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< ol class = "chapter" > < li class = "chapter-item expanded " > < a href = "../index.html" > < strong aria-hidden = "true" > 1.< / strong > Introduction< / a > < / li > < li class = "chapter-item expanded " > < a href = "../quickstart.html" > < strong aria-hidden = "true" > 2.< / strong > Quickstart< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/index.html" > < strong aria-hidden = "true" > 3.< / strong > Type System< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../types/objects/defining_objects.html" > < strong aria-hidden = "true" > 3.1.< / strong > Defining objects< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../types/objects/complex_fields.html" > < strong aria-hidden = "true" > 3.1.1.< / strong > Complex fields< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/using_contexts.html" > < strong aria-hidden = "true" > 3.1.2.< / strong > Using contexts< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/objects/error_handling.html" > < strong aria-hidden = "true" > 3.1.3.< / strong > Error handling< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../types/other-index.html" > < strong aria-hidden = "true" > 3.2.< / strong > Other types< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../types/enums.html" > < strong aria-hidden = "true" > 3.2.1.< / strong > Enums< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/interfaces.html" > < strong aria-hidden = "true" > 3.2.2.< / strong > Interfaces< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/input_objects.html" > < strong aria-hidden = "true" > 3.2.3.< / strong > Input objects< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/scalars.html" > < strong aria-hidden = "true" > 3.2.4.< / strong > Scalars< / a > < / li > < li class = "chapter-item expanded " > < a href = "../types/unions.html" > < strong aria-hidden = "true" > 3.2.5.< / strong > Unions< / a > < / li > < / ol > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../schema/schemas_and_mutations.html" > < strong aria-hidden = "true" > 4.< / strong > Schemas and mutations< / a > < / li > < li class = "chapter-item expanded " > < a href = "../servers/index.html" > < strong aria-hidden = "true" > 5.< / strong > Adding A Server< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../servers/official.html" > < strong aria-hidden = "true" > 5.1.< / strong > Official Server Integrations< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../servers/warp.html" > < strong aria-hidden = "true" > 5.1.1.< / strong > Warp< / a > < / li > < li class = "chapter-item expanded " > < a href = "../servers/rocket.html" > < strong aria-hidden = "true" > 5.1.2.< / strong > Rocket< / a > < / li > < li class = "chapter-item expanded " > < a href = "../servers/hyper.html" > < strong aria-hidden = "true" > 5.1.3.< / strong > Hyper< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../servers/third-party.html" > < strong aria-hidden = "true" > 5.2.< / strong > Third Party Integrations< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/index.html" > < strong aria-hidden = "true" > 6.< / strong > Advanced Topics< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../advanced/introspection.html" > < strong aria-hidden = "true" > 6.1.< / strong > Introspection< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/non_struct_objects.html" > < strong aria-hidden = "true" > 6.2.< / strong > Non-struct objects< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/implicit_and_explicit_null.html" > < strong aria-hidden = "true" > 6.3.< / strong > Implicit and explicit null< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/objects_and_generics.html" > < strong aria-hidden = "true" > 6.4.< / strong > Objects and generics< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/multiple_ops_per_request.html" > < strong aria-hidden = "true" > 6.5.< / strong > Multiple operations per request< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/dataloaders.html" > < strong aria-hidden = "true" > 6.6.< / strong > Dataloaders< / a > < / li > < li class = "chapter-item expanded " > < a href = "../advanced/subscriptions.html" class = "active" > < strong aria-hidden = "true" > 6.7.< / strong > Subscription
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< h1 id = "subscriptions" > < a class = "header" href = "#subscriptions" > Subscriptions< / a > < / h1 >
< h3 id = "how-to-achieve-realtime-data-with-graphql-subscriptions" > < a class = "header" href = "#how-to-achieve-realtime-data-with-graphql-subscriptions" > How to achieve realtime data with GraphQL subscriptions< / a > < / h3 >
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< p > GraphQL subscriptions are a way to push data from the server to clients requesting real-time messages
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from the server. Subscriptions are similar to queries in that they specify a set of fields to be delivered to the client,
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but instead of immediately returning a single answer a result is sent every time a particular event happens on the
server.< / p >
< p > In order to execute subscriptions you need a coordinator (that spawns connections)
and a GraphQL object that can be resolved into a stream--elements of which will then
be returned to the end user. The < a href = "https://github.com/graphql-rust/juniper/tree/master/juniper_subscriptions" > < code > juniper_subscriptions< / code > < / a > crate
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provides a default connection implementation. Currently subscriptions are only supported on the < code > master< / code > branch. Add the following to your < code > Cargo.toml< / code > :< / p >
< pre > < code class = "language-toml" > [dependencies]
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juniper = "0.16.0"
juniper_subscriptions = "0.17.0"
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< / code > < / pre >
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< h3 id = "schema-definition" > < a class = "header" href = "#schema-definition" > Schema Definition< / a > < / h3 >
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< p > The < code > Subscription< / code > is just a GraphQL object, similar to the query root and mutations object that you defined for the
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operations in your < a href = "../schema/schemas_and_mutations.html" > Schema< / a > . For subscriptions all fields/operations should be async and should return a < a href = "https://docs.rs/futures/0.3.4/futures/stream/trait.Stream.html" > Stream< / a > .< / p >
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< p > This example shows a subscription operation that returns two events, the strings < code > Hello< / code > and < code > World!< / code >
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sequentially:< / p >
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< pre > < pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > extern crate futures;
< / span > < span class = "boring" > extern crate juniper;
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< / span > < span class = "boring" > use std::pin::Pin;
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< / span > < span class = "boring" > use futures::Stream;
< / span > < span class = "boring" > use juniper::{graphql_object, graphql_subscription, FieldError};
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< / span > < span class = "boring" >
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct Database;
< / span > < span class = "boring" > impl juniper::Context for Database {}
< / span >
< span class = "boring" > pub struct Query;
< / span > < span class = "boring" > #[graphql_object(context = Database)]
< / span > < span class = "boring" > impl Query {
< / span > < span class = "boring" > fn hello_world() -> & 'static str {
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< / span > < span class = "boring" > "Hello World!"
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > pub struct Subscription;
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type StringStream = Pin< Box< dyn Stream< Item = Result< String, FieldError> > + Send> > ;
#[graphql_subscription(context = Database)]
impl Subscription {
async fn hello_world() -> StringStream {
let stream = futures::stream::iter(vec![
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Ok(String::from("Hello")),
Ok(String::from("World!"))
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]);
Box::pin(stream)
}
}
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< span class = "boring" >
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< / span > < span class = "boring" > fn main () {}< / span > < / code > < / pre > < / pre >
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< h3 id = "coordinator" > < a class = "header" href = "#coordinator" > Coordinator< / a > < / h3 >
< p > Subscriptions require a bit more resources than regular queries and provide a great vector for DOS attacks. This can can bring down a server easily if not handled correctly. The < a href = "https://docs.rs/juniper_subscriptions/0.15.0/trait.SubscriptionCoordinator.html" > < code > SubscriptionCoordinator< / code > < / a > trait provides coordination logic to enable functionality like DOS attack mitigation and resource limits.< / p >
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< p > The < a href = "https://docs.rs/juniper_subscriptions/0.15.0/trait.SubscriptionCoordinator.html" > < code > SubscriptionCoordinator< / code > < / a > contains the schema and can keep track of opened connections, handle subscription
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start and end, and maintain a global subscription id for each subscription. Each time a connection is established,< br / >
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the < a href = "https://docs.rs/juniper_subscriptions/0.15.0/trait.SubscriptionCoordinator.html" > < code > SubscriptionCoordinator< / code > < / a > spawns a < a href = "https://docs.rs/juniper_subscriptions/0.15.0/trait.SubscriptionConnection.html" > < code > SubscriptionConnection< / code > < / a > . The < a href = "https://docs.rs/juniper_subscriptions/0.15.0/trait.SubscriptionConnection.html" > < code > SubscriptionConnection< / code > < / a > handles a single connection, providing resolver logic for a client stream as well as reconnection
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and shutdown logic.< / p >
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< p > While you can implement < a href = "https://docs.rs/juniper_subscriptions/0.15.0/trait.SubscriptionCoordinator.html" > < code > SubscriptionCoordinator< / code > < / a > yourself, Juniper contains a simple and generic implementation called < a href = "https://docs.rs/juniper_subscriptions/0.15.0/struct.Coordinator.html" > < code > Coordinator< / code > < / a > . The < code > subscribe< / code >
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operation returns a < a href = "https://docs.rs/futures/0.3.4/futures/future/trait.Future.html" > < code > Future< / code > < / a > with an < code > Item< / code > value of a < code > Result< Connection, GraphQLError> < / code > ,
where < a href = "https://docs.rs/juniper_subscriptions/0.15.0/struct.Connection.html" > < code > Connection< / code > < / a > is a < code > Stream< / code > of values returned by the operation and < a href = "https://docs.rs/juniper/0.14.2/juniper/enum.GraphQLError.html" > < code > GraphQLError< / code > < / a > is the error when the subscription fails.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(dead_code)]
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< / span > < span class = "boring" > extern crate futures;
< / span > < span class = "boring" > extern crate juniper;
< / span > < span class = "boring" > extern crate juniper_subscriptions;
< / span > < span class = "boring" > extern crate serde_json;
< / span > < span class = "boring" > use juniper::{
< / span > < span class = "boring" > http::GraphQLRequest,
< / span > < span class = "boring" > graphql_object, graphql_subscription,
< / span > < span class = "boring" > DefaultScalarValue, EmptyMutation, FieldError,
< / span > < span class = "boring" > RootNode, SubscriptionCoordinator,
< / span > < span class = "boring" > };
< / span > < span class = "boring" > use juniper_subscriptions::Coordinator;
< / span > < span class = "boring" > use futures::{Stream, StreamExt};
< / span > < span class = "boring" > use std::pin::Pin;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct Database;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl juniper::Context for Database {}
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl Database {
< / span > < span class = "boring" > fn new() -> Self {
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< / span > < span class = "boring" > Self
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub struct Query;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[graphql_object(context = Database)]
< / span > < span class = "boring" > impl Query {
< / span > < span class = "boring" > fn hello_world() -> & 'static str {
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< / span > < span class = "boring" > "Hello World!"
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub struct Subscription;
< / span > < span class = "boring" >
< / span > < span class = "boring" > type StringStream = Pin< Box< dyn Stream< Item = Result< String, FieldError> > + Send> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[graphql_subscription(context = Database)]
< / span > < span class = "boring" > impl Subscription {
< / span > < span class = "boring" > async fn hello_world() -> StringStream {
< / span > < span class = "boring" > let stream =
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< / span > < span class = "boring" > futures::stream::iter(vec![Ok(String::from("Hello")), Ok(String::from("World!"))]);
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< / span > < span class = "boring" > Box::pin(stream)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > type Schema = RootNode< 'static, Query, EmptyMutation< Database> , Subscription> ;
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fn schema() -> Schema {
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Schema::new(Query, EmptyMutation::new(), Subscription)
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}
async fn run_subscription() {
let schema = schema();
let coordinator = Coordinator::new(schema);
let req: GraphQLRequest< DefaultScalarValue> = serde_json::from_str(
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r#"{
"query": "subscription { helloWorld }"
}"#,
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)
.unwrap();
let ctx = Database::new();
let mut conn = coordinator.subscribe(& req, & ctx).await.unwrap();
while let Some(result) = conn.next().await {
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println!("{}", serde_json::to_string(& result).unwrap());
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}
}
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< span class = "boring" >
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< / span > < span class = "boring" > fn main() { }< / span > < / code > < / pre > < / pre >
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< h3 id = "web-integration-and-examples" > < a class = "header" href = "#web-integration-and-examples" > Web Integration and Examples< / a > < / h3 >
< p > Currently there is an example of subscriptions with < a href = "https://github.com/graphql-rust/juniper/tree/master/juniper_warp" > warp< / a > , but it still in an alpha state.
GraphQL over < a href = "https://github.com/apollographql/subscriptions-transport-ws/blob/master/PROTOCOL.md" > WS< / a > is not fully supported yet and is non-standard.< / p >
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< ul >
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< li > < a href = "https://github.com/graphql-rust/juniper/tree/master/juniper_warp/examples/subscription.rs" > Warp Subscription Example< / a > < / li >
< li > < a href = "https://github.com/graphql-rust/juniper/tree/master/juniper_subscriptions/examples/basic.rs" > Small Example< / a > < / li >
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< / ul >
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