HTTP 502

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The 502 Bad Gateway error is an HTTP status code that occurs when a server acting as a gateway or proxy receives an invalid or faulty response from another server in the communication chain. [1] This error indicates a problem with the communication between the involved servers and can result in disruption of internet services. The 502 Bad Gateway error is considered one of the most common error codes on the internet and can occur in various scenarios.

Contents

Specification

The 502 Bad Gateway error is defined in the RFC 7231 specification, in Section 6.6.3. [2] The 502 Bad Gateway error is part of the Hypertext Transfer Protocol (HTTP) specification. It is defined in the HTTP/1.1 specification by the World Wide Web Consortium (W3C). According to the specification, the 502 status code indicates that the server, while acting as a gateway or proxy, received an invalid response from an upstream server.

Occurrence

The 502 Bad Gateway error can occur due to several reasons. Some of the common causes include: [3]

Example

Consider the following example to illustrate the occurrence of a 502 Bad Gateway error:

A user attempts to access a website by entering the URL in their browser. The user's request is first received by a proxy server. The proxy server, acting as an intermediary, forwards the request to an upstream server. The upstream server processes the request but encounters an internal error. Instead of sending a valid response, the upstream server sends an invalid or faulty response back to the proxy server. The proxy server, unable to handle the invalid response, returns a 502 Bad Gateway error to the user's browser. The user sees the error page indicating the 502 Bad Gateway status.

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References

  1. ↑ developer.mozilla.org 502 Bad Gateway
  2. ↑ Fielding; et al. (June 1999). 6.6.3 502 Bad Gateway. IETF. p. 63. sec. 6.6.3. doi: 10.17487/RFC7231 . RFC 7231.
  3. ↑ How do I solve the problem with the 502 Bad Gateway status code?
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