WSO2 CEP uses Execution Plans to store event processing logic. An Execution Plan is bound to an instance of the Siddhi complex event processing runtime, which is responsible for the actual processing of the events. The event processor allows users to configure multiple Execution Plans where by providing multiple isolated event processing environments per Execution Plan. A typical Execution Plan consists of a set of queries and related input and output Event Streams.
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To write an execution plan, start the CEP, log in to its management console, go to Main --> Manage --> Event Processor --> Execution Plans and click Add Execution Plan.
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The execution plan editor supports auto completion. To view the suggestions made by the editor, press control+space keys together. The suggestions contain two sets.
In addition to the above, press shift+2 keys together to view suggestions on annotations. |
Supported annotations
The annotations supported for execution plans are as follows.
| Annotation | Description | Example |
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| The name of the execution plan. | @Plan:name('ExecutionPlan') |
@plan:description (<description about execution plan>) | This provides a description about the execution plan. Details such as the business requirement of the execution plan can be mentioned here. |
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@plan:async (bufferSize=<event queue size>) | WSO2 CEP has a disruptor based implementation to handle streams that are disabled by default. This annotation can be used to enable the disruptor at execution plan level that affects all the streams in the execution plan. The buffer size is an optional parameter. The default buffer size is 1024. | @plan:async(bufferSize=2) |
@async(bufferSize=<event queue size>) | Using this you can enable the disruptor only for a specific event stream. The event flow of the specified stream passes through the disruptor when enabled. |
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@import (<CEP stream definition>) | This is used to import a CEP event stream definition and map it to a Siddhi stream definition. For more information about event stream definitions, see Understanding Event Streams. |
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@export (<CEP stream definition>) | This is used to export a Siddhi event stream definition and map it to a CEP event stream definition. |
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Step 1. Add execution plan info
Add Execution Plan Name:
Give a meaningful name to the execution plan by replacing 'ExecutionPlan' in @Plan:name('ExecutionPlan') with the new name.
For example, if the new name should be 'NewExecutionPlan', then replace @Plan:name('ExecutionPlan') with @Plan:name('NewExecutionPlan').
Description:
This is the description of the execution plan. Giving a description is optional.
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- In the Import Stream field, select an existing stream from the list.
- In the As field, enter a a meaningful name by which this stream should be referred.
- Select the Include Arbitrary check box if you want to append arbitrary configurations to the stream definition when performing the import.
Anchor Arbitrary Attributes Arbitrary Attributes
This imports an available event stream as a new stream.
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Contains the event processing logic written in Siddhi query language. When defining more than one query, each query should end with a semi colon.
Step 4. Export streams
Defines the mappings between the exported (output) stream of the Siddhi runtime to one of the available Event Streams (defined inside query expressions). The parameters are as follows:
- Value Of: The name of the stream exposed by the Siddhi runtime. This can contain only alphanumeric characters and underscore (_).
- StreamId: The CEP Event Stream's ID to which the output events are sent from the execution plan.
- Include Arbitrary: If this check box is selected, the
arbitrary.data='true'setting is added to the export stream definition in the execution plan. This allows you to publish arbitrary data from that stream.
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Step 5. Add execution plan
Before adding the execution plan to the Siddhi runtime, it can be validated by clicking Validate Query Expressions.
Finally click the Add Execution Plan button to deploy the Execution plan.
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Once an execution plan is created as saved, its configuration in WSO2 Siddhi Query Language format is saved in the |
Editing a deployed execution plan
- After an execution plan is successfully created, you can change it and redeploy it as follows.
- Go to Main --> Manage --> Event Processor --> Execution Plans and select the execution plan needs to be edited by clicking on Edit button link associated with it. You can also click other associated links to delete it, enable/disable statistics or enable/disable tracing.
- Edit the execution plan as required, and click Update.
- Alternatively, you can write your execution plan in a text file and save it with the extension '.siddhiql' (which stands for Siddhi Query Language) and drop it in the deployment directory
<PRODUCT_HOME>/repository/deployment/server/executionplans. Since hot deployment is supported you can simply add/remove Execution Plan files to deploy/undeploy Execution Plans from the server.
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