Configuring Proxy Cache

Constraints

• The response cache policy supports only APIs that use the GET and HEAD methods.
• Response bodies larger than 1 MB will not be cached.
• The cache size for backend response is 128 MB.
• APIC processes the cache according to the Cache-Control header in the backend response. If the backend does not return the Cache-Control header, the response is cached by default, and the ttl field configured in the policy is used as the cache expiration time.
• By default, APIC does not process the Cache-Control header of the client. You can change this by configuring client_cache_control in the policy.
• Cache-Control extended cache instructions are not part of the core HTTP cache standard document and are not supported.

  Cache-control: immutable 
  Cache-control: stale-while-revalidate=<seconds> 
  Cache-control: stale-if-error=<seconds>

• APIC can cache only the Content-Type, Content-Encoding, and Content-Language headers. If you want to cache more headers, add them to the Cached Backend Headers in the policy. However, the system response headers (such as x-apig-* and x-request-id) added by APIC cannot be added.

Creating a Response Cache Policy

1. Log in to the ROMA Connect console. On the Instances page, click View Console next to a specific instance.
2. In the navigation pane on the left, choose API Connect > API Policies. On the Policies tab, click Create Policy.
3. On the Select Policy Type page, select Proxy Cache in the Plug-ins area.
4. On the page displayed, configure plug-in policy information.

   Table 1 Parameters

   Parameter	Description
   Name	Enter a policy name. Using naming rules facilitates future search.
   Type	The value is fixed to Proxy Cache.
   Description	Describe the policy.
   Policy Content	Configure the policy in a form or script. For details about how to configure a script, see Script Configuration Example.
   Cache Proxy Key	The configuration is used to distinguish different caches. system_params: default API parameters. For details about the parameters, see API backend system parameter configuration. parameters: request query parameters. headers: request headers
   HTTP Config	The HTTP Status Code and Cache duration determine whether to cache data and how long the cache will be retained. If HTTP parameters are not configured, the default Status Code is 200. Range: 200–599. The default cache duration is 300 seconds. Range: 1–720000.
   Cache Proxy Modes	APIC processes the cache through the Cache-Control request header in the client request. By default, the gateway rejects all client requests with the Cache-Control header. all: All client requests with the Cache-Control header are allowed. off: All client requests with the Cache-Control header are rejected. apps: Clients whose app IDs (credential IDs) are in the datas list are allowed.
   Cached Backend Headers	By default, only the Content-Type, Content-Encoding, and Content-Language headers can be cached. To cache more headers, add them to Cached Backend Headers in the policy. However, the system response headers (such as x-apig-* and x-request-id) added by APIC cannot be added.

Script Configuration Example

{
  "cache_key": {
    "system_params": [
      "$context.sourceIp",
      "$context.requestId"
    ],
    "parameters": [
      "demo_parameters"
    ],
    "headers": [
      "demo_header"
    ]
  },
  "cache_http_status_and_ttl": [
    {
      "http_status": [
        200
      ],
      "ttl": 300
    }
  ],
  "client_cache_control": {
    "mode": "apps",
    "datas": [
      "demo_app_id_1,demo_app_id_2"
    ]
  },
  "cacheable_headers": [
    "demo_cacheable_headers_1,demo_cacheable_headers_2"
  ]
}