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415 Unsupported Media Type - Unsupported Encoding

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View Apigee X documentation.

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:

API Monitoring

To diagnose the error using API Monitoring:

  1. Sign in to your Apigee Edge account.
  2. Switch to the organization in which you want to investigate the issue:

    ui org drop-down
  3. Navigate to the Analyze > API Monitoring > Investigate page.
  4. Select the specific timeframe in which you observed the errors.
  5. Ensure that the Proxy filter is set to All.
  6. Plot Fault Code against Time.
  7. Select a cell which has the fault code protocol.http.UnsupportedEncoding as shown below:

    fault code cell selected
  8. Information about the fault code protocol.http.UnsupportedEncoding is displayed as shown below:

  9. Click View logs and expand one of the requests failing with 415 error to view more information:

  10. From the Logs window, note the following details:
    • Fault Source: This displays that the error is returned by apigee or target.
    • Fault Code: This should match protocol.http.UnsupportedEncoding.
  11. If the Fault Source is apigee, then that indicates that the request contained unsupported encoding in the Content-Encoding header.
  12. If the Fault Source is target, then that indicates that the backend server response contained unsupported encoding in the Content-Encoding header.

Trace tool

To diagnose the error using the Trace tool:

  1. Enable the trace session and either:
    • Wait for the 415 Unsupported Media Type error to occur, or
    • If you can reproduce the issue, make the API call to reproduce 415 Unsupported Media Type error.
  2. Ensure that Show all FlowInfos is enabled:

    view options pane, show all flowinfos
  3. Select one of the failing requests and examine the trace.
  4. Navigate through different phases of the trace and locate where the failure occurred.
  5. You will find the error typically in a flow after the Request sent to target server phase as shown below:

  6. Note the value of the error from the trace.

    The above sample trace shows the error as Unsupported Encoding "utf-8". Since the error is raised by Apigee after the request was sent to the backend server, it indicates that the backend server sent the response header Content-Encoding with the value of "utf-8", which is not a supported encoding in Apigee.

  7. Navigate to the AX (Analytics Data Recorded) Phase in the trace and click it.
  8. Scroll down to the Error / Response Headers section in Phase Details panel and determine the values of X-Apigee-fault-code and X-Apigee-fault-source as shown below:

  9. You will see the values of X-Apigee-fault-code and X-Apigee-fault-source as protocol.http.UnsupportedEncoding and target, indicating that this error is caused because the unsupported encoding value of "utf-8" was passed by the backend server in the response header Content-Encoding.

    Response Headers Value
    X-Apigee-fault-code protocol.http.UnsupportedEncoding
    X-Apigee-fault-source target

  10. Check to see if you are using proxy chaining; that is, if the target server/target endpoint is invoking another proxy in Apigee.
    1. To determine this, navigate back to the Request sent to target server phase. Click Show Curl.

    2. The Curl for Request Sent to Target Server window opens from which you can determine the target server host alias.
    3. If the target server host alias is pointing to a virtual host alias, then it is proxy chaining. In this case, you need to repeat all the above steps for the chained proxy until you determine what is actually causing the 415 Unsupported Media Type error.
    4. If the target server host alias points to your backend server, then that indicates that your backend server is passing the unsupported encoding to Apigee.

Nginix access logs

To diagnose the error using Nginx access logs:

  1. If you are a Private Cloud user, then you can use Nginx access logs to determine the key information about HTTP 415 errors.
  2. Check the Nginx access logs:

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

  3. Search for any 415 Errors during a specific duration (if the problem happened in the past) or if there are any requests still failing with 415.
  4. If you do find any 415 errors with the X-Apigee-fault-code matching the value of protocol.http.UnsupportedEncoding, then determine the value of the X-Apigee-fault-source.

    Sample 415 error from Nginx access log:

    The above sample entry from the Nginx access log has the following values for X- Apigee-fault-code and X-Apigee-fault-source:

    Response Headers Value
    X-Apigee-fault-code protocol.http.Response405WithoutAllowHeader
    X-Apigee-fault-source MP

    The X-Apigee-fault-source could also have the value target.

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 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 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