fix: transaction retries should not timeout (#1009)

Transactions that are retried because of an aborted transaction use the
retry settings of the Rollback RPC. This ensures reasonable backoff values.
It however also meant that transactions that are retried multiple times
could exceed the total timeout of the retry settings, and that again would
cause the Aborted error to propagate. This change sets the total timeout
for transaction retries to 24 hours and disables any max attempts in the
retry settings to prevent retries to fail because the deadline is exceeded.

Transactions can still fail with timeout errors if individual RPC invocations
exceed the configured timeout of that RPC. This change only prevents timeouts
from occurring because of repeated retries of an entire transaction.

Fixes #1008

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerRetryHelper.java

@@ -16,6 +16,7 @@
 
 package com.google.cloud.spanner;
 
+import com.google.api.core.ApiClock;
 import com.google.api.core.NanoClock;
 import com.google.api.gax.retrying.ResultRetryAlgorithm;
 import com.google.api.gax.retrying.RetrySettings;
@@ -24,6 +25,7 @@
 import com.google.cloud.RetryHelper.RetryHelperException;
 import com.google.cloud.spanner.v1.stub.SpannerStub;
 import com.google.cloud.spanner.v1.stub.SpannerStubSettings;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Throwables;
 import com.google.spanner.v1.RollbackRequest;
 import io.grpc.Context;
@@ -45,25 +47,36 @@ class SpannerRetryHelper {
    * retrying aborted transactions will also automatically be updated if the default retry settings
    * are updated.
    *
+   * <p>A read/write transaction should not timeout while retrying. The total timeout of the retry
+   * settings is therefore set to 24 hours and there is no max attempts value.
+   *
    * <p>These default {@link RetrySettings} are only used if no retry information is returned by the
    * {@link AbortedException}.
    */
-  private static final RetrySettings txRetrySettings =
-      SpannerStubSettings.newBuilder().rollbackSettings().getRetrySettings();
+  @VisibleForTesting
+  static final RetrySettings txRetrySettings =
+      SpannerStubSettings.newBuilder()
+          .rollbackSettings()
+          .getRetrySettings()
+          .toBuilder()
+          .setTotalTimeout(Duration.ofHours(24L))
+          .setMaxAttempts(0)
+          .build();
 
   /** Executes the {@link Callable} and retries if it fails with an {@link AbortedException}. */
   static <T> T runTxWithRetriesOnAborted(Callable<T> callable) {
-    return runTxWithRetriesOnAborted(callable, txRetrySettings);
+    return runTxWithRetriesOnAborted(callable, txRetrySettings, NanoClock.getDefaultClock());
   }
 
   /**
    * Executes the {@link Callable} and retries if it fails with an {@link AbortedException} using
    * the specific {@link RetrySettings}.
    */
-  static <T> T runTxWithRetriesOnAborted(Callable<T> callable, RetrySettings retrySettings) {
+  @VisibleForTesting
+  static <T> T runTxWithRetriesOnAborted(
+      Callable<T> callable, RetrySettings retrySettings, ApiClock clock) {
     try {
-      return RetryHelper.runWithRetries(
-          callable, retrySettings, new TxRetryAlgorithm<>(), NanoClock.getDefaultClock());
+      return RetryHelper.runWithRetries(callable, retrySettings, new TxRetryAlgorithm<>(), clock);
     } catch (RetryHelperException e) {
       if (e.getCause() != null) {
         Throwables.throwIfUnchecked(e.getCause());

google-cloud-spanner/src/test/java/com/google/cloud/spanner/SpannerRetryHelperTest.java

@@ -17,8 +17,10 @@
 package com.google.cloud.spanner;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
+import com.google.api.core.ApiClock;
 import com.google.common.base.Stopwatch;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import com.google.protobuf.Duration;
@@ -42,6 +44,66 @@
 
 @RunWith(JUnit4.class)
 public class SpannerRetryHelperTest {
+  private static class FakeClock implements ApiClock {
+    private long currentTime;
+
+    @Override
+    public long nanoTime() {
+      return TimeUnit.NANOSECONDS.convert(currentTime, TimeUnit.MILLISECONDS);
+    }
+
+    @Override
+    public long millisTime() {
+      return currentTime;
+    }
+  }
+
+  @Test
+  public void testRetryDoesNotTimeoutAfterTenMinutes() {
+    final FakeClock clock = new FakeClock();
+    final AtomicInteger attempts = new AtomicInteger();
+    Callable<Integer> callable =
+        new Callable<Integer>() {
+          @Override
+          public Integer call() {
+            if (attempts.getAndIncrement() == 0) {
+              clock.currentTime += TimeUnit.MILLISECONDS.convert(10L, TimeUnit.MINUTES);
+              throw SpannerExceptionFactory.newSpannerException(ErrorCode.ABORTED, "test");
+            }
+            return 1 + 1;
+          }
+        };
+    assertEquals(
+        2,
+        SpannerRetryHelper.runTxWithRetriesOnAborted(
+                callable, SpannerRetryHelper.txRetrySettings, clock)
+            .intValue());
+  }
+
+  @Test
+  public void testRetryDoesFailAfterMoreThanOneDay() {
+    final FakeClock clock = new FakeClock();
+    final AtomicInteger attempts = new AtomicInteger();
+    Callable<Integer> callable =
+        new Callable<Integer>() {
+          @Override
+          public Integer call() {
+            if (attempts.getAndIncrement() == 0) {
+              clock.currentTime += TimeUnit.MILLISECONDS.convert(25L, TimeUnit.HOURS);
+              throw SpannerExceptionFactory.newSpannerException(ErrorCode.ABORTED, "test");
+            }
+            return 1 + 1;
+          }
+        };
+    try {
+      SpannerRetryHelper.runTxWithRetriesOnAborted(
+          callable, SpannerRetryHelper.txRetrySettings, clock);
+      fail("missing expected exception");
+    } catch (SpannerException e) {
+      assertEquals(ErrorCode.ABORTED, e.getErrorCode());
+      assertEquals(1, attempts.get());
+    }
+  }
 
   @Test
   public void testCancelledContext() {