Error Handling

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 <AM_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 <AM_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="http://ws.apache.org/ns/synapse">
 <property name="error_message_type" value="application/json"/>
 <sequence key="_cors_request_handler_"/>
</sequence>

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 code	Error Message	Description	Example
`700700`	API blocked	This API has been blocked temporarily. Please try again later or contact the system administrators.	Invoke an API which is in "BLOCKED" lifecycle state
900800	Message throttled out	The 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
900801	Hard Limit Exceeded	Hard throttle limit reached	Invoke an API exceeding hard throttle limit
900900	Unclassified Authentication Failure	An unspecified error has occurred	Backend service for key validation is not accessible when trying to invoke an API
900901	Invalid Credentials	Invalid Authentication information provided	Using an older access token while access token has been renewed.
900902	Missing Credentials	No authentication information provided	Accessing an API without "Authorization: Bearer" header
900905	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 API with application token, But the resource is only allows application user tokens
900906	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 which is not available
900907	The requested API is temporarily blocked	The status of the API has been changed to an inaccessible/unavailable state.	Invoke API resource with a subscription which has been blocked in the API publisher
900908	Resource forbidden	The user invoking the API has not been granted access to the required resource.	Invoke an unsubscribed API
900909	The subscription to the API is inactive	Happens when the API user is blocked.	Invoke an API resource with a subscription which has not yet approved by the administrator.
900910	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 API resource with an access token which is not generated to be used with resource's scope.

Sequences error codes

Error code	Description
900901	Production/sandbox key offered to the API with no production/sandbox endpoint
400	Server cannot process the request due to an error in the request sent by the client
403	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.

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:

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

<sequence xmlns="http://ws.apache.org/ns/synapse" name="convert">
    <payloadFactory media-type="xml">
        <format>
            <am:fault xmlns:am="http://wso2.org/apimanager">
                <am:code>$1</am:code>
                <am:type>Status report</am:type>
                <am:message>Runtime Error</am:message>
                <am:description>$2</am:description>
            </am:fault>
        </format>
        <args>
            <arg evaluator="xml" expression="$ctx:ERROR_CODE"/>
            <arg evaluator="xml" expression="$ctx:ERROR_MESSAGE"/>
        </args>
    </payloadFactory>
    <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"/>
    <send/>
</sequence>

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.

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

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>

Note that you get following response:

* About to connect() to 127.0.0.1 port 8280 (#0)
*   Trying 127.0.0.1...
* 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 127.0.0.1 (127.0.0.1) port 8280 (#0)
> GET /testam/sanjeewa/1.0.0 HTTP/1.1
> User-Agent: curl/7.32.0
> Host: 127.0.0.1:8280
> 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 127.0.0.1 left intact
{"fault":{"code":"900800","type":"Status report","message":"Runtime Error","description":"Message throttled out"}}