[LIVY-585][SERVER] Avoid duplicate stopping log when stop/interrupt a session

[Ngone51]

What changes were proposed in this pull request?

There's duplicate stopping log when stop/interrupt a session. This happens because server logs stopping info when we stopping/interrupting a session at the first time. And when the session expired, it would be removed from session manager and call stop() and logs stopping info for the second time(Though, it does not really stop the session again at this time).

The fix is quite simple by adding a _stopped flag in Session's stop() method.

How was this patch tested?

N.A.(?)

[Ngone51]

@vanzin please have a look, thx.

[Ngone51]

@mgaido91 Thank you for your review. I've updated it.

[codecov-io]

Codecov Report

Merging #166 into master will decrease coverage by 0.05%. The diff coverage is 44.44%.

@@             Coverage Diff              @@
##             master     #166      +/-   ##
============================================
- Coverage     68.82%   68.77%   -0.06%     
+ Complexity      907      906       -1     
============================================
  Files           100      100              
  Lines          5662     5671       +9     
  Branches        848      852       +4     
============================================
+ Hits           3897     3900       +3     
- Misses         1213     1216       +3     
- Partials        552      555       +3

Impacted Files	Coverage Δ	Complexity Δ
.../main/scala/org/apache/livy/sessions/Session.scala	73.72% <44.44%> (+0.27%)	20 <1> (+1)	:arrow_up:
...cala/org/apache/livy/scalaapi/ScalaJobHandle.scala	52.94% <0%> (-2.95%)	7% <0%> (ø)
...ain/java/org/apache/livy/rsc/driver/RSCDriver.java	78.81% <0%> (-1.28%)	42% <0%> (ø)
...e/livy/server/interactive/InteractiveSession.scala	69.11% <0%> (+0.07%)	44% <0%> (ø)	:arrow_down:

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[Ngone51]

If we are calling stop when it is not necessary, I think we should rather avoid calling it in those cases.

I was thinking about that way, but I was not sure whether it's the only place where calling stop unnecssary. So, I think it may be better to cover those cases(if any) in method stop (just like the thing we do in IteractiveSession.stopSession).

[mgaido91]

I think it may be better to cover those cases(if any) in method stop

I don't really agree with you. Let me cc @vanzin for his opinion too on this.