HTTP Error 409 Conflict

Introduction

The Web server (running the Web site) thinks that the request submitted by the client (e.g. your Web browser or our CheckUpDown robot) can not be completed because it conflicts with some rule already established. For example, you may get a 409 error if you try to upload a file to the Web server which is older than the one already there - resulting in a version control conflict.

Note that the conflict here is usually not related to standard Web server authority/security (for which different errors are generated), but to some application-specific conflict not defined in the HTTP protocol itself.

Fixing 409 errors - general

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The problem can only be resolved by examining what your client system is trying to do then discussing with your ISP why that behaviour is not allowed.

Fixing 409 errors - CheckUpDown

Our service monitors your site for HTTP errors like 409. This error should simply never occur on your CheckUpDown account. If it does, it typically indicates defective programming of our systems or of the Web server which manages the site. The conflict referred to should only apply to HTTP operations which we do not use at all.

Please contact us (email preferred) whenever you encounter 409 errors - there is nothing you can do to sort them out. We then have to liaise with your ISP and the vendor of the Web server software to agree the exact reason for the error.


409 errors in the HTTP cycle

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with the Web server:

(1) Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
(2) Open an IP socket connection to that IP address.
(3) Write an HTTP data stream through that socket.
(4) Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

This error occurs in the final step above when the client receives an HTTP status code that it recognises as '409'.


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