Request Execution Time

Description:
Displays the number of milliseconds that it took to execute the most recent request.

Information:
The execution time begins when the HttpContext for the request is created, and stops before the response is sent to IIS. Assuming that user code does not call HttpResponse.Flush, this implies that execution time stops before sending any bytes to IIS, or to the client. When the process model is enabled, the request execution time includes the time required to write the response to the client, and therefore depends upon the bandwidth of the client's connection. There is no threshold for this counter. The value of this counter should be stable. Experience helps you set a threshold for a particular site.

Note: A baseline is required.

Request Wait Time

Description:
Displays the number of milliseconds that the most recent request was waiting in the queue.

Information:
This does not include any time spent waiting in application queues. The threshold for this counter is 1,000. The average request should spend 0 milliseconds waiting in the queue.

Possible problems:
If this indicator is greater than 1,000 ms, the performance of the IIS server is suffering.

Requests Queued

Description:
This displays the number of requests waiting to be processed.

Information:
The Aspnet_wp process queue is a named pipe through which the request is sent from one process to the other. The number of requests in this queue increases if there is a shortage of available I/O threads in the Aspnet_wp process. When the limit specified by <processModel requestQueueLimit=/> is exceeded, requests are rejected with a 503 error (Service Unavailable).

Note that if a request is rejected for this reason, it will never reach managed code and error handlers will not be notified. Normally this only occurs when the server is under a very heavy load. Virtual directory queues maintain the availability of worker and I/O threads.

The number of requests in queues increases if the number of available worker threads or available I/O threads falls below the limit specified by <httpRuntime minFreeThreads=/>. When the limit specified by <httpRuntime appRequestQueueLimit=/> is exceeded, the request is rejected with a 503 error and the client is sent an HTTP exception with the message, Service Unavailable.

Possible problems:
When this value starts to increment linearly with increased client load, the web server computer has reached the limit of concurrent requests that it can process.

Remediation:
The default maximum value for this counter is 5,000. You can change this setting in the Machine.config file.

Note: A baseline is required.

> 2000 Sustained Status: 3 out of 5 polls

Description:
Displays the number of requests rejected because the request queue was full.

Information:
Requests are rejected when one of the queue limits is exceeded. Back-end latency, such as that caused by a slow computer running SQL Server, is often preceded by a sudden increase in the number of pipeline instances and a decrease in % Processor Time and Requests/second. A server might be overwhelmed during times of heavy load due to processor or memory constraints that ultimately result in the rejection of requests.

Possible problems:
The value of this counter should be 0. Values greater than 0 should be investigated.