[FIXED JENKINS-24095] Ensure only numExecutors exist when reducing

daniel-beck · daniel-beck · commit 05a26da704b9 · 2014-08-05T09:05:35.000+02:00
When reducing the number of executors from M to N, previously it'd kill all idle executors, and then create executors 0...N-1 unless they already exist (busy executors). This can lead to the situation where e.g. executor #5 is busy and retained, and when setting the number of executors to 3, 0...2 are created, resulting temporarily having 4 executors. This change prevents #2 from being created in the example. When #4 is finished, it'll be killed anyway and a new executor #2 created, so after some time the executor indexes are cleaned up matching expectations.
diff --git a/core/src/main/java/hudson/model/Computer.java b/core/src/main/java/hudson/model/Computer.java
@@ -721,9 +721,16 @@ private void addNewExecutorIfNecessary() {
             availableNumbers.remove(executor.getNumber());
 
         for (Integer number : availableNumbers) {
-            Executor e = new Executor(this, number);
-            executors.add(e);
+            /* There may be busy executors with higher index, so only
+               fill up until numExecutors is reached.
+               Extra executors will call removeExecutor(...) and that
+               will create any necessary executors from #0 again. */
+            if (executors.size() < numExecutors) {
+                Executor e = new Executor(this, number);
+                executors.add(e);
+            }
         }
+
     }
 
     /**
