Support ordering constraints on build events

In the build event protocol, we promise to respect certain ordering
constraints that come naturally by causality anyway (e.g., the root
cause of a failure has to come before the failure). However, in the
way the call structure is organized, events might occur on the event
bus in wrong order. So allow events to specify that order and make the
streamer honor it.

--
Change-Id: I1fbe9b93681f0ddfa35d9d00d5d1b02103da38a5
Reviewed-on: https://bazel-review.googlesource.com/#/c/7370
MOS_MIGRATED_REVID=139774946

1 files changed, 29 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventWithOrderConstraint.java b/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventWithOrderConstraint.java
new file mode 100644
index 0000000000..08cd280b7a
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventWithOrderConstraint.java
@@ -0,0 +1,29 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.buildeventstream;
+
+import java.util.Collection;
+
+/** Interface for {@link BuildEvent}s with order constraints. */
+public interface BuildEventWithOrderConstraint extends BuildEvent {
+  /**
+   * Specify events that need to come first.
+   *
+   * <p>Specify events by their {@link BuildEventId} that need to be posted on the build event
+   * stream before this event. In doing so, the event promises that the events to be waited for are
+   * already generated, so that the event does not have to be buffered for an extended time.
+   */
+  Collection<BuildEventId> postedAfter();
+}