TINKERPOP-2950 Add docker shutdown handling to close containers gracefully

[ryn5]

JIRA: https://issues.apache.org/jira/browse/TINKERPOP-2950. Handles SIGTERM when shutting down docker container by sending SIGINT to server processes.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c2e2086) 75.19% compared to head (eff17cd) 75.19%.
Report is 4 commits behind head on 3.6-dev.

Additional details and impacted files

@@              Coverage Diff              @@
##             3.6-dev    #2397      +/-   ##
=============================================
- Coverage      75.19%   75.19%   -0.01%     
- Complexity     12318    12319       +1     
=============================================
  Files           1057     1057              
  Lines          63450    63450              
  Branches        6935     6935              
=============================================
- Hits           47713    47709       -4     
- Misses         13169    13176       +7     
+ Partials        2568     2565       -3     

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[Cole-Greer]

Thanks Ryan, I checked out the branch and tested out the new image, it's working great!

VOTE +1

[xiazcy]

VOTE +1

[vkagamlyk]

VOTE +1

[rcbyron]

I'm still having issues with graceful shutdown even with this code.

I use the default scripts/empty-sample.groovy which has:

globals << [hook : [
        onStartUp: { LifeCycleHook.Context ctx ->
            ctx.logger.info("Executed once at startup of Gremlin Server.")
        },
        onShutDown: { LifeCycleHook.Context ctx ->
            ctx.logger.info("Executed once at shutdown of Gremlin Server.")
            graph.close()  // <-- I ADDED THIS
        }
] as LifeCycleHook]

And Executed once at shutdown... is never called I tried stopping/starting/restarting from Docker Desktop.

[danielcweber]

This is an issue for me as well. It seems that docker-entrypoint.sh forwards SIGTERMS as SIGINTS to /opt/gremlin-server/bin/gremlin-server.sh but it's ignored there. What needs to be sent the signal instead is the java process that gremlin-server.sh starts.

[Cole-Greer]

I'm seeing the same behaviour as well now. The change here is preventing docker from hanging due to /opt/gremlin-server/bin/gremlin-server.sh not terminating, but it does not properly terminate the gremlin server JVM process.

@danielcweber As you've already dug into this, would you be willing to submit a PR with a fix? If not let's reopen the JIRA for tracking and ensure it gets fixed for the next release.

[danielcweber]

I'm basically clueless about bash files but I'll give it a try nonetheless.

[danielcweber]

@Cole-Greer My naive attempt that is working for me would be this change. This is not even PR quality because I don't know what this will break for other users. Basically, through this change, the 'java' process will end up as PID 1 and receive all the signals.

[Cole-Greer]

Thanks @danielcweber. I don't see anything that would break just from looking at the code. I will find some time to run some tests with it, if everything checks out I think we can merge that in.

[danielcweber]

@Cole-Greer If everything is fine, here's a PR.