Logging context information in error flow

Google Cloud Apigee
1

I know that I can read fault related variables within an error flow, but how can I access request-related context variables in the fault flow. For example, within a failed authentication fault, I would like to access and log the username from the request. This way I would know which account attempted to login. Is this possible?

2

Hi @Michael Atkins Accessing request and response variables in Fault flow in exactly same as you would do in a proxy or a target flow. If you want to log the username, which is present in the request header you use a MessageLogging policy in Fault Rules section. You can access username as {request.header.username} in the policy.

I have attached a simple node.js hello world proxy with this answer. In this proxy I am verifying the API key. If the API key is invalid, I am returning a custom error message with the username field. I am assuming Username is passed as a header in the request. In your case, you will have to use a Message logging instead of RaiseFuault.

Proxy Configuration -

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ProxyEndpoint name="default">
    <Description/>
    <PreFlow name="PreFlow">
        <Request>
            <Step>
                <Name>Verify-API-Key-1</Name>
            </Step>
        </Request>
        <Response/>
    </PreFlow>
    <Flows/>
    <PostFlow name="PostFlow">
        <Request/>
        <Response/>
    </PostFlow>
    <HTTPProxyConnection>
        <BasePath>/hello-world-nodejs-faultrule</BasePath>
        <VirtualHost>default</VirtualHost>
        <VirtualHost>secure</VirtualHost>
    </HTTPProxyConnection>
    <RouteRule name="default">
        <TargetEndpoint>default</TargetEndpoint>
    </RouteRule>
    <FaultRules>
        <FaultRule name="invalid_key_rule">
            <Step>
                <Name>fault_invalidkey</Name>
            </Step>
            <Condition>(fault.name = "InvalidApiKey")</Condition>
        </FaultRule>
    </FaultRules>
</ProxyEndpoint>

RaiseFault policy -

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<RaiseFault async="false" continueOnError="false" enabled="true" name="fault_invalidkey">
    <DisplayName>fault_invalidkey</DisplayName>
    <Properties/>
    <FaultResponse>
        <Set>
            <Headers/>
            <Payload contentType="text/plain">
                {request.header.username} is invalid. Please pass a valid Key    
            </Payload>
            <StatusCode>401</StatusCode>
            <ReasonPhrase>Auth Error</ReasonPhrase>
        </Set>
    </FaultResponse>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
</RaiseFault>

Hope this helps!

1 Like
3

As Sudhendra says you have access to context variables in policies through a simple reference mechanism. If you are using the out of the box Messsage Logging policy you can do the following:

<MessageLogging name="LogToSyslog">>
  <Syslog>
    <Message>[3f509b58 tag="{organization.name}.{apiproxy.name}.{environment.name}"] Weather request for WOEID {request.queryparam.w}.</Message>
    <Host>logs-01.loggly.com</Host>
    <Port>514</Port>
    <Protocol>TCP</Protocol>
  </Syslog>
</MessageLogging>

Anything in {} is a reference to a context variable. More information at: http://apigee.com/docs/api-services/reference/message-logging-policy