just a wild guess: could it be that you are hit by #351? though symfony/symfony#21582 is supposedly in 3.2.5. so unless you ended up with an older version of symfony/symfony this should be fixed...

i suggest you add additional logging in the symfony kernel to see whether the request really is received and works out. try to send an invalidation request with the command line curl to isolate whether the problem is in the application not sending the request or the kernel not correctly handling it. or could the request go to the wrong server/port somehow?

Hm, still not sure what's happening. Same behaviour from command line. Requests are going to the right server. I'm on the Symfony 3.2.6.

i suggest you add additional logging in the symfony kernel to see whether the request really is received and works out.

Don't know how to log that.

My feeling that it might be my config issue, but not sure where to look.
I've managed to get invalidatePath() to work, by adding invalidate() to AppCache.php from Symfony docs(see below). refreshPath() still does not refresh the cache. It used to work for me with FOSHttpCacheBundle 1.* , Symfony 2.* , FOSRestBundle 1.* , PHP 5.6. But after the major dependency updates, it just stopped.

<?php

require_once __DIR__ . '/AppKernel.php';

use FOS\HttpCache\SymfonyCache\CacheInvalidation;
use FOS\HttpCache\SymfonyCache\EventDispatchingHttpCache;
use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

class AppCache extends HttpCache implements CacheInvalidation {
	use EventDispatchingHttpCache;

	/**
	 * Made public to allow event listeners to do refresh operations.
	 *
	 * {@inheritDoc}
	 */
	public function fetch(Request $request, $catch = false) {
		return parent::fetch($request, $catch);
	}

	protected function invalidate(Request $request, $catch = false) {
		if ('PURGE' !== $request->getMethod()) {
			return parent::invalidate($request, $catch);
		}

		$response = new Response();
		if ($this->getStore()->purge($request->getUri())) {
			$response->setStatusCode(200, 'Purged');
		} else {
			$response->setStatusCode(404, 'Not found');
		}

		return $response;
	}
}

are you adding the necessary event listeners? https://github.com/FriendsOfSymfony/FOSHttpCache/blob/master/tests/Functional/Fixtures/Symfony/AppCache.php

i fear that the documentation on the bundle could be outdated for this...

I've just added the listeners, but still this call $this->get('fos_http_cache.cache_manager')->refreshPath('/api/post/xyz')->flush() does not update the cache, though I can see that Guzzle does do the GET request to example.dev/api/post/xyz.

<?php

require_once __DIR__ . '/AppKernel.php';

use FOS\HttpCache\SymfonyCache\CacheInvalidation;
use FOS\HttpCache\SymfonyCache\DebugListener;
use FOS\HttpCache\SymfonyCache\EventDispatchingHttpCache;
use FOS\HttpCache\SymfonyCache\RefreshListener;
use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

class AppCache extends HttpCache implements CacheInvalidation {
	use EventDispatchingHttpCache;

	public function __construct(HttpKernelInterface $kernel) {

		parent::__construct($kernel, $kernel->getCacheDir() . '/http_cache', null, null);

		$this->addSubscriber(new RefreshListener());
		
		if (isset($options['debug']) && $options['debug']) {
			$this->addSubscriber(new DebugListener());
		}
	}

	/**
	 * Made public to allow event listeners to do refresh operations.
	 *
	 * {@inheritDoc}
	 */
	public function fetch(Request $request, $catch = false) {
		return parent::fetch($request, $catch);
	}
}

do you see the request arriving at the webserver? you could either build something into the AppCache (or the plugin from us) to write log messages to a tmp file or whatever, just so you see if it happens. also, try to do a curl request with a refresh to see if the problem is in the cache or in sending the invalidation request. i can't debug that for you.

btw, if you run the php built-in webserver and invalidate from a web request, there will be problems (usually a timeout) because the built-in webserver is single threaded.