[FLINK-22431] Add information when and why the AdaptiveScheduler rest…

…arts or fails jobs

This commit adds info log statements to tell the user when and why it restarts or fails a job.

This closes apache#15736.

flink-runtime/src/main/java/org/apache/flink/runtime/scheduler/adaptive/AdaptiveScheduler.java

@@ -1058,7 +1058,7 @@ public Executing.FailureResult howToHandleFailure(Throwable failure) {
         restartBackoffTimeStrategy.notifyFailure(failure);
         if (restartBackoffTimeStrategy.canRestart()) {
             return Executing.FailureResult.canRestart(
-                    Duration.ofMillis(restartBackoffTimeStrategy.getBackoffTime()));
+                    failure, Duration.ofMillis(restartBackoffTimeStrategy.getBackoffTime()));
         } else {
             return Executing.FailureResult.canNotRestart(
                     new JobException(

flink-runtime/src/main/java/org/apache/flink/runtime/scheduler/adaptive/Executing.java

@@ -85,12 +85,14 @@ private void handleAnyFailure(Throwable cause) {
         final FailureResult failureResult = context.howToHandleFailure(cause);
 
         if (failureResult.canRestart()) {
+            getLogger().info("Restarting job.", failureResult.getFailureCause());
             context.goToRestarting(
                     getExecutionGraph(),
                     getExecutionGraphHandler(),
                     getOperatorCoordinatorHandler(),
                     failureResult.getBackoffTime());
         } else {
+            getLogger().info("Failing job.", failureResult.getFailureCause());
             context.goToFailing(
                     getExecutionGraph(),
                     getExecutionGraphHandler(),
@@ -281,9 +283,9 @@ CompletableFuture<String> goToStopWithSavepoint(
     static final class FailureResult {
         @Nullable private final Duration backoffTime;
 
-        @Nullable private final Throwable failureCause;
+        private final Throwable failureCause;
 
-        private FailureResult(@Nullable Duration backoffTime, @Nullable Throwable failureCause) {
+        private FailureResult(Throwable failureCause, @Nullable Duration backoffTime) {
             this.backoffTime = backoffTime;
             this.failureCause = failureCause;
         }
@@ -299,20 +301,18 @@ Duration getBackoffTime() {
         }
 
         Throwable getFailureCause() {
-            Preconditions.checkState(
-                    failureCause != null,
-                    "Failure result must not be restartable to return a failure cause.");
             return failureCause;
         }
 
         /**
          * Creates a FailureResult which allows to restart the job.
          *
+         * @param failureCause failureCause for restarting the job
          * @param backoffTime backoffTime to wait before restarting the job
          * @return FailureResult which allows to restart the job
          */
-        static FailureResult canRestart(Duration backoffTime) {
-            return new FailureResult(backoffTime, null);
+        static FailureResult canRestart(Throwable failureCause, Duration backoffTime) {
+            return new FailureResult(failureCause, backoffTime);
         }
 
         /**
@@ -322,7 +322,7 @@ static FailureResult canRestart(Duration backoffTime) {
          * @return FailureResult which does not allow to restart the job
          */
         static FailureResult canNotRestart(Throwable failureCause) {
-            return new FailureResult(null, failureCause);
+            return new FailureResult(failureCause, null);
         }
     }
 

flink-runtime/src/main/java/org/apache/flink/runtime/scheduler/adaptive/StopWithSavepoint.java

@@ -179,12 +179,14 @@ private void handleAnyFailure(Throwable cause) {
         final Executing.FailureResult failureResult = context.howToHandleFailure(cause);
 
         if (failureResult.canRestart()) {
+            getLogger().info("Restarting job.", failureResult.getFailureCause());
             context.goToRestarting(
                     getExecutionGraph(),
                     getExecutionGraphHandler(),
                     getOperatorCoordinatorHandler(),
                     failureResult.getBackoffTime());
         } else {
+            getLogger().info("Failing job.", failureResult.getFailureCause());
             context.goToFailing(
                     getExecutionGraph(),
                     getExecutionGraphHandler(),

flink-runtime/src/test/java/org/apache/flink/runtime/scheduler/adaptive/ExecutingTest.java

@@ -140,7 +140,7 @@ public void testRecoverableGlobalFailureTransitionsToRestarting() throws Excepti
             ctx.setExpectRestarting(
                     (restartingArguments ->
                             assertThat(restartingArguments.getBackoffTime(), is(duration))));
-            ctx.setHowToHandleFailure((t) -> Executing.FailureResult.canRestart(duration));
+            ctx.setHowToHandleFailure((t) -> Executing.FailureResult.canRestart(t, duration));
             exec.handleGlobalFailure(new RuntimeException("Recoverable error"));
         }
     }
@@ -234,7 +234,8 @@ public void testFailureReportedViaUpdateTaskExecutionStateCausesRestart() throws
                     new ExecutingStateBuilder()
                             .setExecutionGraph(returnsFailedStateExecutionGraph)
                             .build(ctx);
-            ctx.setHowToHandleFailure((ign) -> Executing.FailureResult.canRestart(Duration.ZERO));
+            ctx.setHowToHandleFailure(
+                    (throwable) -> Executing.FailureResult.canRestart(throwable, Duration.ZERO));
             ctx.setExpectRestarting(assertNonNull());
 
             exec.updateTaskExecutionState(createFailingStateTransition());

flink-runtime/src/test/java/org/apache/flink/runtime/scheduler/adaptive/StopWithSavepointTest.java

@@ -174,7 +174,7 @@ public void testRestartOnGlobalFailureIfRestartConfigured() throws Exception {
             StopWithSavepoint sws = createStopWithSavepoint(ctx);
             ctx.setStopWithSavepoint(sws);
             ctx.setHowToHandleFailure(
-                    (ignore) -> Executing.FailureResult.canRestart(Duration.ZERO));
+                    (throwable) -> Executing.FailureResult.canRestart(throwable, Duration.ZERO));
 
             ctx.setExpectRestarting(assertNonNull());
 
@@ -229,7 +229,7 @@ public void testRestartingOnUpdateTaskExecutionStateWithRestart() throws Excepti
                     createStopWithSavepoint(ctx, new StateTrackingMockExecutionGraph());
             ctx.setStopWithSavepoint(sws);
             ctx.setHowToHandleFailure(
-                    (ignore) -> Executing.FailureResult.canRestart(Duration.ZERO));
+                    (throwable) -> Executing.FailureResult.canRestart(throwable, Duration.ZERO));
 
             ctx.setExpectRestarting(assertNonNull());
 
@@ -277,7 +277,7 @@ public void testRestartOnTaskFailureAfterSavepointCompletion() throws Exception
             ctx.setStopWithSavepoint(sws);
 
             ctx.setHowToHandleFailure(
-                    (ignore) -> Executing.FailureResult.canRestart(Duration.ZERO));
+                    (throwable) -> Executing.FailureResult.canRestart(throwable, Duration.ZERO));
 
             ctx.setExpectRestarting(assertNonNull());