Veritas Cluster Server 6.0 for UNIX: Example Application Configurations

Example 1: Clustering Applications

Topic ObjectivesApplication service overview

Describe how application services work in an HA environment.

VCS agents for managing applications

Describe how agents manage applications in a VCS environment.

The Application agent Configure the Application agent.

IMF support Configure IMF for preventing concurrency violations with Application resources.

Lesson objectives

After completing this topic, you will be able to describe how application services work in a high availability environment.

Application service overview

Application service overview

Storage

File systemVolume

Disk groupNetwork

10.10.21.198IP address NIC

ApplicationWeb

server

S1

Application requirements

• Start and stop procedures• Clean up capability after operational failures• Automated monitoring facility• Data storage on external shared disks• Restart capability after sudden failures• Support for multiple servers designated as potential hosts:– No license issues tied to individual servers– No host name dependencies

After completing this topic, you will be able to describe how agents manage applications in a VCS environment.

VCS agents for managing applications

VCS agents for managing applications

Bundled and database

Application andPartner

Custom Developed in-house or by Symantec Consulting Services

– Symantec-developed agents– Independent software vendor (ISV) agents – Quarterly updates– Available from sort.symantec.com

Shipped with VCS IP

NICApplication

Zone Ldom

HAD

Key properties of VCS agents• Only one agent daemon runs on a system for each configured resource

type.• An agent runs a single operation on a resource at one time.• Agents can perform operations on multiple resources of the same type in

parallel.• If there are no resources of a particular type anywhere in the cluster, the

agent for that type is not started.• A resource cannot be managed without an agent.

NICIP

Process

HAD

VCS agent functions

• Start a specified program.

• Stop the specified program.

• Monitor the program.

• Clean up after a fault.

Some agents have multilevel monitoring functions.– Basic-level monitoring, which checks the process table for applicable

processes– Second-level monitoring, which simulates client access to the

application

The VCS agent framework

• Agents consist of:– An agent binary file, which contains all necessary

functions within a single binary

or

– An agent binary and a collection of scripts that correspond to agent functions not included in the binary

• Agent functions are referred to as entry points.• Most agents include the online, offline, monitor, and

clean entry points.

onlineoffline

monitor

clean

– Entry points are often implemented as Perl or shell scripts and are easily customized.

– Agents can also be implemented as compiled executable files.

How agents work

$1 webdg$2 webdatadg

DiskGroup webdg ( DiskGroup = webdatadg)

main.cf

hares -online webdg -sys s1

vxdg –t import webdatadg

onlineoffline

monitorclean

type Diskgroup( . . . static str ArgList[] = { DiskGroup . . .}. . .)

types.cf webdg

In-memory configuration

DiskGroup agent

online

HAD

After completing this topic, you will be able to configure the application agent.

The Application agent

The Application agent

• Simplifies managing applications with multiple processes • Enables second-level monitoring• Is easily customized by creating scripts that the agent uses within its

entry points

Entry Point Function

Online Brings an application online

Offline Takes an application offline

Monitor Monitors the status of the application

CleanTakes the application offline or kills all processes specified for the application

Application resource definition

Optional attributesCleanProgram Executable file that forcibly kills the application and

performs cleanup tasksUser UNIX account used as the execute environment for entry

points (the default is root)EnvFile Environment file sourced before running entry points

UseSUDash Runs su – user before running entry points

Required attributesStartProgram Executable file to start applicationStopProgram Executable file to stop applicationPlus one or more of the following:MonitorProgram Executable file to monitor applicationMonitorProcesses List of processes to be monitoredPidFiles List of files containing the process IDs to be monitored

Application resource configuration

Configuration prerequisites– Ensure the application has start and stop programs.– Determine which processes can be used to monitor the application

main.cf

Application payroll_app (StartProgram = “/etc/init.d/payroll start”StopProgram = “/etc/init.d/payroll stop”PidFiles = { “/paydata/payroll.pid” }MonitorProcesses = { “paydebit payvendor” }

)

After completing this topic, you will be able to configure IMF for preventing concurrency violations with Application resources.

IMF support and prevention of concurrency violation

• Type Attributes Defaults:– IMF

• Mode 3 online and offline monitoring• MonitorFreq 1 runs monitor entry point every 1 minute

(MonitorInterval = 60 seconds by default)• RegisterRetryLimit 3

– IMFRegList MonitorProcesses, User, PidFiles, MonitorProgram

– LevelTwoMonitorFreq 0

IMF-related attributes

Supported configurations

MonitorProgram MonitorProcesses PidFiles IMF Mode

n n n n/a

n n Y Online only (2)

n Y n Online, Offline (3)

n Y Y Online, Offline (3)

Y n n None (0)

Y n Y None (0)

Y Y n None (0)

Y Y Y None (0)

• Is enabled by the ProPCV service group attribute (default = 0)• Is supported for Application agent only• Requires IMF enabled and Mode set to 3 (online and offline

monitoring)

Prevention of concurrency violation (PCV) configuration

main.cf snippet

Application myappd ( StartProgram = "/usr/bin/myappd start" StopProgram = "/usr/bin/myappd stop" MonitorProcesses = { " myappd " })

StartProgram example

myappd

• Is only supported for failover service groups• Works only with MonitorProcesses attribute specified• Is not supported if StartProgram refers to a wrapper-type script

Requires exact match between path and arguments in MonitorProcesses attribute and process table

• MonitorProgram and PidFiles attributes cannot can be specified

Limitations of PCV

Lesson summary

• Key points – VCS provides a variety of agents to manage all types of applications.– The Application agent is easily configurable for basic management of an

application.• Reference materials– Veritas Cluster Server Bundled Agents Reference Guide– Veritas Cluster Server Agent Developer’s Guide– Veritas Cluster Server: Install and Configure Course– www.symantec.com

End of Presentation