Sun Java System Web Server 6.1 SP6 Performance Tuning, Sizing, and Scaling Guide

Maximum Simultaneous Requests

The RqThrottle parameter in the magnus.conf file specifies the maximum number of simultaneous transactions the Web Server can handle. The default value is 128. Changes to this value can be used to throttle the server, minimizing latencies for the transactions that are performed. The RqThrottle value acts across multiple virtual servers, but does not attempt to load balance.

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 it is already processing the maximum number of requests. If it has reached the limit, it defers processing new requests until the number of active requests drops below the maximum amount.

In theory, you could set the maximum simultaneous requests to 1 and still have a functional server. Setting this value to 1 would mean that the server could only handle one request at a time, but since HTTP requests for static files generally have a very short duration (response time can be as low as 5 milliseconds), processing one request at a time would still allow you to process up to 200 requests per second.

However, in actuality, Internet clients frequently connect to the server and then do not complete their requests. In these cases, the server waits 30 seconds or more for the data before timing out. You can define this timeout period using the AcceptTimeout directive in magnus.conf. The default value is 30 seconds. By setting it to less than the default you can free up threads sooner, but you might also disconnect users with slower connections. Also, some sites perform heavyweight transactions that take minutes to complete. Both of these factors add to the maximum simultaneous requests that are required. If your site is processing many requests that take many seconds, you may need to increase the number of maximum simultaneous requests. For more information about AcceptTimeout, see the Sun Java System Web Server 6.1 SP6 Administrator’s Configuration File Reference.

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

RqThrottleMin is the minimum number of threads the server initiates upon startup. The default value is 48. RqThrottle represents a hard limit for the maximum number of active threads that can run simultaneously, which can become a bottleneck for performance. The default value is 128.

Note –

If you are using older NSAPI plugins that are not reentrant, they will not work with the multi-threading model described in this document. To continue using them, you should revise them so that they are reentrant. If this is not possible, you can configure your server to work with them by setting RqThrottle to 1, and then using a high value for MaxProcs, such as 48 or greater, but this will adversely impact your server’s performance.

Note –

When configuring Sun Java System Web Server to be used with SNCA (the Solaris Network Cache and Accelerator), setting the RqThrottle and ConnQueueSize parameters to 0 provides better performance. Because SNCA manages the client connections, it is not necessary to set these parameters. These parameters can also be set to 0 with non-SNCA configurations, especially for cases in which short latency responses with no keep-alives must be delivered. It is important to note that RqThrottle and ConnQueueSize must both be set to 0.

For more information about RqThrottle and ConnQueueSize, see the chapter pertaining to magnus.conf in the Sun Java System Web Server 6.1 SP6 Administrator’s Configuration File Reference. Also consult the RqThrottle and ConnQueueSize entries in the index in this book. For information about using SNCA, seeUsing the Solaris Network Cache and Accelerator (SNCA)


You can tune the number of simultaneous requests by: