Symfony2: You have requested a non-existent parameter

Question

I have checked similar questions on SO, but they did not solve my issue.

I am deploying a Symfony2 application on Openshift. It works well on my Windows 10 laptop, but I am getting the following error message on Openshift:

Fatal error: Uncaught exception 'Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException'
with message 'You have requested a non-existent parameter "database_path".
Did you mean one of these: "database_host", "database_port", "database_name", "database_user"?'
in /var/lib/openshift/55eed4837628e1199f0000bb/app-root/runtime/repo/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/ParameterBag/ParameterBag.php:106 Stack trace: #0 
/var/lib/openshift/55eed4837628e1199f0000bb/app-root/runtime/repo/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/ParameterBag/ParameterBag.php(248):
Symfony\Component\DependencyInjection\ParameterBag\ParameterBag->get('database_path') #1 [internal function]:
Symfony\Component\DependencyInjection\ParameterBag\ParameterBag->Symfony\Component\DependencyInjection\ParameterBag\{closure}(Array) #2
/var/lib/openshift/55eed4837628e1199f0000bb/app-root/runtime/repo/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/ParameterBag/ParameterBag.php in
/var/lib/openshift/55eed4837628e1199f0000bb/app-root/runtime/repo/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/ParameterBag/ParameterBag.php on line 106

My config.yml is:

imports:
    - { resource: parameters.yml }
    - { resource: security.yml }
    - { resource: services.yml }
...

doctrine:
    dbal:
        driver:   pdo_sqlite
        charset:  UTF8
        path:     "%kernel.root_dir%/../%database_path%"
...

My parameters.yml is:

parameters:
    database_driver: pdo_sqlite
    database_host: localhost
    database_port: null
    database_name: demo.db
    database_user: root
    database_password: null
    database_path: /data/demo.db
    ...

and my config_prod.yml is:

imports:
    - { resource: config.yml }
...

What am I doing wrong?

Update

I have changed my config.yml to:

path:     "%kernel.root_dir%/../data/demo.db"

and the issue is gone, but I don't know why!

Answer 1

This is a common mistake.

Just like I have commented above:
When running composer install, symfony will regenerate a new parameters.yml file based on parameters.yml.dist (if any).
So it's a good idea always check if parameters.yml generated by symfony (on post install event, composer) is okay.

Also:

Whenever you update the parameters.yml file (with configs that should be in the prod server also well), you must update the file parameters.yml.dist too.

So the deployment process will be much less painful.