Github user srdo commented on a diff in the pull request:
https://github.com/apache/storm/pull/2218#discussion_r129113343
--- Diff:
examples/storm-starter/src/jvm/org/apache/storm/starter/PersistentWindowingTopology.java
---
@@ -0,0 +1,176 @@
+/*
+ * 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.storm.starter;
+
+import static org.apache.storm.topology.base.BaseWindowedBolt.Duration;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import org.apache.storm.Config;
+import org.apache.storm.StormSubmitter;
+import org.apache.storm.starter.spout.RandomIntegerSpout;
+import org.apache.storm.state.KeyValueState;
+import org.apache.storm.streams.Pair;
+import org.apache.storm.task.OutputCollector;
+import org.apache.storm.task.TopologyContext;
+import org.apache.storm.topology.OutputFieldsDeclarer;
+import org.apache.storm.topology.TopologyBuilder;
+import org.apache.storm.topology.base.BaseStatefulWindowedBolt;
+import org.apache.storm.tuple.Fields;
+import org.apache.storm.tuple.Tuple;
+import org.apache.storm.tuple.Values;
+import org.apache.storm.windowing.TupleWindow;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * An example that demonstrates the usage of {@link
org.apache.storm.topology.IStatefulWindowedBolt} with window
+ * persistence.
+ * <p>
+ * The framework automatically checkpoints the tuples in window along with
the bolt's state and restores the same
+ * during restarts.
+ * </p>
+ *
+ * <p>
+ * This topology uses 'redis' for state persistence, so you should also
start a redis instance before deploying.
+ * If you are running in local mode you can just start a redis server
locally which will be used for storing the state. The default
+ * RedisKeyValueStateProvider parameters can be overridden by setting
"topology.state.provider.config", for e.g.
+ * <pre>
+ * {
+ * "jedisPoolConfig": {
+ * "host": "redis-server-host",
+ * "port": 6379,
+ * "timeout": 2000,
+ * "database": 0,
+ * "password": "xyz"
+ * }
+ * }
+ * </pre>
+ * </p>
+ */
+public class PersistentWindowingTopology {
+ private static final Logger LOG =
LoggerFactory.getLogger(PersistentWindowingTopology.class);
+
+ // wrapper to hold global and window averages
+ private static class Averages {
+ private final double global;
+ private final double window;
+
+ Averages(double global, double window) {
+ this.global = global;
+ this.window = window;
+ }
+
+ @Override
+ public String toString() {
+ return "Averages{" + "global=" + String.format("%.2f", global)
+ ", window=" + String.format("%.2f", window) + '}';
+ }
+ }
+
+ /**
+ * A bolt that uses stateful persistence to store the windows along
with the state (global avg).
+ */
+ private static class AvgBolt extends
BaseStatefulWindowedBolt<KeyValueState<String, Pair<Long, Long>>> {
+ private static final String STATE_KEY = "avg";
+
+ private OutputCollector collector;
+ private KeyValueState<String, Pair<Long, Long>> state;
+ private Pair<Long, Long> globalAvg;
+
+ @Override
+ public void prepare(Map<String, Object> topoConf, TopologyContext
context, OutputCollector collector) {
+ this.collector = collector;
+ }
+
+ @Override
+ public void initState(KeyValueState<String, Pair<Long, Long>>
state) {
+ this.state = state;
+ globalAvg = state.get(STATE_KEY, Pair.of(0L, 0L));
+ LOG.info("initState with global avg [" + (double) globalAvg._1
/ globalAvg._2 + "]");
--- End diff --
Nit: Consider using the getters instead of _1 and _2. It's a little weird
that those fields are public when they also have getters IMO.
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