Start using the experimental_worker_multiplex flag.

RELNOTES: Puts the experimental_worker_multiplex flag to use.
PiperOrigin-RevId: 327794094

Author: larsrc-google

src/main/java/com/google/devtools/build/lib/worker/WorkerModule.java

@@ -154,12 +154,14 @@ public void registerSpawnStrategies(
       SpawnStrategyRegistry.Builder registryBuilder, CommandEnvironment env) {
     Preconditions.checkNotNull(workerPool);
     SandboxOptions sandboxOptions = env.getOptions().getOptions(SandboxOptions.class);
+    options = env.getOptions().getOptions(WorkerOptions.class);
     LocalEnvProvider localEnvProvider = LocalEnvProvider.forCurrentOs(env.getClientEnv());
     WorkerSpawnRunner spawnRunner =
         new WorkerSpawnRunner(
             new SandboxHelpers(sandboxOptions.delayVirtualInputMaterialization),
             env.getExecRoot(),
             workerPool,
+            options.workerMultiplex,
             env.getReporter(),
             createFallbackRunner(env, localEnvProvider),
             localEnvProvider,

src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnRunner.java

@@ -84,6 +84,7 @@ final class WorkerSpawnRunner implements SpawnRunner {
   private final SandboxHelpers helpers;
   private final Path execRoot;
   private final WorkerPool workers;
+  private final boolean multiplex;
   private final ExtendedEventHandler reporter;
   private final SpawnRunner fallbackRunner;
   private final LocalEnvProvider localEnvProvider;
@@ -96,6 +97,7 @@ public WorkerSpawnRunner(
       SandboxHelpers helpers,
       Path execRoot,
       WorkerPool workers,
+      boolean multiplex,
       ExtendedEventHandler reporter,
       SpawnRunner fallbackRunner,
       LocalEnvProvider localEnvProvider,
@@ -106,6 +108,7 @@ public WorkerSpawnRunner(
     this.helpers = helpers;
     this.execRoot = execRoot;
     this.workers = Preconditions.checkNotNull(workers);
+    this.multiplex = multiplex;
     this.reporter = reporter;
     this.fallbackRunner = fallbackRunner;
     this.localEnvProvider = localEnvProvider;
@@ -211,7 +214,7 @@ private SpawnResult actuallyExec(Spawn spawn, SpawnExecutionContext context)
             workerFilesCombinedHash,
             workerFiles,
             context.speculating(),
-            Spawns.supportsMultiplexWorkers(spawn),
+            multiplex && Spawns.supportsMultiplexWorkers(spawn),
             protocolFormat);
 
     SpawnMetrics.Builder spawnMetrics =

src/test/shell/integration/bazel_worker_multiplexer_test.sh

@@ -36,6 +36,7 @@ add_to_bazelrc "build -s"
 add_to_bazelrc "build --spawn_strategy=worker,standalone"
 add_to_bazelrc "build --worker_verbose --worker_max_instances=3"
 add_to_bazelrc "build --debug_print_action_contexts"
+add_to_bazelrc "build --experimental_worker_multiplex"
 add_to_bazelrc "build ${ADDITIONAL_BUILD_FLAGS}"
 
 function set_up() {