Creating a Standalone Execution Plan

WSO2 DAS uses execution plans to store event processing logic. An execution plan is bound to an instance of Siddhi Data Analytics Server runtime, which is responsible for the actual processing of events. DAS allows users to configure multiple execution plans and provides 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.

Writing an execution plan

Follow the instructions below to write an execution plan.

1. Start WSO2 DAS and log into its Management Console. Click Main and then click Execution Plans to open the Available Execution Plans page.

2. Click Add Execution Plan to open the Create a New Execution Plan page in which a template is displayed as shown in the example below.
   
   You can edit this template to create a new execution plan. Follow the steps below to edit the template and create a new execution plan.

   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.

   1. Siddhi keywords, in alphabetical order
   2. All the other words which are already inserted into the editor. For example, stream names which are defined in step 2 will be suggested when writing the queries in step 3. These will appear in alphabetical order after the keyword  list.

   In addition to the above, press shift+2 keys together to view suggestions on annotations.

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.

To give a description to the execution plan,

• uncomment the line -- @Plan:description('ExecutionPlan'). 
• replace 'ExecutionPlan' with the description

For example, @Plan:description('This is the description for my NewExecutionPlan').

Step 2: Import streams

To import a stream:

• 1. Select an existing stream for the Import Stream parameter. This is the event stream from which events will be taken to be processed by the execution plan.
  2. Enter a meaningful name for the stream in the As parameter. This is the name that is used when feeding the stream to the Siddhi engine. This can contain only alphanumeric characters and underscore (_). 
  3. Click Import.

This will import an available event stream as a new stream.

Step 3: Add query expressions

Query expressions are 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.