Cache control

Production environments often rely on caching to improve performance.

A GraphQL query will call multiple resolver functions and each resolver can have a different cache definition. Some may cache for a few seconds, some may cache for a few hours, some may be the same for all users, and some may be different for each session.

Async-graphql provides a mechanism that allows you to define the cache time and scope for each resolver.

You can define cache parameters on the object or on its fields. The following example shows two uses of cache control parameters.

You can use max_age parameters to control the age of the cache (in seconds), and you can also use public and private to control the scope of the cache. When you do not specify it, the scope will default to public.

when querying multiple resolvers, the results of all cache control parameters will be combined and the max_age minimum value will be taken. If the scope of any object or field is private, the result will be private.

We can use QueryResponse to get a merged cache control result from a query result, and call CacheControl::value to get the corresponding HTTP header.

#![allow(unused)]
fn main() {
extern crate async_graphql;
use async_graphql::*;
struct Query;
#[Object(cache_control(max_age = 60))]
impl Query {
    #[graphql(cache_control(max_age = 30))]
    async fn value1(&self) -> i32 {
        1
    }

    #[graphql(cache_control(private))]
    async fn value2(&self) -> i32 {
        2
    }

    async fn value3(&self) -> i32 {
        3
    }
}
}

The following are different queries corresponding to different cache control results:

# max_age=30
{ value1 }

# max_age=30, private
{ value1 value2 }

# max_age=60
{ value3 }