[hyades-dev] HCE Requirements: Service Control Agent

[Victor Havin <vhavin@xxxxxxxxxx>]

Additional details for the HCE Service
Control Agent requirement (attached).


--Victor

System Service Control Agent.

[Draft requirement]

Problem Definition

Current RAC implementation has built-in capabilities for launching a process on a RAC hosting system. There is a set of predefined commands for querying/setting environment variables, creating a process and receiving notifications on process status change. On the client side this subsystem is represented by the Appropriate Java API. In the current implementation functionality of the execution subsystem is limited by launching a Java process only. HCE already has a requirement for being able to launch any user process; however this requirement doesn’t cover system services. This proposal introduces the concept of System Services Control Agent.

System Services

The concept of System Services is not universal. Services can be found in most Windows systems, most Linux versions and on some UNIX platforms. (ToDo: find out about i-series and z-series). System Services, unlike user processes are not started by a user or another process, but are rather controlled by a System Service Manager. Platforms that support services usually provide service control API. Most common functions of service control API include:

•  Start service
•  Stop service
•  Restart service
•  Query service status
•  Query service properties
•  Set service properties

Proposed Solution

System service management implementation should extend the current Hyades execution subsystem and will have two parts:

1. Execution API extension for service control
2. System Service Control

Agent Service Control API should provide following features:

•  System queries (enumerate services etc.)
•  Service Execution Control (Start, Stop, Restart)
•  Service status query
•  Service status change notification events
•  Service properties control
•  Service properties query

Service Control Agent should provide commands and data sets for supporting the Service Control API (above).

Sample use case

Applications, components and HCE elements named in this use case are for illustration only.

One of the tires of distributed system is implemented as relational database system running as a system service on one of the network nodes. The SQL request processor for the database is implemented in Java. One of the Hyades teams implemented a SQL request profiler based on the Probe Kit. Probes hook SQL related APIs and send XML data stream describing API invocations back to HCE client(s). However, to start the dynamic probe insertion it is necessary to restart the database service on the node of interest and instruct the JVM to hook the class loader with probe insertion API.

Eclipse user selects profiling perspective, selects remote node, opens service control tab, selects the SQL Broker Service from the list of services, assigns the SQL Request Profiler Probe to it, clicks restart button, waits for the service status to become ‘running’, opens statistical view, starts a database application and enjoys the SQL queries per second graph.

The remote node was started with HCE service running. Opening the service control tab is initiating a sequence of invocations into Service Control API

services = org.eclipse.hyades.execution.ServiceManager.getServiceList(node);

foreach(service in services) {

properties = service.getProperties();

if(properties.find(“service_name”, property) {

if(property.getValue.equals(selectedServiceName); service.restart();

}

}

 

This results in the following message interchange between Eclipse and HCE:

Eclipse->HCE

<hce:command code=”start_agent” target=”AgentControler”>

<hce:property name =”AgentName” value=”ServiceControlAgent” />

<hce:property name=”user” value=”root”/>

</hce:command>

HCE->Eclipse

<hce:response source=”ServiceControlAgent”>

<hce:property name=”return_code” value=”0”/>

</hce_response>

Eclipse->HCE

<hce:command code=”list_services” target=”ServiceControlAgent”>

<hce:property name=”filter” value=”*”/>

</hce:command>

HCE->Eclipse

<hce:response source=”ServiceControlAgent”>

<service name=”Telnet” process_id=”123” status=”stopped”>

<hce:property name=”user” value=”root”/>

</service>

<service name=”SQL Broker” process_id=”125” status=”running”>

<hce:property name=”user” value=”root”/>

</service>

</hce:response>

Eclipse->HCE

<hce:command code=”restart_service” target=”AgentController”>

<hce:property name=”service_name” value”=”SQL Broker”/>

</hce:command>