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<ol class="chapter"><li class="chapter-item expanded "><a href="../warpgrapher/intro.html"><strong aria-hidden="true">1.</strong> Warpgrapher</a></li><li class="chapter-item expanded "><a href="../warpgrapher/quickstart.html"><strong aria-hidden="true">2.</strong> Quickstart</a></li><li class="chapter-item expanded "><a href="../integrations/intro.html"><strong aria-hidden="true">3.</strong> Server Integration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../integrations/actix.html"><strong aria-hidden="true">3.1.</strong> Actix Web</a></li><li class="chapter-item expanded "><a href="../integrations/lambda.html"><strong aria-hidden="true">3.2.</strong> AWS Lambda</a></li></ol></li><li class="chapter-item expanded "><a href="../configuration/intro.html"><strong aria-hidden="true">4.</strong> Configuration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../configuration/databases.html"><strong aria-hidden="true">4.1.</strong> Databases</a></li><li class="chapter-item expanded "><a href="../configuration/formats.html"><strong aria-hidden="true">4.2.</strong> Formats</a></li><li class="chapter-item expanded "><a href="../configuration/types.html"><strong aria-hidden="true">4.3.</strong> Types</a></li><li class="chapter-item expanded "><a href="../configuration/relationships.html"><strong aria-hidden="true">4.4.</strong> Relationships</a></li></ol></li><li class="chapter-item expanded "><a href="../api/intro.html"><strong aria-hidden="true">5.</strong> CRUD API Usage Examples</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../api/node_create.html"><strong aria-hidden="true">5.1.</strong> Node Create</a></li><li class="chapter-item expanded "><a href="../api/node_read.html"><strong aria-hidden="true">5.2.</strong> Node Read</a></li><li class="chapter-item expanded "><a href="../api/node_update.html"><strong aria-hidden="true">5.3.</strong> Node Update</a></li><li class="chapter-item expanded "><a href="../api/node_delete.html"><strong aria-hidden="true">5.4.</strong> Node Delete</a></li><li class="chapter-item expanded "><a href="../api/rel_create.html"><strong aria-hidden="true">5.5.</strong> Relationship Create</a></li><li class="chapter-item expanded "><a href="../api/rel_read.html"><strong aria-hidden="true">5.6.</strong> Relationship Read</a></li><li class="chapter-item expanded "><a href="../api/rel_update.html"><strong aria-hidden="true">5.7.</strong> Relationship Update</a></li><li class="chapter-item expanded "><a href="../api/rel_delete.html"><strong aria-hidden="true">5.8.</strong> Relationship Delete</a></li></ol></li><li class="chapter-item expanded "><a href="../engine/intro.html"><strong aria-hidden="true">6.</strong> Engine Features</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../engine/endpoints_static.html"><strong aria-hidden="true">6.1.</strong> Static Endpoints</a></li><li class="chapter-item expanded "><a href="../engine/endpoints_defined.html"><strong aria-hidden="true">6.2.</strong> Defined Endpoints</a></li><li class="chapter-item expanded "><a href="../engine/dynamic_props.html"><strong aria-hidden="true">6.3.</strong> Dynamic Props</a></li><li class="chapter-item expanded "><a href="../engine/dynamic_rels.html"><strong aria-hidden="true">6.4.</strong> Dynamic Relationships</a></li><li class="chapter-item expanded "><a href="../engine/context_request.html" class="active"><strong aria-hidden="true">6.5.</strong> Request Context</a></li><li class="chapter-item expanded "><a href="../engine/input_validation.html"><strong aria-hidden="true">6.6.</strong> Input Validation</a></li><li class="chapter-item expanded "><a href="../engine/event_handlers.html"><strong aria-hidden="true">6.7.</strong> Event Handlers</a></li></ol></li></ol>
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<h1 id="request-context"><a class="header" href="#request-context">Request Context</a></h1>
<p>In some cases, it's desirable to pass custom state information from your application into the Warpgrapher request cycle, so that your custom resolvers can make use of that information. The request context makes this passing of state possible.</p>
<h2 id="define-the-requestcontext"><a class="header" href="#define-the-requestcontext">Define the RequestContext</a></h2>
<p>Every system using Warpgrapher defines a struct that implements <code>RequestContext</code>. In addition to implementing the trait, that struct is free to carry additional state information. However, the context must implement <code>Clone</code>, <code>Debug</code>, <code>Sync</code>, <code>Send</code>, as well as Warpgrapher's <code>RequestContext</code> trait. See the code snippet below for an example.</p>
<pre><code class="language-rust no_run noplayground">#[derive(Clone, Debug)]
struct AppRequestContext {
request_id: String,
}
impl RequestContext for AppRequestContext {
type DBEndpointType = CypherEndpoint;
fn new() -> AppRequestContext {
// generate random request id
let request_id = "1234".to_string();
AppRequestContext { request_id }
}
}
</code></pre>
<h2 id="engine-type-parameter"><a class="header" href="#engine-type-parameter">Engine Type Parameter</a></h2>
<p>The struct that implements <code>RequestContext</code> is passed to the <code>Engine</code> as a type parameter, as shown in the code snippet below.</p>
<pre><code class="language-rust no_run noplayground"> // create warpgrapher engine
let engine: Engine<AppRequestContext> = Engine::new(config, db)
.with_resolvers(resolvers)
.build()
.expect("Failed to build engine");
</code></pre>
<h2 id="access-the-context"><a class="header" href="#access-the-context">Access the Context</a></h2>
<p>Once passed to the <code>Engine</code>, the struct implementing <code>RequestContext</code> is available to functions that implement custom endpoints and resolvers, as shown in the snippet below.</p>
<pre><code class="language-rust no_run noplayground">fn resolve_echo_request(facade: ResolverFacade<AppRequestContext>) -> BoxFuture<ExecutionResult> {
Box::pin(async move {
let request_context = facade.request_context().unwrap();
let request_id = request_context.request_id.clone();
facade.resolve_scalar(format!("echo! (request_id: {})", request_id))
})
}
</code></pre>
<h2 id="full-example-source"><a class="header" href="#full-example-source">Full Example Source</a></h2>
<pre><code class="language-rust no_run noplayground">use std::collections::HashMap;
use std::convert::TryFrom;
use warpgrapher::engine::config::Configuration;
use warpgrapher::engine::context::RequestContext;
use warpgrapher::engine::database::cypher::CypherEndpoint;
use warpgrapher::engine::database::DatabaseEndpoint;
use warpgrapher::engine::resolvers::{ExecutionResult, ResolverFacade, Resolvers};
use warpgrapher::juniper::BoxFuture;
use warpgrapher::Engine;
static CONFIG: &str = "
version: 1
model:
- name: User
props:
- name: email
type: String
endpoints:
- name: EchoRequest
class: Query
input: null
output:
type: String
";
#[derive(Clone, Debug)]
struct AppRequestContext {
request_id: String,
}
impl RequestContext for AppRequestContext {
type DBEndpointType = CypherEndpoint;
fn new() -> AppRequestContext {
// generate random request id
let request_id = "1234".to_string();
AppRequestContext { request_id }
}
}
fn resolve_echo_request(facade: ResolverFacade<AppRequestContext>) -> BoxFuture<ExecutionResult> {
Box::pin(async move {
let request_context = facade.request_context().unwrap();
let request_id = request_context.request_id.clone();
facade.resolve_scalar(format!("echo! (request_id: {})", request_id))
})
}
#[tokio::main]
async fn main() {
// parse warpgrapher config
let config = Configuration::try_from(CONFIG.to_string()).expect("Failed to parse CONFIG");
// define database endpoint
let db = CypherEndpoint::from_env()
.expect("Failed to parse cypher endpoint from environment")
.pool()
.await
.expect("Failed to create cypher database pool");
// define resolvers
let mut resolvers = Resolvers::<AppRequestContext>::new();
resolvers.insert("EchoRequest".to_string(), Box::new(resolve_echo_request));
// create warpgrapher engine
let engine: Engine<AppRequestContext> = Engine::new(config, db)
.with_resolvers(resolvers)
.build()
.expect("Failed to build engine");
// execute query on `GetEnvironment` endpoint
let query = "
query {
EchoRequest
}
"
.to_string();
let metadata = HashMap::new();
let result = engine.execute(query, None, metadata).await.unwrap();
// verify result
println!("result: {:#?}", result);
assert_eq!(
"echo! (request_id: 1234)",
result
.get("data")
.unwrap()
.get("EchoRequest")
.unwrap()
.as_str()
.unwrap(),
);
}
</code></pre>
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