Fix potential OOM when parsing logs in workflows

[jorgenpt]

📝 Description

WorkflowRun.getLogInputStream will read the entire log output into a ByteArrayOutputStream, then construct a ByteArrayInputStream from that buffer, which we then construct a InputStreamReader from. (https://github.com/jenkinsci/workflow-job-plugin/blob/1551f82/src/main/java/org/jenkinsci/plugins/workflow/job/WorkflowRun.java#L1105)

If the log is large, this will potentially cause a java.lang.OutOfMemoryError. Instead, use build.getLogReader(), which simply constructs an InputStreamReader that wraps the underlying source log session.

For hudson.model.Run this should have no impact, as its getLogReader() just constructs an InputStreamReader the same way we used to.

💎 Type of change

• Bug fix (non-breaking change which fixes an issue)

🚦 How Has This Been Tested?

Deployed to our Jenkins that (due to some overactive logging facilities) spewed ~130MB of logs, causing an OOM in the log parser.

Here's the exception we'd hit before this change had been deployed:

  java.lang.OutOfMemoryError: Java heap space
  	at java.base/java.util.Arrays.copyOf(Arrays.java:3745)
  	at java.base/java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:120)
  	at java.base/java.io.ByteArrayOutputStream.ensureCapacity(ByteArrayOutputStream.java:95)
  	at java.base/java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:156)
  	at org.apache.commons.io.output.ProxyOutputStream.write(ProxyOutputStream.java:92)
  	at org.kohsuke.stapler.framework.io.LargeText$HeadMark.moveTo(LargeText.java:329)
  	at org.kohsuke.stapler.framework.io.LargeText.writeLogTo(LargeText.java:244)
  	at hudson.console.AnnotatedLargeText.writeRawLogTo(AnnotatedLargeText.java:173)
  	at org.jenkinsci.plugins.workflow.job.WorkflowRun$$Lambda$842/0x00000008414b1840.writeLogTo(Unknown Source)
  	at org.jenkinsci.plugins.workflow.job.WorkflowRun.writeLogTo(WorkflowRun.java:1140)
  	at org.jenkinsci.plugins.workflow.job.WorkflowRun.getLogInputStream(WorkflowRun.java:1108)
  	at hudson.plugins.logparser.LogParserParser.parseLogBody(LogParserParser.java:357)
  	at hudson.plugins.logparser.LogParserParser.parseLog(LogParserParser.java:161)
  	at hudson.plugins.logparser.LogParserPublisher.perform(LogParserPublisher.java:117)
  	at jenkins.tasks.SimpleBuildStep.perform(SimpleBuildStep.java:123)
  	at org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:101)
  	at org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:71)
  	at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution.lambda$start$0(SynchronousNonBlockingStepExecution.java:47)
  	at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution$$Lambda$719/0x00000008410b6040.run(Unknown Source)
  	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
  	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
  	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
  	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
  	at java.base/java.lang.Thread.run(Thread.java:829)

🏁 Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works -- I don't see any unit tests that cover this functionality, and I'm not sure how to construct a test that generates an OOM.
• New and existing unit tests pass locally with my changes

[hypery2k]

thx for the PR and the explanation