Improve FutureUtils.get exception handling (#50339) (#50417)

FutureUtils.get() would unwrap ElasticsearchWrapperExceptions. This
is trappy, since nearly all usages of FutureUtils.get() expected only to
not have to deal with checked exceptions.

In particular, StepListener builds upon ListenableFuture which uses
FutureUtils.get to be informed about the exception passed to onFailure.
This had the bad consequence of masking away any exception that was an
ElasticsearchWrapperException like RemoteTransportException.
Specifically for recovery, this made CircuitBreakerExceptions happening
on the target node look like they originated from the source node.

The only usage that expected that behaviour was AdapterActionFuture.
The unwrap behaviour has been moved to that class.

Author: henningandersen

server/src/main/java/org/elasticsearch/action/support/AdapterActionFuture.java

@@ -19,19 +19,25 @@
 
 package org.elasticsearch.action.support;
 
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.ActionFuture;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.concurrent.BaseFuture;
 import org.elasticsearch.common.util.concurrent.FutureUtils;
+import org.elasticsearch.common.util.concurrent.UncategorizedExecutionException;
 
 import java.util.concurrent.TimeUnit;
 
 public abstract class AdapterActionFuture<T, L> extends BaseFuture<T> implements ActionFuture<T>, ActionListener<L> {
 
     @Override
     public T actionGet() {
-        return FutureUtils.get(this);
+        try {
+            return FutureUtils.get(this);
+        } catch (ElasticsearchException e) {
+            throw unwrapEsException(e);
+        }
     }
 
     @Override
@@ -51,7 +57,11 @@ public T actionGet(TimeValue timeout) {
 
     @Override
     public T actionGet(long timeout, TimeUnit unit) {
-        return FutureUtils.get(this, timeout, unit);
+        try {
+            return FutureUtils.get(this, timeout, unit);
+        } catch (ElasticsearchException e) {
+            throw unwrapEsException(e);
+        }
     }
 
     @Override
@@ -66,4 +76,11 @@ public void onFailure(Exception e) {
 
     protected abstract T convert(L listenerResponse);
 
+    private static RuntimeException unwrapEsException(ElasticsearchException esEx) {
+        Throwable root = esEx.unwrapCause();
+        if (root instanceof RuntimeException) {
+            return (RuntimeException) root;
+        }
+        return new UncategorizedExecutionException("Failed execution", root);
+    }
 }

server/src/main/java/org/elasticsearch/cluster/action/index/MappingUpdatedAction.java

@@ -31,7 +31,7 @@
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
-import org.elasticsearch.common.util.concurrent.FutureUtils;
+import org.elasticsearch.common.util.concurrent.UncategorizedExecutionException;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.mapper.MapperService;
@@ -89,7 +89,16 @@ public void onFailure(Exception e) {
             });
     }
 
+    // todo: this explicit unwrap should not be necessary, but is until guessRootCause is fixed to allow wrapped non-es exception.
     private static Exception unwrapException(Exception cause) {
-        return cause instanceof ElasticsearchException ? FutureUtils.unwrapEsException((ElasticsearchException) cause) : cause;
+        return cause instanceof ElasticsearchException ? unwrapEsException((ElasticsearchException) cause) : cause;
+    }
+
+    private static RuntimeException unwrapEsException(ElasticsearchException esEx) {
+        Throwable root = esEx.unwrapCause();
+        if (root instanceof RuntimeException) {
+            return (RuntimeException) root;
+        }
+        return new UncategorizedExecutionException("Failed execution", root);
     }
 }

server/src/main/java/org/elasticsearch/common/util/concurrent/FutureUtils.java

@@ -19,7 +19,6 @@
 
 package org.elasticsearch.common.util.concurrent;
 
-import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ElasticsearchTimeoutException;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.SuppressForbidden;
@@ -86,21 +85,10 @@ public static  <T> T get(Future<T> future, long timeout, TimeUnit unit) {
     }
 
     public static RuntimeException rethrowExecutionException(ExecutionException e) {
-        if (e.getCause() instanceof ElasticsearchException) {
-            ElasticsearchException esEx = (ElasticsearchException) e.getCause();
-            return unwrapEsException(esEx);
-        } else if (e.getCause() instanceof RuntimeException) {
+        if (e.getCause() instanceof RuntimeException) {
             return (RuntimeException) e.getCause();
         } else {
             return new UncategorizedExecutionException("Failed execution", e);
         }
     }
-
-    public static RuntimeException unwrapEsException(ElasticsearchException esEx) {
-        Throwable root = esEx.unwrapCause();
-        if (root instanceof ElasticsearchException || root instanceof RuntimeException) {
-            return (RuntimeException) root;
-        }
-        return new UncategorizedExecutionException("Failed execution", root);
-    }
 }

server/src/test/java/org/elasticsearch/action/StepListenerTests.java

@@ -22,11 +22,13 @@
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.threadpool.TestThreadPool;
 import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.transport.RemoteTransportException;
 import org.junit.After;
 import org.junit.Before;
 
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 
 import static org.hamcrest.Matchers.equalTo;
@@ -110,4 +112,20 @@ private void executeAction(Runnable runnable) {
             runnable.run();
         }
     }
+
+    /**
+     * This test checks that we no longer unwrap exceptions when using StepListener.
+     */
+    public void testNoUnwrap() {
+        StepListener<String> step = new StepListener<>();
+        step.onFailure(new RemoteTransportException("test", new RuntimeException("expected")));
+        AtomicReference<RuntimeException> exception = new AtomicReference<>();
+        step.whenComplete(null, e -> {
+            exception.set((RuntimeException) e);
+        });
+
+        assertEquals(RemoteTransportException.class, exception.get().getClass());
+        RuntimeException e = expectThrows(RuntimeException.class, () -> step.result());
+        assertEquals(RemoteTransportException.class, e.getClass());
+    }
 }

server/src/test/java/org/elasticsearch/action/support/AdapterActionFutureTests.java

@@ -19,12 +19,16 @@
 
 package org.elasticsearch.action.support;
 
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.unit.TimeValue;
+import org.elasticsearch.common.util.concurrent.UncategorizedExecutionException;
 import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.transport.RemoteTransportException;
 
 import java.util.Objects;
 import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -90,4 +94,28 @@ protected String convert(final Integer listenerResponse) {
         thread.join();
     }
 
+    public void testUnwrapException() {
+        checkUnwrap(new RemoteTransportException("test", new RuntimeException()), RuntimeException.class, RemoteTransportException.class);
+        checkUnwrap(new RemoteTransportException("test", new Exception()),
+            UncategorizedExecutionException.class, RemoteTransportException.class);
+        checkUnwrap(new Exception(), UncategorizedExecutionException.class, Exception.class);
+        checkUnwrap(new ElasticsearchException("test", new Exception()), ElasticsearchException.class, ElasticsearchException.class);
+    }
+
+    private void checkUnwrap(Exception exception, Class<? extends Exception> actionGetException,
+                             Class<? extends Exception> getException) {
+        final AdapterActionFuture<Void, Void> adapter = new AdapterActionFuture<Void, Void>() {
+            @Override
+            protected Void convert(Void listenerResponse) {
+                fail();
+                return null;
+            }
+        };
+
+        adapter.onFailure(exception);
+        assertEquals(actionGetException, expectThrows(RuntimeException.class, adapter::actionGet).getClass());
+        assertEquals(actionGetException, expectThrows(RuntimeException.class, () -> adapter.actionGet(10, TimeUnit.SECONDS)).getClass());
+        assertEquals(getException, expectThrows(ExecutionException.class, () -> adapter.get()).getCause().getClass());
+        assertEquals(getException, expectThrows(ExecutionException.class, () -> adapter.get(10, TimeUnit.SECONDS)).getCause().getClass());
+    }
 }