Automated rollback of commit d5d65ec3410e9228f92ba77b730c542f399fec47.

*** Reason for rollback ***

Multiplex regression fixed with https://github.com/bazelbuild/bazel/commit/6bf44ba9339a59c852a5da5f72e14bdb87af6483. To be submitted after next java toolchain release.

*** Original change description ***

Automated rollback of commit aab567cbde4f1817b598207d99a93393dad4a094.

*** Reason for rollback ***

Saw regression of 10% on a normal machine, up to 50% on a manycore machine.

*** Original change description ***

Turns on multiplex workers in Java toolchain rule.

RELNOTES: Javac now supports multiplex workers.
PiperOrigin-RevId: 339280531

src/main/java/com/google/devtools/build/lib/rules/java/JavaToolchainRule.java

diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaToolchainRule.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaToolchainRule.java
index b76be38..9725233 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaToolchainRule.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaToolchainRule.java
@@ -116,7 +116,7 @@
         /* <!-- #BLAZE_RULE(java_toolchain).ATTRIBUTE(javac_supports_multiplex_workers) -->
         True if JavaBuilder supports running as a multiplex persistent worker, false if it doesn't.
         <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
-        .add(attr("javac_supports_multiplex_workers", BOOLEAN).value(false))
+        .add(attr("javac_supports_multiplex_workers", BOOLEAN).value(true))
         /* <!-- #BLAZE_RULE(java_toolchain).ATTRIBUTE(javac) -->
         Label of the javac jar.
         <!-- #END_BLAZE_RULE.ATTRIBUTE --> */

src/test/java/com/google/devtools/build/lib/worker/ExampleWorker.java

diff --git a/src/test/java/com/google/devtools/build/lib/worker/ExampleWorker.java b/src/test/java/com/google/devtools/build/lib/worker/ExampleWorker.java
index 7a31a62..16fe7d9 100644
--- a/src/test/java/com/google/devtools/build/lib/worker/ExampleWorker.java
+++ b/src/test/java/com/google/devtools/build/lib/worker/ExampleWorker.java
@@ -138,7 +138,11 @@
           System.out.flush();
         } else {
           WorkResponse response =
-              WorkResponse.newBuilder().setOutput(baos.toString()).setExitCode(exitCode).build();
+              WorkResponse.newBuilder()
+                  .setOutput(baos.toString())
+                  .setExitCode(exitCode)
+                  .setRequestId(request.getRequestId())
+                  .build();
           workerProtocol.writeResponse(response);
         }
 

src/test/shell/integration/bazel_worker_test.sh

diff --git a/src/test/shell/integration/bazel_worker_test.sh b/src/test/shell/integration/bazel_worker_test.sh
index cbac89f..f1dc2e2 100755
--- a/src/test/shell/integration/bazel_worker_test.sh
+++ b/src/test/shell/integration/bazel_worker_test.sh
@@ -38,6 +38,7 @@
 add_to_bazelrc "build --experimental_worker_allow_json_protocol"
 add_to_bazelrc "build --worker_verbose --worker_max_instances=1"
 add_to_bazelrc "build --debug_print_action_contexts"
+add_to_bazelrc "build --noexperimental_worker_multiplex"
 add_to_bazelrc "build ${ADDITIONAL_BUILD_FLAGS}"
 
 function set_up() {