Users moving to Windows Azure Web Sites (WAWS) is increasing day by day. Happy to see many of the PHP websites being hosted with WAWS. If you are hosting your high traffic website with WAWS, I would like you to consider increasing the queueLength property of FastCGI handler for PHP that handles your request. By default, the value for queueLength property is 1000, which means only 1000 concurrent requests can be in the queue getting processed. For a many high traffic websites, this might seem to be a low number, and you would start seeing 503 errors in your instance logs.
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