Only run the worker if the build is incremental.

This feature is tunable through --worker_max_changed_files flag. If unspecified, all builds are considered incremental.

--
MOS_MIGRATED_REVID=96968367

5 files changed, 64 insertions, 6 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/actions/ChangedFilesMessage.java b/src/main/java/com/google/devtools/build/lib/actions/ChangedFilesMessage.java
index 56f688284c..47c48ec015 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ChangedFilesMessage.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ChangedFilesMessage.java
@@ -19,7 +19,8 @@ import com.google.devtools.build.lib.vfs.PathFragment;
 import java.util.Set;
 
 /**
- * A message sent conveying a set of changed files.
+ * A message sent conveying a set of changed files. This is sent over the event bus if a build is
+ * discovered to have few changed files. If many files have changed, it will not be sent at all.
  */
 public class ChangedFilesMessage {
 
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerActionContextProvider.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerActionContextProvider.java
index 6d4e419391..0db3a46595 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerActionContextProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerActionContextProvider.java
@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.worker;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.eventbus.EventBus;
 import com.google.devtools.build.lib.actions.ActionContextProvider;
 import com.google.devtools.build.lib.actions.Executor.ActionContext;
 import com.google.devtools.build.lib.buildtool.BuildRequest;
@@ -24,9 +25,10 @@ import com.google.devtools.build.lib.buildtool.BuildRequest;
 final class WorkerActionContextProvider extends ActionContextProvider {
   private final ImmutableList<ActionContext> strategies;
 
-  public WorkerActionContextProvider(BuildRequest buildRequest, WorkerPool workers) {
+  public WorkerActionContextProvider(
+      BuildRequest buildRequest, WorkerPool workers, EventBus eventBus) {
     this.strategies =
-        ImmutableList.<ActionContext>of(new WorkerSpawnStrategy(buildRequest, workers));
+        ImmutableList.<ActionContext>of(new WorkerSpawnStrategy(buildRequest, workers, eventBus));
   }
 
   @Override
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerModule.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerModule.java
index 81d5024610..b7de57fee1 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerModule.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerModule.java
@@ -32,6 +32,7 @@ public class WorkerModule extends BlazeModule {
   private final WorkerPool workers;
 
   private BuildRequest buildRequest;
+  private BlazeRuntime blazeRuntime;
 
   public WorkerModule() {
     GenericKeyedObjectPoolConfig config = new GenericKeyedObjectPoolConfig();
@@ -41,8 +42,8 @@ public class WorkerModule extends BlazeModule {
 
   @Override
   public Iterable<ActionContextProvider> getActionContextProviders() {
-    return ImmutableList.<ActionContextProvider>of(new WorkerActionContextProvider(buildRequest,
-        workers));
+    return ImmutableList.<ActionContextProvider>of(
+        new WorkerActionContextProvider(buildRequest, workers, blazeRuntime.getEventBus()));
   }
 
   @Override
@@ -54,6 +55,7 @@ public class WorkerModule extends BlazeModule {
 
   @Override
   public void beforeCommand(BlazeRuntime blazeRuntime, Command command) {
+    this.blazeRuntime = blazeRuntime;
     blazeRuntime.getEventBus().register(this);
   }
 
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerOptions.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerOptions.java
index 5dd7db01b9..b4471c0400 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerOptions.java
@@ -36,4 +36,14 @@ public class WorkerOptions extends OptionsBase {
       help = "Enable the experimental persistent Java compiler.",
       expansion = {"--strategy=Javac=worker", "--strategy=JavaIjar=local"})
   public Void experimentalPersistentJavac;
+
+  @Option(
+    name = "worker_max_changed_files",
+    defaultValue = "0",
+    category = "strategy",
+    help =
+        "Don't run local worker if more files than this were changed. 0 means always use "
+            + "workers."
+  )
+  public int workerMaxChangedFiles;
 }
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnStrategy.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnStrategy.java
index 697a57de4d..13673ef3ae 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnStrategy.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnStrategy.java
@@ -17,17 +17,23 @@ import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Iterables;
+import com.google.common.eventbus.EventBus;
+import com.google.common.eventbus.Subscribe;
 import com.google.devtools.build.lib.actions.ActionExecutionContext;
+import com.google.devtools.build.lib.actions.ChangedFilesMessage;
 import com.google.devtools.build.lib.actions.ExecException;
 import com.google.devtools.build.lib.actions.ExecutionStrategy;
 import com.google.devtools.build.lib.actions.Spawn;
 import com.google.devtools.build.lib.actions.SpawnActionContext;
 import com.google.devtools.build.lib.actions.UserExecException;
+import com.google.devtools.build.lib.concurrent.ThreadSafety;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.worker.WorkerProtocol.WorkRequest;
 import com.google.devtools.build.lib.worker.WorkerProtocol.WorkResponse;
 import com.google.devtools.common.options.OptionsClassProvider;
 
+import java.util.concurrent.atomic.AtomicBoolean;
+
 /**
  * A spawn action context that launches Spawns the first time they are used in a persistent mode and
  * then shards work over all the processes.
@@ -35,18 +41,31 @@ import com.google.devtools.common.options.OptionsClassProvider;
 @ExecutionStrategy(name = { "worker" }, contextType = SpawnActionContext.class)
 final class WorkerSpawnStrategy implements SpawnActionContext {
   private final WorkerPool workers;
+  private final IncrementalHeuristic incrementalHeuristic;
 
-  public WorkerSpawnStrategy(OptionsClassProvider optionsProvider, WorkerPool workers) {
+  public WorkerSpawnStrategy(
+      OptionsClassProvider optionsProvider, WorkerPool workers, EventBus eventBus) {
+    Preconditions.checkNotNull(optionsProvider);
     WorkerOptions options = optionsProvider.getOptions(WorkerOptions.class);
     workers.setMaxTotalPerKey(options.workerMaxInstances);
     workers.setMaxIdlePerKey(options.workerMaxInstances);
     workers.setMinIdlePerKey(options.workerMaxInstances);
     this.workers = workers;
+    this.incrementalHeuristic = new IncrementalHeuristic(options.workerMaxChangedFiles);
+    eventBus.register(incrementalHeuristic);
   }
 
   @Override
   public void exec(Spawn spawn, ActionExecutionContext actionExecutionContext)
       throws ExecException, InterruptedException {
+    if (!incrementalHeuristic.shouldUseWorkers()) {
+      SpawnActionContext context = actionExecutionContext.getExecutor().getSpawnActionContext("");
+      if (context != this) {
+        context.exec(spawn, actionExecutionContext);
+        return;
+      }
+    }
+
     String paramFile = Iterables.getLast(spawn.getArguments());
 
     // We assume that the spawn to be executed always gets a single argument, which is a flagfile
@@ -106,4 +125,28 @@ final class WorkerSpawnStrategy implements SpawnActionContext {
   public boolean isRemotable(String mnemonic, boolean remotable) {
     return false;
   }
+
+  /**
+   * For installation with remote execution, non-incremental builds may be slowed down by the
+   * persistent worker system. To avoid this we only use workers for builds where few files
+   * changed.
+   */
+  @ThreadSafety.ThreadSafe
+  private static class IncrementalHeuristic {
+    private final AtomicBoolean fewFilesChanged = new AtomicBoolean(false);
+    private int limit = 0;
+
+    public boolean shouldUseWorkers() {
+      return limit == 0 || fewFilesChanged.get();
+    }
+
+    IncrementalHeuristic(int limit) {
+      this.limit = limit;
+    }
+
+    @Subscribe
+    public void changedFiles(ChangedFilesMessage msg) {
+      fewFilesChanged.set(msg.getChangedFiles().size() <= limit);
+    }
+  }
 }