37 lines
1.1 KiB
Scala
37 lines
1.1 KiB
Scala
package com.twitter.tweetypie.caching
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import com.twitter.stitch.Stitch
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/**
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* Apply caching to a [[Stitch]] function.
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*
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* @see CacheResult for more information about the semantics
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* implemented here.
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*/
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class StitchCaching[K, V](operations: CacheOperations[K, V], repo: K => Stitch[V])
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extends (K => Stitch[V]) {
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private[this] val stitchOps = new StitchCacheOperations(operations)
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override def apply(key: K): Stitch[V] =
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stitchOps.get(key).flatMap {
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case CacheResult.Fresh(value) =>
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Stitch.value(value)
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case CacheResult.Stale(staleValue) =>
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StitchAsync(repo(key).flatMap(refreshed => stitchOps.set(key, refreshed)))
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.map(_ => staleValue)
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case CacheResult.Miss =>
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repo(key)
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.applyEffect(value => StitchAsync(stitchOps.set(key, value)))
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case CacheResult.Failure(_) =>
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// In the case of failure, we don't attempt to write back to
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// cache, because cache failure usually means communication
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// failure, and sending more requests to the cache that holds
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// the value for this key could make the situation worse.
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repo(key)
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}
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}
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