Add a random number to action temp dir

Fix for #4035

@laszlocsomor

Closes #4110.

PiperOrigin-RevId: 176346381

1 files changed, 10 insertions, 9 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunner.java
index c6892e6479..e33c010263 100644
--- a/src/main/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/exec/local/LocalSpawnRunner.java
@@ -47,6 +47,7 @@ import java.util.ArrayList;
 import java.util.EnumMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.annotation.Nullable;
@@ -130,15 +131,15 @@ public final class LocalSpawnRunner implements SpawnRunner {
   }
 
   private static Path createActionTemp(Path execRoot) throws IOException {
-    // Use this executor thread's ID as the directory name's suffix.
-    // The ID is safe for the following reasons:
-    // - being a thread ID, it's guaranteed to be unique among other action executor threads
-    // - this thread will only execute one action at a time, so there's no risk of concurrently
-    //   running actions using the same temp directory.
-    // The next action that this thread executes can reuse the temp directory name. The only caveat
-    // is, if {@link #start} fails to delete directory after the action is done, the next
-    // action will see stale files in its temp directory.
-    String idStr = Long.toHexString(Thread.currentThread().getId());
+    String idStr =
+        // Make the name unique among other executor threads.
+        Long.toHexString(Thread.currentThread().getId())
+            + "_"
+            // Make the name unique among other temp directories that this thread has ever created.
+            // On Windows, file and directory deletion is asynchronous, meaning the previous temp
+            // directory name isn't immediately available for the next action that this thread runs.
+            // See https://github.com/bazelbuild/bazel/issues/4035
+            + Long.toHexString(ThreadLocalRandom.current().nextLong());
     Path result = execRoot.getRelative("tmp" + idStr);
     if (!result.exists() && !result.createDirectory()) {
       throw new IOException(String.format("Could not create temp directory '%s'", result));