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Create and configure ODRs

The on demand router (ODR) is an intelligent HTTP and SIP proxy server used as a point of entry into an Intelligent Management environment. An ODR is a gateway through which HTTP requests and SIP messages flow to back-end application servers. We can configure the ODR to determine how it handles failure scenarios and how it tunes certain work requests.

As an alternative gateway into Intelligent Management, WAS ND v9 supports a subset of ODR functions in an Apache or IBM HTTP web server plug-in.

The ODR can queue requests for less important applications, allowing requests from more important applications to be handled more quickly or to protect back-end application servers from being overloaded. The ODR is aware of the current location of a dynamic cluster instance so that requests can be routed to the correct endpoint. The ODR can also dynamically adjust the amount of traffic sent to each individual server instance based on process utilization and response times. The ODR performs Weighted Least Outstanding Request (WLOR) load balancing for selecting a server within a cluster when there is no affinity or when affinity is broken.

By default, the ODR binds to ports 80 and 443 for listening on HTTP and HTTPS, which requires running the ODR as a root user. To run the ODR as a non-root user, change the PROXY listening ports to values greater than 1024.

By default, if no rules are specified in the ODR Routing policy HTTP rules section, all the requested contexts are accepted and are routed to the backend application servers within the cell.

The ODR is aware of the dynamic state of the cell, so that if one server in the cell fails, the requests are routed to another server. When the ODR is notified that the application has initialized on the restarted server, the ODR routes requests to that server again.

The ODR does not route any requests to the application on the application server until the application completes starting or initializing. If the application is started on other application servers, then the requests are routed to them. If the application is not started on any other servers, then the ODR still does not route to the starting-in-progress application server. Instead, a 503 message is returned.

The configuration of the ODR in the DMZ is not supported.

SIP is not supported on the z/OS operating system.

The SIP ODR is stabilized, and is currently not recommended. Use the SIP proxy server instead.


ODR Tasks


Web server Tasks :

  • Intelligent Management for IHS Web Servers
  • Configure Intelligent Management for web servers


    Related:

  • Overview of request flow prioritization
  • Set up Intelligent Management for dynamic operations
  • Define routing policies for generic server clusters
  • Define service policies for generic server clusters
  • Add middleware servers to configurations
  • Create dynamic clusters
  • createodr.jacl script
  • Proxy server settings SIP proxy server
  • Propagating plugin-cfg.xml to web servers
  • propagatePluginCfg.py script