Hypertext Transfer Protocol or HTTP
503 Service Unavaiable server error response code indicates that the server is not ready to handle the request. Also HTTPS protocol will use the same code for the same reason. In this tutorial we will examine the 503 error code causes, client and server side solutions.
HTTP 503 code can be expressed a little bit differently for different web servers. There are different web servers like Apache, IIS, lighttpd, Nginx etc.
503 Service Unavailable
503 Service Temporarily Unavailable
Http/1.1 Service Unavailable
HTTP Server Error 503
Service Unavailable - DNS Failure
HTTP Error 503
Error 503 Service Unavailable
This error code simply means
Service Unavailable which means server can not handle and response to the request properly. Here the list of the HTTP 503 error causes.
- There is an update on the web server
- There is a bug in the server software
- There is a bug in the web application
- The request is an comply with the request filter
- There is a lot of request to the server which can not handled in the same time
- There is regular DDOS attack to the web server
- Client cache is poisoned with improper data
Client or Browser Solutions
Actually the error is mainly related with the server side but there may be some steps on the client side to try.
- Using different browser where some browser can send improper request.
- Clearing browser cache where poisoned data can be retrieved from cache
Server Side Solutions
The error is mainly related with the server side. We can do a lot of things to solve
503 error. In some cases we may require to complete multiple of the following solutions.
- Restart the web server service
- Reload the web application
- Examine the server logs
- Check DNS server
- Increase concurrent request limit of web server
- Increase bandwidth of network connection
- Check the application logic related with URL
Programming Language and Frameworks Code References
In some cases we may want to sent
503 code to the client HTTP request. This can be done easily with the all ready defined codes in the programming languages and frameworks.
Rails HTTP 503 Status Code
Go HTTP 503 Status Code
Symfony HTTP 503 Status Code
Python2 HTTP 503 Status Code
Python3 HTTP 503 Status Code
Python 3.5+ HTTP 503 Status Code
PHP HTTP 503 Status Code