CODEWITHSUNDEEP
scalaspray
Mario Camou
Mario Camou

Reputation: 2353

spray-cache: Return old value if the future fails

We are using spray-cache (can't move to akka-http yet) to cache results from a downstream service we are calling. The effect we want is, if the data is more than 15 minutes old, do the call, otherwise return the cached data.

Our problem is that, if the service call fails, spray-cache will remove the entry from the cache. What we need is to return the old cached data (even if it's stale), and retry the downstream request when the next request comes in.

Upvotes: 1

Views: 88

Answers (1)

Mark Kegel
Mark Kegel

Reputation: 4510

It looks like Spray does not ship with a default cache implementation that does what you want. According to the spray-caching docs there are two implementations to the Cache trait: SimpleLruCache and ExpiringLruCache.

What you want is a Cache that distinguishes entry expiration (removal of the entry from the cache) from entry refresh (fetching or calculating a more recent copy of the entry).

Since both default implementations merge these two concepts into a single timeout value I think your best bet will be a write a new Cache implementation that distinguishes refresh from expiration.

Upvotes: 3

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