[WIP][RFC] Fastly support

[hpatoio]

Adding Fastly support. At the moment only tag invalidation. Goes with FriendsOfSymfony/FOSHttpCache#403

[dbu]

will need to be updated once FriendsOfSymfony/FOSHttpCache#451 is wrapped up

[andrerom]

+1

Besides the composer change suggested, and a rebase, anything else needed here @dbu?

[dbu]

uh, i completely forgot to look at this again after fastly support was merged into FOSHttpCache

this looks good, i think there are some things to be removed.

and can you please add a test to ConfigurationTest? testSupportsFastly, similar to testSupportsVarnish and the others.

[dbu]

if not specified, we use a default client, right? i notice that we do not have this option for the other caching systems like varnish, why do we need it for fastly?

[dbu]

imho we should have this as default value in the configuration. maybe some people have an experimental fastly api, or a test system with fastly or something... it feels bad to have this as a string in here.

[dbu]

why do we create the definition for the dispatcher in PHP and not in the service configuration file? we could set the 3 parameters as container parameters instead, that would be more consistent with the other services.

[dbu]

i don't think a FastlyProxy class exists.

we use this pattern to start a varnish / nginx instance during testing. i don't think we can do that for fastly.

can we remove this config file and the DI method that loads it?

[andrerom]

@hpatoio You ok with doing the fix-ups or would you like us to take over on it?

[proeinfo]

To allow tag support, fastly also needs to be included here:

FOSHttpCacheBundle/src/DependencyInjection/FOSHttpCacheExtension.php

Line 454 in 4d8e632

if (!in_array($client, ['varnish', 'symfony', 'custom', 'noop'])) {

and with changes in Master, included here to disregard http.servers: https://github.com/FriendsOfSymfony/FOSHttpCacheBundle/blob/master/src/DependencyInjection/Configuration.php#L492

[proeinfo]

typo

[andrerom]

Hi @proeinfo

So did you try this as well? Would be great if that is the case.
Either way, would you be able to use the github suggest feature to suggest fixes to the two things you point out here?

[proeinfo]

Hi @andrerom

I'm working on getting this to work, will post patch once that happens.

[proeinfo]

An additional issue: since Fastly doesn't use proxy servers for invalidating, the HttpDispatcher's approach of running through proxy servers (done in the fanOut() method) won't work.

A simple solution is to make a copy of the HttpDispatcher class and remove any mentions of servers and baseUris.

Attached example of such a class.
FastlyDispatcher.txt

This would just require that the Fastly proxy client is instantiated with the FastlyDispatcher instead:

$some_example_tags = [
  'product1',
  'product2',
];
$httpDispatcher = new \FOS\HttpCache\ProxyClient\FastlyDispatcher();
$options = [
    'service_identifier' => '...',
    'authentication_token' => '...',
    'soft_purge' => true,
];
$fastly = new \FOS\HttpCache\ProxyClient\Fastly($httpDispatcher, $options);
$cacheInvalidator = new \FOS\HttpCache\CacheInvalidator($fastly);
$cacheInvalidator->invalidateTags($some_example_tags)->flush();

[proeinfo]

Additionally, since Fastly uses space separated surrogate keys, the default comma-separated tag header formatter won't work.
Again it may make sense to create a new class for Fastly.

Example implementation:

<?php

namespace FOS\HttpCache\TagHeaderFormatter;

class FastlyTagHeaderFormatter implements TagHeaderFormatter
{
    const FASTLY_TAG_HEADER = 'Surrogate-Key';
    const FASTLY_TAG_HEADER_GLUE = ' ';

    /**
     * @var string
     */
    private $headerName = self::FASTLY_TAG_HEADER;

    /**
     * @var string
     */
    private $glue = self::FASTLY_TAG_HEADER_GLUE;

    /**
     * {@inheritdoc}
     */
    public function getTagsHeaderName()
    {
        return $this->headerName;
    }

    /**
     * {@inheritdoc}
     */
    public function getTagsHeaderValue(array $tags)
    {
        return implode($this->glue, $tags);
    }
}

From there its a simple matter of overriding the service id in the user Symfony application:

services:
    fos_http_cache.tag_handler.header_formatter:
        class: FOS\HttpCache\TagHeaderFormatter\FastlyTagHeaderFormatter