Carefully avoid the harbormaster/differential race

Summary: Ref T8650. This should stop the problem, but isn't a root cause fix. See discussion on the task.

Test Plan: Made some local diffs, but this is a bit hard to reproduce reliably.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8650

Differential Revision: https://secure.phabricator.com/D13441

src/applications/differential/editor/DifferentialTransactionEditor.php

@@ -585,6 +585,8 @@ final class DifferentialTransactionEditor
               'a race?'));
         }
 
+        // TODO: This can race with diff updates, particularly those from
+        // Harbormaster. See discussion in T8650.
         $diff->setRevisionID($object->getID());
         $diff->save();
 
@@ -593,6 +595,8 @@ final class DifferentialTransactionEditor
         // the old (`null`) container.
 
         // TODO: This is a bit iffy, maybe we can find a cleaner approach?
+        // In particular, this could (rarely) be overwritten by Harbormaster
+        // workers.
         $table = new HarbormasterBuildable();
         $conn_w = $table->establishConnection('w');
         queryfx(

src/applications/harbormaster/engine/HarbormasterBuildEngine.php

@@ -406,15 +406,34 @@ final class HarbormasterBuildEngine extends Phobject {
     $should_publish = $did_update &&
                       $new_status != HarbormasterBuildable::STATUS_BUILDING &&
                       !$buildable->getIsManualBuildable();
-    if ($should_publish) {
+
+    if (!$should_publish) {
+      return;
+    }
+
     $object = id(new PhabricatorObjectQuery())
       ->setViewer($viewer)
       ->withPHIDs(array($buildable->getBuildablePHID()))
       ->executeOne();
+    if (!$object) {
+      return;
+    }
+
+    if (!($object instanceof PhabricatorApplicationTransactionInterface)) {
+      return;
+    }
+
+    // TODO: Publishing these transactions is causing a race. See T8650.
+    // We shouldn't be publishing to diffs anyway.
+    if ($object instanceof DifferentialDiff) {
+      return;
+    }
 
-      if ($object instanceof PhabricatorApplicationTransactionInterface) {
     $template = $object->getApplicationTransactionTemplate();
-        if ($template) {
+    if (!$template) {
+      return;
+    }
+
     $template
       ->setTransactionType(PhabricatorTransactions::TYPE_BUILDABLE)
       ->setMetadataValue(
@@ -441,9 +460,6 @@ final class HarbormasterBuildEngine extends Phobject {
       $object->getApplicationTransactionObject(),
       array($template));
   }
-      }
-    }
-  }
 
   private function releaseAllArtifacts(HarbormasterBuild $build) {
     $targets = id(new HarbormasterBuildTargetQuery())