Forwarding Sensor Events to Oracle Streams by Using the Oracle Sensor Edge Server

Purpose

This tutorial shows how to use Streams Dispatcher with Sensor Edge Server.

Time to Complete

Approximately 30 minutes.

Topics

This tutorial covers the following topics:

	Overview
	Prerequisites
	Configuring the Streams Dispatcher
	Adding Rules
	Summary
	Related information

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Overview

The Oracle Sensor Edge Server is a middle-tier component that integrates sensors and other types of command or response indication equipment with applications. Sensors are hardware or software endpoints that make observations of certain changes of state in the environment. The Sensor Edge Server uses these sensors to integrate sensor data and applications.

Oracle Sensor Edge Server supports using Streams as one of the event distribution methods. When events are read in the devices, they are normalized by the drivers and sent to filters for filtering. After the data is "cleansed" and filtered, they are passed to the dispatchers for distribution. Oracle Sensor Edge Server uses plug-ins called dispatchers to communicate with applications and event distribution systems. One of the built-in dispatcher is the Streams Dispatcher. The Streams Dispatcher is a plug-in that sends and receives events using Oracle Streams technology.

Instead of talking directly to an application, the Streams Dispatcher hands off all the events into a Streams Staging area. Once the events are dropped off in the staging area, a background job will pick them up and evaluate it against a set of rules.

A rule is a condition that can be either matched or not matched by an event. If the condition is satisfied for this event, a corresponding user-defined action will be taken. A rule has four parts:

1. Name: A unique name of this rule provided by the caller that created the rule.
2. Condition: This is like a "WHERE" clause, but without the WHERE keyword.
3. Command: This provides instructions on what to do, and it can be either "call" to call a PL/SQL procedure, or "queue" to push the event to another queue.
4. Parameter: Param is the parameter for the command. For a "call" command, it is the PL/SQL name. For a "queue" command, it is the queue name.

Before you use the Streams Dispatcher, you have to set up a database instance to hold the Streams staging area, the rules, the queues, Sensor Data Archive, and other related data. Once the schema is ready, you point the Streams Dispatcher to it and start collecting data. This tutorial describes how to collect and route events using Streams technology.

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Prerequisites

Before starting this tutorial, you should complete the following tasks:

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Configuring the Streams Dispatcher

Configuring the Oracle Sensor Edge Server to use Oracle Streams and Advanced Queuing enables you to control how the edge dispatcher retrieves and distributes event messages. Unlike the Web Services, or HTTP Dispatcher options, event messages dispatched using the Streams Dispatcher do not have to be relayed directly to an entry point. The Streams Dispatcher supports rule-based process and agent technologies.

To configure Sensor Edge Server to use the streams dispatcher, perform the following steps:

The Streams Dispatcher will attempt to connect to the Sensor Data Streams schema.

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Adding Rules

This section shows how to invoke a PL/SQL procedure to handle data from the streams apply process. When you create a rule and add it, the rule will fire when an event occurs and a specified condition is met. This in turn calls the PL/SQL procedure. To add rules to the instance, perform the following steps:

1.	Open a browser window and enter the following URL: http://<hostname>.<domain>:<port>/edge/tools/rules.jsp If required, enter the username and password as oc4jadmin and welcome1. Click Login.
2.	Scroll down to Add New Rule in the SDS Rules section. Enter or select the following: Name: myrule Condition: :event.type=200 Action: Call PL/SQL Procedure Parameter: testProc Click Add Rule. You are creating a rule, which will fire if the incoming event type is 200 (which means an RFID sensor reading).
3.	Invoke the URL and verify that the rule has been added (Observe the top section of the table). http://<hostname>.<domain>:<port>/edge/tools/rules.jsp
4.	Open a command window and change directory to <edgeserver_home>\edge\sql\10.1.3 where edgeserver_home is the folder in which edge server is installed. Log in to SQL*Plus as the edge user by issuing the following command: sqlplus edge/<password for edge user>
5.	If you run events in to the SDS, and you have registered the PL/SQL callback, you will see the event being logged in to edg_log table. All logging is done at the edg_utl.tcDebug log level. Execute the following command to set the log level: exec edg_utl.set_log_level(edg_utl.tcdebug);
6.	The Streams Apply process that calls these procedures runs in a separate database session, setting the log level in your SQL*Plus session will not be reflected in the session in which the Streams Apply process is running. You must stop and start the Streams Apply process called EDG_APPLY to get the value of the log level using the following commands: exec DBMS_APPLY_ADM.STOP_APPLY('EDG_APPLY'); exec DBMS_APPLY_ADM.START_APPLY('EDG_APPLY');
7.	Only events with ID = 200 will cause the callback to get called. Look at your Sensor Data Archive. Execute the following query: SELECT count(*) FROM edg_log;
8.	You can now test the rule that you have created. To test the rule, send a false event by invoking the procedure as follows: http://<hostname>.<domain>:<port>/edge/tools/sendEvent.html Enter the following values: Type: 200 SubType: 1 Id: 125 Direction: true Click Submit Query. The procedure generates a dummy event with ID set to 125 and sends it out. The Direction parameter has to be set to true since SendEvents simulates events that comes from the device to SDS.
9.	You receive confirmation that the send event was successful.
10.	Open a browser window and enter the URL for Sensor Edge Server: http://<hostname>.<domain>:<port>/edge Enter the OC4J administrator username and OC4J administrator password. Click Login.
11.	Click Monitor Events. You should be able to view the following: Type Description: Custom (type=200 subtype=1) ID: 200
12.	Open a command window and change directory to <edgeserver_home>\edge\sql\10.1.3 where edgeserver_home is the folder in which edge server is installed. Log in to SQL*Plus as the edge user by issuing the following command: sqlplus edge/<password for edge user>
13.	If you run events in to the SDS, and you have registered the PL/SQL callback, you will see the event being logged in to edg_log table. All logging is done at the edg_utl.tcDebug log level. Execute the following command to set the log level: exec edg_utl.set_log_level(edg_utl.tcdebug);
14.	The Streams Apply process that calls these procedures runs in a separate database session, setting the log level in your SQL*Plus session will not be reflected in the session in which the Streams Apply process is running. You must stop and start the Streams Apply process called EDG_APPLY to get the value of the log level using the following commands: exec DBMS_APPLY_ADM.STOP_APPLY('EDG_APPLY'); exec DBMS_APPLY_ADM.START_APPLY('EDG_APPLY');
15.	Only events with ID = 200 will cause the callback to get called. Look at the Sensor Data Archive. Execute the following query SELECT count(*) FROM edg_log;

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Summary

In this lesson, you have learned how to:

Configure Streams Dispatcher for sensor events

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Related Information

	To learn more about Sensor Edge Server Enterprise Edition, refer to additional OBEs on the OTN Web site
	To ask a question about this OBE tutorial, post a query on the OBE Discussion Forum

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