HTTP response status codes indicate whether a specific HTTP request has been successfully completed. When running applications on MedStack Control, it can be helpful to understand how response codes relate to parts of the stack managed by MedStack and those managed in the application.
The chain of responsibility
In the chain of responsibility, the application layer sits on top of MedStack, which sits on top of the cloud provider. As traffic routes through the load balancer, requests to services that are misconfigured may occur with the following response codes.
Common response codes
The following response codes commonly occur due to misconfigurations in the request or the services powering the application running on MedStack Control.
302 Found
- MedStack Control upgrades HTTP requests (port 80) to HTTPS requests (port 443) to ensure ingress encryption in transit. When this happens a 302 response code informs the client of the redirect.
400 Bad Request
- This tends to happen when the HTTP request was formatted incorrectly.
403 Forbidden
- This is a client-side or application-side misconfiguration that determines client is not authorized to access to the content.
404 Not Found
- Generic pages with this response code indicate that there is no service configured for the requested domain.
500 Internal Server Error
- In most cases, this indicates that there is an issue with the configuration of the service hosted at the domain.
- If it can be determined that the request was never received by the application layer, it's possible that the load balancer is failing to pass through requests.
502 Bad Gateway
- In most cases, this indicates that the service hosted at the domain responded incorrectly. This can happen when the connection to the service is terminated with no response.
503 Service Unavailable
- The service has been configured correctly to respond to requests to the domain, but the internal port the service is listening on is not configured correctly. Ensure that the internal port is configured to the port on which it will listen for traffic coming through the load balancer.
504 Gateway Timeout
- The most common reason for this response code is due to the service failing to respond back to the client. This response code returns after 30 seconds of no response to the client.
- Timeouts can sometimes occur when the node running the service container has exhausted its CPU or memory resources. Rebooting the server can help temporarily resolve this, but it should be investigated as to why the resources were exhausted and scale the node accordingly.
- This response code can also occur when there are no active containers of a service that's configured to serve requests to the domain.
Other response codes
If a service is responding with a different code, you can learn more about the response in the following resource:
HTTP response code look up table
For quick reference, here is a list of HTTP response codes.
RFC 7231 HTTP/1.1 Semantics and Content June 2014
+------+-------------------------------+--------------------------+
| Code | Reason-Phrase | Defined in... |
+------+-------------------------------+--------------------------+
| 100 | Continue | Section 6.2.1 |
| 101 | Switching Protocols | Section 6.2.2 |
| 200 | OK | Section 6.3.1 |
| 201 | Created | Section 6.3.2 |
| 202 | Accepted | Section 6.3.3 |
| 203 | Non-Authoritative Information | Section 6.3.4 |
| 204 | No Content | Section 6.3.5 |
| 205 | Reset Content | Section 6.3.6 |
| 206 | Partial Content | Section 4.1 of [RFC7233] |
| 300 | Multiple Choices | Section 6.4.1 |
| 301 | Moved Permanently | Section 6.4.2 |
| 302 | Found | Section 6.4.3 |
| 303 | See Other | Section 6.4.4 |
| 304 | Not Modified | Section 4.1 of [RFC7232] |
| 305 | Use Proxy | Section 6.4.5 |
| 307 | Temporary Redirect | Section 6.4.7 |
| 400 | Bad Request | Section 6.5.1 |
| 401 | Unauthorized | Section 3.1 of [RFC7235] |
| 402 | Payment Required | Section 6.5.2 |
| 403 | Forbidden | Section 6.5.3 |
| 404 | Not Found | Section 6.5.4 |
| 405 | Method Not Allowed | Section 6.5.5 |
| 406 | Not Acceptable | Section 6.5.6 |
| 407 | Proxy Authentication Required | Section 3.2 of [RFC7235] |
| 408 | Request Timeout | Section 6.5.7 |
| 409 | Conflict | Section 6.5.8 |
| 410 | Gone | Section 6.5.9 |
| 411 | Length Required | Section 6.5.10 |
| 412 | Precondition Failed | Section 4.2 of [RFC7232] |
| 413 | Payload Too Large | Section 6.5.11 |
| 414 | URI Too Long | Section 6.5.12 |
| 415 | Unsupported Media Type | Section 6.5.13 |
| 416 | Range Not Satisfiable | Section 4.4 of [RFC7233] |
| 417 | Expectation Failed | Section 6.5.14 |
| 426 | Upgrade Required | Section 6.5.15 |
| 500 | Internal Server Error | Section 6.6.1 |
| 501 | Not Implemented | Section 6.6.2 |
| 502 | Bad Gateway | Section 6.6.3 |
| 503 | Service Unavailable | Section 6.6.4 |
| 504 | Gateway Timeout | Section 6.6.5 |
| 505 | HTTP Version Not Supported | Section 6.6.6 |
+------+-------------------------------+--------------------------+