public interface IBolt extends java.io.Serializable
A bolt's lifecycle is as follows:
IBolt object created on client machine. The IBolt is serialized into the topology (using Java serialization) and submitted to the master machine of the cluster (Nimbus). Nimbus then launches workers which deserialize the object, call prepare on it, and then start processing tuples.
If you want to parameterize an IBolt, you should set the parameter's through its constructor and save the parameterization state as instance variables (which will then get serialized and shipped to every task executing this bolt across the cluster).
When defining bolts in Java, you should use the IRichBolt interface which adds necessary methods for using the Java TopologyBuilder API.
|Modifier and Type||Method and Description|
Called when an IBolt is going to be shutdown.
Process a single tuple of input.
Called when a task for this component is initialized within a worker on the cluster.
void prepare(java.util.Map<java.lang.String,java.lang.Object> stormConf, TopologyContext context, OutputCollector collector)
This includes the:
stormConf- The Storm configuration for this bolt. This is the configuration provided to the topology merged in with cluster configuration on this machine.
context- This object can be used to get information about this task's place within the topology, including the task id and component id of this task, input and output information, etc.
collector- The collector is used to emit tuples from this bolt. Tuples can be emitted at any time, including the prepare and cleanup methods. The collector is thread-safe and should be saved as an instance variable of this bolt object.
void execute(Tuple input)
Tuples should be emitted using the OutputCollector provided through the prepare method. It is required that all input tuples are acked or failed at some point using the OutputCollector. Otherwise, Storm will be unable to determine when tuples coming off the spouts have been completed.
For the common case of acking an input tuple at the end of the execute method, see IBasicBolt which automates this.
input- The input tuple to be processed.
The one context where cleanup is guaranteed to be called is when a topology is killed when running Storm in simulator.