[GitHub] storm pull request: [STORM-1176] Checkpoint window evaluated/expir...

[ptgoetz <gi...@git.apache.org>]

Github user ptgoetz commented on a diff in the pull request:

    https://github.com/apache/storm/pull/963#discussion_r49506460
  
    --- Diff: examples/storm-starter/src/jvm/storm/starter/StatefulWindowingTopology.java ---
    @@ -0,0 +1,110 @@
    +/**
    + * 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 storm.starter;
    +
    +import org.apache.storm.Config;
    +import org.apache.storm.LocalCluster;
    +import org.apache.storm.StormSubmitter;
    +import org.apache.storm.generated.StormTopology;
    +import org.apache.storm.starter.bolt.PrinterBolt;
    +import org.apache.storm.starter.spout.RandomIntegerSpout;
    +import org.apache.storm.state.KeyValueState;
    +import org.apache.storm.state.State;
    +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.utils.Utils;
    +import org.apache.storm.windowing.TupleWindow;
    +
    +import java.util.Map;
    +
    +import static org.apache.storm.topology.base.BaseWindowedBolt.Count;
    +
    +/**
    + * A simple example that demonstrates the usage of {@link org.apache.storm.topology.IStatefulWindowedBolt} to
    + * save the state of the windowing operation to avoid re-computation in case of failures.
    + * <p>
    + * The framework internally manages the window boundaries and does not invoke
    + * {@link org.apache.storm.topology.IWindowedBolt#execute(TupleWindow)} for the already evaluated windows in case of restarts
    + * during failures. The {@link org.apache.storm.topology.IStatefulBolt#initState(State)}
    + * is invoked with the previously saved state of the bolt after prepare, before the execute() method is invoked.
    + * </p>
    + */
    +public class StatefulWindowingTopology {
    +
    +    private static class WindowSumBolt extends BaseStatefulWindowedBolt<KeyValueState<String, Long>> {
    +        private KeyValueState<String, Long> state;
    +        private long sum;
    +
    +        private OutputCollector collector;
    +
    +        @Override
    +        public void prepare(Map stormConf, TopologyContext context, OutputCollector collector) {
    +            this.collector = collector;
    +        }
    +
    +        @Override
    +        public void initState(KeyValueState<String, Long> state) {
    +            this.state = state;
    +            sum = state.get("sum", 0L);
    +            System.out.println("initState with state [" + state + "] current sum [" + sum + "]");
    --- End diff --
    
    Could we use slf4j here instead of `System.out`?


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