Github user davidyan74 commented on a diff in the pull request:
https://github.com/apache/apex-malhar/pull/324#discussion_r73073399
--- Diff:
library/src/main/java/org/apache/apex/malhar/lib/state/spillable/SpillableStateStore.java
---
@@ -0,0 +1,33 @@
+/**
+ * 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.apex.malhar.lib.state.spillable;
+
+import org.apache.apex.malhar.lib.state.BucketedState;
+
+import com.datatorrent.api.Component;
+import com.datatorrent.api.Context;
+import com.datatorrent.api.Operator;
+
+public interface SpillableStateStore extends BucketedState,
Component<Context.OperatorContext>,
--- End diff --
Should we make this more generic and have a separate interface called
WindowListener that is basically:
```java
interface WindowListener
{
void beginWindow(long windowId);
void endWindow();
}
```
and have SpillableStateStore extends WindowListener, BucketedState, and
Component<Context.OperatorContext>?
The reason is the operator code will have to call these beginWindow and
endWindow callbacks and it's better to make this as generic as possible.
For example, I would have something like this in the operator code:
```java
class SomeOperator extends BaseOperator
{
List<Component> components;
@Override
void setup(OperatorContext context)
{
for (Component c : components) {
c.setup(context);
}
}
@Override
void beginWindow(long windowId)
{
for (Component c : components) {
if (c instanceof WindowListener) {
((WindowListener)c).beginWindow(windowId);
}
}
}
// similar for endWindow and CheckpointListener callbacks
}
```
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