Added a new article about applications with multiple kernels #6840

javiereguiluz · 2016-08-03T15:33:06Z

This fixes #997 (opened in January 2012 !!!).

I don't know which is the best location for this article (probably not request/)
When merging up, in the 2.8 branch the following must be added:

At the end of Step 2), add this:

In order to make this class available in the front controller, don't forget to
add it to the ``classmap`` configuration of the ``composer.json`` file:

.. code-block:: json

    {
        "autoload": {
            "psr-4": { "": "src/" },
            "classmap": ["app/AppKernel.php", "app/ApiKernel.php"]
        },
        ...
    }

At the end of the article, add this:

.. tip:

    Symfony 2.8 introduced a `new micro kernel`_ PHP trait that simplifies the
    creation of kernels. You can even define them in a single PHP file.

.. _`new micro kernel`: http://symfony.com/blog/new-in-symfony-2-8-symfony-as-a-microframework

yceruto · 2016-08-03T19:51:07Z

request/multiple_kernels.rst

+
+    // web/api.php
+    // ...
+    $kernel = new ApiKernel('prod', true);


I guess the second parameter "debug" must be false here ?

You guessed right. Fixed. Thanks.

yceruto · 2016-08-03T19:56:37Z

request/multiple_kernels.rst

+the ``app/config/api/`` directory.
+
+The new configuration can be created from scratch when you load just a few
+bundles, because it it will be very simple. Otherwise, duplicate the existing


typo "it it" ?

yceruto · 2016-08-03T20:01:54Z

@javiereguiluz very nice article, thank!

ogizanagi · 2016-08-03T22:57:31Z

I wonder if we shouldn't explain more the differences between kernel environments & using multiple kernels ? Because I know it can be confusing, especially for newcomers.

Especially as you state:

This is useful to execute the same application using a different configuration

But multiple kernels are not meant to execute the very same application with a different configuration. That's pretty much what kernel environments are for.

Different kernels are meant to execute different parts of a whole that can eventually be called "the application". It is true it doesn't often share much configuration, but what is important is that it's not the same part of the application at all. And thus, won't share the same components/bundles usage, nor sometimes some part of the business code, and above all not the same infrastructure stuff.

javiereguiluz · 2016-08-04T07:44:32Z

@ogizanagi I completely agree with you. I've refactored the "use cases" section. Thanks!

ogizanagi · 2016-08-04T09:22:28Z

request/multiple_kernels.rst

+  only load the routes that match the parts of the application exposed to the
+  public. The second kernel would load the rest of the application and its
+  access would be protected by the web server;
+* An application that uses a bundle which doesn't allow multiple instances could


I'm not sure about this one.
It is presented as a solution to bundles registering a single service instead of allowing the creation of multiple instances through configuration. But creating new kernels has way too much impact to be considered for this use-case.
Once again, a kernel environment is probably more appropriate to define a different bundle configuration. But anyway, none of the 2 solutions would allow to make the different bundle configurations cohabit within the very same request. In my opinion, the sentence is misleading regarding this 😕.
The only solution for this use case is to not use the bundle/bundle configuration, and register services yourself.

OK. I'm probably going to remove this use case. I added because the other day one person asked me if EasyAdmin supported defining two different backends in the same app. The bundle itself doesn't support that ... but with this multi-kernel trick, everything is easily solved.

Can anyone think of other use cases or do we just leave the first two proposed ones? Thanks.

What about micro-services oriented apps ? You can split your services in multiple optimized modules, allowing to enable/disable a group of micro services on a server instance, by simply exposing or not a kernel instance.
It avoids dealing with multiple git repositories and allow to share code/configuration more easily.
However, it's very close to the mentioned API use-case, but with more advanced partitioning.

That's nice! I've added that use case. Thanks.

Maybe the most common use case is the front-end/back-end sceneries, a big e-commerce application, for example ?

javiereguiluz · 2016-10-04T11:04:30Z

Lately I've been playing with multi-kernel apps, so I've just added a section which may be important: running commands using different kernels. I think this is ready for the final review. Thanks!

stof · 2016-10-12T15:33:46Z

request/multiple_kernels.rst

+
+    // web/api.php
+    // ...
+    $kernel = new ApiKernel('prod', false);


if you don't put a require call to load the file defining it, you already need to show the update of the autoload config

weaverryan · 2016-10-25T15:46:02Z

request/multiple_kernels.rst

@@ -0,0 +1,183 @@
+.. index::


Maybe this should be in the configuration/ directory?

weaverryan · 2016-10-25T15:50:58Z

request/multiple_kernels.rst

+
+Creating a new kernel in a Symfony application is a three-step process:
+
+1. Create a new front controller to load the new kernel;


There is another way to do this (which is done on a BIG Symfony site I know of): keeping app.php and app_dev.php and using some URL matching to load different kernels. For example, if the URL starts with /admin, then load the AdminKernel, else AppKernel. I think it's worth mentioning both. So, what about:

A) Making step (1) actually step (3) (I think creating the kernel and hooking up the configuration makes sense to have first, then finally show how you can instantiate the now-created kernel)

B) Rename this step to Step 3) Executing the kernel from a front controller

C) Mention the if statement approach above (it could be mentioned first or second).

weaverryan · 2016-10-25T15:52:31Z

request/multiple_kernels.rst

+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Instead of creating the new front controller from scratch, it's recommended to
+duplicate the existing ones. For example, create ``web/api_dev.php`` from


.> ... from scratch, it's easier to duplicate the existing ones

(it just sounds a bit more relaxed)

weaverryan · 2016-10-25T15:52:59Z

request/multiple_kernels.rst

+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Now you need to define the ``ApiKernel`` class used by the new front controller.
+The recommendation again is to duplicate the existing ``app/AppKernel.php`` file


The easiest way to do this is by duplicating the existing...

weaverryan · 2016-10-25T15:54:06Z

request/multiple_kernels.rst

+The recommendation again is to duplicate the existing ``app/AppKernel.php`` file
+and make the needed changes.
+
+In this example, the changes of the new ``ApiKernel`` would be to load less


In this example, the ApiKernel will load less bundles than AppKernel. Be sure to also change
the location of the cache, logs and config files so they don't collide with the files
from AppKernel

weaverryan · 2016-10-25T15:54:59Z

request/multiple_kernels.rst

+config files to not mess with the regular application::
+
+    // app/ApiKernel.php
+    <?php


We usually don't have the <?php. If you do want it for some specific reason, the filename should probably be moved inside of it, so that the comment is in PHP. But probably, we should just remove <?php

weaverryan · 2016-10-25T15:55:53Z

request/multiple_kernels.rst

+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Finally, define the configuration used by the application when it executes the
+new API kernel. According to the previous code, this config must be defined in


Finally, define the configuration files that the new ApiKernel will load. According to the
above code, this config will live in the...

weaverryan · 2016-10-25T15:57:38Z

request/multiple_kernels.rst

+        - { resource: ../config_dev.yml }
+
+    # override option values ...
+


Another option is to share some configuration files, especially if both kernels use some of the same bundles that you want configured in the same ways. I'm haven't done this enough to settle on the best organization for this... but we could at least mention it. Perhaps a app/config/shared.yml file where we show just a little bit of config and mention how you could import this from the config.yml file of both kernels.

weaverryan · 2016-10-25T15:58:24Z

request/multiple_kernels.rst

+
+Then, replace the ``AppKernel`` instantiation by your own kernel instantiation
+(e.g. ``ApiKernel``) and now you can execute commands using the new kernel
+(e.g. ``php bin/api cache:clear``) Now you can use execute commands using the new kernel


Extra:

Now you can use execute commands using the new kernel

and missing . at the end

weaverryan · 2016-10-25T15:59:20Z

request/multiple_kernels.rst

+--------------------------------------
+
+If your application is very complex and you create several kernels, it's better
+to store them on their own directories instead of messing with lots of files in


store them in their...

weaverryan · 2016-10-25T16:01:25Z

This is really solid! 👍 from me if the changes are made.

Status: Needs Work

…rnels (javiereguiluz) This PR was merged into the 2.7 branch. Discussion ---------- Added a new article about applications with multiple kernels This fixes #997 (opened in January 2012 !!!). --- 1) I don't know which is the best location for this article (probably not `request/`) 2) When merging up, in the 2.8 branch the following must be added: At the end of `Step 2)`, add this: ``` rst In order to make this class available in the front controller, don't forget to add it to the ``classmap`` configuration of the ``composer.json`` file: .. code-block:: json { "autoload": { "psr-4": { "": "src/" }, "classmap": ["app/AppKernel.php", "app/ApiKernel.php"] }, ... } ``` At the end of the article, add this: ``` rst .. tip: Symfony 2.8 introduced a `new micro kernel`_ PHP trait that simplifies the creation of kernels. You can even define them in a single PHP file. .. _`new micro kernel`: http://symfony.com/blog/new-in-symfony-2-8-symfony-as-a-microframework ``` Commits ------- bc3618d Made a bunch of fixes recommended by Ryan 2613810 Added a note about rendering templates from different kernels e403fd8 Added a new section about running commands under a different kernel af4ff18 Added a new use case related to micro-services 2c5aeb1 Removed a use case 097a73d Reworded the use cases section 5c8ed87 Fixed typo d45e1f4 Fixed an example code a23d82d Fixed another syntax issue 21329ec Fixed some syntax issues 7cb2aa1 Added a new article about applications with multiple kernels

weaverryan · 2016-12-15T00:11:00Z

It's merged! Woohoo!

* 2.7: (22 commits) [#6894] Adding link to Doctrine [#6857] Re-wording the section a bit [#6840] Adding note based on Stof's feedback Moving file - I think configuration is more appropriate Revert "Updated the contents for the new Symfony 3 dir structure" Updated the contents for the new Symfony 3 dir structure Remove "Symfony3 will use" Using lower case on "Form" Made a bunch of fixes recommended by Ryan Added a note about rendering templates from different kernels Added a new section about running commands under a different kernel Integrated improvement by javiereguiluz Explain what happens if `flush()` fails Update events.rst Added a new use case related to micro-services Removed a use case Reworded the use cases section Fixed typo Fixed an example code Fixed another syntax issue ...

* 2.8: (22 commits) [#6894] Adding link to Doctrine [#6857] Re-wording the section a bit [#6840] Adding note based on Stof's feedback Moving file - I think configuration is more appropriate Revert "Updated the contents for the new Symfony 3 dir structure" Updated the contents for the new Symfony 3 dir structure Remove "Symfony3 will use" Using lower case on "Form" Made a bunch of fixes recommended by Ryan Added a note about rendering templates from different kernels Added a new section about running commands under a different kernel Integrated improvement by javiereguiluz Explain what happens if `flush()` fails Update events.rst Added a new use case related to micro-services Removed a use case Reworded the use cases section Fixed typo Fixed an example code Fixed another syntax issue ...

* 3.1: (25 commits) [#6894] Adding link to Doctrine [#6857] Re-wording the section a bit [#6840] Adding note based on Stof's feedback Moving file - I think configuration is more appropriate Revert "Updated the contents for the new Symfony 3 dir structure" Updated the contents for the new Symfony 3 dir structure Remove "Symfony3 will use" Using lower case on "Form" Make lines shorter to comply with our soft limit of 80 chars per line Made a bunch of fixes recommended by Ryan Added a note about rendering templates from different kernels Fix comments [Serializer] Docs for the @MaxDepth annotation Added a new section about running commands under a different kernel Integrated improvement by javiereguiluz Explain what happens if `flush()` fails Update events.rst Added a new use case related to micro-services Removed a use case Reworded the use cases section ...

* 3.2: (26 commits) [#6894] Adding link to Doctrine [#6857] Re-wording the section a bit [#6840] Adding note based on Stof's feedback Moving file - I think configuration is more appropriate Revert "Updated the contents for the new Symfony 3 dir structure" Updated the contents for the new Symfony 3 dir structure Remove "Symfony3 will use" Using lower case on "Form" Added a mention to sameSite cookie option Make lines shorter to comply with our soft limit of 80 chars per line Made a bunch of fixes recommended by Ryan Added a note about rendering templates from different kernels Fix comments [Serializer] Docs for the @MaxDepth annotation Added a new section about running commands under a different kernel Integrated improvement by javiereguiluz Explain what happens if `flush()` fails Update events.rst Added a new use case related to micro-services Removed a use case ...

Added a new article about applications with multiple kernels

7cb2aa1

carsonbot added the Status: Needs Review label Aug 3, 2016

javiereguiluz added 2 commits August 3, 2016 17:38

Fixed some syntax issues

21329ec

Fixed another syntax issue

a23d82d

yceruto reviewed Aug 3, 2016
View reviewed changes

Fixed an example code

d45e1f4

yceruto reviewed Aug 3, 2016
View reviewed changes

Fixed typo

5c8ed87

Reworded the use cases section

097a73d

ogizanagi reviewed Aug 4, 2016
View reviewed changes

javiereguiluz added 3 commits August 4, 2016 20:19

Removed a use case

2c5aeb1

Added a new use case related to micro-services

af4ff18

Added a new section about running commands under a different kernel

e403fd8

Added a note about rendering templates from different kernels

2613810

stof reviewed Oct 12, 2016

View reviewed changes

weaverryan reviewed Oct 25, 2016

View reviewed changes

carsonbot added Status: Needs Work Status: Needs Review and removed Status: Needs Review Status: Needs Work labels Oct 25, 2016

Made a bunch of fixes recommended by Ryan

bc3618d

weaverryan merged commit bc3618d into symfony:2.7 Dec 15, 2016

weaverryan added a commit that referenced this pull request Dec 15, 2016

[#6840] Adding note based on Stof's feedback

fd3b1d7

javiereguiluz deleted the multiple_kernels branch May 24, 2018 16:04

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weaverryan commented Dec 15, 2016


		Creating a new kernel in a Symfony application is a three-step process:

		1. Create a new front controller to load the new kernel;

		- { resource: ../config_dev.yml }

		# override option values ...

Added a new article about applications with multiple kernels #6840

Added a new article about applications with multiple kernels #6840

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