This documentation is for WSO2 API Manager 2.0.0. View documentation for the latest release.
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When errors/exceptions occur in the system, the API Manager throws XML-based error responses to the client by default. To change the format of these error responses, you change the relevant XML file in the <APIM_HOME>/repository/deployment/server/synapse-configs/default/sequences directory. The directory includes multiple XML files, named after the type of errors that occur. You must select the correct file.

For example, to change the message type of authorization errors, open the <APIM_HOME>/repository/deployment/server/synapse-configs/default/sequences/_auth_failure_handler.xml file and change  application/xml to something like application/json .

<sequence name="_auth_failure_handler_" xmlns="">
 <property name="error_message_type" value="application/json"/>
 <sequence key="_cors_request_handler_"/>

Similarly, to change the error messages of throttling errors (e.g., quota exceeding), change the _throttle_out_handler_.xml file; resource mismatch errors, the _resource_mismatch_handler_.xml file, etc.

Given below are some error codes and their meanings.

API handlers error codes

Error codeError MessageDescriptionExample
API blockedThis API has been blocked temporarily. Please try again later or contact the system administrators.Invoke an API in the BLOCKED lifecycle state.
Message throttled outThe maximum number of requests that can be made to the API within a designated time period is reached and the API is throttled for the user.Invoke an API exceeding the tier limit.
Hard limit exceededHard throttle limit has been reached.When the access token is invalid or inactive.
900802Resource level throttle outMessage is throttled out because resource level has exceeded.Sending/Receiving messages beyond authorized resource level.
900803Application level throttle outMessage is throttled out because application level is exceeded.Sending/Receiving messages beyond authorized application level.
900804Subscription level throttled outMessage throttled out due to subscription level throttling limit reached.Sending/Receiving messages beyond configured throttling limit of subscription level policy.
900805Message blockedAccessing an API which is blocked on user, IP, application, or API Context.An admin user can block API invocations in real time by user, IP, application, or API context. The API invocation meets the blocked condition.
900806Custom policy throttled outMessage throttled out due to exceeding the limit configured through the custom throttling policy rules.The API invocations meet custom throttle policy rules, exceeding the limits of the configured custom policy.
900807Message throttled outMessaged throttled out because of exceeding the burst control/rate limit (requests per second) in the subscription level policy.Sending/Receiving messages exceeding the configured burst control/rate limit within second.

Unclassified authentication failure

An unspecified error has occurredBackend service for key validation is not accessible when trying to invoke an API

Invalid credentials

Invalid authentication information provided

The error codes 900903 (Access token expired) and 900904 (Access token inactive) are deprecated from API Manager 1.9.0 onwards. Alternatively, error code 900901 will be sent when the token is invalid or inactive.

When the access token is invalid or inactive.

Missing credentials

No authentication information providedAccessing an API without Authorization: Bearer header

Incorrect access token type is provided

The access token type used is not supported when invoking the API. The supported access token types are application and user accesses tokens. See Access Tokens.

Invoke an API with application token, where the resource only allows application user tokens.

No matching resource found in the API for the given request

A resource with the name in the request can not be found in the API.Invoke an API resource that is not available.

The requested API is temporarily blocked

Happens when the API user is blocked.Invoke API resource with a subscription that has been blocked by the API publisher.

Resource forbidden

The user invoking the API has not been granted access to the required resource.Invoke an unsubscribed API.

The subscription to the API is inactive

The status of the API has changed to an inaccessible/unavailable state.Invoke an API resource with a subscription that has not yet been approved by the administrator.

The access token does not allow you to access the requested resource

Can not access the required resource with the provided access token. Check the valid resources that can be accessed with this token.

Invoke an API resource with an access token that is not generated to be used with the resource's scope.
102511Incomplete payloadThe payload sent with the request is too large and the client is unable to keep the connection alive until the payload is completely transferred to the API GatewaySending a large PDF file with the POST request.

Sequences error codes

Error codeDescription
Production/sandbox key offered to the API with no production/sandbox endpoint.
Server cannot process the request due to an error in the request sent by the client.
No matching resource found in the API for the given request.

In addition to the above error codes, we have engaged Synapse-level error codes to the default fault sequence and custom fault sequences (e.g.,_token_fault_.xml) of the API Manager. For information, see Error Handling in WSO2 ESB documentation.

The HTTP Status Codes and the corresponding error codes from the error responses are given below.

HTTP Status CodeError Code
401900901, 900902, 900905, 900907, 900909
403900906, 900908, 900910
429900800, 900802, 900803, 900804, 900805, 900806, 900807
503700700, 900801

Transport error codes

Error CodeDetail
101000Receiver input/output error sending
101001Receiver input/output error receiving
101500Sender input/output error sending
101501Sender input/output error receiving
101503Connection failed
101504Connection timed out (no input was detected on this connection over the maximum period of inactivity)
101505Connection closed
101506NHTTP protocol violation

Connection canceled

101508Request to establish new connection timed out
101509Send abort
101510Response processing failed

If the HTTP PassThrough transport is used, and a connection-level error occurs, the error code is calculated using the following equation:

Error code = Base error code + Protocol State

There is a machine state in the transport sender side, where the protocol state changes according to the phase of the message.

Following are the possible protocol states and the description for each:

Protocol State
REQUEST_READY (0)Connection is at the initial stage ready to send a request
REQUEST_HEAD(1)Sending the request headers through the connection
REQUEST_BODY(2)Sending the request body
REQUEST_DONE(3)Request is completely sent
RESPONSE_HEAD(4)The connection is reading the response headers
RESPONSE_BODY(5)The connection is reading the response body
RESPONSE_DONE(6)The response is completed
CLOSING(7)The connection is closing
CLOSED(8)The connection is closed

Since there are several possible protocol states in which a request can time out, you can calculate the error code accordingly using the values in the table above. For example, in a scenario where you send a request and the request is completely sent to the backend, but a timeout happens before the response headers are received, the error code is calculated as follows:

In this scenario, the base error code is CONNECTION_TIMEOUT(101504) and the protocol state is REQUEST_DONE(3).


Error code = 101504 + 3 = 101507

These Transport error codes are used in Advanced Configurations of Endpoints.

Custom error messages

To send a custom message with a custom HTTP status code, you execute an additional sequence that can generate a new error message. You then override the message body, HTTP status code and other values.

The following steps demonstrate how to override a throttled-out message's HTTP status code as a custom error message:

  1. Go to <APIM_HOME> /repository/deployment/server/synapse-configs/default/sequences directory and create the file convert.xml as follows.

    <sequence xmlns="" name="convert">
        <payloadFactory media-type="xml">
                <am:fault xmlns:am="">
                    <am:type>Status report</am:type>
                    <am:message>Runtime Error</am:message>
                <arg evaluator="xml" expression="$ctx:ERROR_CODE"/>
                <arg evaluator="xml" expression="$ctx:ERROR_MESSAGE"/>
        <property name="RESPONSE" value="true"/>
        <header name="To" action="remove"/>
        <property name="HTTP_SC" value="555" scope="axis2"/>
        <property name="NO_ENTITY_BODY" scope="axis2" action="remove"/>
        <property name="ContentType" scope="axis2" action="remove"/>
        <property name="Authorization" scope="transport" action="remove"/>
        <property name="Access-Control-Allow-Origin" value="*" scope="transport"/>
        <property name="Host" scope="transport" action="remove"/>
        <property name="Accept" scope="transport" action="remove"/>
        <property name="X-JWT-Assertion" scope="transport" action="remove"/>
        <property name="messageType" value="application/json" scope="axis2"/>

    Alternatively, you can use the Source View of the APIm Management Console as follows to edit the synapse configuration:

    • Start the API Manager and log in to the Management Console. (https://<Server Host>:9443/carbon).
    • Go to Manager > Source View.
    • Copy the content of the sequence in convert.xml, paste it as a new sequence in the source view and update it.
  2. Check the logs to see whether there are issues in the deployment.  If the deployment is successful, you see a message like the following in the system logs:

    [2015-04-13 09:17:38,885]  INFO - SequenceDeployer Sequence named 'convert' has been deployed from file : <APIM_HOME>/repository/deployment/server/synapse-configs/default/sequences/convert.xml
  3. Invoke the API until the throttling limit exceeds and the new requests get throttled out. 

    curl -v -H "Authorization: Bearer <Access_Token>" http://localhost:8280/<API_name>/<context>/<version>
  4. Note that you get following response:

    * About to connect() to port 8280 (#0)
    *   Trying
    * Adding handle: conn: 0x17a2db0
    * Adding handle: send: 0
    * Adding handle: recv: 0
    * Curl_addHandleToPipeline: length: 1
    * - Conn 0 (0x17a2db0) send_pipe: 1, recv_pipe: 0
    * Connected to ( port 8280 (#0)
    > GET /testam/sanjeewa/1.0.0 HTTP/1.1
    > User-Agent: curl/7.32.0
    > Host:
    > Accept: */*
    > Authorization: Bearer 7f855a7d70aed820a78367c362385c86
    < HTTP/1.1 555 
    < Access-Control-Allow-Origin: *
    < Content-Type: application/json
    < Date: Mon, 13 Apr 2015 05:30:12 GMT
    * Server WSO2-PassThrough-HTTP is not blacklisted
    < Server: WSO2-PassThrough-HTTP
    < Transfer-Encoding: chunked
    * Connection #0 to host left intact
    {"fault":{"code":"900800","type":"Status report","message":"Runtime Error","description":"Message throttled out"}}

WSO2 API Manager has the following default fault sequences located in <APIM_HOME> /repository/deployment/server/synapse-configs/default/sequences directory.

Fault SequenceDescription

This is the primary fault sequence that gets invoked when an error occurs during the execution of an API resources

main.xmlThis sequence is called when the endpoint being called does not exist
auth_failure_handler.xmlThis sequence is called when an API authentication error is encountered
production_key_error.xmlThis sequence is called when a Production key is used to invoke an API that does not have a Production endpoint defined
sandbox_key_error.xmlThis sequence is called when a Sandbox key is used to invoke an API that does not have a Sandbox endpoint defined
throttle_out_handler.xmlThis sequence is called when a given request to an API gets throttled out
token_fault.xmlThis sequence is called when there is an error in invoking the token API
resource_mismatch_handler.xmlThis sequence is called when a matching resource cannot be found by the gateway to the corresponding resource being invoked

The default sequences can also be customized as shown in the section above.

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