[GitHub] starpit opened a new issue #3228: very expensive fillInStackTrace in Either[ActivationId,WhiskActivation]

[GitBox <gi...@apache.org>]

starpit opened a new issue #3228: very expensive fillInStackTrace in Either[ActivationId,WhiskActivation]
URL: https://github.com/apache/incubator-openwhisk/issues/3228
 
 
   the controller spends a large number of CPU cycles filling in stack traces, due to the nature of the `CompletionMessage` and spray's deserialization of scala's `Either`.
   
   First, note how spray uses a try/catch pattern for `Either`, starting with the `Left`, the backing up to the `Right`: https://github.com/spray/spray-json/blob/master/src/main/scala/spray/json/AdditionalFormats.scala#L107
   
   Next, observe that CompletionMessage has an `Either[ActivationId, WhiskActivation]`, where the common case, for blocking invokes, is the latter.  Note that this means, for blocking invokes than take less than 60 seconds, we will always incur a fillInStackTrace, because the completion message will contain a `Right[WhiskActivation]` in those (common) cases.
   
   The fix is probably to use a custom serdes for our Either, perhaps reversing the order. Better, we should find a way to avoid the try/catch pattern to parsing altogether.

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