An analysis of 503 errors in the website what to do

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First we have to figure out what a 503 error is, and 503 is an HTTP status code. The English name 503 Service Unavailable and 404 (404 Service Unavailable) are the same kind of Web page state error codes. The former is a server error return state, the latter is a Web page program has no relevant results after the return of a state, the need to optimize the site is usually required to make 404 error page has been the overall optimization of the site. The server is currently unable to process the request due to temporary server maintenance or overloading. This condition is temporary and will be restored after a period of time. If the latency can be predicted, the response can contain a retry-after beginning to indicate the delay time. If this retry-after information is not given, the client should handle it in a way that handles the Server Internal Error response. 503

Note: The presence of a 503 status code does not mean that the server must use it when it is overloaded. Some servers simply want to deny client connections.

The second is to figure out the cause of 503, 503 errors are mainly the following situations, 1, network administrators may close the application pool to perform maintenance. 2. The application pool queue is full when the request arrives. 3, the application pool identity does not use a predefined account: A network service that is configured with its own identity, but the configured user does not belong to the IIS_WPG group, 4, the application pool has CPU monitoring enabled, and the CPU utilization is set to close the application pool, while the developer writes a server-side page (. 　　Asp,.aspx execution is inefficient, resulting in a long CPU footprint that eventually reaches the percentage set, which causes the application pool to shut down 5, the application pool's Performance tab's request queue limit is too small, and the default is 1000. 6, the value of the appRequestQueueLimit property set for the System.web/httpruntime node of web.config is too low.

Another situation is the use of the virtual host site 503 error, the main reason for two points: 1, the site is being attacked. For the latest attack, is actually a kind of DDoS derivation, the principle is to find thousands of IP, at the same time to the server Apache issued a request, and then immediately disconnect, so that Apache is in the waiting state, resulting in all the Apache thread is filled, resulting in server panic. Therefore, in order to ensure the interests of most customers, we give each space, made 64 PHP requests per 19 seconds limit. 　　Note that PHP requests are not included in general picture requests and HTML requests. 2, the program occupies too many PHP threads, some programs did not do a good job optimization, a click can produce several, or even dozens of PHP threads. In this case, a few clicks will fill up all 64 PHP threads for that period. Therefore, there are 503 errors. The proposal optimizes the procedure, as far as possible uses the Require ("request" the meaning) and so on the statement.

The last is high understanding how to solve; To resolve 503 problems, follow these steps: 1. Verify that the application pool has been configured for the virtual server. 　　The default application pool is MSSharePointPortalAppPool. 　　Follow these steps to determine which application pool the virtual server is using. 　　A. Click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager. 　　B. Expand ServerName, expand Web Sites, right-click the virtual server, and then click Properties. C. Click the Home Directory tab. 　　The application pool configured for the virtual server is listed in the Application pool box. 　　D. Click OK. 2. Verify that the password used by the application pool account is correct. IIS does not automatically poll for password changes in the ActiveDirectory directory service. 　　If the application pool account is a domain account and its password has expired, you may receive the error message that is described in the "Symptoms" section of this article after you reassign a new password for this account. 　　3. Verify that the application pool account is a member of the IIS_WPG and STS_WPG groups on the server. 4. Restart IIS to reclaim the application pool.