Azure APIM policy samples - Part 2

Below are some additional samples of commonly used API management policies that can be useful.

Caching a specific key value

The cache-store-value performs cache storage by key. The key can have an arbitrary string value and is typically provided using a policy expression.

<cache-store-value key="MyCacheKey" value="@((string)context.Variables["varCacheValue"])" duration="360" caching-type="internal" />

Parameters used in above policy are-

• key: Name of cache to be referenced for retrieval.

• value: The value to be cached. Policy expressions are allowed.

• duration: cache alive duration in seconds.

• caching-type: this parameter refers to where cache is stored. Accepted values are-

  internal to use the built-in API Management cache
  external to use the external cache
  prefer-external to use external cache if configured or internal cache otherwise.

Built-in cache is volatile and is shared by all units in the same region in the same API Management service.

Get value from cache

The cache-store-value performs cache storage by key. The key can have an arbitrary string value and is typically provided using a policy expression.

<cache-lookup-value key="MyCacheKey" variable-name="retrievedCacheValue" default-value="0" caching-type="internal" />

Parameters used in above policy are-

• key: Name of cache to be retrieved.

• variable-name: name of context-variable which will get the cache lookup value assigned.

• default-value: if cache not found, then this default value will be assigned to variable. This parameter is optional, if not used then null will be assigned.

• caching-type: this parameter refers to where cache is stored. Accepted values are-

  internal to use the built-in API Management cache
  external to use the external cache
  prefer-external to use external cache if configured or internal cache otherwise.

Custom trace log

Below sample adds a custom trace log into APIM trace which will also be captured in application insights.

<trace source="Global APIM Policy" severity="information">
            <message>@(String.Format("{0} | {1}", context.Api.Name, context.Operation.Name))</message>
            <metadata name="correlation-id" value="@((string)context.Variables["correlation-id"])" />
        </trace>

Above policy logs “<API_name> | <Operation_name>“ as custom trace message and captured “correlation-id“ as custom dimension property.

Convert SOAP API XML response to JSON

Below outbound policy will convert XML response of API to JSON before sending it to caller.

<outbound>
    <base />
    <xml-to-json kind="direct" apply="always" consider-accept-header="true" />
</outbound>

Construct JSON using c# in set-body

Below policy uses c# code to construct JSON message as body.

<set-body>@{
                        return new JObject(
                            new JProperty("org_name", (string)context.Variables["organization_name"]),
                            new JProperty("emp_id", 1111),
                            new JProperty("job_profile", new JObject(
                                new JProperty("title","Analyst"),
                                new JProperty("department","Finance")
                                ))
                        ).ToString();
                    }</set-body>

Above policy generates JSON as -

{
    "org_name":"<value from variable>",
    "emp_id":1111,
    "job_profile":{
        "title":"Analyst",
        "depeartment":"Finance"
    }
}