This is hardly an unbreak! now issue.

See T140207: Consider alternative processes for Unbreak Now bugs, especially those which cross-cut components

In T140333#2464797, @matmarex wrote:

Perhaps I'm oversimplifying, but… can't we just do this?

diff --git a/src/utils/AbstractDirectedGraph.php b/src/utils/AbstractDirectedGraph.php
index 40242fa..5771827 100644
--- a/src/utils/AbstractDirectedGraph.php
+++ b/src/utils/AbstractDirectedGraph.php
@@ -218,6 +218,7 @@ abstract class AbstractDirectedGraph extends Phobject {
    * @task build
    */
   final public function loadGraph() {
+    $max_nodes = 100;
 
     $new_nodes = $this->knownNodes;
     while (true) {
@@ -230,11 +231,13 @@ abstract class AbstractDirectedGraph extends Phobject {
         }
       }
 
-      if (empty($load)) {
-        break;
-      }
-
+      $max_to_load = $max_nodes - count($this->knownNodes);
       $load = array_keys($load);
+      $load = array_slice($load, 0, $max_to_load);
+
+      if (empty($load)) {
+        break;
+      }
 
       $new_nodes = $this->loadEdges($load);
       foreach ($load as $node) {

This already loads the nodes in breadth-first order, so it should load the directly blocked/blocking tasks first, then blocked/blocking tasks of them, etc.

@matmarex: What good does that do when there are more than 100 subtasks? There needs to be a fallback, apparently.