[6.3.0] Use failure_rate instead of failure count for circuit breaker (…

…#18559)

* feat: Implement failure circuit breaker

Copy of #18120: I accidentally closed #18120 during rebase and doesn't have permission to reopen.

We have noticed that any problems with the remote cache have a detrimental effect on build times. On investigation we found that the interface for the circuit breaker was left unimplemented.

To address this issue, implemented a failure circuit breaker, which includes three new Bazel flags: 1) experimental_circuitbreaker_strategy, 2) experimental_remote_failure_threshold, and 3) experimental_emote_failure_window.

In this implementation, I have implemented failure strategy for circuit breaker and used failure count to trip the circuit.

Reasoning behind using failure count instead of failure rate : To measure failure rate I also need the success count. While both the failure and success count need to be an AtomicInteger as both will be modified concurrently by multiple threads. Even though getAndIncrement is very light weight operation, at very high request it might contribute to latency.

Reasoning behind using failure circuit breaker : A new instance of Retrier.CircuitBreaker is created for each build. Therefore, if the circuit breaker trips during a build, the remote cache will be disabled for that build. However, it will be enabled again
for the next build as a new instance of Retrier.CircuitBreaker will be created. If needed in the future we may add cool down strategy also. e.g. failure_and_cool_down_startegy.

closes #18136

Closes #18359.

PiperOrigin-RevId: 536349954
Change-Id: I5e1c57d4ad0ce07ddc4808bf1f327bc5df6ce704

* remove target included in cherry-pick by mistake

* Use failure_rate instead of failure count for circuit breaker

---------

Co-authored-by: Ian (Hee) Cha <heec@google.com>

src/main/java/com/google/devtools/build/lib/remote/circuitbreaker/CircuitBreakerFactory.java

@@ -23,6 +23,7 @@ public class CircuitBreakerFactory {
 
   public static final ImmutableSet<Class<? extends Exception>> DEFAULT_IGNORED_ERRORS =
       ImmutableSet.of(CacheNotFoundException.class);
+  public static final int DEFAULT_MIN_CALL_COUNT_TO_COMPUTE_FAILURE_RATE = 100;
 
   private CircuitBreakerFactory() {}
 
@@ -37,7 +38,7 @@ private CircuitBreakerFactory() {}
   public static Retrier.CircuitBreaker createCircuitBreaker(final RemoteOptions remoteOptions) {
     if (remoteOptions.circuitBreakerStrategy == RemoteOptions.CircuitBreakerStrategy.FAILURE) {
       return new FailureCircuitBreaker(
-          remoteOptions.remoteFailureThreshold,
+          remoteOptions.remoteFailureRateThreshold,
           (int) remoteOptions.remoteFailureWindowInterval.toMillis());
     }
     return Retrier.ALLOW_ALL_CALLS;

src/main/java/com/google/devtools/build/lib/remote/circuitbreaker/FailureCircuitBreaker.java

@@ -21,34 +21,38 @@
 import java.util.concurrent.atomic.AtomicInteger;
 
 /**
- * The {@link FailureCircuitBreaker} implementation of the {@link Retrier.CircuitBreaker} prevents
- * further calls to a remote cache once the number of failures within a given window exceeds a
- * specified threshold for a build. In the context of Bazel, a new instance of {@link
- * Retrier.CircuitBreaker} is created for each build. Therefore, if the circuit breaker trips during
- * a build, the remote cache will be disabled for that build. However, it will be enabled again for
- * the next build as a new instance of {@link Retrier.CircuitBreaker} will be created.
+ * The {@link FailureCircuitBreaker} implementation of the {@link Retrier.CircuitBreaker} prevents further calls to
+ * a remote cache once the failures rate within a given window exceeds a specified threshold for a build.
+ * In the context of Bazel, a new instance of {@link Retrier.CircuitBreaker} is created for each build. Therefore, if
+ * the circuit breaker trips during a build, the remote cache will be disabled for that build. However, it will be
+ * enabled again for the next build as a new instance of {@link Retrier.CircuitBreaker} will be created.
  */
 public class FailureCircuitBreaker implements Retrier.CircuitBreaker {
 
   private State state;
+  private final AtomicInteger successes;
   private final AtomicInteger failures;
-  private final int failureThreshold;
+  private final AtomicInteger ignoredFailures;
+  private final int failureRateThreshold;
   private final int slidingWindowSize;
+  private final int minCallCountToComputeFailureRate;
   private final ScheduledExecutorService scheduledExecutor;
   private final ImmutableSet<Class<? extends Exception>> ignoredErrors;
 
   /**
    * Creates a {@link FailureCircuitBreaker}.
    *
-   * @param failureThreshold is used to set the number of failures required to trip the circuit
-   *     breaker in given time window.
-   * @param slidingWindowSize the size of the sliding window in milliseconds to calculate the number
-   *     of failures.
+   * @param failureRateThreshold  is used to set the min percentage of failure required to trip the circuit breaker in
+   *                             given time window.
+   * @param slidingWindowSize the size of the sliding window in milliseconds to calculate the number of failures.
    */
-  public FailureCircuitBreaker(int failureThreshold, int slidingWindowSize) {
-    this.failureThreshold = failureThreshold;
+  public FailureCircuitBreaker(int failureRateThreshold, int slidingWindowSize) {
     this.failures = new AtomicInteger(0);
+    this.successes = new AtomicInteger(0);
+    this.ignoredFailures = new AtomicInteger(0);
+    this.failureRateThreshold = failureRateThreshold;
     this.slidingWindowSize = slidingWindowSize;
+    this.minCallCountToComputeFailureRate = CircuitBreakerFactory.DEFAULT_MIN_CALL_COUNT_TO_COMPUTE_FAILURE_RATE;
     this.state = State.ACCEPT_CALLS;
     this.scheduledExecutor =
         slidingWindowSize > 0 ? Executors.newSingleThreadScheduledExecutor() : null;
@@ -64,20 +68,36 @@ public State state() {
   public void recordFailure(Exception e) {
     if (!ignoredErrors.contains(e.getClass())) {
       int failureCount = failures.incrementAndGet();
+      int totalCallCount = successes.get() + failureCount + ignoredFailures.get();
       if (slidingWindowSize > 0) {
         var unused =
             scheduledExecutor.schedule(
                 failures::decrementAndGet, slidingWindowSize, TimeUnit.MILLISECONDS);
       }
+
+      if (totalCallCount < minCallCountToComputeFailureRate) {
+        // The remote call count is below the threshold required to calculate the failure rate.
+        return;
+      }
+      double failureRate = (failureCount * 100.0) / totalCallCount;
+
       // Since the state can only be changed to the open state, synchronization is not required.
-      if (failureCount > this.failureThreshold) {
+      if (failureRate > this.failureRateThreshold) {
         this.state = State.REJECT_CALLS;
       }
+    } else {
+      ignoredFailures.incrementAndGet();
+      if (slidingWindowSize > 0) {
+        scheduledExecutor.schedule(ignoredFailures::decrementAndGet, slidingWindowSize, TimeUnit.MILLISECONDS);
+      }
     }
   }
 
   @Override
   public void recordSuccess() {
-    // do nothing, implement if we need to set threshold on failure rate instead of count.
+    successes.incrementAndGet();
+    if (slidingWindowSize > 0) {
+      scheduledExecutor.schedule(successes::decrementAndGet, slidingWindowSize, TimeUnit.MILLISECONDS);
+    }
   }
 }

src/main/java/com/google/devtools/build/lib/remote/options/RemoteOptions.java

@@ -695,15 +695,16 @@ public RemoteOutputsStrategyConverter() {
   public CircuitBreakerStrategy circuitBreakerStrategy;
 
   @Option(
-      name = "experimental_remote_failure_threshold",
-      defaultValue = "100",
+      name = "experimental_remote_failure_rate_threshold",
+      defaultValue = "10",
       documentationCategory = OptionDocumentationCategory.REMOTE,
       effectTags = {OptionEffectTag.EXECUTION},
+      converter = Converters.PercentageConverter.class,
       help =
-          "Sets the allowed number of failures in a specific time window after which it stops"
-              + " calling to the remote cache/executor. By default the value is 100. Setting this"
-              + " to 0 or negative means no limitation.")
-  public int remoteFailureThreshold;
+          "Sets the allowed number of failure rate in percentage for a specific time window after which it stops "
+              + "calling to the remote cache/executor. By default the value is 10. Setting this to 0 means no "
+              + "limitation.")
+  public int remoteFailureRateThreshold;
 
   @Option(
       name = "experimental_remote_failure_window_interval",
@@ -712,7 +713,7 @@ public RemoteOutputsStrategyConverter() {
       effectTags = {OptionEffectTag.EXECUTION},
       converter = RemoteDurationConverter.class,
       help =
-          "The interval in which the failure count of the remote requests are computed. On zero or"
+          "The interval in which the failure rate of the remote requests are computed. On zero or"
               + " negative value the failure duration is computed the whole duration of the"
               + " execution.Following units can be used: Days (d), hours (h), minutes (m), seconds"
               + " (s), and milliseconds (ms). If the unit is omitted, the value is interpreted as"

src/test/java/com/google/devtools/build/lib/remote/circuitbreaker/FailureCircuitBreakerTest.java

@@ -18,51 +18,71 @@
 import build.bazel.remote.execution.v2.Digest;
 import com.google.devtools.build.lib.remote.Retrier.CircuitBreaker.State;
 import com.google.devtools.build.lib.remote.common.CacheNotFoundException;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
+import java.util.stream.IntStream;
+
 @RunWith(JUnit4.class)
 public class FailureCircuitBreakerTest {
 
   @Test
-  public void testRecordFailure() throws InterruptedException {
-    final int failureThreshold = 10;
+  public void testRecordFailure_withIgnoredErrors() throws InterruptedException {
+    final int failureRateThreshold = 10;
     final int windowInterval = 100;
     FailureCircuitBreaker failureCircuitBreaker =
-        new FailureCircuitBreaker(failureThreshold, windowInterval);
+        new FailureCircuitBreaker(failureRateThreshold, windowInterval);
 
     List<Exception> listOfExceptionThrownOnFailure = new ArrayList<>();
-    for (int index = 0; index < failureThreshold; index++) {
+    for (int index = 0; index < failureRateThreshold; index++) {
       listOfExceptionThrownOnFailure.add(new Exception());
     }
-    for (int index = 0; index < failureThreshold * 9; index++) {
+    for (int index = 0; index < failureRateThreshold * 9; index++) {
       listOfExceptionThrownOnFailure.add(new CacheNotFoundException(Digest.newBuilder().build()));
     }
 
     Collections.shuffle(listOfExceptionThrownOnFailure);
 
     // make calls equals to threshold number of not ignored failure calls in parallel.
-    listOfExceptionThrownOnFailure.stream()
-        .parallel()
-        .forEach(failureCircuitBreaker::recordFailure);
+    listOfExceptionThrownOnFailure.stream().parallel().forEach(failureCircuitBreaker::recordFailure);
     assertThat(failureCircuitBreaker.state()).isEqualTo(State.ACCEPT_CALLS);
 
     // Sleep for windowInterval + 1ms.
     Thread.sleep(windowInterval + 1 /*to compensate any delay*/);
 
     // make calls equals to threshold number of not ignored failure calls in parallel.
-    listOfExceptionThrownOnFailure.stream()
-        .parallel()
-        .forEach(failureCircuitBreaker::recordFailure);
+    listOfExceptionThrownOnFailure.stream().parallel().forEach(failureCircuitBreaker::recordFailure);
     assertThat(failureCircuitBreaker.state()).isEqualTo(State.ACCEPT_CALLS);
 
     // Sleep for less than windowInterval.
     Thread.sleep(windowInterval - 5);
     failureCircuitBreaker.recordFailure(new Exception());
     assertThat(failureCircuitBreaker.state()).isEqualTo(State.REJECT_CALLS);
   }
+
+  @Test
+  public void testRecordFailure_minCallCriteriaNotMet() throws InterruptedException {
+    final int failureRateThreshold = 10;
+    final int windowInterval = 100;
+    final int minCallToComputeFailure = CircuitBreakerFactory.DEFAULT_MIN_CALL_COUNT_TO_COMPUTE_FAILURE_RATE;
+    FailureCircuitBreaker failureCircuitBreaker =
+        new FailureCircuitBreaker(failureRateThreshold, windowInterval);
+
+    // make half failure call, half success call and number of total call less than minCallToComputeFailure.
+    IntStream.range(0, minCallToComputeFailure >> 1).parallel()
+        .forEach(i -> failureCircuitBreaker.recordFailure(new Exception()));
+    IntStream.range(0, minCallToComputeFailure >> 1).parallel().forEach(i -> failureCircuitBreaker.recordSuccess());
+    assertThat(failureCircuitBreaker.state()).isEqualTo(State.ACCEPT_CALLS);
+
+    // Sleep for less than windowInterval.
+    Thread.sleep(windowInterval - 20);
+    failureCircuitBreaker.recordFailure(new Exception());
+    assertThat(failureCircuitBreaker.state()).isEqualTo(State.REJECT_CALLS);
+  }
 }