Sample 106 - Using in-memory event tables

Introduction

This sample demonstrates how to set up an execution plan to filter out credit card transactions that makes use of an in-memory event table to identify blacklisted transactions. This sample uses Event simulator for inputs and the logger publisher for logging the outputs to the CEP console.

The execution plan used in this sample are as follows:

define table CardUserTable (name string, cardNum string, blacklisted bool) ; 

Given above is the table definition,

• Defines a table named CardUserTable with the given attributes. This is by default an in-memory table. 

from CardUserStream
select * 
insert into CardUserTable;

The first query,

• Processes the events received through the CardUserStream
• Selects all the attributes under the select clause, from each event received. 
• Inserts it to the CardUserTable.

from BlackListStream
select cardNo as cardNum, true as blacklisted  
update CardUserTable
	on cardNum == CardUserTable.cardNum;

The second query,

• Processes the events received through the BlackListStream
• Selects cardNo and renames it as cardNum, introduces a new attribute named blacklisted with the value 'true' under the select clause, for each event received. 
• Updates the CardUserTable with the condition cardNum == CardUserTable.cardNum. Here the 'blacklisted' attribute in the table will be updated with the new value.

from PurchaseStream#window.length(1) as p join CardUserTable as c
	on  p.cardNo == c.cardNum and c.blacklisted == false
select p.cardNo as cardNo, c.name as name, p.price as price
insert into WhiteListPurchaseStream ;

The third query,

• Defines a length window that keeps 1 event of the input stream PurchaseStream.
• Joins it with the CardUserTable with the condition p.cardNo == c.cardNum and c.blacklisted == false. In this condition, the events with blacklisted == true in the table gets filtered out and then the remaining events will be joined based on the card number.
• Emits those events as output events through the TransformedRoomTempStream.

from DeleteAllUsers 
delete CardUserTable
	on deleteAll == true;

The last query is used to clean up the table from an external trigger event through DeleteAllUsers stream,

• It processes the events received through the DeleteAllUsers.
• Checks for the condition deleteAll == true and if it's true, deletes all the records in the CardUserTable. 
  
  

Prerequisites

See Prerequisites in CEP Samples Setup page.

Building the sample

Start the WSO2 CEP server with the sample configuration numbered 0106. For instructions, see Starting sample CEP configurations. This sample configuration does the following:

• Points the default Axis2 repo to <CEP_HOME>/sample/artifacts/0106 (by default, the Axis2 repo is <CEP_HOME>/repository/deployment/server).

Executing the sample

1. Log into the CEP management console which is located at https://localhost:9443/carbon.

    

2. Go to Tools -> Event Simulator. Under the 'Multiple Events' section, you can see the listed 'events.csv' file which contains some sample data. Click 'play' to start sending sample events from the file.

3. See the output events received from the CEP console. This sample uses the logger adaptor to log output events to the console.

   For example, given below is a screenshot of the output of the consumer sending events from the producer: