What Is a 502 Status Code?
The server, while acting as a gateway or proxy, received an invalid response from an inbound server it accessed while attempting to fulfill the request.
- Source: RFC7231 Section 6.6.3
502 CODE REFERENCES
Rails HTTP Status Symbol
Go HTTP Status Constant
Symfony HTTP Status Constant
Python2 HTTP Status Constant
Python3+ HTTP Status Constant
Python3.5+ HTTP Status Constant
HttpComponents Core org.apache.hc.core5.http.HttpStatus.SC_BAD_GATEWAY
502 status code example
Here is an example of a request and response for a 502 bad gateway status code:
GET /example-page HTTP/1.1
HTTP/1.1 502 Bad Gateway
Content-Type: text/html; charset=utf-8
<title>502 Bad Gateway</title>
<p>The server received an invalid response from the upstream server while trying to fulfill the request.</p>
What causes a 502 status code error?
A 502 Bad Gateway status code indicates that the server acting as a gateway or proxy was unable to connect to the upstream server or received an invalid response from it. Here are some common causes of a 502 error:
- Server overload: If the upstream server is overloaded or experiencing high traffic, it may be unable to respond to requests, causing a 502 error.
- Network issues: Network connectivity issues between the gateway or proxy server and the upstream server can cause a 502 error. This could be due to DNS resolution errors, firewall or routing issues, or other network-related problems.
- Server misconfiguration: Incorrect configuration of the gateway or proxy server or the upstream server can cause a 502 error. This could include incorrect SSL/TLS settings, incorrect port or protocol settings, or incorrect caching or load-balancing settings.
- Server maintenance: If the upstream server is undergoing maintenance or is temporarily offline, it may be unable to respond to requests, causing a 502 error.
- Application errors: If the upstream server is running an application that generates errors or crashes, it may be unable to respond to requests, causing a 502 error.
- Security measures: In some cases, security measures such as firewalls or content filters may be blocking requests or causing a 502 error.
It’s important to note that the exact cause of a 502 error may vary depending on the specific server and network configuration, so careful troubleshooting and analysis are required to identify and resolve the issue.
How to troubleshoot a 502 status code
Here are a few steps that can help troubleshoot and resolve a 502 Bad Gateway status code:
- Refresh the page: In some cases, a 502 error may be temporary and caused by a transient network issue. Refreshing the page or trying again later may resolve the issue.
- Check server logs: The server logs can provide valuable information about the cause of the error. Check the server logs for any error messages or stack traces that can help identify the root cause of the problem.
- Check upstream servers: A 502 error can occur when the server is acting as a gateway or proxy and is unable to connect to the upstream server. Check the upstream server’s status and logs to see if it is functioning properly.
- Check network connectivity: Verify that the network connection between the client and server is stable and reliable. Test the connection between the client and server using a ping or traceroute tool.
- Check DNS settings: Ensure that the DNS settings for the domain name being requested are correct and that the DNS server is responding correctly.
- Check server configuration: Check the server configuration for any errors or misconfigurations that could be causing the error. This could include settings related to the gateway or proxy, caching, or SSL/TLS certificates.
If these steps do not resolve the issue, it may be necessary to consult with a system administrator or web developer with experience troubleshooting server issues.
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