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[improvement] Add support for tracing-aware Guava FutureCallbacks. #77

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[improvement] Add support for tracing-aware Guava FutureCallbacks. #77

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2f95228
Add support for tracing-aware Guava FutureCallbacks.
Feb 19, 2019
c7e322d
Addressing CR comments
Feb 20, 2019
e219419
Merge branch 'develop' into dd/wrappedFutures
Feb 21, 2019
e627b57
Add operation names
Feb 21, 2019
00a7021
Fix concurrency with separate thread tests
Feb 22, 2019
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38 changes: 38 additions & 0 deletions tracing/src/main/java/com/palantir/tracing/Tracers.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,13 @@

package com.palantir.tracing;

import com.google.common.util.concurrent.FutureCallback;
import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadLocalRandom;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;

/** Utility methods for making {@link ExecutorService} and {@link Runnable} instances tracing-aware. */
public final class Tracers {
Expand Down Expand Up @@ -133,6 +135,11 @@ public static Runnable wrap(Runnable delegate) {
return new TracingAwareRunnable(Optional.empty(), delegate);
}

/** Like {@link #wrap(String, Callable)}, but for Guava's FutureCallback. */
public static <V> FutureCallback<V> wrap(String operation, FutureCallback<V> delegate) {
return new TracingAwareFutureCallback<>(operation, delegate);
}

/**
* Like {@link #wrap(Runnable)}, but using the given {@link String operation} is used to create a span for the
* execution.
Expand Down Expand Up @@ -352,6 +359,37 @@ public void run() {
}
}

/**
* Wrap a given guava future callback such that its execution operated with the {@link Trace thread-local Trace} of
* the thread the constructs the {@link TracingAwareFutureCallback} instance rather than the thread that executes
* the callback.
*/
private static class TracingAwareFutureCallback<V> implements FutureCallback<V> {
private final FutureCallback<V> delegate;
private DeferredTracer deferredTracer;

TracingAwareFutureCallback(String operation, FutureCallback<V> delegate) {
this.delegate = delegate;
this.deferredTracer = new DeferredTracer(operation);
}

@Override
public void onSuccess(@NullableDecl V result) {
deferredTracer.withTrace(() -> {
delegate.onSuccess(result);
return null;
});
}

@Override
public void onFailure(Throwable throwable) {
deferredTracer.withTrace(() -> {
delegate.onFailure(throwable);
return null;
});
}
}

public interface ThrowingCallable<T, E extends Throwable> {
T call() throws E;
}
Expand Down
220 changes: 220 additions & 0 deletions tracing/src/test/java/com/palantir/tracing/TracersTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,18 +20,27 @@
import static org.assertj.core.api.Assertions.assertThatThrownBy;

import com.google.common.collect.Lists;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.common.util.concurrent.MoreExecutors;
import com.palantir.tracing.api.OpenSpan;
import com.palantir.tracing.api.Span;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
Expand Down Expand Up @@ -500,6 +509,150 @@ public void testWrapRunnableWithAlternateTraceId_traceStateRestoredToCleared() {
assertThat(Tracer.hasTraceId()).isFalse();
}

@Test
public void testWrappingFutureCallback_futureCallbackTraceIsIsolated_success() throws Exception {
CompletionAwareFutureCallback<Void> futureCallback = createFutureCallbackWithFunction(
() -> Tracer.startSpan("inside"));

ListeningExecutorService listeningExecutorService =
MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor());
ListenableFuture<Void> future = listeningExecutorService.submit(() -> null);

Tracer.startSpan("outside");
FutureCallback<Void> callback = Tracers.wrap("callback", futureCallback);
// Using direct executor to use same thread to verify callback doesn't modify thread state
Futures.addCallback(future, callback, MoreExecutors.directExecutor());

assertThat(futureCallback.waitForCompletion(10, TimeUnit.SECONDS)).isTrue();
assertThat(futureCallback.wasSuccess()).isTrue();
future.get();

assertThat(Tracer.completeSpan().get().getOperation()).isEqualTo("outside");
}

@Test
public void testWrappingFutureCallback_futureCallbackTraceIsIsolated_failure() throws Exception {
CompletionAwareFutureCallback<Void> futureCallback = createFutureCallbackWithFunction(
() -> Tracer.startSpan("inside"));

ListeningExecutorService listeningExecutorService =
MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor());
ListenableFuture<Void> future = listeningExecutorService.submit(() -> {
throw new IllegalStateException();
});
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Should use separate test cases for these


Tracer.startSpan("outside");
FutureCallback<Void> callback = Tracers.wrap("callback", futureCallback);
// Using direct executor to use same thread to verify callback doesn't modify thread state
Futures.addCallback(future, callback, MoreExecutors.directExecutor());

assertThat(futureCallback.waitForCompletion(10, TimeUnit.SECONDS)).isTrue();
assertThat(futureCallback.wasSuccess()).isFalse();
assertThatThrownBy(future::get).isInstanceOf(ExecutionException.class);

assertThat(Tracer.completeSpan().get().getOperation()).isEqualTo("outside");
}

@Test
public void testWrappingFutureCallback_traceStateShowsCorrectlyParentedNewOperation_success_sameThread()
throws Exception {
AtomicReference<Span> span = new AtomicReference<>();
CompletionAwareFutureCallback<Void> futureCallback = createFutureCallbackWithFunction(
() -> span.set(Tracer.completeSpan().get()));

ListeningExecutorService listeningExecutorService =
MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor());
ListenableFuture<Void> future = listeningExecutorService.submit(() -> null);

OpenSpan beforeSpan = Tracer.startSpan("before-construction");
FutureCallback<Void> callback = Tracers.wrap("callback", futureCallback);
Tracer.startSpan("after-construction");
Futures.addCallback(future, callback, MoreExecutors.directExecutor());

assertThat(futureCallback.waitForCompletion(10, TimeUnit.SECONDS)).isTrue();
assertThat(futureCallback.wasSuccess()).isTrue();
future.get();

assertThat(span.get().getOperation()).isEqualTo("callback");
assertThat(span.get().getParentSpanId().get()).isEqualTo(beforeSpan.getSpanId());
}

@Test
public void testWrappingFutureCallback_traceStateShowsCorrectlyParentedNewOperation_success_differentThread()
throws Exception {
AtomicReference<Span> span = new AtomicReference<>();
CompletionAwareFutureCallback<Void> futureCallback = createFutureCallbackWithFunction(
() -> span.set(Tracer.completeSpan().get()));

ListeningExecutorService listeningExecutorService =
MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor());
ListenableFuture<Void> future = listeningExecutorService.submit(() -> null);

OpenSpan beforeSpan = Tracer.startSpan("before-construction");
FutureCallback<Void> callback = Tracers.wrap("callback", futureCallback);
Tracer.startSpan("after-construction");
Futures.addCallback(future, callback, Executors.newSingleThreadExecutor());

assertThat(futureCallback.waitForCompletion(10, TimeUnit.SECONDS)).isTrue();
assertThat(futureCallback.wasSuccess()).isTrue();
future.get();

assertThat(span.get().getOperation()).isEqualTo("callback");
assertThat(span.get().getParentSpanId().get()).isEqualTo(beforeSpan.getSpanId());
}

@Test
public void testWrappingFutureCallback_traceStateShowsCorrectlyParentedNewOperation_failure_sameThread()
throws Exception {
AtomicReference<Span> span = new AtomicReference<>();
CompletionAwareFutureCallback<Void> futureCallback = createFutureCallbackWithFunction(
() -> span.set(Tracer.completeSpan().get()));

ListeningExecutorService listeningExecutorService =
MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor());
ListenableFuture<Void> future = listeningExecutorService.submit(() -> {
throw new IllegalStateException();
});

OpenSpan beforeSpan = Tracer.startSpan("before-construction");
FutureCallback<Void> callback = Tracers.wrap("callback", futureCallback);
Tracer.startSpan("after-construction");
Futures.addCallback(future, callback, MoreExecutors.directExecutor());

assertThat(futureCallback.waitForCompletion(10, TimeUnit.SECONDS)).isTrue();
assertThat(futureCallback.wasSuccess()).isFalse();
assertThatThrownBy(future::get).isInstanceOf(ExecutionException.class);

assertThat(span.get().getOperation()).isEqualTo("callback");
assertThat(span.get().getParentSpanId().get()).isEqualTo(beforeSpan.getSpanId());
}

@Test
public void testWrappingFutureCallback_traceStateShowsCorrectlyParentedNewOperation_failure_differentThread()
throws Exception {
AtomicReference<Span> span = new AtomicReference<>();
CompletionAwareFutureCallback<Void> futureCallback = createFutureCallbackWithFunction(
() -> span.set(Tracer.completeSpan().get()));

ListeningExecutorService listeningExecutorService =
MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor());
ListenableFuture<Void> future = listeningExecutorService.submit(() -> {
throw new IllegalStateException();
});

OpenSpan beforeSpan = Tracer.startSpan("before-construction");
FutureCallback<Void> callback = Tracers.wrap("callback", futureCallback);
Tracer.startSpan("after-construction");
Futures.addCallback(future, callback, Executors.newSingleThreadExecutor());

assertThat(futureCallback.waitForCompletion(10, TimeUnit.SECONDS)).isTrue();
assertThat(futureCallback.wasSuccess()).isFalse();
assertThatThrownBy(future::get).isInstanceOf(ExecutionException.class);

assertThat(span.get().getOperation()).isEqualTo("callback");
assertThat(span.get().getParentSpanId().get()).isEqualTo(beforeSpan.getSpanId());
}

@Test
public void testTraceIdGeneration() throws Exception {
assertThat(Tracers.randomId()).hasSize(16); // fails with p=1/16 if generated string is not padded
Expand Down Expand Up @@ -615,4 +768,71 @@ private static List<OpenSpan> getCurrentTrace() {
return Lists.reverse(spans);
}).orElse(Collections.emptyList());
}

private static <V> CompletionAwareFutureCallback<V> createFutureCallbackWithFunction(Runnable runnable) {
return new CompletionAwareFutureCallback<>(new FutureCallback<V>() {
@Override
public void onSuccess(@NullableDecl V result) {
runnable.run();
}

@Override
public void onFailure(Throwable throwable) {
runnable.run();
}
});
}

/**
* Defines an interface for providing information on completion of execution and the ability to wait on completion
* for use with tests involving FutureCallback.
*/
private interface CompletionAware {
boolean waitForCompletion(long timeout, TimeUnit unit) throws InterruptedException;
boolean wasSuccess();
}

/**
* There is no guarantee when a FutureCallback will actually run. In order to verify state from inside the
* FutureCallback, a CountDownLatch is used to track when the FutureCallback has finished executing and to provide
* a condition to wait on.
*/
private static final class CompletionAwareFutureCallback<V> implements FutureCallback<V>, CompletionAware {
private final CountDownLatch latch = new CountDownLatch(1);
private final FutureCallback<V> delegate;
private AtomicReference<Boolean> success = new AtomicReference<>(Boolean.FALSE);

CompletionAwareFutureCallback(FutureCallback<V> delegate) {
this.delegate = delegate;
}

@Override
public void onSuccess(@NullableDecl V result) {
try {
success.set(Boolean.TRUE);
delegate.onSuccess(result);
} finally {
latch.countDown();
}
}

@Override
public void onFailure(Throwable throwable) {
try {
delegate.onFailure(throwable);
} finally {
latch.countDown();
}
}

@Override
public boolean waitForCompletion(long timeout, TimeUnit unit) throws InterruptedException {
return latch.await(timeout, unit);
}

@Override
public boolean wasSuccess() {
return success.get();
}
}
}