[play-ws] Cache serving stale response instead of error

[Pablo Romanelli]

Hi, I think I found a bug on play ws cache.

I'm requesting a resource with the following header:

1. Accept-Ranges:
   bytes
2. Cache-Control:
   max-age=20
3. Connection:
   keep-alive
4. Content-Length:
   271
5. Content-Type:
   application/json
6. Date:
   Tue, 06 Mar 2018 15:31:58 GMT
7. ETag:
   "5a9ea88c-10f"
8. Last-Modified:
   Tue, 06 Mar 2018 14:41:16 GMT
9. Server:
   nginx/1.13.9

Play ws correctly makes request once every 20 seconds.

But if I shutdown the remote service, the ws client returns 200 OK responses instead of an error (that is what I'm expecting if the server is not available).

I even try with "max-age=20, stale-while-revalidate=30, stale-if-error=600" but after the "stale-if-error" time, the client continues to return 200 OK responses even if the HTTP service is offline.

I think this behaviour is due to the following code:

https://github.com/playframework/play-ws/blob/ed7fcabf80aafd9b7a60a0c8db489e7f1620eaa0/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/cache/AhcHttpCache.scala#L266

	/**
	* Calculates the time to live. Currently hardcoded to 24 hours.
	*/
	protected def calculateTimeToLive(request: Request, status: CacheableHttpResponseStatus, headers: CacheableHttpResponseHeaders): Option[DateTime] = {
	Some(DateTime.now.plusHours(24))
	}

I'm using play-ahc-ws-standalone 1.1.6 with Caffeine ("com.github.ben-manes.caffeine" % "caffeine" % "2.6.2") like this:

class CaffeineHttpCache @Inject()(config: Config)(implicit ec: ExecutionContext) extends Cache {
  val underlying = Caffeine.newBuilder()
    .build[EffectiveURIKey, ResponseEntry]()

  override def remove(key: EffectiveURIKey) = Future(underlying.invalidate(key))

  override def put(key: EffectiveURIKey, entry: ResponseEntry) = Future(underlying.put(key, entry))

  override def get(key: EffectiveURIKey) = Future(Option(underlying.getIfPresent(key)))

  override def close(): Unit = underlying.cleanUp()
}

object WsModule extends AbstractModule {
  override def configure(): Unit = {
    bind(classOf[ActorSystem]).toInstance(ActorSystem())
  }

  @Provides
  @Singleton
  def clientProvider(cache: CaffeineHttpCache)
                    (implicit actorSystem: ActorSystem, ec: ExecutionContext): StandaloneAhcWSClient = {
    implicit val materializer = ActorMaterializer()
    StandaloneAhcWSClient(httpCache = Some(new AhcHttpCache(cache)))
  }
}

Thank you!

[Will Sargent]

Okay, I will look at this.

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[Will Sargent]

What happens when you turn on logging?  The cache is deliberately chatty at TRACE level.