Merge branch 'asf-site' of https://git-wip-us.apache.org/repos/asf/storm into asf-site
diff --git a/documentation/State-checkpointing.md b/documentation/State-checkpointing.md
index c7a81f5..7c59aad 100644
--- a/documentation/State-checkpointing.md
+++ b/documentation/State-checkpointing.md
@@ -25,18 +25,24 @@
```java
public class WordCountBolt extends BaseStatefulBolt<KeyValueState<String, Long>> {
private KeyValueState<String, Long> wordCounts;
+ private OutputCollector collector;
...
@Override
+ public void prepare(Map stormConf, TopologyContext context, OutputCollector collector) {
+ this.collector = collector;
+ }
+ @Override
public void initState(KeyValueState<String, Long> state) {
wordCounts = state;
}
@Override
- public void execute(Tuple tuple, BasicOutputCollector collector) {
+ public void execute(Tuple tuple) {
String word = tuple.getString(0);
Integer count = wordCounts.get(word, 0);
count++;
wordCounts.put(word, count);
- collector.emit(new Values(word, count));
+ collector.emit(tuple, new Values(word, count));
+ collector.ack(tuple);
}
...
}
@@ -110,6 +116,8 @@
The state abstraction does not eliminate duplicate evaluations and currently provides only at-least once guarantee.
+In order to provide the at-least once guarantee, all bolts in a stateful topology are expected to anchor the tuples while emitting and ack the input tuples once its processed. For non-stateful bolts, the anchoring/acking can be automatically managed by extending the `BaseBasicBolt`. Stateful bolts are expected to anchor tuples while emitting and ack the tuple after processing like in the `WordCountBolt` example in the State management section above.
+
### IStateful bolt hooks
IStateful bolt interface provides hook methods where in the stateful bolts could implement some custom actions.
```java
