Big round of sandbox fixes / performance improvements.

- The number of stat() syscalls in the SymlinkedSandboxedSpawn was way too high. Do less, feel better.

- When using --experimental_sandbox_base, ensure that symlinks in the path are resolved. Before this, you had to check whether on your system /dev/shm is a symlink to /run/shm and then use that instead. Now it no longer matters, as symlinks are resolved.

- Remove an unnecessary directory creation from each sandboxed invocation. Turns out that the "tmpdir" that we created was no longer used after some changes to Bazel's TMPDIR handling.

- Use simpler sandbox paths, by using the unique ID for each Spawn provided by SpawnExecutionPolicy instead of a randomly generated temp folder name. This also saves a round-trip from our VFS to NIO and back. Clean up the sandbox base before each build to ensure that the unique IDs are actually unique. ;)

- Use Java 8's Process#isAlive to check whether a process is alive instead of trying to get the exitcode and catching an exception.

Closes #4913.

PiperOrigin-RevId: 190472170

1 files changed, 8 insertions, 13 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/shell/JavaSubprocessFactory.java b/src/main/java/com/google/devtools/build/lib/shell/JavaSubprocessFactory.java
index 7647d17dd3..bfc867d991 100644
--- a/src/main/java/com/google/devtools/build/lib/shell/JavaSubprocessFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/shell/JavaSubprocessFactory.java
@@ -54,20 +54,15 @@ public class JavaSubprocessFactory implements SubprocessFactory {
 
     @Override
     public boolean finished() {
-      try {
-        if (deadlineMillis > 0
-            && System.currentTimeMillis() > deadlineMillis
-            && deadlineExceeded.compareAndSet(false, true)) {
-          // We use compareAndSet here to avoid calling destroy multiple times. Note that destroy
-          // returns immediately, and we don't want to wait in this method.
-          process.destroy();
-        }
-        // this seems to be the only non-blocking call for checking liveness
-        process.exitValue();
-        return true;
-      } catch (IllegalThreadStateException e) {
-        return false;
+      if (deadlineMillis > 0
+          && System.currentTimeMillis() > deadlineMillis
+          && deadlineExceeded.compareAndSet(false, true)) {
+        // We use compareAndSet here to avoid calling destroy multiple times. Note that destroy
+        // returns immediately, and we don't want to wait in this method.
+        process.destroy();
       }
+      // this seems to be the only non-blocking call for checking liveness
+      return !process.isAlive();
     }
 
     @Override