Expose session state

[Quinn-With-Two-Ns]

Expose session state to users so they can understand if their activity failed because the session worker failed.

resolves:#1021

[cretz]

For this one we might want a test that confirms that session state shows as failed if an in-flight activity fails due to session failure. My concern is something crashes the session

Not sure how such a test looks (an integration test or maybe a "features" test that shuts the session worker down).

[cretz]

How about the SessionState type itself?

[Quinn-With-Two-Ns]

hmmm yes I guess I should. Originally I didn't think I needed to, but If someone wants to make a function that takes the state as a parameter it would be useful to expose.

[Quinn-With-Two-Ns]

For this one we might want a test that confirms that session state shows as failed if an in-flight activity fails due to session failure. My concern is something crashes the session

I can make an integration test for this.

I will also note again it is pretty easy, I think, to create a scenario where a session worker fails, but the activity fails firsts so the workflow thinks the session is still open. I think we should document this behaviour.

[cretz]

I will also note again it is pretty easy, I think, to create a scenario where a session worker fails, but the activity fails firsts so the workflow thinks the session is still open. I think we should document this behaviour.

Hrmm, that a common scenario? I wonder if that makes this whole issue moot. If the user needs to know that their activity was cancelled due to session failure, it seems we can't do that. Sure we can show activity was cancelled due to session complete but not session workflow failure.

Do we have to document that session HeartbeatTimeout has to be less than half that of an activity heartbeat timeout for this to be reported correctly? Or do we just tell users the session may still show open after activity failure due to session worker failure for the duration of the session heartbeat timeout? Or do we just scrap this issue due to these caveats and just document that knowing whether an activity failed due to session failure is unknowable?

[cretz]

Good enough for me, but we need to let that user know that they need to understand what they want to consider a "session failure" because it may be an activity failure on crash before the session reports failure.