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Overview
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Because API Versions use endpoints generated in the SnapLogic IIP, the HTTP Response Cache policy supports Proxy endpoints only by design. In the UI, the API Policy Manager menus API and Version Details tabs do not display this policy.
Policy Execution Order
This policy runs after every request and response policy.
Known Issue
Both the HTTP Cache Response and HTTP Retry Policies fail to evaluate expressions. As a result, the When this policy should be applied field should not be set. Doing so can cause issues with the way the policy is applied.
Architecture
Each Snaplex node has its own cache, so the cache for an incoming request might miss on each node until properly distributed and hydrated on each node.
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The policy supports incorporating headers and query parameters as part of the cache key (not to access the cache key). The headers and query parameter values are used as part of the generated cache key to ensure unique cache entries as needed.
Usage Guidelines
We limit each policy to have 100 entries in the cache per policy. Accordingly, the policy evicts the least used entry after 100.
Expired caches cannot be accessed, and new entries overwrite any existing ones. The maximum quantity of bytes that an HTTP response caches in the default configuration is 85.83 MB of the payload.
These properties are configurable through Feature Flags. Refer to your CSM to modify these property settings.
Limitations
Each response cache can only contain 85 MB. The policy always returns the response, but any data over the limit renders the payload incomplete without notice.
A response cache is not effective to use for POST and PUT HTTP methods because these operations are meant to alter the state of data, and therefore should not be cached.
Settings
Parameter Name | Description | Default Value |
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Label | Required. The name for the API policy. | HTTP Respone Cache |
When this policy should be applied | An expression-enabled field that determines the condition to be fulfilled for the API policy to execute. For example, if the value in this field is | N/A |
Cache Interval | The time period of the current cache before it is evicted. | 1 |
Time Unit | The time unit for the Cache Interval value. | Hour |
Use HTTP Request Headers to Create Cache Keys | Enables use of all header values as part of the generated cache key. | Unselected |
Use HTTP Request Query Parameter to Create Cache Keys | Enables use of all query parameter values as part of the generated cache key. | Unselected |
Status | Specifies whether the API policy is enabled or disabled. | Enabled |
Example
The policy supports using headers and query parameters to generate keys:
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The entire HTTP response is cached, including headers.
Best Practices
Do not use any headers and query string parameters, like a timestamp, as part of your cache key, or it will never result in a fulfilled request. You can optionally remove those headers using the Request Transformer policy. Or, avoid headers query string parameters as part of the cache key and only as needed when a unique value is present per request.