RaiseFault policy

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What

Generates a custom message in response to an error condition. Use RaiseFault to define a fault response that is returned to the requesting app when a specific condition arises.

For general information on handling faults, see Handling faults.

Samples

<RaiseFault name="404">
 <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
 <FaultResponse>
   <Set>
     <StatusCode>404</StatusCode>
     <ReasonPhrase>The resource requested was not found</ReasonPhrase>
   </Set>
 </FaultResponse>
</RaiseFault>

<RaiseFault name="ExceptionHandler">
 <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
 <FaultResponse>
   <Set>
     <Payload contentType="text/xml">
       <root>Please contact support@company.com</root>
     </Payload>
     <StatusCode>{response.status.code}</StatusCode>
     <ReasonPhrase>Server error</ReasonPhrase>
   </Set>
   <Add>
     <Headers>
       <Header name="FaultHeader">{fault.name}</Header>
     </Headers>
   </Add>
 </FaultResponse>
</RaiseFault>

About the RaiseFault policy

Apigee Edge enables you to perform custom exception handling using a policy of type RaiseFault. The RaiseFault policy, which is similar to the AssignMessage policy, lets you generate a custom fault response in response to an error condition.

Use the RaiseFault policy to define a fault response that is returned to the requesting app when a specific error condition arises. The fault response can consist of HTTP headers, query parameters, and a message payload. A custom fault response can be more useful to app developers and app end users than generic error messages or HTTP response codes.

When executed, the RaiseFault policy transfers control from the current flow to the Error flow, which then returns the designated fault response to the requesting client app. When the message Flow switches to the Error flow, no further policy processing occurs. All remaining processing Steps are bypassed, and the fault response is returned directly to the requesting app.

You can use RaiseFault in a ProxyEndpoint or a TargetEndpoint. Usually, you will attach a Condition to the RaiseFault policy. After RaiseFault executes, Apigee will perform normal fault processing, evaluating FaultRules, or if there are no fault rules defined, it terminates processing of the request.

Element reference

The element reference describes the elements and attributes of the RaiseFault policy.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<RaiseFault async="false" continueOnError="false" enabled="true" name="Raise-Fault-1">
    <DisplayName>RaiseFault 1</DisplayName>
    <FaultResponse>
        <AssignVariable>
          <Name/>
          <Value/>
        </AssignVariable>
        <Add>
            <Headers/>
        </Add>
        <Copy source="request">
            <Headers/>
            <StatusCode/>
            <ReasonPhrase/>
        </Copy>
        <Remove>
            <Headers/>
        </Remove>
        <Set>
            <Headers/>
            <Payload/>
            <ReasonPhrase/>
            <StatusCode/>
        </Set>
    </FaultResponse>
    <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
</RaiseFault>

<RaiseFault> attributes

<RaiseFault async="false" continueOnError="false" enabled="true" name="Raise-Fault-1">

The following table describes attributes that are common to all policy parent elements:

<DisplayName> element

Use in addition to the name attribute to label the policy in the management UI proxy editor with a different, natural-language name.

<DisplayName>Policy Display Name</DisplayName>

<IgnoreUnresolvedVariables> element

(Optional) Ignores any unresolved variable error in the Flow. Valid values: true/false. Default true.

<FaultResponse> element

(Optional) Defines the response message returned to the requesting client. FaultResponse uses the same settings as the AssignMessage policy (not available in Apigee Edge for Private Cloud).

<FaultResponse><AssignVariable> element

Assigns a value to a destination flow variable. If the flow variable does not exist, then AssignVariable creates it.

For example, use the following code to set the variable named myFaultVar in the RaiseFault policy:

<FaultResponse>
  <AssignVariable>
    <Name>myFaultVar</Name>
    <Value>42</Value>
  </AssignVariable>
  ...
</FaultResponse>

You can then refer to that variable in message templates later in the RaiseFault policy. Also, a policy attached to a FaultRule can then access the variable. For example, the following AssignMessage policy uses the variable set in the RaiseFault to set a Header in the fault response:

<AssignMessage enabled="true" name="Assign-Message-1">
  <Add>
    <Headers>
      <Header name="newvar">{myFaultVar}</Header>
    </Headers>
  </Add>
  <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
  <AssignTo createNew="false" transport="http" type="response"/>
</AssignMessage>

<AssignVariable> in the RaiseFault policy uses the same syntax as the <AssignVariable> element in the AssignMessage policy. Note that this functionality is not currently available in Apigee Edge for Private Cloud.

<FaultResponse><Add>/<Headers> element

Adds HTTP headers to the error message. Note that the empty header <Add><Headers/></Add> does not add any header. This example copies the value of the request.user.agent flow variable into the header.

<Add>
    <Headers>
        <Header name="user-agent">{request.user.agent}</Header>
    </Headers>
</Add>

<FaultResponse><Copy> element

Copies information from the message specified by the source attribute to the error message.

    <Copy source="request">
        <Headers/>
        <StatusCode/>
        <ReasonPhrase/>
    </Copy>

Attributes

 <Copy source="response">

<FaultResponse><Copy>/<Headers> element

Copies the specified HTTP header from the source to the error message. To copy all headers, specify <Copy><Headers/></Copy>.

<Copy source='request'>
    <Headers>      
        <Header name="headerName"/>
    </Headers> 
</Copy>

If there are multiple headers with the same name, use the following syntax:

<Copy source='request'>
    <Headers>
      <Header name="h1"/>
      <Header name="h2"/>
      <Header name="h3.2"/>
    </Headers>
</Copy>

This example copies "h1", "h2", and the second value of "h3". If "h3" has only one value, then it is not copied.

<FaultResponse><Copy>/<StatusCode> element

The HTTP status code to copy from the object specified by the source attribute to the error message.

<Copy source='response'>
    <StatusCode>404</StatusCode>      
</Copy>

<FaultResponse><Copy>/<ReasonPhrase> element

The reason description to copy from the object specified by the source attribute to the error message.

<Copy source='response'>     
    <ReasonPhrase>The resource requested was not found.</ReasonPhrase>     
</Copy>

<FaultResponse><Remove>/<Headers> element

Removes specified HTTP headers from the error message. To remove all the headers, specify <Remove><Headers/></Remove>. This example removes the user-agent header from the message.

<Remove>     
    <Headers>      
        <Header name="user-agent"/>     
    </Headers> 
</Remove>

If there are multiple headers with the same name, use the following syntax:

<Remove>
    <Headers>
      <Header name="h1"/>
      <Header name="h2"/>
      <Header name="h3.2"/>
    </Headers>
</Remove>

This example removes "h1", "h2", and the second value of "h3". If "h3" has only one value, then it is not removed.

<FaultResponse><Set> element

Sets information in the error message.

    <Set>
        <Headers/>
        <Payload> </Payload>
        <StatusCode/>
        <ReasonPhrase/>
    </Set>

<FaultResponse>/<Set>/<Headers> element

Sets or overwrites HTTP headers in the error message. Note that the empty header <Set><Headers/></Set> does not set any header. This example sets the user-agent header to the message variable specified with the <AssignTo> element.

<Set>
    <Headers>
        <Header name="user-agent">{request.header.user-agent}</Header>     
    </Headers>
</Set>

<FaultResponse>/<Set>/<Payload> element

Sets the payload of the error message.

<Set>
    <Payload contentType="text/plain">test1234</Payload>
</Set>

Set a JSON payload:

<Set>
    <Payload contentType="application/json">
        {"name":"foo", "type":"bar"}
    </Payload>
</Set>

In a JSON payload, you can insert variables using the variablePrefix and variableSuffix attributes with delimiter characters as shown in the following example.

<Set>
    <Payload contentType="application/json" variablePrefix="@" variableSuffix="#">
        {"name":"foo", "type":"@variable_name#"}
    </Payload>
</Set>

or, as of cloud release 16.08.17, you can also curly braces to insert variables:

<Set>
    <Payload contentType="application/json">
        {"name":"foo", "type":"{variable_name}"}
    </Payload>
</Set>

Set a mixed payload in XML:

<Set>
    <Payload contentType="text/xml">
        <root>
          <e1>sunday</e1>
          <e2>funday</e2>
          <e3>{var1}</e3>
    </Payload>
</Set>

Attributes

 
<Payload contentType="content_type" variablePrefix="char" variableSuffix="char">

<FaultResponse>/<Set>/<StatusCode> element

Sets the status code of the response.

<Set source='request'>
    <StatusCode>404</StatusCode>
</Set>

<FaultResponse>/<Set>/<ReasonPhrase> element

Sets the reason phrase of the response.

<Set source='request'>     
    <ReasonPhrase>The resource requested was not found.</ReasonPhrase>
</Set>

<ShortFaultReason> element

Specifies to display a short fault reason in the response:

<ShortFaultReason>true|false</ShortFaultReason>

By default, the fault reason in the response of the policy is:

"fault":{"faultstring":"Raising fault. Fault name : Raise-Fault-1","detail":{"errorcode":"errorCode"}}}

To make the message more readable, you can set the <ShortFaultReason> element to true to shorten the faultstring to just the policy name:

"fault":{"faultstring":"Raise-Fault-1","detail":{"errorcode":"errorCode"}}}

Valid values: true/false(default).

Flow variables

Flow variables enable dynamic behavior of policies and Flows at runtime, based on HTTP headers, message content, or Flow context. The following predefined Flow variables are available after a RaiseFault policy executes. For more information about Flow variables, see Variables reference.

Example use of RaiseFault

The following example uses a Condition to enforce the presence of a queryparam with the name zipcode on the inbound request. If that queryparam is not present, the flow will raise a fault via RaiseFault:

<Flow name="flow-1">
  <Request>
    <Step>
        <Name>RF-Error-MissingQueryParam</Name>
        <Condition>request.queryparam.zipcode = null</Condition>
    </Step>
   ...
   </Request>
   ...
   <Condition>(proxy.pathsuffix MatchesPath "/locations") and (request.verb = "GET")</Condition>
</Flow>

<RaiseFault name='RF-Error-MissingQueryParam'>
  <IgnoreUnresolvedVariables>true</IgnoreUnresolvedVariables>
  <FaultResponse>
    <Set>
      <Payload contentType='application/json'>{
  "error" : {
    "code" : 400.02,
    "message" : "invalid request. Pass a zipcode queryparam."
  }
}
</Payload>
      <StatusCode>400</StatusCode>
      <ReasonPhrase>Bad Request</ReasonPhrase>
    </Set>
  </FaultResponse>
</RaiseFault>

Error reference

This section describes the fault codes and error messages that are returned and fault variables that are set by Edge when this policy triggers an error. This information is important to know if you are developing fault rules to handle faults. To learn more, see What you need to know about policy errors and Handling faults.

Runtime errors

These errors can occur when the policy executes.

Deployment errors

None.

Fault variables

These variables are set when a runtime error occurs. For more information, see What you need to know about policy errors.

Example error response

{
   "fault":{
      "detail":{
         "errorcode":"steps.raisefault.RaiseFault"
      },
      "faultstring":"Raising fault. Fault name: [name]"
   }
}

Schema

Each policy type is defined by an XML schema (.xsd). For reference, policy schemas are available on GitHub.

Related topics

See Handling faults