Github user arunmahadevan commented on a diff in the pull request: https://github.com/apache/storm/pull/939#discussion_r48323100 --- Diff: storm-core/src/jvm/backtype/storm/spout/CheckpointSpout.java --- @@ -0,0 +1,280 @@ +/** + * 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 backtype.storm.spout; + +import backtype.storm.Config; +import backtype.storm.state.KeyValueState; +import backtype.storm.state.StateFactory; +import backtype.storm.task.TopologyContext; +import backtype.storm.topology.OutputFieldsDeclarer; +import backtype.storm.topology.base.BaseRichSpout; +import backtype.storm.tuple.Fields; +import backtype.storm.tuple.Tuple; +import backtype.storm.tuple.Values; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.Map; +import static backtype.storm.spout.CheckPointState.State.COMMITTED; +import static backtype.storm.spout.CheckPointState.State.COMMITTING; +import static backtype.storm.spout.CheckPointState.State.PREPARING; + +/** + * Emits checkpoint tuples which is used to save the state of the {@link backtype.storm.topology.IStatefulComponent} + * across the topology. If a topology contains Stateful bolts, Checkpoint spouts are automatically added + * to the topology. There is only one Checkpoint task per topology. + * <p/> + * Checkpoint spout stores its internal state in a {@link KeyValueState}. The state transitions are as follows. + * <p/> + * <pre> + * ROLLBACK(tx2) + * <------------- PREPARE(tx2) COMMIT(tx2) + * COMMITTED(tx1)-------------> PREPARING(tx2) --------------> COMMITTING(tx2) -----------------> COMMITTED (tx2) + * + * + * </pre> + */ +public class CheckpointSpout extends BaseRichSpout { + private static final Logger LOG = LoggerFactory.getLogger(CheckpointSpout.class); + + public static final String CHECKPOINT_STREAM_ID = "$checkpoint"; + public static final String CHECKPOINT_COMPONENT_ID = "$checkpointspout"; + public static final String CHECKPOINT_FIELD_TXID = "txid"; + public static final String CHECKPOINT_FIELD_ACTION = "action"; + public static final String CHECKPOINT_ACTION_PREPARE = "prepare"; + public static final String CHECKPOINT_ACTION_COMMIT = "commit"; + public static final String CHECKPOINT_ACTION_ROLLBACK = "rollback"; + public static final String CHECKPOINT_ACTION_INITSTATE = "initstate"; + + private static final String TX_STATE_KEY = "__state"; + private static final int DEFAULT_CHECKPOINT_INTERVAL = 1000; // every sec + + private TopologyContext context; + private SpoutOutputCollector collector; + private long lastCheckpointTs; + private int checkpointInterval; + private boolean recoveryStepInProgress; + private boolean checkpointStepInProgress; + private boolean recovering; + private KeyValueState<String, CheckPointState> checkpointState; + + @Override + public void open(Map conf, TopologyContext context, SpoutOutputCollector collector) { + open(context, collector, loadCheckpointInterval(conf), loadCheckpointState(conf, context)); + } + + // package access for unit test + void open(TopologyContext context, SpoutOutputCollector collector, + int checkpointInterval, KeyValueState<String, CheckPointState> checkpointState) { + this.context = context; + this.collector = collector; + this.checkpointInterval = checkpointInterval; + this.checkpointState = checkpointState; + lastCheckpointTs = 0; + recoveryStepInProgress = false; + checkpointStepInProgress = false; + recovering = true; + } + + @Override + public void nextTuple() { + if (shouldRecover()) { + LOG.debug("In recovery"); + handleRecovery(); + startProgress(); + } else if (shouldCheckpoint()) { + LOG.debug("In checkpoint"); + doCheckpoint(); + startProgress(); + } + } + + @Override + public void ack(Object msgId) { + CheckPointState txState = getTxState(); + LOG.debug("Got ack with txid {}, current txState {}", msgId, txState); + if (txState.txid == ((Number) msgId).longValue()) { + if (recovering) { + handleRecoveryAck(); + } else { + handleCheckpointAck(); + } + } else { + LOG.warn("Ack msgid {}, txState.txid {} mismatch", msgId, txState.txid); + } + resetProgress(); + } + + @Override + public void fail(Object msgId) { + LOG.debug("Got fail with msgid {}", msgId); + resetProgress(); + } + + @Override + public void declareOutputFields(OutputFieldsDeclarer declarer) { + declarer.declareStream(CHECKPOINT_STREAM_ID, new Fields(CHECKPOINT_FIELD_TXID, CHECKPOINT_FIELD_ACTION)); + } + + @Override + public Map<String, Object> getComponentConfiguration() { + Config conf = new Config(); + conf.put(Config.TOPOLOGY_SLEEP_SPOUT_WAIT_STRATEGY_TIME_MS, 100); --- End diff -- It was added to sleep for slightly longer time rather than spinning in the nextTuple. Instead of hard coding, will change this to 10% of the checkpoint interval time.
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