Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/204#discussion_r11469937
--- Diff:
core/src/main/scala/org/apache/spark/scheduler/ApplicationEventListener.scala
---
@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.scheduler
+
+/**
+ * A simple listener for application events.
+ *
+ * This listener assumes at most one of each of
SparkListenerApplicationStart and
--- End diff --
I found this a little hard to grok. The meat of this seems to be that
basically this assumes it only sees events from one application. What about
something like:
```
This listener expects to hear events from a single application only. If
events from multiple
applications are seen, the behavior is unspecified.
```
Then even if this implementation evolves to actually track stuff using the
other events, you've already made a general carve-out in the javadoc with the
high level assumption.
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