Refine delay jitter for exponential backoff (#7206)

exporters/sender/jdk/src/main/java/io/opentelemetry/exporter/sender/jdk/internal/JdkHttpSender.java

@@ -213,9 +213,11 @@ public final class JdkHttpSender implements HttpSender {
     do {
       if (attempt > 0) {
         // Compute and sleep for backoff
-        long upperBoundNanos = Math.min(nextBackoffNanos, retryPolicy.getMaxBackoff().toNanos());
-        long backoffNanos = ThreadLocalRandom.current().nextLong(upperBoundNanos);
-        nextBackoffNanos = (long) (nextBackoffNanos * retryPolicy.getBackoffMultiplier());
+        long currentBackoffNanos =
+            Math.min(nextBackoffNanos, retryPolicy.getMaxBackoff().toNanos());
+        long backoffNanos =
+            (long) (ThreadLocalRandom.current().nextDouble(0.8d, 1.2d) * currentBackoffNanos);
+        nextBackoffNanos = (long) (currentBackoffNanos * retryPolicy.getBackoffMultiplier());
         try {
           TimeUnit.NANOSECONDS.sleep(backoffNanos);
         } catch (InterruptedException e) {
@@ -227,16 +229,11 @@ public final class JdkHttpSender implements HttpSender {
           break;
         }
       }
-
-      attempt++;
+      httpResponse = null;
+      exception = null;
       requestBuilder.timeout(Duration.ofNanos(timeoutNanos - (System.nanoTime() - startTimeNanos)));
       try {
         httpResponse = sendRequest(requestBuilder, byteBufferPool);
-      } catch (IOException e) {
-        exception = e;
-      }
-
-      if (httpResponse != null) {
         boolean retryable = retryableStatusCodes.contains(httpResponse.statusCode());
         if (logger.isLoggable(Level.FINER)) {
           logger.log(
@@ -251,8 +248,8 @@ public final class JdkHttpSender implements HttpSender {
         if (!retryable) {
           return httpResponse;
         }
-      }
-      if (exception != null) {
+      } catch (IOException e) {
+        exception = e;
         boolean retryable = retryExceptionPredicate.test(exception);
         if (logger.isLoggable(Level.FINER)) {
           logger.log(
@@ -268,7 +265,7 @@ public final class JdkHttpSender implements HttpSender {
           throw exception;
         }
       }
-    } while (attempt < retryPolicy.getMaxAttempts());
+    } while (++attempt < retryPolicy.getMaxAttempts());
 
     if (httpResponse != null) {
       return httpResponse;

exporters/sender/okhttp/src/main/java/io/opentelemetry/exporter/sender/okhttp/internal/RetryInterceptor.java

@@ -18,6 +18,7 @@ import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
 import java.util.function.Predicate;
+import java.util.function.Supplier;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import okhttp3.Interceptor;
@@ -37,7 +38,7 @@ public final class RetryInterceptor implements Interceptor {
   private final Function<Response, Boolean> isRetryable;
   private final Predicate<IOException> retryExceptionPredicate;
   private final Sleeper sleeper;
-  private final BoundedLongGenerator randomLong;
+  private final Supplier<Double> randomJitter;
 
   /** Constructs a new retrier. */
   public RetryInterceptor(RetryPolicy retryPolicy, Function<Response, Boolean> isRetryable) {
@@ -48,7 +49,7 @@ public final class RetryInterceptor implements Interceptor {
             ? RetryInterceptor::isRetryableException
             : retryPolicy.getRetryExceptionPredicate(),
         TimeUnit.NANOSECONDS::sleep,
-        bound -> ThreadLocalRandom.current().nextLong(bound));
+        () -> ThreadLocalRandom.current().nextDouble(0.8d, 1.2d));
   }
 
   // Visible for testing
@@ -57,12 +58,12 @@ public final class RetryInterceptor implements Interceptor {
       Function<Response, Boolean> isRetryable,
       Predicate<IOException> retryExceptionPredicate,
       Sleeper sleeper,
-      BoundedLongGenerator randomLong) {
+      Supplier<Double> randomJitter) {
     this.retryPolicy = retryPolicy;
     this.isRetryable = isRetryable;
     this.retryExceptionPredicate = retryExceptionPredicate;
     this.sleeper = sleeper;
-    this.randomLong = randomLong;
+    this.randomJitter = randomJitter;
   }
 
   @Override
@@ -75,9 +76,10 @@ public final class RetryInterceptor implements Interceptor {
       if (attempt > 0) {
         // Compute and sleep for backoff
         // https://github.com/grpc/proposal/blob/master/A6-client-retries.md#exponential-backoff
-        long upperBoundNanos = Math.min(nextBackoffNanos, retryPolicy.getMaxBackoff().toNanos());
-        long backoffNanos = randomLong.get(upperBoundNanos);
-        nextBackoffNanos = (long) (nextBackoffNanos * retryPolicy.getBackoffMultiplier());
+        long currentBackoffNanos =
+            Math.min(nextBackoffNanos, retryPolicy.getMaxBackoff().toNanos());
+        long backoffNanos = (long) (randomJitter.get() * currentBackoffNanos);
+        nextBackoffNanos = (long) (currentBackoffNanos * retryPolicy.getBackoffMultiplier());
         try {
           sleeper.sleep(backoffNanos);
         } catch (InterruptedException e) {
@@ -88,31 +90,31 @@ public final class RetryInterceptor implements Interceptor {
         if (response != null) {
           response.close();
         }
+        exception = null;
       }
-
-      attempt++;
       try {
         response = chain.proceed(chain.request());
+        if (response != null) {
+          boolean retryable = Boolean.TRUE.equals(isRetryable.apply(response));
+          if (logger.isLoggable(Level.FINER)) {
+            logger.log(
+                Level.FINER,
+                "Attempt "
+                    + attempt
+                    + " returned "
+                    + (retryable ? "retryable" : "non-retryable")
+                    + " response: "
+                    + responseStringRepresentation(response));
+          }
+          if (!retryable) {
+            return response;
+          }
+        } else {
+          throw new NullPointerException("response cannot be null.");
+        }
       } catch (IOException e) {
         exception = e;
-      }
-      if (response != null) {
-        boolean retryable = Boolean.TRUE.equals(isRetryable.apply(response));
-        if (logger.isLoggable(Level.FINER)) {
-          logger.log(
-              Level.FINER,
-              "Attempt "
-                  + attempt
-                  + " returned "
-                  + (retryable ? "retryable" : "non-retryable")
-                  + " response: "
-                  + responseStringRepresentation(response));
-        }
-        if (!retryable) {
-          return response;
-        }
-      }
-      if (exception != null) {
+        response = null;
         boolean retryable = retryExceptionPredicate.test(exception);
         if (logger.isLoggable(Level.FINER)) {
           logger.log(
@@ -128,8 +130,7 @@ public final class RetryInterceptor implements Interceptor {
           throw exception;
         }
       }
-
-    } while (attempt < retryPolicy.getMaxAttempts());
+    } while (++attempt < retryPolicy.getMaxAttempts());
 
     if (response != null) {
       return response;
@@ -172,11 +173,6 @@ public final class RetryInterceptor implements Interceptor {
     return false;
   }
 
-  // Visible for testing
-  interface BoundedLongGenerator {
-    long get(long bound);
-  }
-
   // Visible for testing
   interface Sleeper {
     void sleep(long delayNanos) throws InterruptedException;

exporters/sender/okhttp/src/test/java/io/opentelemetry/exporter/sender/okhttp/internal/RetryInterceptorTest.java

@@ -9,8 +9,9 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doNothing;
-import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
@@ -32,9 +33,11 @@ import java.net.UnknownHostException;
 import java.time.Duration;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Predicate;
+import java.util.function.Supplier;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.stream.Stream;
+import okhttp3.Interceptor;
 import okhttp3.OkHttpClient;
 import okhttp3.Request;
 import okhttp3.Response;
@@ -47,7 +50,9 @@ import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 import org.junit.jupiter.params.provider.ValueSource;
 import org.mockito.Mock;
+import org.mockito.invocation.InvocationOnMock;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.mockito.stubbing.Answer;
 
 @ExtendWith(MockitoExtension.class)
 class RetryInterceptorTest {
@@ -55,7 +60,7 @@ class RetryInterceptorTest {
   @RegisterExtension static final MockWebServerExtension server = new MockWebServerExtension();
 
   @Mock private RetryInterceptor.Sleeper sleeper;
-  @Mock private RetryInterceptor.BoundedLongGenerator random;
+  @Mock private Supplier<Double> random;
   private Predicate<IOException> retryExceptionPredicate;
 
   private RetryInterceptor retrier;
@@ -91,6 +96,24 @@ class RetryInterceptorTest {
     client = new OkHttpClient.Builder().addInterceptor(retrier).build();
   }
 
+  @Test
+  void noRetryOnNullResponse() throws IOException {
+    Interceptor.Chain chain = mock(Interceptor.Chain.class);
+    when(chain.proceed(any())).thenReturn(null);
+    when(chain.request())
+        .thenReturn(new Request.Builder().url(server.httpUri().toString()).build());
+    assertThatThrownBy(
+            () -> {
+              retrier.intercept(chain);
+            })
+        .isInstanceOf(NullPointerException.class)
+        .hasMessage("response cannot be null.");
+
+    verifyNoInteractions(retryExceptionPredicate);
+    verifyNoInteractions(random);
+    verifyNoInteractions(sleeper);
+  }
+
   @Test
   void noRetry() throws Exception {
     server.enqueue(HttpResponse.of(HttpStatus.OK));
@@ -109,17 +132,8 @@ class RetryInterceptorTest {
   @ValueSource(ints = {5, 6})
   void backsOff(int attempts) throws Exception {
     succeedOnAttempt(attempts);
-
-    // Will backoff 4 times
-    when(random.get((long) (TimeUnit.SECONDS.toNanos(1) * Math.pow(1.6, 0)))).thenReturn(100L);
-    when(random.get((long) (TimeUnit.SECONDS.toNanos(1) * Math.pow(1.6, 1)))).thenReturn(50L);
-    // Capped
-    when(random.get(TimeUnit.SECONDS.toNanos(2))).thenReturn(500L).thenReturn(510L);
-
-    doNothing().when(sleeper).sleep(100);
-    doNothing().when(sleeper).sleep(50);
-    doNothing().when(sleeper).sleep(500);
-    doNothing().when(sleeper).sleep(510);
+    when(random.get()).thenReturn(1.0d);
+    doNothing().when(sleeper).sleep(anyLong());
 
     try (Response response = sendRequest()) {
       if (attempts <= 5) {
@@ -139,16 +153,26 @@ class RetryInterceptorTest {
     succeedOnAttempt(5);
 
     // Backs off twice, second is interrupted
-    when(random.get((long) (TimeUnit.SECONDS.toNanos(1) * Math.pow(1.6, 0)))).thenReturn(100L);
-    when(random.get((long) (TimeUnit.SECONDS.toNanos(1) * Math.pow(1.6, 1)))).thenReturn(50L);
+    when(random.get()).thenReturn(1.0d).thenReturn(1.0d);
+    doAnswer(
+            new Answer<Void>() {
+              int counter = 0;
 
-    doNothing().when(sleeper).sleep(100);
-    doThrow(new InterruptedException()).when(sleeper).sleep(50);
+              @Override
+              public Void answer(InvocationOnMock invocation) throws Throwable {
+                if (counter++ == 1) {
+                  throw new InterruptedException();
+                }
+                return null;
+              }
+            })
+        .when(sleeper)
+        .sleep(anyLong());
 
     try (Response response = sendRequest()) {
       assertThat(response.isSuccessful()).isFalse();
     }
-
+    verify(sleeper, times(2)).sleep(anyLong());
     for (int i = 0; i < 2; i++) {
       server.takeRequest(0, TimeUnit.NANOSECONDS);
     }
@@ -157,7 +181,7 @@ class RetryInterceptorTest {
   @Test
   void connectTimeout() throws Exception {
     client = connectTimeoutClient();
-    when(random.get(anyLong())).thenReturn(1L);
+    when(random.get()).thenReturn(1.0d);
     doNothing().when(sleeper).sleep(anyLong());
 
     // Connecting to a non-routable IP address to trigger connection error
@@ -174,7 +198,7 @@ class RetryInterceptorTest {
   @Test
   void connectException() throws Exception {
     client = connectTimeoutClient();
-    when(random.get(anyLong())).thenReturn(1L);
+    when(random.get()).thenReturn(1.0d);
     doNothing().when(sleeper).sleep(anyLong());
 
     // Connecting to localhost on an unused port address to trigger java.net.ConnectException