remote: concurrent blob downloads. Fixes #5215

This change introduces concurrent downloads of action outputs
for remote caching/execution. So far, for an action we would
download one output after the other which isn't as bad as it
sounds as we would typically run dozens or hundreds of actions
in parallel. However, for actions with a lot of outputs or graphs
that allow limited parallelism we expect this change to positively
impact performance.

Note, that with this change the AbstractRemoteActionCache will
attempt to always download all outputs concurrently. The actual
parallelism is controlled by the underlying network transport.
The gRPC transport currently enforces no limits on the concurrent
calls, which should be fine given that all calls are multiplexed
on a single network connection. The HTTP/1.1 transport also
enforces no parallelism by default, but I have added the
--remote_max_connections=INT flag which allows to specify an upper
bound on the number of network connections to be open concurrently.
I have introduced this flag as a defensive mechanism for users
who's environment might enforce an upper bound on the number of open
connections, as with this change its possible for the number of
concurrently open connections to dramatically increase (from
NumParallelActions to NumParallelActions * SumParallelActionOutputs).

A side effect of this change is that it puts the infrastructure
for retries and circuit breaking for the HttpBlobStore in place.

RELNOTES: None
PiperOrigin-RevId: 199005510

1 files changed, 47 insertions, 9 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/remote/RetrierTest.java b/src/test/java/com/google/devtools/build/lib/remote/RetrierTest.java
index 945c27d66d..624d074468 100644
--- a/src/test/java/com/google/devtools/build/lib/remote/RetrierTest.java
+++ b/src/test/java/com/google/devtools/build/lib/remote/RetrierTest.java
@@ -21,16 +21,22 @@ import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import com.google.common.util.concurrent.ListeningScheduledExecutorService;
+import com.google.common.util.concurrent.MoreExecutors;
 import com.google.devtools.build.lib.remote.Retrier.Backoff;
 import com.google.devtools.build.lib.remote.Retrier.CircuitBreaker;
 import com.google.devtools.build.lib.remote.Retrier.CircuitBreaker.State;
 import com.google.devtools.build.lib.remote.Retrier.CircuitBreakerException;
 import com.google.devtools.build.lib.remote.Retrier.RetryException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 import javax.annotation.concurrent.ThreadSafe;
+import org.junit.AfterClass;
 import org.junit.Before;
+import org.junit.BeforeClass;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -49,19 +55,31 @@ public class RetrierTest {
   private static final Predicate<Exception> RETRY_ALL = (e) -> true;
   private static final Predicate<Exception> RETRY_NONE = (e) -> false;
 
+  private static ListeningScheduledExecutorService retryService;
+
+  @BeforeClass
+  public static void beforeEverything() {
+    retryService = MoreExecutors.listeningDecorator(Executors.newScheduledThreadPool(1));
+  }
+
   @Before
   public void setup() {
     MockitoAnnotations.initMocks(this);
     when(alwaysOpen.state()).thenReturn(State.ACCEPT_CALLS);
   }
 
+  @AfterClass
+  public static void afterEverything() {
+    retryService.shutdownNow();
+  }
+
   @Test
   public void retryShouldWork_failure() throws Exception {
     // Test that a call is retried according to the backoff.
     // All calls fail.
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, alwaysOpen);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, alwaysOpen);
     try {
       r.execute(() -> {
         throw new Exception("call failed");
@@ -81,7 +99,7 @@ public class RetrierTest {
     // All calls fail.
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/2);
-    Retrier r = new Retrier(s, RETRY_NONE, alwaysOpen);
+    Retrier r = new Retrier(s, RETRY_NONE, retryService, alwaysOpen);
     try {
       r.execute(() -> {
         throw new Exception("call failed");
@@ -101,7 +119,7 @@ public class RetrierTest {
     // The last call succeeds.
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, alwaysOpen);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, alwaysOpen);
     AtomicInteger numCalls = new AtomicInteger();
     int val = r.execute(() -> {
       numCalls.incrementAndGet();
@@ -121,7 +139,7 @@ public class RetrierTest {
     // Test that nested calls using retries compose as expected.
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/1);
-    Retrier r = new Retrier(s, RETRY_ALL, alwaysOpen);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, alwaysOpen);
 
     AtomicInteger attemptsLvl0 = new AtomicInteger();
     AtomicInteger attemptsLvl1 = new AtomicInteger();
@@ -152,7 +170,7 @@ public class RetrierTest {
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/3);
     TripAfterNCircuitBreaker cb = new TripAfterNCircuitBreaker(/*maxConsecutiveFailures=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, cb);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, cb);
 
     try {
       r.execute(() -> {
@@ -174,7 +192,7 @@ public class RetrierTest {
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/3);
     TripAfterNCircuitBreaker cb = new TripAfterNCircuitBreaker(/*maxConsecutiveFailures=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, cb);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, cb);
 
     cb.trialCall();
 
@@ -192,7 +210,7 @@ public class RetrierTest {
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/3);
     TripAfterNCircuitBreaker cb = new TripAfterNCircuitBreaker(/*maxConsecutiveFailures=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, cb);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, cb);
 
     cb.trialCall();
 
@@ -214,7 +232,7 @@ public class RetrierTest {
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/3);
     TripAfterNCircuitBreaker cb = new TripAfterNCircuitBreaker(/*maxConsecutiveFailures=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, cb);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, cb);
 
     try {
       Thread.currentThread().interrupt();
@@ -230,7 +248,7 @@ public class RetrierTest {
 
     Supplier<Backoff> s  = () -> new ZeroBackoff(/*maxRetries=*/3);
     TripAfterNCircuitBreaker cb = new TripAfterNCircuitBreaker(/*maxConsecutiveFailures=*/2);
-    Retrier r = new Retrier(s, RETRY_ALL, cb);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, cb);
 
     try {
       Thread.currentThread().interrupt();
@@ -242,6 +260,26 @@ public class RetrierTest {
     }
   }
 
+  @Test
+  public void asyncRetryShouldWork() throws Exception {
+    // Test that a call is retried according to the backoff.
+    // All calls fail.
+
+    Supplier<Backoff> s = () -> new ZeroBackoff(/*maxRetries=*/ 2);
+    Retrier r = new Retrier(s, RETRY_ALL, retryService, alwaysOpen);
+    try {
+      r.executeAsync(
+              () -> {
+                throw new Exception("call failed");
+              })
+          .get();
+      fail("exception expected.");
+    } catch (ExecutionException e) {
+      assertThat(e.getCause()).isInstanceOf(RetryException.class);
+      assertThat(((RetryException) e.getCause()).getAttempts()).isEqualTo(3);
+    }
+  }
+
   /**
    * Simple circuit breaker that trips after N consecutive failures.
    */