415 Unsupported Media Type - Unsupported Encoding

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Symptom

The client application gets an HTTP status code of 415 Unsupported Media Type with error code protocol.http.UnsupportedEncoding as a response to API calls.

Error message

Client application gets the following response code:

HTTP/1.1 415 Unsupported Media Type

In addition, you may observe an error message similar to the one shown below:

{
   "fault":{
      "faultstring":"Unsupported Encoding \"UTF-8\"",
      "detail":{
         "errorcode":"protocol.http.UnsupportedEncoding"
      }
   }
}

Possible causes

This error occurs if the value of the Content-Encoding header specified either in the HTTP request sent by the client to Apigee or HTTP response sent by the backend server to Apigee doesn’t contain the encoding supported by Apigee, as per the specification RFC 7231, section 6.5.13: 415 Unsupported Media Type.

The possible causes for this error are as follows:

Cause	Description	Troubleshooting instructions applicable for
Unsupported encoding used in request	The request header Content-Encoding contains encoding that is not supported by Apigee Edge.	Edge Public and Private Cloud users
Unsupported encoding used in response	The backend server response header Content-Encoding contains encoding that is not supported by Apigee Edge.	Edge Public and Private Cloud users

Common diagnosis steps

To diagnose the error, you can use any of the following methods:

Cause: Unsupported encoding in request

Diagnosis

1. Determine the Fault Code and Fault Source for the error observed using API Monitoring or NGINX access logs as explained in Common diagnosis steps.
2. If the Fault Code is protocol.http.UnsupportedEncoding and the Fault Source has the value apigee or MP, then this indicates that the request sent by the client application contains unsupported encoding in the request header Content-Encoding.
3. You can determine the value of unsupported encoding passed as part of the HTTP request using one of the following methods:

   Error message

   Using the error message:

   1. If you have access to the complete error message received from Apigee Edge, then refer to the faultstring. The faultstring contains the value of the unsupported endcoding.

      Sample Error Message:

      "faultstring":"Unsupported Encoding \"UTF-8\""
      

   2. In the above error message, notice that the value of the unsupported encoding is “UTF-8” as seen in the faultstring.

      Since “UTF-8” is not a supported encoding in Apigee Edge, this request fails with the 415 Unsupported Media Type error with the error code: protocol.http.UnsupportedEncoding.

   Actual request

   Using the actual request:

   1. If you don’t have access to the actual request made by the client application, then go to Resolution.
   2. If you have access to the actual request made by the client application, then perform the following steps:
      1. Determine the value passed to the request header Content-Encoding.
      2. If the value passed to the request header Content-Encoding is not one of the values listed in Supported encoding, then that’s the cause for this error.

         Sample request:

         curl -v "https://HOSTALIAS/v1/testgzip" -H "Content-Encoding: UTF-8" -X POST -d @request_payload.gz
         

         The above sample request sends the value "UTF-8" to the Content- Encoding header, which is not a Supported Encoding in Apigee Edge. Therefore, this request fails with 415 Unsupported Media Type error with the error code: protocol.http.UnsupportedEncoding.

Resolution

1. Refer to the list of encoding supported by Apigee in Supported encoding.
2. Ensure that the client application always sends the following:
   • Only the supported encoding as the value to the Content-Encoding header in the request
   • The request payload in the supported format to Apigee Edge and matches the format specified in Content-Encoding header

3. In the above example, the request payload has a gz extension which indicates that the content must be gzip. You can fix the issue by sending the request header as Content-Encoding: gzip and the request payload in gzip format:

   curl -v "https://HOSTALIAS/v1/testgzip" -H "Content-Encoding: gzip" -X POST -d @request_payload.gz
   

Cause: Unsupported encoding in response

Diagnosis

1. Determine the Fault Code and Fault Source for the error observed using API Monitoring, Trace Tool or NGINX access logs as explained in Common diagnosis steps.
2. If the Fault Source has the value target, then this indicates that the response sent by the backend server contains unsupported encoding in the Content-Encoding header.
3. You can determine the value of unsupported encoding passed as part of the HTTP response from the backend server using one of the following methods:

   Error message

   Using the error message:

   1. If you have access to the complete error message received from Apigee Edge, then refer to the faultstring. The faultstring contains the value of the unsupported encoding.

      Sample error message:

      "faultstring":"Unsupported Encoding \"UTF-8\""
      

   2. In the above error message, notice that the value of the unsupported encoding is “UTF-8” as seen in the faultstring.

      Since “UTF-8” is not a supported encoding in Apigee Edge, this request fails with 415 Unsupported Media Type error with the error code: protocol.http.UnsupportedEncoding.

   Trace tool

   Using Trace:

   1. If you do not have the trace for the failing request, then go to Resolution.
   2. If you have captured a trace for the failure, then you can determine the unsupported encoding passed by the backend server as part of the Content-Encoding response header as explained in Trace tool.

Resolution

1. Refer to the list of encoding supported by Apigee in Supported encoding
2. Ensure that the backend server always sends the following:
   • Only the supported encoding as the value to the Content-Encoding header in the request
   • The response payload in the supported format to Apigee Edge and matches the format specified in Content-Encoding header

Supported encoding

The following table lists the encoding format supported by Apigee Edge:

Header	Encoding	Description
Content-Encoding	gzip	The Unix gzip format
	deflate	This format uses zlib structure with deflate compression algorithm.

Specification

Apigee responds with the 415 Unsupported Media Type error response as per the following RFC specification:

Specification
RFC 7231, section 6.5.13: 415 Unsupported Media Type

Key points to note

Note the following:

• If the 415 error is returned by Apigee due to unsupported encoding passed in the Content-Encoding header as part of the API request, then:
  • You will not be able to capture the trace for such requests.

  • You will not be able to modify the format or the content of the error response sent by Apigee Edge using the policies such as RaiseFault, AssignMessage.

  This is because this error occurs at an early phase in the Message Processor before any policy can be executed.

• If the 415 error is returned by Apigee due to unsupported encoding passed in the response header from your backend server, then it has to be fixed in the backend server to avoid this error. Please work with your backend team as appropriate to fix this issue.

If you still need any assistance from Apigee Edge Support, go to Must gather diagnostic information.

Must gather diagnostic information

If you still need any assistance from Apigee Support, gather the following diagnostic information, and then contact Apigee Edge Support:

If you are a Public Cloud user, provide the following information:

• Organization name
• Environment name
• API Proxy name
• Complete curl command used to reproduce the 415 error
• Trace file for the API requests

If you are a Private Cloud user, provide the following information:

• Complete error message observed for the failing requests
• Environment name
• API Proxy bundle
• Trace file for the API requests

• NGINX access logs /opt/apigee/var/log/edge-router/nginx/ORG~ENV.PORT#_access_log

  Where: ORG, ENV and PORT# are replaced with actual values.

• Message Processor system logs /opt/apigee/var/log/edge-message- processor/logs/system.log