Caching Strategies

The application utilises an in-memory cache for a number of different API endpoints to improve performance. The main things that are cached are listed below:

1. Environment flags - the application utilises an in memory cache for the flags returned when calling /flags. The number of seconds this is cached for is configurable using the environment variable "CACHE_FLAGS_SECONDS"
2. Project segments - the application utilises an in memory cache for returning the segments for a given project. The number of seconds this is cached for is configurable using the environment variable "CACHE_PROJECT_SEGMENTS_SECONDS".
3. Flags and identities endpoint caching - the application provides the ability to cache the responses to the GET /flags and GET /identities endpoints. The application exposes the configuration to allow the caching to be handled in a manner chosen by the developer. The configuration options are explained in more detail below.
4. Environment document - when making heavy use of the environment document, it is often wise to utilise caching to reduce the load on the database. Details are provided below.

Flags & Identities Endpoint Caching

To enable caching on the flags and identities endpoints (GET requests only), you must set the following environment variables:

Environment Variable	Description	Example value	Default
GET_[FLAGS|IDENTITIES]_ENDPOINT_CACHE_SECONDS	Number of seconds to cache the response to GET /api/v1/flags	60	0
GET_[FLAGS|IDENTITIES]_ENDPOINT_CACHE_BACKEND	Python path to the django cache backend chosen. See documentation here.	django.core.cache.backends.memcached.PyMemcacheCache	django.core.cache.backends.dummy.DummyCache
GET_[FLAGS|IDENTITIES]_ENDPOINT_CACHE_LOCATION	The location for the cache. See documentation here.	127.0.0.1:11211	get_flags_endpoint_cache

An example configuration to cache both flags and identities requests for 30 seconds in a memcached instance hosted at memcached-container:

GET_FLAGS_ENDPOINT_CACHE_SECONDS: 30
GET_FLAGS_ENDPOINT_CACHE_BACKEND: django.core.cache.backends.memcached.PyMemcacheCache
GET_FLAGS_ENDPOINT_CACHE_LOCATION: memcached-container:11211
GET_IDENTITIES_ENDPOINT_CACHE_SECONDS: 30
GET_IDENTITIES_ENDPOINT_CACHE_BACKEND: django.core.cache.backends.memcached.PyMemcacheCache
GET_IDENTITIES_ENDPOINT_CACHE_LOCATION: memcached-container:11211

Environment Document Caching

To enable caching on the environment document endpoint, you must set the following environment variables:

caution

Persistent cache should only be used with cache backends that offer a centralised cache. It should not be used with e.g. LocMemCache.

info

When using a persistent cache, a change can take a few seconds to update the cache. This can also be optimised by increasing the performance of your task processor.

Environment Variable	Description	Example value	Default
CACHE_ENVIRONMENT_DOCUMENT_MODE	The caching mode. One of PERSISTENT or EXPIRING. Note that although the default is EXPIRING there is no caching by default due to the default value of CACHE_ENVIRONMENT_DOCUMENT_SECONDS	PERSISTENT	EXPIRING
CACHE_ENVIRONMENT_DOCUMENT_SECONDS	Number of seconds to cache the environment for (only relevant when CACHE_ENVIRONMENT_DOCUMENT_MODE=EXPIRING)	60	0 ( = don't cache)