CachePolicy with default cache key strategy results in the cache never been called

[ymor]

The DefaultCacheKeyStrategy uses the ExecutionKey from the Polly Context. However this seems to never get set and so the Polly CacheEngineAsync never tries the cache.

There doesn't seem to be enough information on the Context to even create a custom CacheKeyStrategy. Is it possible to add some of the request information onto the Context?

[reisenberger]

@ymor Before placing the call through HttpClient, you can use this extension method on HttpRequestMessage to set the Polly.Context to use with the request.

request.SetPolicyExecutionContext(new Polly.Context("CacheKeyToUseWithThisRequest"));

That example assumes your CachePolicy is using the default cache key strategy. If you use a custom cache key strategy you can vary the Context you pass to request.SetPolicyExecutionContext(...); to fit your custom strategy.

@rynowak @stevejgordon We need to get this in the documentation, whether Polly's (I'll draft something there) or the official aspnet/docs version.

[reisenberger]

I have added some initial notes here in Polly's doco around IHttpClientFactory and Polly CachePolicy. The doco notes some considerations around caching at the low level of the raw HttpResponseMessage.

[ymor]

Thanks, those considerations were things i hadn't thought about!

[mkArtakMSFT]

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