Cache POST and OPTIONS responses

Application Accelerator unlocks the caching of POST and OPTIONS responses, beyond the GET and HEAD requests an application caches natively. You select the methods in a cache setting from Azion Console, then apply that cache setting with Rules Engine.

A cached POST object does not share a cache key with the GET response for the same path. Azion prefixes the method to the key of any request other than GET or HEAD. For a cached POST or OPTIONS object, the key also appends @@ and the MD5 hash of the request body. An OPTIONS request to https://static.yourdomain.com/page is stored under the key optionshttpsstatic.yourdomain.com/page. A POST to a dynamic path is stored under httpsdynamic.yourdomain.com/path@@md5_of_post_arguments.

A POST body that varies per request therefore produces one cached object per request. For what a variation costs, refer to Cache variation.

Prerequisites

An application. To create one, refer to Applications quickstart.
Access to Azion Console. Refer to Access Azion Console.
Application Accelerator can generate usage-related costs. For the rates, refer to Pricing.

Turn on Application Accelerator

The module is off by default, and a cache setting stores a POST or OPTIONS response only while the module is on. To turn it on:

Open the application

Access Azion Console > Applications > your application.

Turn on the module

On the Main Settings tab, in the Modules section, turn on Application Accelerator.

Select Save

The application runs with Application Accelerator, and its cache settings can select the POST and OPTIONS methods.

Cache the responses to POST requests

An application serves a search API at /api/search. The endpoint answers a POST request whose body carries the search terms, and the results change every 30 seconds. To store one object per body, and to expire it at the same interval:

Open the Cache Settings tab

Access Azion Console > Applications > your application, then go to the Cache Settings tab.

Select + Cache

Name the cache setting

In Name, enter a name that identifies the setting. For example: search-post.

Set Max Age

Under Cache, select Override cache behavior and set Max Age to 30.

Select the POST method

Under Application Accelerator, open Cache vary by Method and select the POST checkbox.

Select Save

The cache setting appears in the Cache Settings tab. It stores the response to a POST request once a rule applies it.

Cache vary by Method holds two checkboxes, POST and OPTIONS. To cache OPTIONS responses, select OPTIONS in the same control; one cache setting can carry both methods. The Azion API sets the same methods with the cache_vary_by_method field of a cache setting, documented in Application Accelerator settings.

A cache setting takes effect only when a rule applies it. To apply this one to the /api/search URI:

Go to the Rules Engine tab

Select + Rule

Name the rule

Enter a name for the rule. For example: search-post rule.

Select Request Phase

Select the variable in the Criteria section

In the Criteria section, select the ${uri} variable.

Select starts with as the comparison operator

Enter the argument

Enter /api/search as the argument.

In the Behaviors section, select Set Cache Policy

Select the cache setting you created

Select Save

Requests whose URI starts with /api/search carry the cache setting. Azion stores one object per request body and holds each object for 30 seconds. A new rule takes a few minutes to propagate.

Before a cache setting selects POST, a POST request logs no cache status: the X-Cache header carries -, because the content is restricted from caching. To read the header on a request, refer to Verify cache indicators with ModHeader.

A cached POST or OPTIONS object expires with a cache key purge that lists each variation, or with a wildcard purge ending in @@*. For the purge types, refer to Real-Time Purge.

Next steps

Cache variationWhat the request body adds to the cache key, and what a variation costs you in stored objects.Application Accelerator settingsEvery field the module adds to a cache setting, with its values and defaults.Real-Time PurgeExpire a cached POST object with a cache key purge or a wildcard purge.Configure Advanced Cache KeyVary a cached object by a query string argument or by a cookie.