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Appendix B. Worker Node Reference
B.1. Worker Configuration
Configuration values are sent to proxies under the following conditions:
- During server startup.
- When a proxy is detected through the advertise mechanism.
- During error recovery, when a proxy’s configuration is reset.
Table B.1. Proxy Configuration Values for Tomcat
| Value | Default | Description |
|---|---|---|
| stickySession | true | Specifies whether subsequent requests for a given session should be routed to the same node, if possible. |
| stickySessionRemove | false |
Specifies whether the Apache HTTP Server proxy should remove session stickiness if the balancer is unable to route a request to the node to which it is stuck. This property is ignored if |
| stickySessionForce | true |
Specifies whether the Apache HTTP Server proxy should return an error if the balancer is unable to route a request to the node to which it is stuck. This property is ignored if |
| workerTimeout | -1 |
Specifies the number of seconds to wait for a worker to become available to handle a request. When all the workers of a balancer are unusable, mod_cluster will retry after a while ( |
| maxAttempts | 1 |
Specifies the number of times the Apache HTTP Server proxy will attempt to send a given request to a worker before aborting. The minimum value is |
| flushPackets | false | Specifies whether packet flushing is enabled or disabled. |
| flushWait | -1 |
Specifies the time to wait before flushing packets. A value of |
| ping | 10 | Time to wait (in seconds) for a pong answer to a ping. |
| smax |
Specifies the soft maximum idle connection count. The maximum value is determined by the Apache HTTP Server thread configuration ( | |
| ttl | 60 |
Specifies the time (in seconds) idle connections persist, above the |
| nodeTimeout | -1 |
Specifies the time (in seconds) mod_cluster waits for the back-end server response before returning an error. mod_cluster always uses a |
| balancer | mycluster | Specifies the name of the load-balancer. |
| loadBalancingGroup |
Specifies the load balancing among |
B.2. mod_cluster Proxy and Proxy Discovery Configuration Attributes
The following tables contain attributes and information about mod_cluster proxy, and proxy discovery configuration attributes.
Table B.2. mod_cluster Proxy Discovery Configuration Attributes
| Attribute | Property | Default Value |
|---|---|---|
| proxy-list | proxyList | |
| proxy-url | proxyURL | |
| advertise | advertise | true |
| advertise-security-key | advertiseSecurityKey | |
| excluded-contexts | excludedContexts | |
| auto-enable-contexts | autoEnableContexts | true |
| stop-context-timeout | stopContextTimeout | 10 seconds (in seconds) |
| socket-timeout | nodeTimeout | 20 seconds (in milliseconds) |
When nodeTimeout is not defined, the ProxyTimeout directive, Proxy, is used. If ProxyTimeout is not defined, the server timeout (Timeout) is used (120 seconds by default in the JBCS httpd.conf). nodeTimeout, ProxyTimeout, and Timeout are set at the socket level.
Table B.3. mod_cluster Proxy Configuration Attributes
| Attribute | Property | Default Value |
|---|---|---|
| sticky-session | stickySession | true |
| sticky-session-remove | stickySessionRemove | false |
| sticky-session-force | stickySessionForce | true |
| node-timeout | workerTimeout | -1 |
| max-attempts | maxAttempts | 1 |
| flush-packets | flushPackets | false |
| flush-wait | flushWait | -1 |
| ping | ping | 10 (seconds) |
| smax | smax | -1 (uses the default value) |
| ttl | ttl | -1 (uses the default value) |
| domain | loadBalancingGroup | |
| load-balancing-group | loadBalancingGroup |
B.3. Load Configuration
The following table contains additional configuration properties that are used when mod_cluster is configured with Tomcat.
Table B.4. Load Configuration for Tomcat
| Attribute | Default Value | Description |
|---|---|---|
| loadMetricClass | org.jboss.modcluster.load.metric.impl.BusyConnectorsLoadMetric |
The class name of an object that is implementing |
| loadMetricCapacity | 1 |
The capacity of the load metric defined via the |
| loadHistory | 9 | The number of historic load values that must be considered in the load balance factor computation. |
| loadDecayFactor | 2 | The factor by which the historic load values decrease in significance. |
