Tuning the on demand router (ODR)

ODRs are servers that act as an intermediary for HTTP requests that are serviced by application servers or Web servers. There are many factors that affect ODR performance. If you discover that your ODRs are not operating in the most optimal manner, then you might want to tune your ODRs.

Before you begin

Before modifying the JVM heap size, read:

About this task

Use the topics in this section to troubleshoot your ODRs when they are not operating in a typical fashion, or you are experiencing unusual problems. For example, the following list contains tuning suggestions for improving ODR performance in order of importance for troubleshooting.

Procedure

  1. Check the JVM settings. See Modifying the JVM heap size for the on demand router (ODR).
  2. [For HP-UX operating system] HP and Sun provide additional tuning parameters to optimize garbage collection. For generational garbage collection JVMs such as Sun and HP, or IBM's J9 JVM when using gencon garbage collection, set the permanent memory region to approximately 100MB to encompass the base 90MB foot print that exists in the ODR. Further, a SurvivorRation of 16 further optimizes processing in the young generation. On HP JVM, you can turn NIO to yield an increase in performance by using the -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.DevPollSelectorProvider selector provider and disabling the extra poll before a read: -XX:-ExtraPollBeforeRead.
  3. Tune the connection keep alive settings. See Tuning ODR persistent connections.
  4. Increase the ODR maximum connections per server. See Tuning ODR maximum connections
  5. Disable ODR caching when not in use. When the ODR caching is enabled, the ODR must go through the process of determining whether a request should be cached, then examine the cache repository to check whether the request was previously cached. This causes additional overhead.
  6. Disable access logging if not needed. If you do need access logging, then the proxy logging is preferred over the HTTP Channel/NCSA logging as the proxy access logging happens outside of the request/reply path. Thus, it does not affect the response time of the request. Access logging on a fairly fast disk is typically 5% overhead, but the percentage is highly dependant on disk performance.
  7. Use the same thread group for both inbound and outbound work, which will avoid moving requests across threads and eliminate the resulting overhead. The ODR has a set of threads that tune itself under most circumstances. Queuing and throttling requests are dispatched to the default thread pool, which you can tune so that it will only handle the overflow requests. The primary thread group will continue to handle most requests. All requests on the thread pool are asynchronous with no blocking calls, so the number should not be more than one or two threads per CPU. Complete the following steps to use the same thread group for both inbound and outbound work:
    1. Select Servers > On Demand Routers > on demand router > Thread Pools default thread pool > Custom Properties > New
    2. Specify combineSelectors for the name.
    3. Specify 1 for the value.
    4. Click OK.
    5. Click Save.

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