@landingexp/apollo-cache-control
v1.0.3
Published
A GraphQL extension for cache control
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Apollo Cache Control (for Node.js)
This package is used to collect and expose cache control data in the Apollo Cache Control format.
It relies on instrumenting a GraphQL schema to collect cache control hints, and exposes cache control data for an individual request under extensions
as part of the GraphQL response.
This data can be consumed by any tool to inform caching and visualize the cache policies that are in effect for a particular request.
Uses for this data include apollo-server-plugin-response-cache (which implements a full response cache) and setting cache-control HTTP headers.
See https://www.apollographql.com/docs/apollo-server/performance/caching/ for more details.
Usage
Apollo Server
Apollo Server includes built-in support for Apollo Cache Control from version 1.2.0 onwards.
The only code change required is to add tracing: true
and cacheControl: true
to the options passed to the Apollo Server middleware function for your framework of choice. For example, for Express:
app.use('/graphql', bodyParser.json(), graphqlExpress({
schema,
context: {},
tracing: true,
cacheControl: true
}));
If you are using
express-graphql
, we recommend you switch to Apollo Server. Bothexpress-graphql
and Apollo Server are based on thegraphql-js
reference implementation, and switching should only require changing a few lines of code.
Add cache hints to your schema
Cache hints can be added to your schema using directives on your types and fields. When executing your query, these hints will be used to compute an overall cache policy for the response. Hints on fields override hints specified on the target type.
type Post @cacheControl(maxAge: 240) {
id: Int!
title: String
author: Author
votes: Int @cacheControl(maxAge: 30)
readByCurrentUser: Boolean! @cacheControl(scope: PRIVATE)
}
If you need to add cache hints dynamically, you can use a programmatic API from within your resolvers.
const resolvers = {
Query: {
post: (_, { id }, _, { cacheControl }) => {
cacheControl.setCacheHint({ maxAge: 60 });
return find(posts, { id });
}
}
}
If you're using TypeScript, you need the following:
import 'apollo-cache-control';
If set up correctly, for this query:
query {
post(id: 1) {
title
votes
readByCurrentUser
}
}
You should receive cache control data in the extensions
field of your response:
"cacheControl": {
"version": 1,
"hints": [
{
"path": [
"post"
],
"maxAge": 240
},
{
"path": [
"post",
"votes"
],
"maxAge": 30
},
{
"path": [
"post",
"readByCurrentUser"
],
"scope": "PRIVATE"
}
]
}
Setting a default maxAge
The power of cache hints comes from being able to set them precisely to different values on different types and fields based on your understanding of your implementation's semantics. But when getting started with Apollo Cache Control, you might just want to apply the same maxAge
to most of your resolvers. You can specify a default max age when you set up cacheControl
in your server. This max age will be applied to all resolvers which don't explicitly set maxAge
via schema hints (including schema hints on the type that they return) or the programmatic API. You can override this for a particular resolver or type by setting @cacheControl(maxAge: 0)
. For example, for Express:
app.use('/graphql', bodyParser.json(), graphqlExpress({
schema,
context: {},
tracing: true,
cacheControl: {
defaultMaxAge: 5,
},
}));