[KYUUBI #985] Add logCaptureThreadReleased flag

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### _Why are the changes needed?_
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  1. If you add a feature, you can talk about the use case of it.
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`isInterrupted` is always false if some `InterruptedException` are throwed. So we should use a new flag to check if log capture thread is released.

### _How was this patch tested?_
- [x] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #985 from ulysses-you/flaky-test.

Closes #985

1fcc0a9 [ulysses-you] empty
463a996 [ulysses-you] empty
d1f2ea5 [ulysses-you] eventually
f9f3734 [ulysses-you] fix

Authored-by: ulysses-you <ulyssesyou18@gmail.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>
(cherry picked from commit 3afd20e)
Signed-off-by: Cheng Pan <chengpan@apache.org>

kyuubi-server/src/main/scala/org/apache/kyuubi/engine/ProcBuilder.scala

@@ -65,7 +65,8 @@ trait ProcBuilder {
   @volatile private var error: Throwable = UNCAUGHT_ERROR
   @volatile private var lastRowOfLog: String = "unknown"
   // Visible for test
-  private[kyuubi] var logCaptureThread: Thread = _
+  @volatile private[kyuubi] var logCaptureThreadReleased: Boolean = true
+  private var logCaptureThread: Thread = _
 
   private[kyuubi] lazy val engineLog: File = ProcBuilder.synchronized {
     val engineLogTimeout = conf.get(KyuubiConf.ENGINE_LOG_TIMEOUT)
@@ -136,10 +137,12 @@ trait ProcBuilder {
         case _: IOException =>
         case _: InterruptedException =>
       } finally {
+        logCaptureThreadReleased = true
         reader.close()
       }
     }
 
+    logCaptureThreadReleased = false
     logCaptureThread = PROC_BUILD_LOGGER.newThread(redirect)
     logCaptureThread.start()
     proc

kyuubi-server/src/test/scala/org/apache/kyuubi/engine/spark/SparkProcessBuilderSuite.scala

@@ -126,13 +126,16 @@ class SparkProcessBuilderSuite extends KerberizedTestHelper {
   test("log capture should release after close") {
     val process = new FakeSparkProcessBuilder(KyuubiConf())
     try {
+      assert(process.logCaptureThreadReleased)
       val subProcess = process.start
-      assert(!process.logCaptureThread.isInterrupted)
+      assert(!process.logCaptureThreadReleased)
       subProcess.waitFor(3, TimeUnit.SECONDS)
     } finally {
       process.close()
     }
-    assert(process.logCaptureThread.isInterrupted)
+    eventually(timeout(3.seconds), interval(100.milliseconds)) {
+      assert(process.logCaptureThreadReleased)
+    }
   }
 
   test(s"sub process log should be overwritten") {