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40 lines
1.2 KiB
Scala
40 lines
1.2 KiB
Scala
package com.twitter.recos.decider
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import com.twitter.decider.Decider
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import com.twitter.decider.RandomRecipient
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import com.twitter.util.Future
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import scala.util.control.NoStackTrace
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/*
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Provides deciders-controlled load shedding for a given endpoint.
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The format of the decider keys is:
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enable_loadshedding_<graphNamePrefix>_<endpoint name>
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E.g.:
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enable_loadshedding_user-tweet-graph_relatedTweets
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Deciders are fractional, so a value of 50.00 will drop 50% of responses. If a decider key is not
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defined for a particular endpoint, those requests will always be
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served.
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We should therefore aim to define keys for the endpoints we care most about in decider.yml,
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so that we can control them during incidents.
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*/
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class EndpointLoadShedder(
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decider: GraphDecider) {
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import EndpointLoadShedder._
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private val keyPrefix = "enable_loadshedding"
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def apply[T](endpointName: String)(serve: => Future[T]): Future[T] = {
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val key = s"${keyPrefix}_${decider.graphNamePrefix}_${endpointName}"
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if (decider.isAvailable(key, recipient = Some(RandomRecipient)))
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Future.exception(LoadSheddingException)
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else serve
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}
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}
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object EndpointLoadShedder {
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object LoadSheddingException extends Exception with NoStackTrace
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}
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