EZP-30562: Make it possible to ignore tags over configurable max length

docs/using_tags.md

@@ -238,12 +238,21 @@ code involved to see if amount of tags can be reduced.
 
 #### Limit tags header output by system
 
-Typical case with too many tags would be when inline rendering some form of embed content object.
+Typical case with too many tags would be when inline rendering a lot of embed content object.
 Normally the system will add all the tags for this content, to handle every possible scenario of updates to them.
 
-So if you embed hundreds of content on the same page _(in richtext, using relations, or using page builder)_, it will explode the tag usage.
+So if you embed hundreds of content on the same page _(i.e. in richtext, using relations, or using page builder)_, it will explode the tag usage.
 
 However if for instance you just display the content name, image attribute, and/or link, then it would be enough to:
 - Just use `r<id>` tag, or preferably the abstractions for it.
 - Optionally: Set reduced cache TTL for the given view in order to reduce remote risk of subtree operations affecting the cached page
   without correctly purging the view.
+
+If that is not an option, you can opt-in to set a max length parameter (in bytes) and corresponding ttl (in seconds):
+```yaml
+parameters:
+    # Warning, setting this means you risk losing tag information, risking stale cache. Here set below 8k:
+    ezplatform.http_cache.tags.header_max_length: 7900
+    # In order to reduce risk of stale cache issues, you should set a lower TTL here then globally (here set as 2h)
+    ezplatform.http_cache.tags.header_reduced_ttl: 7200
+```

spec/Handler/TagHandlerSpec.php

@@ -11,6 +11,7 @@
 use FOS\HttpCacheBundle\CacheManager;
 use PhpSpec\ObjectBehavior;
 use Prophecy\Argument;
+use Psr\Log\LoggerInterface;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpFoundation\ResponseHeaderBag;
 
@@ -21,12 +22,15 @@ public function let(
         PurgeClientInterface $purgeClient,
         Response $response,
         ResponseHeaderBag $responseHeaderBag,
-        RepositoryTagPrefix $tagPrefix
+        RepositoryTagPrefix $tagPrefix,
+        LoggerInterface $logger
     ) {
         $response->headers = $responseHeaderBag;
         $cacheManager->supports(CacheManager::INVALIDATE)->willReturn(true);
 
-        $this->beConstructedWith($cacheManager, 'xkey', $purgeClient, $tagPrefix);
+        $this->beConstructedWith($cacheManager, 'xkey', $purgeClient, $tagPrefix, $logger, 1000, 300);
+
+        $tagPrefix->getRepositoryPrefix()->willReturn('');
     }
 
     public function it_calls_purge_on_invalidate()
@@ -98,7 +102,7 @@ public function it_tags_all_tags_we_add(Response $response, ResponseHeaderBag $r
     public function it_tags_all_tags_we_add_and_prefix_with_repo_id(Response $response, ResponseHeaderBag $responseHeaderBag, RepositoryTagPrefix $tagPrefix)
     {
         $tagPrefix->getRepositoryPrefix()->willReturn('0');
-        $responseHeaderBag->set('xkey', Argument::exact('0ez-all 0l4 0c4 0p2 ez-all'))->shouldBeCalled();
+        $responseHeaderBag->set('xkey', Argument::exact('ez-all 0ez-all 0l4 0c4 0p2'))->shouldBeCalled();
 
         $this->addTags(['l4', 'c4']);
         $this->addTags(['p2']);
@@ -110,10 +114,55 @@ public function it_tags_all_tags_we_add_and_prefix_with_repo_id_also_with_existi
         $tagPrefix->getRepositoryPrefix()->willReturn('2');
         $responseHeaderBag->has('xkey')->willReturn(true);
         $responseHeaderBag->get('xkey', null, false)->willReturn(['tag1']);
-        $responseHeaderBag->set('xkey', Argument::exact('2tag1 2ez-all 2l4 2c4 2p2 ez-all'))->shouldBeCalled();
+        $responseHeaderBag->set('xkey', Argument::exact('ez-all 2tag1 2ez-all 2l4 2c4 2p2'))->shouldBeCalled();
 
         $this->addTags(['l4', 'c4']);
         $this->addTags(['p2']);
         $this->tagResponse($response, false);
     }
+
+    public function it_ignores_too_long_tag_header(Response $response, ResponseHeaderBag $responseHeaderBag, LoggerInterface $logger)
+    {
+        $underLimitTags = 'ez-all';
+        $length = 6;
+        while(true) {
+            $tag = ' c' . $length;
+            $tagLength = strlen($tag);
+            if ($length + $tagLength  > 1000) {
+                break; // too long if we add more
+            }
+            $underLimitTags .= $tag;
+            $length += $tagLength;
+        }
+        $responseHeaderBag->getCacheControlDirective('s-maxage')->shouldBeCalled()->willReturn(200);
+        $response->setSharedMaxAge(300)->shouldNotBeCalled();
+        $logger->warning(Argument::containingString('HTTP Cache tags header max length reached and truncated to'))->shouldBeCalled();
+        $responseHeaderBag->set('xkey', Argument::exact($underLimitTags))->shouldBeCalled();
+
+        $this->addTags(explode(' ', $underLimitTags));
+        $this->addTags(['l1111111', 'c1111111']); // these tags are ignored
+        $this->tagResponse($response, true);
+    }
+
+    public function it_ignores_too_long_tag_header_and_reduces_ttl(Response $response, ResponseHeaderBag $responseHeaderBag)
+    {
+        $underLimitTags = 'ez-all';
+        $length = 6;
+        while(true) {
+            $tag = ' c' . $length;
+            $tagLength = strlen($tag);
+            if ($length + $tagLength  > 1000) {
+                break; // too long if we add more
+            }
+            $underLimitTags .= $tag;
+            $length += $tagLength;
+        }
+        $responseHeaderBag->getCacheControlDirective('s-maxage')->shouldBeCalled()->willReturn(500);
+        $response->setSharedMaxAge(300)->shouldBeCalled();
+        $responseHeaderBag->set('xkey', Argument::exact($underLimitTags))->shouldBeCalled();
+
+        $this->addTags(explode(' ', $underLimitTags));
+        $this->addTags(['l1111111', 'c1111111']); // these tags are ignored
+        $this->tagResponse($response, true);
+    }
 }

src/Handler/TagHandler.php

@@ -9,6 +9,7 @@
 use EzSystems\PlatformHttpCacheBundle\PurgeClient\PurgeClientInterface;
 use EzSystems\PlatformHttpCacheBundle\RepositoryTagPrefix;
 use FOS\HttpCacheBundle\Handler\TagHandler as FOSTagHandler;
+use Psr\Log\LoggerInterface;
 use Symfony\Component\HttpFoundation\Response;
 use FOS\HttpCacheBundle\CacheManager;
 
@@ -26,15 +27,30 @@ class TagHandler extends FOSTagHandler implements ContentTagInterface
     private $prefixService;
     private $tagsHeader;
 
+    /** @var \Psr\Log\LoggerInterface */
+    private $logger;
+
+    /** @var int|null */
+    private $tagsHeaderMaxLength;
+
+    /** @var int|null */
+    private $tagsHeaderReducedTTl;
+
     public function __construct(
         CacheManager $cacheManager,
         $tagsHeader,
         PurgeClientInterface $purgeClient,
-        RepositoryTagPrefix $prefixService
+        RepositoryTagPrefix $prefixService,
+        LoggerInterface $logger,
+        $maxTagsHeaderLength = null,
+        $tagsHeaderReducedTTl = null
     ) {
         $this->tagsHeader = $tagsHeader;
         $this->purgeClient = $purgeClient;
         $this->prefixService = $prefixService;
+        $this->logger = $logger;
+        $this->tagsHeaderMaxLength = $maxTagsHeaderLength;
+        $this->tagsHeaderReducedTTl = $tagsHeaderReducedTTl;
 
         parent::__construct($cacheManager, $tagsHeader);
         $this->addTags(['ez-all']);
@@ -88,10 +104,37 @@ static function ($tag) use ($repoPrefix) {
                 },
                 $tags
             );
-            // Also add a un-prefixed `ez-all` in order to be able to purge all across repos
-            $tags[] = 'ez-all';
 
-            $response->headers->set($this->tagsHeader, implode(' ', array_unique($tags)));
+            if ($repoPrefix !== '') {
+                // An un-prefixed `ez-all` for purging across repos, add to start of array to avoid being truncated
+                array_unshift($tags, 'ez-all');
+            }
+
+            $tagsString = implode(' ', array_unique($tags));
+            $tagsLength = strlen($tagsString);
+            if ($this->tagsHeaderMaxLength && $tagsLength > $this->tagsHeaderMaxLength) {
+                $tagsString = substr(
+                    $tagsString,
+                    0,
+                    // Seek backwards from point of max length using negative offset
+                    strrpos($tagsString, ' ', $this->tagsHeaderMaxLength - $tagsLength)
+                );
+
+                $responseSharedMaxAge = $response->headers->getCacheControlDirective('s-maxage');
+                if (
+                    $this->tagsHeaderReducedTTl &&
+                    $responseSharedMaxAge &&
+                    $this->tagsHeaderReducedTTl < $responseSharedMaxAge
+                ) {
+                    $response->setSharedMaxAge($this->tagsHeaderReducedTTl);
+                }
+
+                $this->logger->warning(
+                    'HTTP Cache tags header max length reached and truncated to ' . $this->tagsHeaderMaxLength
+                );
+            }
+
+            $response->headers->set($this->tagsHeader, $tagsString);
         }
 
         return $this;

src/Resources/config/services.yml

@@ -1,6 +1,8 @@
 parameters:
     ezplatform.http_cache.controller.invalidatetoken.class: EzSystems\PlatformHttpCacheBundle\Controller\InvalidateTokenController
     ezplatform.http_cache.listener.vary_header.class: EzSystems\PlatformHttpCacheBundle\EventListener\ConditionallyRemoveVaryHeaderListener
+    ezplatform.http_cache.tags.header_max_length: null
+    ezplatform.http_cache.tags.header_reduced_ttl: null
 
 services:
     ezplatform.http_cache.cache_manager:
@@ -50,6 +52,9 @@ services:
          - '%ezplatform.http_cache.tags.header%'
          - '@ezplatform.http_cache.purge_client'
          - '@ezplatform.http_cache.repository_tag_prefix'
+         - '@logger'
+         - '%ezplatform.http_cache.tags.header_max_length%'
+         - '%ezplatform.http_cache.tags.header_reduced_ttl%'
 
     ezplatform.http_cache.user_context_provider.role_identify:
         class: EzSystems\PlatformHttpCacheBundle\ContextProvider\RoleIdentify