workers: WorkerSpawnStrategy will now only execute SpawnActions if their ExecutionInfo contains the tag "support-workers" set to "1" and fallback to non-worker execution if it is not present.

This will eventually allow us to safely automatically decide whether to use workers to execute an action or not.

RELNOTES[INC]: If you maintain a rule that uses persistent workers, you'll have to specify execution_requirements={"supports-workers": 1} in the ctx.action that intends to run a tool with workers. The WorkerSpawnStrategy will alert you with a warning message if you forget to make this change and fallback to non-worker based execution.

--
MOS_MIGRATED_REVID=127822788

1 files changed, 26 insertions, 0 deletions

diff --git a/src/test/shell/bazel/bazel_worker_test.sh b/src/test/shell/bazel/bazel_worker_test.sh
index 274e67320d..91e2749230 100755
--- a/src/test/shell/bazel/bazel_worker_test.sh
+++ b/src/test/shell/bazel/bazel_worker_test.sh
@@ -99,6 +99,7 @@ def _impl(ctx):
       executable=worker,
       progress_message="Working on %s" % ctx.label.name,
       mnemonic="Work",
+      execution_requirements={"supports-workers": "1"},
       arguments=ctx.attr.worker_args + ["@" + argfile.path],
   )
 
@@ -408,4 +409,29 @@ EOF
     || fail "Worker log was not deleted"
 }
 
+function test_missing_execution_requirements_gives_warning() {
+  prepare_example_worker
+  cat >>BUILD <<'EOF'
+work(
+  name = "hello_world",
+  worker = ":worker",
+  args = ["--write_uuid", "--write_counter"],
+)
+EOF
+
+  sed -i.bak '/execution_requirements/d' work.bzl
+  rm -f work.bzl.bak
+
+  bazel build --worker_verbose --strategy=Work=worker --worker_max_instances=1 --worker_quit_after_build :hello_world &> $TEST_log \
+    || fail "build failed"
+
+  expect_log "Worker strategy cannot execute this Work action, because the action's execution info does not contain 'supports-workers=1'"
+  expect_not_log "Created new Work worker (id [0-9]\+)"
+  expect_not_log "Destroying Work worker (id [0-9]\+)"
+
+  # WorkerSpawnStrategy falls back to standalone strategy, so we still expect the output to be generated.
+  [ -e "bazel-bin/hello_world.out" ] \
+    || fail "Worker did not produce output"
+}
+
 run_suite "Worker integration tests"