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Proxy Cache

You are browsing documentation for an outdated plugin version. See the latest documentation here.

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

This plugin is compatible with DB-less mode.

In DB-less mode, you configure Kong Gateway declaratively. Therefore, the Admin API is mostly read-only. The only tasks it can perform are all related to handling the declarative config, including:

  • Setting a target's health status in the load balancer
  • Validating configurations against schemas
  • Uploading the declarative configuration using the /config endpoint

Example plugin configuration

The following examples provide some typical configurations for enabling the proxy-cache plugin on a service.

Make the following request:

curl -X POST http://localhost:8001/services/SERVICE_NAME|SERVICE_ID/plugins \
    --data "name=proxy-cache"  \
    --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_ttl=300" \
    --data "config.strategy=memory"

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: proxy-cache-example
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_ttl: 300
  strategy: memory
plugin: proxy-cache

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

apiVersion: v1
kind: Service
metadata:
  name: SERVICE_NAME|SERVICE_ID
  labels:
    app: SERVICE_NAME|SERVICE_ID
  annotations:
    konghq.com/plugins: proxy-cache-example
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: SERVICE_NAME|SERVICE_ID
  selector:
    app: SERVICE_NAME|SERVICE_ID

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

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.

Add this section to your declarative configuration file:

plugins:
- name: proxy-cache
  service: SERVICE_NAME|SERVICE_ID
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_ttl: 300
    strategy: memory

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

You can configure this plugin through the Konnect UI.

From the servicehub icon Service Hub, select a service version, then set up the plugin:

  1. In the Plugins section, click Add Plugin.
  2. Find and select the Proxy Cache plugin.

  3. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Strategy: memory
  4. Click Create.

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. From the Services section, click View for the service row.
  3. From the plugin section, click Add Plugin.
  4. Find and select the Proxy Cache plugin.
  5. If the option is available, select Scoped.
  6. Add the service name and ID to the Service field if it is not already pre-filled.

  7. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Strategy: memory
  8. Click Create.

The following examples provide some typical configurations for enabling the proxy-cache plugin on a route.

Make the following request:

curl -X POST http://localhost:8001/routes/ROUTE_NAME|ROUTE_ID/plugins \
  --data "name=proxy-cache"  \
    --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_ttl=300" \
    --data "config.strategy=memory"

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: proxy-cache-example
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_ttl: 300
  strategy: memory
plugin: proxy-cache

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

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ROUTE_NAME|ROUTE_ID
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: proxy-cache-example
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          service:
            name: echo
            port:
              number: 80

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

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.

Add this section to your declarative configuration file:

plugins:
- name: proxy-cache
  route: ROUTE_NAME
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_ttl: 300
    strategy: memory

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

You can configure this plugin through the Konnect UI.

From the servicehub icon Service Hub, select a service version, then set up the plugin:

  1. Select a route.
  2. In the Plugins section, click Add Plugin.
  3. Find and select the Proxy Cache plugin.

  4. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Strategy: memory
  5. Click Create.

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. Open Routes from the menu, then click View for the route row.
  3. From the plugin section, click Add Plugin.
  4. Find and select the Proxy Cache plugin.
  5. If the option is available, select Scoped.
  6. Add the route ID if it is not already prefilled.

  7. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Strategy: memory
  8. Click Create.

The following examples provide some typical configurations for enabling the proxy-cache plugin on a consumer.

Make the following request:

curl -X POST http://localhost:8001/consumers/CONSUMER_NAME|CONSUMER_ID/plugins \
  --data "name=proxy-cache"  \
    --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_ttl=300" \
    --data "config.strategy=memory"

Replace CONSUMER_NAME|CONSUMER_ID with the id or name of the consumer that this plugin configuration will target.

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-example
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_ttl: 300
  strategy: memory
plugin: proxy-cache

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

apiVersion: configuration.konghq.com/v1
kind: KongConsumer
metadata:
  name: CONSUMER_NAME|CONSUMER_ID
  annotations:
    konghq.com/plugins: proxy-cache-example
    kubernetes.io/ingress.class: kong

Replace CONSUMER_NAME|CONSUMER_ID with the id or name of the consumer that this plugin configuration will target.

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.

Add this section to your declarative configuration file:

plugins:
- name: proxy-cache
  consumer: CONSUMER_NAME|CONSUMER_ID
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_ttl: 300
    strategy: memory

Replace CONSUMER_NAME|CONSUMER_ID with the id or name of the consumer that this plugin configuration will target.

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. From the Consumers section, click View for the consumer row.
  3. Select the Plugins tab, then click Add Plugin.
  4. Find and select the Proxy Cache plugin.
  5. If the option is available, select Scoped.
  6. Add the consumer ID if it is not already prefilled.

  7. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Strategy: memory
  8. Click Create.

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.

The following examples provide some typical configurations for enabling the proxy-cache plugin globally.

Make the following request:

curl -X POST http://localhost:8001/plugins/ \
  --data "name=proxy-cache"  \
    --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_ttl=300" \
    --data "config.strategy=memory"

Create a KongClusterPlugin resource and label it as global:

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: <global-proxy-cache>
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: \"true\"
config: 
  response_code:
  - 200
  request_method:
  - GET
  - HEAD
  content_type:
  - text/plain
  - application/json
  cache_ttl: 300
  strategy: memory
plugin: proxy-cache

Add a plugins entry in the declarative configuration file:

plugins:
- name: proxy-cache
  config: 
    response_code:
    - 200
    request_method:
    - GET
    - HEAD
    content_type:
    - text/plain
    - application/json
    cache_ttl: 300
    strategy: memory

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. Open Plugins from the menu, then click New Plugin.
  3. Find and select the Proxy Cache plugin.
  4. If the option is available, set the plugin scope to Global.

  5. Configure the plugin’s parameters.

    You can test out the plugin with the following sample configuration:

    • Config.Strategy: memory
  6. Click Create.

Parameters

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

Form Parameter Description
name

required

Type: string

 The name of the plugin, in this case proxy-cache.
service.name or service.id

optional

Type: string

The name or ID of the service the plugin targets.

Set one of these parameters if adding the plugin to a service through the top-level /plugins endpoint.

Not required if using /services/SERVICE_NAME|SERVICE_ID/plugins.
route.name or route.id

optional

Type: string

The name or ID of the route the plugin targets.

Set one of these parameters if adding the plugin to a route through the top-level /plugins endpoint.

Not required if using /routes/ROUTE_NAME|ROUTE_ID/plugins.
consumer.name or consumer.id

optional


Type: string

The name or ID of the consumer the plugin targets.

Set one of these parameters if adding the plugin to a consumer through the top-level /plugins endpoint.

Not required if using /consumers/CONSUMER_NAME|CONSUMER_ID/plugins.
enabled

optional

Type: boolean

Default value: true

 Whether this plugin will be applied.
config.response_code

Type: array integer elements

Default value: 200, 301, 404


Upstream response status code considered cacheable.
config.request_method

Type: array of string elements

Default value: ["GET","HEAD"]


Downstream request methods considered cacheable.
config.content_type

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

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. The only accepted value is memory.
config.memory.dictionary_name

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.
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-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_db_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 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.

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. This is 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. This 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 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 been previously 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 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 plugins data stores for the given cache key. Both endpoints have the same return value.

Endpoint

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

Endpoint

/proxy-cache/: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 Cache Entity

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

Endpoint

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

Endpoint

/proxy-cache/: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 204 No Content

If the entity with the given key does not exist

HTTP 400 Not Found

Purge All Cache Entities

Endpoint

/proxy-cache/

Response

HTTP 204 No Content

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