Number of Threads

The RqThrottle parameter in the magnus.conf file specifies the maximum number of simultaneous transactions the Proxy Server can handle. The default value is 128. Changes to this value can be used to throttle the server, minimizing latencies for transactions that are performed.

To compute the number of simultaneous requests, the server counts the number of active requests, adding one to the number when a new request arrives, subtracting one when it finishes the request. When a new request arrives, the server checks to see if the maximum number of requests is already being processed. If the limit has been reached, the processing of new requests is deferred until the number of active requests drops below the maximum amount.

You can monitor the number of simultaneous requests by viewing the SessionCreationInfo portion of data generated by perfdump, or proxystats.xml data. From this information, you can determine the maximum number of simultaneous (peak) requests as compared to the total number (limit) of threads. The following information came from a perfdump output:

SessionCreationInfo:
------------------------
Active Sessions          1
Keep-Alive Sessions      0
Total Sessions Created   48/128

Active Sessions shows the number of sessions (request processing threads) currently servicing requests. Keep-Alive Sessions is similar to Active Sessions, but is specific to whether the client is requesting a keep-alive connection. Total Sessions Created shows both the number of sessions created and the maximum number of sessions allowed. These are the minimum and maximum values for the RqThrottle value.

RqThrottleMin is the minimum number of threads the server initiates upon startup. The default value is 48. This parameter can also be set in the magnus.conf file, but does not appear by default.

Reaching the maximum number of configured threads is not necessarily undesirable, and you do not need to automatically increase the RqThrottle value if you see this. Reaching this limit means that the server needed this many threads at peak load, but as long as it was able to serve requests in a timely manner, the server is adequately tuned. However, at this point, connections will queue up in the connection queue, potentially overflowing it. If you check your perfdump output on a regular basis and notice that total sessions created is often near the RqThrottle maximum, consider increasing your thread limits.

Suitable RqThrottle values range from 100 to 500, depending on the load.