RFR: 8321718: ProcessTools.executeProcess calls waitFor before logging

[David Holmes]

On Mon, 11 Dec 2023 11:16:05 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> There is some logging printed when tests spawns processes. This logging is triggered from calls to `OutputAnalyzer`, when it delegates calls to `LazyOutputBuffer`.
> 
> If we write code like this:
> 
> ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(...);
> OutputAnalyzer output = new OutputAnalyzer(pb.start());
> int exitValue = output.getExitValue();
> 
> 
> We get the following logging:
> 
> [timestamp0] "Gathering output for process <pid>
> [timestamp1] Waiting for completion for process <pid>
> [timestamp2] Waiting for completion finished for process <pid>
> 
> 
> The first line comes from the `OutputAnalyzer` constructor and the two other lines comes from the `getExitValue` call, which calls logs the above messages around the call to `waitFor`.
> 
> If instead write the code above as:
> 
> ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(...);
> OutputAnalyzer output = ProcessTools.executeProcess(pb);
> int exitValue = output.getExitValue();
> 
> 
> We get the same logging, but timestamp1 and timestamp2 are almost the same. This happens because there's an extra call to `waitFor` inside `executeProcess`, but that `waitFor` does not have the "wait for" logging. So, instead we get the logging for the no-op `waitFor` inside `getExitValue`.
> 
> I would like to propose a small workaround to solve this. The workaround is that `executeProcess` delegates the `waitFor` call to the `LazyOutputBuffer` via `OutputAnalyzer`.  This is a small, limited workaround for this issue. Ideally I would like to extract the entire Process handling code out of LazyOutputBuffer and OutputAnalyzer, but the prototype for that rewrites all usages of `new OutputAnalyzer(pb.start())` and stretches far and wide in the test directories, so I'm starting out with this suggestion.
> 
> We can see of this patch by looking at the timestamps generated from the included test. Without the proposed workaround:
> 
> Without
> 
> testExecuteProcessExit
> [2023-12-11T11:05:41.854579260Z] Gathering output for process 2547719
> [2023-12-11T11:05:44.018335073Z] Waiting for completion for process 2547719
> [2023-12-11T11:05:44.018851972Z] Waiting for completion finished for process 2547719
> 
> testExecuteProcessStdout
> [2023-12-11T11:05:44.049509860Z] Gathering output for process 2547741
> [2023-12-11T11:05:46.227768897Z] Waiting for completion for process 2547741
> [2023-12-11T11:05:46.228021173Z] Waiting for completion finished for process 2547741
> 
> 
> testNewOutputAnalyzerExit
> [2023-12-11T11:05:46.231475003Z] Gathering output for process 2547782
> [2023...

Looks good.

Thanks

test/lib/jdk/test/lib/process/OutputAnalyzer.java line 111:

> 109:     /**
> 110:      * Delegate waitFor to the OutputBuffer. This ensures that
> 111:      * the progress and timestmaps are logged correctly.

Typo: timestmaps

-------------

Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17052#pullrequestreview-1776831148
PR Review Comment: https://git.openjdk.org/jdk/pull/17052#discussion_r1423565527