Sample 0118 - Using Hazelcast Event Tables

Introduction

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

The execution plan used in this sample are as follows:

@from(eventtable = 'hazelcast', cluster.name = 'cluster_a', cluster.password = 'pass@cluster_a')
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 will create a event table backed by a new Hazelcast Instance in a new Hazelcast Cluster.
  
  

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 is 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 are joined based on the card number.
• Emits those events as output events through the WhiteListPurchaseStream.
  
  

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 exists, deletes all the records in the CardUserTable. 

Prerequisites

Set up prerequisites required for all samples.

Building the sample

Start the WSO2 DAS server with the sample configuration numbered 0118. For instructions, see Starting sample CEP configurations. This sample configuration does the following:

• Points the default Axis2 repo to <DAS_HOME>/samples/cep/artifacts/0118 (by default, the Axis2 repo is <DAS_HOME>/repository/deployment/server).

Executing the sample

1. Log into the DAS management console.

2. In the Tools tab, click Event Simulator to open the Event Stream Simulator page. In the Send multiple events section, 4 files that contain sample data are listed as follows. 
   

3. The userEvents.csv file contains sample data that is used to fill the in-memory CardUserTable. Click play start sending events to fill the table.

4. The blackListUserEvents.csv file contains sample data that is used to mark user entries in CardUserTable as blacklisted. Click Play to start sending blacklisted events and mark some table entries as blacklisted.
5. The purchaseEvents.csv contains credit card transactions data. Play it and send the transaction data. 

6. After sending sample events from purchaseEvents.csv, you will be able to see the outputs as follows.