Proxy Caching Advanced plugin

Kong Enterprise only: This plugin is only available with a Kong Enterprise subscription. Please inquire about Kong Enterprise by contacting us, or start a free trial today.

This plugin provides a reverse proxy cache implementation for Kong. It caches response entities based on configurable response code and content type, as well as request method. It can cache per-Consumer or per-API. Cache entities are stored for a configurable period of time, after which subsequent requests to the same resource will re-fetch and re-store the resource. Cache entities can also be forcefully purged via the Admin API prior to their expiration time.

Configuration Reference

You can configure this plugin using the Kong Admin API or through declarative configuration, which involves directly editing the Kong configuration file.

This plugin is compatible with requests with the following protocols:

http
https
grpc
grpcs

Enabling the plugin on a Service

Kong Admin API

Kubernetes

Declarative (YAML)

For example, configure this plugin on a Service by making the following request:

$ curl -X POST http://<admin-hostname>:8001/services/<service>/plugins \
    --data "name=proxy-cache-advanced"  \
    --data "config.response_code=200" \
    --data "config.request_method=GET" \
    --data "config.request_method=HEAD" \
    --data "config.content_type=text/plain" \
    --data "config.content_type=application/json" \
    --data "config.cache_control=false" \
    --data "config.strategy=memory" \
    --data "config.memory.dictionary_name=kong_db_cache"

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <proxy-cache-advanced-example>
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_control: false
  strategy: memory
  memory.dictionary_name: kong_db_cache
plugin: proxy-cache-advanced

Next, apply the KongPlugin resource to a Service by annotating the Service as follows:

apiVersion: v1
kind: Service
metadata:
  name: <service>
  labels:
    app: <service>
  annotations:
    konghq.com/plugins: <proxy-cache-advanced-example>
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: <service>
  selector:
    app: <service>

Note: The KongPlugin resource only needs to be defined once and can be applied to any Service, Consumer, or Route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

For example, configure this plugin on a Service by adding this section to your declarative configuration file:

plugins:
- name: proxy-cache-advanced
  service: <service>
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_control: false
    strategy: memory
    memory.dictionary_name: kong_db_cache

<service> is the id or name of the Service that this plugin configuration will target.

Enabling the plugin on a Route

Kong Admin API

Kubernetes

Declarative (YAML)

For example, configure this plugin on a Route with:

$ curl -X POST http://<admin-hostname>:8001/routes/<route>/plugins \
    --data "name=proxy-cache-advanced"  \
    --data "config.response_code=200" \
    --data "config.request_method=GET" \
    --data "config.request_method=HEAD" \
    --data "config.content_type=text/plain" \
    --data "config.content_type=application/json" \
    --data "config.cache_control=false" \
    --data "config.strategy=memory" \
    --data "config.memory.dictionary_name=kong_db_cache"

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <proxy-cache-advanced-example>
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_control: false
  strategy: memory
  memory.dictionary_name: kong_db_cache
plugin: proxy-cache-advanced

Then, apply it to an ingress (Route or Routes) by annotating the ingress as follows:

apiVersion: networking/v1beta1
kind: Ingress
metadata:
  name: <route>
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: <proxy-cache-advanced-example>
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          serviceName: echo
          servicePort: 80

For example, configure this plugin on a Route by adding this section to your declarative configuration file:

plugins:
- name: proxy-cache-advanced
  route: <route>
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_control: false
    strategy: memory
    memory.dictionary_name: kong_db_cache

<route> is the id or name of the Route that this plugin configuration will target.

Enabling the plugin on a Consumer

Kong Admin API

Kubernetes

Declarative (YAML)

For example, configure this plugin on a Consumer with:

$ curl -X POST http://<admin-hostname>:8001/consumers/<consumer>/plugins \
    --data "name=proxy-cache-advanced"  \
    --data "config.response_code=200" \
    --data "config.request_method=GET" \
    --data "config.request_method=HEAD" \
    --data "config.content_type=text/plain" \
    --data "config.content_type=application/json" \
    --data "config.cache_control=false" \
    --data "config.strategy=memory" \
    --data "config.memory.dictionary_name=kong_db_cache"

You can combine consumer.id, service.id, or route.id in the same request, to further narrow the scope of the plugin.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <proxy-cache-advanced-example>
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_control: false
  strategy: memory
  memory.dictionary_name: kong_db_cache
plugin: proxy-cache-advanced

Then, apply it to a Consumer by annotating the KongConsumer resource as follows:

apiVersion: configuration.konghq.com/v1
kind: KongConsumer
metadata:
  name: <consumer>
  annotations:
    konghq.com/plugins: <proxy-cache-advanced-example>
    kubernetes.io/ingress.class: kong

For example, configure this plugin on a Consumer by adding this section to your declarative configuration file:

plugins:
- name: proxy-cache-advanced
  consumer: <consumer>
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_control: false
    strategy: memory
    memory.dictionary_name: kong_db_cache

<consumer> is the id or username of the Consumer that this plugin configuration will target.

Enabling the plugin globally

A plugin which is not associated to any Service, Route, or Consumer is considered global, and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

Kong Admin API

Kubernetes

Declarative (YAML)

For example, configure this plugin globally with:

$ curl -X POST http://<admin-hostname>:8001/plugins/ \
    --data "name=proxy-cache-advanced"  \
    --data "config.response_code=200" \
    --data "config.request_method=GET" \
    --data "config.request_method=HEAD" \
    --data "config.content_type=text/plain" \
    --data "config.content_type=application/json" \
    --data "config.cache_control=false" \
    --data "config.strategy=memory" \
    --data "config.memory.dictionary_name=kong_db_cache"

Create a KongClusterPlugin resource and label it as global:

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: <global-proxy-cache-advanced>
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: \"true\"
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_control: false
  strategy: memory
  memory.dictionary_name: kong_db_cache
plugin: proxy-cache-advanced

For example, configure this plugin using the plugins: entry in the declarative configuration file:

plugins:
- name: proxy-cache-advanced
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_control: false
    strategy: memory
    memory.dictionary_name: kong_db_cache

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Form Parameter	Description
`name` Type: string	The name of the plugin to use, in this case `proxy-cache-advanced`.
`service.id` Type: string	The ID of the Service the plugin targets.
`route.id` Type: string	The ID of the Route the plugin targets.
`consumer.id` Type: string	The ID of the Consumer the plugin targets.
`enabled` Type: boolean Default value: `true`	Whether this plugin will be applied.
`config.response_code` required Type: array of type integer Default value: 200, 301, 404	Upstream response status code considered cacheable. The integers must be a value between 100 and 900.
`config.request_method` required Type: array of string elements Default value: ["GET","HEAD"]	Downstream request methods considered cacheable. Available options: `HEAD`, `GET`, `POST`, `PATCH`, `PUT`.
`config.content_type` required Type: array of string elements Default value: text/plain, application/json	Upstream response content types considered cacheable. The plugin performs an exact match against each specified value; for example, if the upstream is expected to respond with a `application/json; charset=utf-8` content-type, the plugin configuration must contain said value or a `Bypass` cache status is returned.
`config.vary_headers` optional Type: array of string elements	Relevant headers considered for the cache key. If undefined, none of the headers are taken into consideration.
`config.vary_query_params` optional Type: array of string elements	Relevant query parameters considered for the cache key. If undefined, all params are taken into consideration.
`config.cache_ttl` Type: integer Default value: 300	TTL in seconds of cache entities.
`config.cache_control` required Type: boolean Default value: false	When enabled, respect the Cache-Control behaviors defined in RFC7234.
`config.storage_ttl` optional Type: integer	Number of seconds to keep resources in the storage backend. This value is independent of `cache_ttl` or resource TTLs defined by Cache-Control behaviors.
`config.strategy` required Type: string	The backing data store in which to hold cache entities. Accepted values are: `memory` and `redis`.
`config.memory.dictionary_name` required Type: string Default value: kong_db_cache	The name of the shared dictionary in which to hold cache entities when the memory strategy is selected. Note that this dictionary currently must be defined manually in the Kong Nginx template.
`config.redis.host` semi-optional Type: string	Host to use for Redis connection when the redis strategy is defined.
`config.redis.port` semi-optional Type: integer Default value: 6379	Port to use for Redis connections when the `redis` strategy is defined. Must be a value between 0 and 65535. Default: 6379.
`config.redis.ssl` optional Type: boolean Default value: false	If set to `true`, then uses SSL to connect to Redis. Note: This parameter is only available for Kong Enterprise versions 2.2.x and later.
`config.redis.ssl_verify` optional Type: boolean Default value: false	If set to `true`, then verifies the validity of the server SSL certificate. Note that you need to configure the lua_ssl_trusted_certificate to specify the CA (or server) certificate used by your Redis server. You may also need to configure lua_ssl_verify_depth accordingly. Note: This parameter is only available for Kong Enterprise versions 2.2.x and later.
`config.redis.server_name` optional Type: string	Specifies the server name for the new TLS extension Server Name Indication (SNI) when connecting over SSL. Note: This parameter is only available for Kong Enterprise versions 2.2.x and later.
`config.redis.timeout` semi-optional Type: number Default value: 2000	Connection timeout to use for Redis connection when the `redis` strategy is defined.
`config.redis.password` semi-optional Type: string	Password to use for Redis connection when the `redis` strategy is defined. If undefined, no AUTH commands are sent to Redis.
`config.redis.database` semi-optional Type: integer Default value: 0	Database to use for Redis connection when the `redis` strategy is defined.
`config.redis.sentinel_master` semi-optional Type: string	Sentinel master to use for Redis connection when the `redis` strategy is defined. Defining this value implies using Redis Sentinel.
`config.redis.sentinel_role` semi-optional Type: string	Sentinel role to use for Redis connections when the `redis` strategy is defined. Defining this value implies using Redis Sentinel. Available options: `master`, `slave`, `any`.
`config.redis.sentinel_addresses` semi-optional Type: array of string elements	Sentinel addresses to use for Redis connections when the `redis` strategy is defined. Defining this value implies using Redis Sentinel. Each string element must be a hostname. The minimum length of the array is 1 element.
`config.redis.cluster_addresses` semi-optional Type: array of string elements	Cluster addresses to use for Redis connection when the `redis` strategy is defined. Defining this value implies using Redis cluster. Each string element must be a hostname. The minimum length of the array is 1 element.
`config.bypass_on_err` optional Type: boolean Default value: false	Unhandled errors while trying to retrieve a cache entry (such as redis down) are resolved with `Bypass`, with the request going upstream.

Warning: The content_type parameter requires an exact match. For example, if your Upstream expects application/json; charset=utf-8 and the config.content_type value is only application/json (a partial match), then the proxy cache is bypassed.

Strategies

kong-plugin-enterprise-proxy-cache is designed to support storing proxy cache data in different backend formats. Currently, the following strategies are provided:

memory: A lua_shared_dict. Note that the default dictionary, kong_cache, is also used by other plugins and elements of Kong to store unrelated database cache entities. Using this dictionary is an easy way to bootstrap the proxy-cache-advanced plugin, but it is not recommended for large-scale installations as significant usage will put pressure on other facets of Kong’s database caching operations. It is recommended to define a separate lua_shared_dict via a custom Nginx template at this time.
redis: Supports Redis and Redis Sentinel deployments.

Cache Key

Kong keys each cache elements based on the request method, the full client request (e.g., the request path and query parameters), and the UUID of either the API or Consumer associated with the request. This also implies that caches are distinct between APIs and/or Consumers. Currently the cache key format is hard-coded and cannot be adjusted. Internally, cache keys are represented as a hexadecimal-encoded MD5 sum of the concatenation of the constituent parts calculated as follows:

key = md5(UUID | method | request)

Where method is defined via the OpenResty ngx.req.get_method() call, and request is defined via the Nginx $request variable. Kong will return the cache key associated with a given request as the X-Cache-Key response header. It is also possible to precalculate the cache key for a given request as noted above.

Cache Control

When the cache_control configuration option is enabled, Kong will respect request and response Cache-Control headers as defined by RFC7234, with a few exceptions:

Cache revalidation is not yet supported, and so directives such as proxy-revalidate are ignored.
Similarly, the behavior of no-cache is simplified to exclude the entity from being cached entirely.
Secondary key calculation via Vary is not yet supported.

Cache Status

Kong identifies the status of the request’s proxy cache behavior via the X-Cache-Status header. There are several possible values for this header:

Miss: The request could be satisfied in cache, but an entry for the resource was not found in cache, and the request was proxied upstream.
Hit: The request was satisfied and served from cache.
Refresh: The resource was found in cache, but could not satisfy the request, due to Cache-Control behaviors or reaching its hard-coded cache_ttl threshold.
Bypass: The request could not be satisfied from cache based on plugin configuration.

Storage TTL

Kong can store resource entities in the storage engine longer than the prescribed cache_ttl or Cache-Control values indicate. This allows Kong to maintain a cached copy of a resource past its expiration, which in turn allows clients capable of using max-age and max-stale headers to request stale copies of data if necessary.

Upstream Outages

Due to an implementation in Kong’s core request processing model, at this point, the proxy-cache-advanced plugin cannot be used to serve stale cache data when an upstream is unreachable. To equip Kong to serve cache data in place of returning an error when an upstream is unreachable, we recommend defining a very large storage_ttl (on the order of hours or days) in order to keep stale data in the cache. In the event of an upstream outage, stale data can be considered fresh by increasing the cache_ttl plugin configuration value. By doing so, data that would have previously been considered stale is now served to the client, before Kong attempts to connect to a failed upstream service.

Admin API

This plugin provides several endpoints to managed cache entities. These endpoints are assigned to the proxy-cache-advanced RBAC resource.

The following endpoints are provided on the Admin API to examine and purge cache entities:

Retrieve a Cache Entity

Two separate endpoints are available: one to look up a known plugin instance, and another that searches all proxy-cache-advanced plugins data stores for the given cache key. Both endpoints have the same return value.

Endpoint

/proxy-cache-advanced/:plugin_id/caches/:cache_id

Attributes	Description
`plugin_id`	The UUID of the proxy-cache-advanced plugin
`cache_id`	The cache entity key as reported by the X-Cache-Key response header

Endpoint

/proxy-cache-advanced/:cache_id

Attributes	Description
`cache_id`	The cache entity key as reported by the X-Cache-Key response header

Response

If the cache entity exists

HTTP 200 OK

If the entity with the given key does not exist

HTTP 400 Not Found

Delete a Cache Entity

Endpoint

/proxy-cache-advanced/:plugin_id/caches/:cache_id

Attributes	Description
`plugin_id`	The UUID of the proxy-cache-advanced plugin
`cache_id`	The cache entity key as reported by the `X-Cache-Key` response header

Endpoint

/proxy-cache-advanced/:cache_id

Attributes	Description
`cache_id`	he cache entity key as reported by the `X-Cache-Key` response header

Response

If the cache entity exists:

HTTP 204 No Content

If the entity with the given key does not exist:

HTTP 400 Not Found

Purge All Cache Entities

Endpoint

/proxy-cache-advanced/

Response

HTTP 204 No Content

Note that this endpoint purges all cache entities across all proxy-cache-advanced plugins.

About this Plugin
Made by
Categories	Traffic Control
Bundled with...
Kong Enterprise 2.2.x 2.1.x 1.5.x 1.3-x 0.36-x 0.35-x 0.34-x