commit 46706aef724c69016d9eae914cbe7a96349442c2
author janakr <janakr@google.com> Mon Apr 30 16:18:50 2018 -0700
committer Copybara-Service <copybara-piper@google.com> Mon Apr 30 16:19:58 2018 -0700
tree fdf8821a7077f4c973d0806bcbf21fdba9e4f158
parent b9f8627289294407ef93efda894ce138f1881a38

Allow SkyFunctions to return a sentinel value indicating that all of a node's in-progress data should be forgotten, and its evaluation should be restarted from scratch, as if it were freshly created/dirtied. To guard against this happening unexpectedly, any such events are passed to a GraphInconsistencyReceiver, which can verify that the SkyFunction is behaving properly.

This is the first change in a series to permit action rewinding when it is discovered that a previously generated input file is no longer available. When an action detects that one of its inputs is unusable, it can return this sentinel value, causing it to be re-evaluated from scratch. Follow-up changes will make the node corresponding to the input, and the node corresponding to the action that generated the input, dirty when this happens, causing the upstream action to be re-run, regenerating the desired input.

Currently works for builds that do not keep edges, although follow-ups may make this possible for all builds.

PiperOrigin-RevId: 194863097

src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java

diff --git a/src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java b/src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java
index cdcec82..afd0279 100644
--- a/src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java
+++ b/src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java
@@ -42,7 +42,8 @@
       ErrorInfoManager errorInfoManager,
       boolean keepGoing,
       int threadCount,
-      DirtyTrackingProgressReceiver progressReceiver) {
+      DirtyTrackingProgressReceiver progressReceiver,
+      GraphInconsistencyReceiver graphInconsistencyReceiver) {
     super(
         graph,
         graphVersion,
@@ -53,7 +54,8 @@
         errorInfoManager,
         keepGoing,
         threadCount,
-        progressReceiver);
+        progressReceiver,
+        graphInconsistencyReceiver);
   }
 
   public ParallelEvaluator(
@@ -66,6 +68,7 @@
       ErrorInfoManager errorInfoManager,
       boolean keepGoing,
       DirtyTrackingProgressReceiver progressReceiver,
+      GraphInconsistencyReceiver graphInconsistencyReceiver,
       ForkJoinPool forkJoinPool,
       CycleDetector cycleDetector) {
     super(
@@ -78,6 +81,7 @@
         errorInfoManager,
         keepGoing,
         progressReceiver,
+        graphInconsistencyReceiver,
         forkJoinPool,
         cycleDetector);
   }