1 files changed, 31 insertions, 1 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerFactory.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerFactory.java
index 3c444a2577..8f997536e9 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerFactory.java
@@ -79,6 +79,36 @@ final class WorkerFactory extends BaseKeyedPooledObjectFactory<WorkerKey, Worker
   @Override
   public boolean validateObject(WorkerKey key, PooledObject<Worker> p) {
     Worker worker = p.getObject();
-    return key.getWorkerFilesHash().equals(worker.getWorkerFilesHash()) && worker.isAlive();
+
+    boolean hashMatches = key.getWorkerFilesHash().equals(worker.getWorkerFilesHash());
+    boolean workerIsAlive = worker.isAlive();
+    boolean workerIsStillValid = hashMatches && workerIsAlive;
+
+    if (reporter != null && !workerIsStillValid) {
+      StringBuilder msg = new StringBuilder();
+      msg.append(key.getMnemonic());
+      msg.append(" worker (id ");
+      msg.append(p.getObject().getWorkerId());
+      msg.append(") can no longer be used, because");
+
+      if (!workerIsAlive) {
+        msg.append(" its process terminated itself or got killed");
+      }
+
+      if (!hashMatches) {
+        if (!workerIsAlive) {
+          msg.append(" and");
+        }
+        msg.append(" its files have changed on disk [");
+        msg.append(worker.getWorkerFilesHash());
+        msg.append(" -> ");
+        msg.append(key.getWorkerFilesHash());
+        msg.append("]");
+      }
+
+      reporter.handle(Event.warn(msg.toString()));
+    }
+
+    return workerIsStillValid;
   }
 }