis-bundle/DependencyInjection/SncRedisExtension.php on line 277

Symfony\Component\Debug\Exception\UndefinedMethodException: Attempted to call an undefined method named "getSocket" of class "Snc\RedisBundle\DependencyInjection\Configuration\RedisEnvDsn". in /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/snc/redis-bundle/DependencyInjection/SncRedisExtension.php on line 277

Call Stack:
    0.3484   12233472   1. Symfony\Component\Debug\ErrorHandler->handleException() /Users/aniekis/Projects/Work/Web/PHP/core-api/vendor/symfony/debug/ErrorHandler.php:0

There is half of getters missing on RedisEnvDsn compared to RedisDsn...

[snc]

#378 includes related changes, it would be nice if some of you can test their setups.

[aurimasniekis]

Sorry, but I am not using this anymore as it was causing problems back in the days...