Update the worker protocol proto (bazelbuild#622)

third_party/bazel_protos/README.md

@@ -1,3 +1,4 @@
-This directory contains protocol buffers vendored from the main Bazel
-repository, so that rules_swift does not need to depend on the entire
+This directory contains protocol buffers vendored from the
+[main Bazel repository](https://raw.githubusercontent.com/bazelbuild/bazel/master/src/main/protobuf/worker_protocol.proto),
+so that rules_swift does not need to depend on the entire
 `@io_bazel` workspace, which is approximately 100MB.

third_party/bazel_protos/worker_protocol.proto

@@ -31,16 +31,31 @@ message Input {
   bytes digest = 2;
 }
 
-// This represents a single work unit that Bazel sends to the worker.
+// This represents a single work unit that Blaze sends to the worker.
 message WorkRequest {
   repeated string arguments = 1;
 
   // The inputs that the worker is allowed to read during execution of this
   // request.
   repeated Input inputs = 2;
+
+  // Each WorkRequest must have either a unique
+  // request_id or request_id = 0. If request_id is 0, this WorkRequest must be
+  // processed alone (singleplex), otherwise the worker may process multiple
+  // WorkRequests in parallel (multiplexing). As an exception to the above, if
+  // the cancel field is true, the request_id must be the same as a previously
+  // sent WorkRequest. The request_id must be attached unchanged to the
+  // corresponding WorkResponse. Only one singleplex request may be sent to a
+  // worker at a time.
+  int32 request_id = 3;
+
+  // EXPERIMENTAL: When true, this is a cancel request, indicating that a
+  // previously sent WorkRequest with the same request_id should be cancelled.
+  // The arguments and inputs fields must be empty and should be ignored.
+  bool cancel = 4;
 }
 
-// The worker sends this message to Bazel when it finished its work on the
+// The worker sends this message to Blaze when it finished its work on the
 // WorkRequest message.
 message WorkResponse {
   int32 exit_code = 1;
@@ -49,4 +64,18 @@ message WorkResponse {
   // supposed to contain compiler warnings / errors etc. - thus we'll use a
   // string type here, which gives us UTF-8 encoding.
   string output = 2;
+
+  // This field must be set to the same request_id as the WorkRequest it is a
+  // response to. Since worker processes which support multiplex worker will
+  // handle multiple WorkRequests in parallel, this ID will be used to
+  // determined which WorkerProxy does this WorkResponse belong to.
+  int32 request_id = 3;
+
+  // EXPERIMENTAL When true, indicates that this response was sent due to
+  // receiving a cancel request. The exit_code and output fields should be empty
+  // and will be ignored. Exactly one WorkResponse must be sent for each
+  // non-cancelling WorkRequest received by the worker, but if the worker
+  // received a cancel request, it doesn't matter if it replies with a regular
+  // WorkResponse or with one where was_cancelled = true.
+  bool was_cancelled = 4;
 }

tools/worker/work_processor.cc

@@ -145,4 +145,5 @@ void WorkProcessor::ProcessWorkRequest(
 
   response->set_exit_code(exit_code);
   response->set_output(stderr_stream.str());
+  response->set_request_id(request.request_id());
 }