Sun Java System Web Server 7.0 Update 4 Performance Tuning, Sizing, and Scaling Guide

Connection Queue Information

In Web Server, a connection is first accepted by acceptor threads associated with the HTTP listener. The acceptor threads accept the connection and put it into the connection queue. Then, request processing threads take the connection in the connection queue and process the request. For more information, see Connection-Handling Overview.

Connection queue information shows the number of sessions in the connection queue, and the average delay before the connection is accepted by the request processing thread.

The following is an example of how these statistics are displayed in perfdump:

Current/Peak/Limit Queue Length            0/1853/160032
Total Connections Queued                   11222922
Average Queue Length (1, 5, 15 minutes)    90.35, 89.64, 54.02
Average Queueing Delay                     4.80 milliseconds

The same information is displayed in a different format through the Admin Console or command-line interface, with some slight differences. The following table shows the information displayed in the Admin Console when accessing monitoring information for the server instance:

Table 2–2 Connection Queue Statistics

Present Number of Connections Queued 

Total Number of Connections Queued 


Average Connections Over Last 1 Minute 


Average Connections Over Last 5 Minutes 


Average Connections Over Last 15 Minutes 


Maximum Queue Size 


Peak Queue Size 


Number of Connections Overflowed 

Ticks Spent 


Total Number of Connections Added 


Current /Peak /Limit Queue Length

Current/Peak/Limit queue length shows, in order:


If the peak queue length, also known as the maximum queue size, is close to the limit, you can increase the maximum connection queue size to avoid dropping connections under heavy load.

You can increase the maximum connection queue size in the Admin Console by changing the value of the thread pool Queue Size field on the configuration's Performance tab ⇒ HTTP sub tab. The default is selected based on the total number of available file descriptors in the system.

To change the queue size using the command-line interface, use the wadm set-thread-pool-prop command's queue-size property.

Total Connections Queued

Total Connections Queued is the total number of times a connection has been queued. This number includes newly-accepted connections and connections from the keep-alive system.

This setting is not tunable.

Average Queue Length

The Average Queue Length shows the average number of connections in the queue over the most recent one-minute, five-minute, and 15–minute intervals.

This setting is not tunable.

Average Queuing Delay

The Average Queueing Delay is the average amount of time a connection spends in the connection queue. This represents the delay between when a request connection is accepted by the server and when a request processing thread begins servicing the request. It is the Ticks Spent divided by the Total Connections Queued, and converted to milliseconds.

This setting is not tunable.

Ticks Spent

A tick is a system-dependent value and provided by the tickPerSecond attribute of the server element in stats.xml. The ticks spent value is the total amount of time that connections spent in the connection queue and is used to calculate the average queuing delay.

This setting is not tunable.

Total Number of Connections Added

The new connections added to the connection queue. This setting is not tunable.