Extreme Networks Px Series manual Health Checking Procedure

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Health Checking Procedure

Health Checking Procedure

You configure health checks for each server group. All the members of a given server group have the same health check performed on them. The health check process uses the following procedure:

1As soon as a server is enabled or the system comes up, a health check is performed on the server. If it passes, the server goes up immediately

2Health checks are performed at the configured interval.

—If a health check fails, it is retried at approximate intervals specified by retry-interval, until it has failed fail-aftertimes. Then the server is removed from service.

—If the server passes a health check, it is retried at intervals specified by retry-interval, until it passes restore-aftertimes.

By default, interval is 30 seconds, retry-intervalis 10 seconds, fail-afteris 2 seconds, and restore-afteris 2 seconds. You can change these default timer settings locally on an individual server, or globally. If you set them globally, the timers are modified on all hosts that use the default settings.

If health checks are enabled but not specifically configured, the default check is ping, with the default timer values. If the CPU is swamped by too many health checks or other tasks, the times may stretch.

The TCP and HTTP health checks open a connection to the port configured for each server in the server group. For HTTP health checks, you must specify the name of the object to retrieve and a string to match, which must be a substring of the returned page.

After the connection is opened, the health check requests the specified object. If the object is returned, the health check checks the first 1000 bytes of returned text to see if it contains the string. If the string is found, the application is up and functioning. Otherwise, the server fails the health check. If the server has failed too many times, it is removed from the server group.

If you do not specify an object to retrieve, the health check does a “head /”. If anything is returned, the check passes.

All data requests use HTTP 1.0.

Px Series Application Switch Installation and Configuration Guide

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Contents Published April Part number 100101-00 Rev Page Contents Installing the PxM Application Switch Module Configuring Servers and Services Index Index of Commands Introduction PrefaceText Conventions ConventionsIcon Alerts you to Convention DescriptionRelated Publications Preface Purpose of Server Load Balancing Server Load Balancing Concepts1Conceptual view of server load balancing TermsLayer 4 Load Balancing Load Balancing Modes2Single client-server transaction using layer Layer 7 Load Balancing and Content Analysis3Establishing a layer 7 request Port Rewrite Getting Started on Load Balancing ConfigurationGetting Started on Load Balancing Configuration Page SummitPx1 Front View Installing the SummitPx1 Application SwitchOverview of the SummitPx1 Application Switch Color Indicates 1Px series application switch LEDsSignal Description SummitPx1 Application Switch Rear View2DB-9 Adapter Pinouts To DB-9Rack Mounting Installing the SummitPx1 Application SwitchDetermining the Location Free-Standing Powering On the SummitPx1Setting Up Console Communication Configuring Switch IP Parameters Configuring the 10/100 Ethernet Management Port Installing I/O Modules Installing the PxM Application Switch ModuleRemoving I/O Modules Removing I/O Modules Page Managing the Switch Abbreviated Syntax and Command Completion Using the Command-Line InterfaceSyntax Symbols 1Command Syntax SymbolsLine-Editing Keys Symbol DescriptionSpecifying Text Values 2Line-Editing KeysPrompt Text Configuring Management AccessCommand History Changing the Default Passwords Modifying Accounts Creating AccountsManaging the PxM Command DescriptionConfiguring VLANs 4SNMP Configuration Settings Configuring SnmpSetting Description System ContactSettingDescription Configuring DNS Client Services5DNS Client Configuration Commands Using Secure Shell 2 SSH2Config ssh2 key Enabling SSH2 for Inbound Switch AccessUsing SCP2 from an External SSH2 Client SSH2 Client Functions on the Switch Checking Basic Connectivity UtilitiesShowing CPU Load Logging Starting the GlobalPx Content Director Agent Configuring a Startup Banner MessageInternet DNS server Example ConfigurationFollowing commands configure all system-related facilities Page Configuring Real Servers Configuring Servers and ServicesConfiguring Server Groups Configuring Virtual Services Layer 4 Port-based Load Balancing Layer 7 Virtual ServicesConfiguring Traffic Tagging Tag Specification Description Tag Range Configuration Example1Tag Specifications Configuration Example Page Scheduling Policies Choosing Policies, Persistence Modes, and NATSpecifier Policy Description Persistence Modes1Scheduling Policies UDP Flow Persistence Client IP Persistence Mode1Client IP persistence mode Cookie Persistence Modes Configuring Client IP Stickiness2Self-identifying cookie persistence mode Persistence Modes Hashed Cookie Persistence Session Learned Cookie Persistence Mode 4Learned cookie persistence mode Configuring Cookie Stickiness SSL Session Identifier Persistence NAT Modes Full-NAT ModeConfiguring Full-NAT Mode and Proxy IP Addresses Server-only Half-NAT ModeConfiguring Half-NAT Mode Config source-flow name next-hop gateway-mode ip Real Syslog server SummitPx1 Configuration Example Page Domain and URL Switching URL Switching1Typical switching scenario Domain Switching2Domain switching example URL Switching Configuring URL Switching3Simple URL switching example 4More Complicated URL switching example 5Hierarchical approach to pattern rules Wildcard Example Definition Creating Domain and URL Switching Rules1Wildcard Combinations Modifying Existing URL Rules and Domains Application Servers Management net Configuration Example Page Using Vrrp with the SummitPx1 Configuring RedundancyGive backup systems lower priorities Adding and Configuring VRRPsUsing Vrrp in Existing Redundant Networks Vrrp Automatic Synchronization 1Application switch using multiple VLANsFollowing commands can be passed from master to backup Using Esrp with the PxM Configuring Redundancy for the PxMFor SW2 Configuring the PxM for Multiple VLANsConfiguring a Default Gateway Overview Health ChecksServer Startup Pacing Health Checking Procedure Types of Health Checks Configuring Health ChecksTimers and Counters You can disable health checks for a server group Page Showing Traffic Statistics Monitoring the Switch1Statistics Display Commands Displays packet-level counters for 2Configuration Display Commands Showing Configuration DetailsConfiguration Displays SummitPx128 # show server details Status DisplaysColumn Description Show health Information5Management and Troubleshooting Commands Managing and Troubleshooting OperationCommandDescription Esrp IndexHttp GET AUX Page Index of Commands