A library to integrate Esper with Storm.
Esper is GPLv2 licensed, which means that this library is GPLv2 licensed, as well. You can find the license here.
The storm-esper library provides a bolt that allows you to use Esper queries on Storm data streams.
The bolt is created via a builder:
EsperBolt esperBolt =
new EsperBolt.Builder()
.addInputAlias("some-spout", "default", "Test")
.setAnonymousOutput("default", "min", "max")
.addStatement("select max(a) as max, min(b) as min from Test.win:length_batch(4)")
.build();
An input alias defines an alias for a Storm stream that can be used in the Esper queries. By default, the bolt will assign the event name <component id>_<stream id> where component id is the name of the spout/bolt that generates the data to be fed into the Esper bolt, and stream id being the id of the specific stream that the Esper bolt is connected to (if the source spout/bolt only has one output, then this is usually default). The method addInputAlias allows to define a different name for a specific stream of a specific component, e.g. in the example Stream for the stream default of component some-spout.
By default, the bolt defines a single output stream which corresponds to the unnamed stream that basic SELECT esper statements select values into. In order to tell Storm about the generated tuples, you need to declare the fields of this stream via the setAnonymousOutput method. It takes the target stream id to use (usually default) and the names of the fields which are the union of the output tuples of all Esper statements. E.g. if you have two SELECT statements that select a and b respectively, then you'd call setAnonymousOutput("default", "a", "b").
If the Esper statements generate names streams (e.g. insert into <name>), then you can use the addNamedOutput(<stream id>, <name>, <field 1>, <field 2>, ...) method instead to map named Esper streams to Storm streams. This allows you to generate more than stream from one Esper bolt.
Finally, you add the individual Esper statements via the addStatement method. Note that it does not support adding more than one Esper statement at the same time - use multiple addStatement calls for this.
Use a Maven dependency in your pom.xml:
<dependency>
<groupId>org.tomdz.storm</groupId>
<artifactId>storm-esper</artifactId>
<version>0.6.2-SNAPSHOT</version>
</dependency>