MINOR: improve Session expiration notice

[vvcephei]

The log for expired session windows only shows the window end time and expiration time, not the current stream time, which makes it not obvious why the window is expired, unless you are intimately familiar with stream-time calculations. Explicitly logging the current stream time should help.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[vvcephei]

@cadonna @mjsax , do you mind taking a quick look at this logging improvement? Thanks!

[mjsax]

LGTM.

[vvcephei]

Thanks! Should we cherry-pick this to 2.2 and 2.1 as well?

[mjsax]

@vvcephei Test failure seems related:

java.lang.AssertionError: 
Expected: a collection containing "Skipping record for expired window. key=[A] topic=[topic] partition=[-3] offset=[-2] timestamp=[0] window=[0,0) expiration=[10]"
     but: mismatches were: [was "Skipping record for expired window. key=[A] topic=[topic] partition=[-3] offset=[-2] timestamp=[0] window=[0,0) expiration=[10] streamTime=[20]", was "Skipping record for expired window. key=[A] topic=[topic] partition=[-3] offset=[-2] timestamp=[1] window=[1,1) expiration=[10] streamTime=[20]"]
	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:6)
	at org.apache.kafka.streams.kstream.internals.KStreamSessionWindowAggregateProcessorTest.shouldLogAndMeterWhenSkippingLateRecord(KStreamSessionWindowAggregateProcessorTest.java:383)

[vvcephei]

Oops! Thanks for capturing that.

[ableegoldman]

@vvcephei Would this be helpful for time-based windows as well?

[vvcephei]

@ableegoldman , yes, that's a good thought. I'll add it.

[vvcephei]

Ok, all comments are addressed so far... Do you mind taking another look @mjsax and @ableegoldman ?

[ableegoldman]

LGTM

[mjsax]

@vvcephei Test failures seem to be related?

[vvcephei]

Weird, I couldn't reproduce the test failures.

Retest this, please.

[mjsax]

@vvcephei Failed again -- there seems to be something... no clue what. Maybe try to rebase to trunk ?

[vvcephei]

Ok, got it. The tests may log extra messages that didn't get logged on my machine, so we can't use equality for validating the log results.

[vvcephei]

Thanks, @mjsax ! Can we also cherry-pick this to 2.2 and 2.1 ? (there is only one minor conflict in the 2.1 branch)

[mjsax]

Cherry-picked to 2.2 and 2.1 branches.

[vvcephei]

Thanks so much!