Grâce aux tags Varnish, j'ai switché ma prod sur Raspberry Pi

Le moyen le plus rapide d'obtenir une réponse d'un Backend est de ne pas l'appeler ;-) Une solution fournie par les "reverse-proxy" me direz-vous, mais pas si simple d'invalider le cache... Ce talk aborde une fonctionnalité méconnue de Varnish: les tags. Nous verrons comment en tirer partie via les "event listeners" d'une application Symfony standard. Au menu, un cluster de Rasberry Pi, une API, et des données toujours fraîches sous la milliseconde

Transcript

1. Going to production on
   a Raspberry Pi with
   varnish tags
   

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2. Who am I?
   Jérémy DERUSSÉ
   Web Technical Leader
   author of Symfony Lock Component 3.3
   @jderusse
   

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3. How to get fast responses
   from a PHP application?
   you can't
   

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4. How to get fast responses
   from a PHP application?
   your backend
   you can't
   

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5. Solution
   using http shared cache
   describe in RFC-2616 RFC-7234
   

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6. Integration in Symfony
   use Sensio\Bundle\FrameworkExtraBundle\Configuration\Cache;
   /**
   * @Cache(smaxage="3600")
   */
   public function indexAction()
   {
   // ...
   }
   Advanced usage with FriendsOfSymfony/FOSHttpCache
   

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7. Issue #1
   Unsharable resources
   private resources (ie. invoice, shopping cart, ...)
   per role representations
   Solution
   vary cache on user/role/other
   Repousser les limites : HTTP cache et utilisateurs connectés
   

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8. Issue #2
   Cache invalidation
   “ There are only two hard things in Computer Science: cache
   invalidation and naming things.
   Phil Karlton
   

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9. Cache models
   Validation model
   etag
   last-modified
   drawbacks
   application is booted
   hard to implement
   Expiration model
   expires
   cache-control
   drawback
   no control on invalidation
   

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10. cache model
    In a real world
    Backend can't validate every cache HIT
    Life time is not predictable
    BUT
    Varnish can be requested to partially invalidate responses
    Backend knows when resources change
    Responses are build on top of resources
    

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11. curl -I "http://varnish.myapp.com/c"
    curl -I "http://varnish.myapp.com/b"
    curl -I "http://varnish.myapp.com/a"
    HTTP/1.1 200 OK
    Cache-Control: public, s-maxage=3600
    X-Cache-Tags: Foo,Bar
    HTTP/1.1 200 OK
    Cache-Control: public, s-maxage=3600
    X-Cache-Tags: Foo
    Varnish tags
    curl \
    -X "BAN" \
    -H "X-Cache-Tags: Foo" \
    "http://varnish.myapp.com"
    HTTP/1.1 200 OK
    Cache-Control: public, s-maxage=3600
    X-Cache-Tags: Bar,Qux
    

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12. Varnish tags
    curl "http://varnish.myapp.com/posts/42"
    HTTP/1.1 200 OK
    Cache-Control: public, s-maxage=86400
    X-Cache-Tags: Post:42,Author:12,Comment:314,Comment:1337
    {
    "id": 42,
    "title": "My blog post.",
    "body": "Lorem Ipsum.",
    "author": {
    "id": 12,
    "username": "jderusse"
    },
    "comments": [
    {
    "id": 314,
    "message": "Wow such post"
    },
    {
    "id": 1337,
    "message": "much performance"
    }
    ]
    }
    

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13. Automate Tagging
    Tagging Response
    1. Collect displayed resources
    2. Generate resource identifier
    3. Tag response
    

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14. Automate Tagging
    Tagging Response - 1. Collect displayed resources
    namespace App\EventListener;
    use JMS\Serializer\EventDispatcher\Events;
    use JMS\Serializer\EventDispatcher\EventSubscriberInterface;
    use JMS\Serializer\EventDispatcher\ObjectEvent;
    class SerializationTagListener implements EventSubscriberInterface
    {
    public function onPostSerialize(ObjectEvent $event)
    {
    $resource = $event->getObject();
    // TODO
    }
    public static function getSubscribedEvents()
    {
    return [
    [
    'event' => Events::POST_SERIALIZE,
    'format' => 'json',
    'method' => 'onPostSerialize',
    ],
    ];
    }
    }
    

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15. Automate Tagging
    Tagging Response - 2. Generate resource identifier
    namespace App\EventListener;
    use App\Tag\TagExtractorInterface;
    use JMS\Serializer\EventDispatcher\EventSubscriberInterface;
    use JMS\Serializer\EventDispatcher\ObjectEvent;
    class SerializationTagListener implements EventSubscriberInterface
    {
    private $tagExtractor;
    public function __construct(TagExtractorInterface $tagExtractor)
    {
    $this->tagExtractor = $tagExtractor;
    }
    public function onPostSerialize(ObjectEvent $event): void
    {
    //...
    $tags = $this->tagExtractor->extract($event->getObject());
    }
    //...
    }
    

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16. Automate Tagging
    Tagging Response - 3. Tag response
    namespace App\EventListener;
    use App\Tag\TagExtractorInterface;
    use FOS\HttpCache\Handler\TagHandler;
    use JMS\Serializer\EventDispatcher\EventSubscriberInterface;
    use JMS\Serializer\EventDispatcher\ObjectEvent;
    class SerializationTagListener implements EventSubscriberInterface
    {
    private $tagExtractor;
    private $tagHandler;
    public function __construct(TagExtractorInterface $tagExtractor, TagHandler $tagHandler)
    {
    $this->tagExtractor = $tagExtractor;
    $this->tagHandler = $tagHandler;
    }
    public function onPostSerialize(ObjectEvent $event): void
    {
    $tags = $this->tagExtractor->extract($event->getObject());
    $this->tagHandler->addTags($tags);
    }
    //...
    }
    

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17. Automate Tagging
    Tagging Response
    1. Collect displayed resources
    2. Generate resource identifier
    3. Tag response
    Invalidate cache
    1. Listen changes
    2. Generate resource identifier
    3. Call varnish
    

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18. Automate Tagging
    Invalidate Cache - 1. Listen changes
    namespace App\EventListener;
    use Doctrine\Common\EventSubscriber;
    use Doctrine\ORM\Event\OnFlushEventArgs;
    use Doctrine\ORM\Events;
    class DoctrineInvalidationTagListener implements EventSubscriber
    {
    public function getSubscribedEvents()
    {
    return [Events::onFlush];
    }
    public function onFlush(OnFlushEventArgs $eventArgs)
    {
    $uow = $eventArgs->getEntityManager()->getUnitOfWork();
    foreach ($uow->getScheduledEntityUpdates() as $resource) {
    // TODO
    }
    foreach ($uow->getScheduledEntityDeletions() as $resource) {
    // TODO
    }
    }
    }
    

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19. Automate Tagging
    Invalidate Cache - 2. Generate resource identifier
    namespace App\EventListener;
    use App\Tag\TagExtractorInterface;
    use Doctrine\Common\EventSubscriber;
    class DoctrineInvalidationTagListener implements EventSubscriber
    {
    private $tagExtractor;
    public function __construct(TagExtractorInterface $tagExtractor)
    {
    $this->tagExtractor = $tagExtractor;
    }
    public function onFlush(OnFlushEventArgs $eventArgs)
    {
    $uow = $eventArgs->getEntityManager()->getUnitOfWork();
    $tags = [];
    foreach ($uow->getScheduledEntityUpdates() as $resource) {
    $tags = array_merge($tags, $this->tagExtractor->extract($resource));
    }
    foreach ($uow->getScheduledEntityDeletions() as $resource) {
    $tags = array_merge($tags, $this->tagExtractor->extract($resource));
    }
    // TODO
    }
    }
    

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20. Automate Tagging
    Invalidate Cache - 3. Call varnish
    namespace App\EventListener;
    use App\Tag\TagExtractorInterface;
    use Doctrine\Common\EventSubscriber;
    use FOS\HttpCache\Handler\TagHandler;
    class DoctrineInvalidationTagListener implements EventSubscriber
    {
    private $tagExtractor;
    public function __construct(TagExtractorInterface $tagExtractor, TagHandler $tagHandler)
    {
    $this->tagExtractor = $tagExtractor;
    $this->tagHandler = $tagHandler;
    }
    public function onFlush(OnFlushEventArgs $eventArgs)
    {
    // ...
    $this->tagHandler->invalidateTags($tags);
    }
    }
    

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21. Automate Tagging
    Tagging Response
    1. Collect displayed resources
    2. Generate resource identifier
    3. Tag response
    Invalidate cache
    1. Listen changes
    2. Generate resource identifier
    3. Call varnish
    Enjoy
    

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22. Silver bullet?
    Works well when
    HIT >> MISS
    Read >> Write
    Application knows resources used to build
    response
    Drawback
    Operations are not Atomic
    B ackend handles writes
    Backend knows infrastructure
    It slows writes
    

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23. Demo
    - env=dev
    - fetch=lazy
    symfony/symfony
    doctrine/orm
    marmelab/admin-on-rest
    

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24. Demo
    Raspberry Pi Orange Pi
    docker
    NGINX
    PHP7-FPM
    Varnish
    9.99$
    

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25. Demo
    

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26. ab -n 8000 -c 26 192.168.1.17:81/comments/1
    This is ApacheBench, Version 2.3 <$Revision: 1757674 $>
    Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net
    Licensed to The Apache Software Foundation, http://www.apache.org/
    Server Software: nginx/1.10.3
    Server Hostname: 192.168.1.16
    Server Port: 80
    Document Path: /comments/1
    Document Length: 576 bytes
    Concurrency Level: 26
    Time taken for tests: 26.912 seconds
    Complete requests: 200
    Failed requests: 0
    Total transferred: 193400 bytes
    HTML transferred: 115200 bytes
    Requests per second: 7.43 [#/sec] (mean)
    Time per request: 3498.553 [ms] (mean)
    Time per request: 134.560 [ms] (mean, across all concurrent
    Transfer rate: 7.02 [Kbytes/sec] received
    Connection Times (ms)
    min mean[+/-sd] median max
    Connect: 1 2 1.4 1 6
    Processing: 546 3342 1156.7 3020 7204
    Waiting: 546 3342 1156.7 3020 7204
    Total: 550 3344 1156.5 3021 7205
    in numbers
    ab -n 8000 -c 26 192.168.1.17/comments/1
    This is ApacheBench, Version 2.3 <$Revision: 1757674 $>
    Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net
    Licensed to The Apache Software Foundation, http://www.apache.org/
    Server Software: nginx/1.10.3
    Server Hostname: 192.168.1.17
    Server Port: 80
    Document Path: /comments/1
    Document Length: 576 bytes
    Concurrency Level: 26
    Time taken for tests: 2.340 seconds
    Complete requests: 8000
    Failed requests: 0
    Total transferred: 8948504 bytes
    HTML transferred: 4608000 bytes
    Requests per second: 3418.52 [#/sec] (mean)
    Time per request: 7.606 [ms] (mean)
    Time per request: 0.293 [ms] (mean, across all concurrent
    Transfer rate: 3734.21 [Kbytes/sec] received
    Connection Times (ms)
    min mean[+/-sd] median max
    Connect: 0 2 0.8 2 7
    Processing: 2 5 3.3 5 55
    Waiting: 2 5 3.3 4 55
    Total: 2 8 3.3 7 56
    app varnish
    

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27. Thank You
    

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28. Questions?
    @jderusse
    https://joind.in/talk/0a509
    

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29. Credits
    http://linuxgizmos.com/10-dollar-orange-pi-one-pits-quad-core-cortex-a7-against-pi-zero/
    http://toutsurlesbisounours.centerblog.net/rub-bisounours-3eme-generation-.html
    https://rcgo.com.br/recursos.html
    

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