Add example that routes to LB cluster based on request uri

.bleep

@@ -1 +1 @@
-d2ed77868cbf900541c50e562644d946b55a33fc
+69cdf488ece81b5a77ba555b98509d231c48af96

pingora-proxy/examples/multi_lb.rs

@@ -0,0 +1,93 @@
+// Copyright 2024 Cloudflare, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use async_trait::async_trait;
+use std::sync::Arc;
+
+use pingora_core::{prelude::*, services::background::GenBackgroundService};
+use pingora_load_balancing::{
+    health_check::TcpHealthCheck,
+    selection::{BackendIter, BackendSelection, RoundRobin},
+    LoadBalancer,
+};
+use pingora_proxy::{http_proxy_service, ProxyHttp, Session};
+
+struct Router {
+    cluster_one: Arc<LoadBalancer<RoundRobin>>,
+    cluster_two: Arc<LoadBalancer<RoundRobin>>,
+}
+
+#[async_trait]
+impl ProxyHttp for Router {
+    type CTX = ();
+    fn new_ctx(&self) {}
+
+    async fn upstream_peer(&self, session: &mut Session, _ctx: &mut ()) -> Result<Box<HttpPeer>> {
+        // determine LB cluster based on request uri
+        let cluster = if session.req_header().uri.path().starts_with("/one/") {
+            &self.cluster_one
+        } else {
+            &self.cluster_two
+        };
+
+        let upstream = cluster
+            .select(b"", 256) // hash doesn't matter for round robin
+            .unwrap();
+
+        println!("upstream peer is: {upstream:?}");
+
+        // Set SNI to one.one.one.one
+        let peer = Box::new(HttpPeer::new(upstream, true, "one.one.one.one".to_string()));
+        Ok(peer)
+    }
+}
+
+fn build_cluster_service<S: BackendSelection>(
+    upstreams: &[&str],
+) -> GenBackgroundService<LoadBalancer<S>>
+where
+    S: BackendSelection + 'static,
+    S::Iter: BackendIter,
+{
+    let mut cluster = LoadBalancer::try_from_iter(upstreams).unwrap();
+    cluster.set_health_check(TcpHealthCheck::new());
+    cluster.health_check_frequency = Some(std::time::Duration::from_secs(1));
+
+    background_service("cluster health check", cluster)
+}
+
+// RUST_LOG=INFO cargo run --example multi_lb
+// curl 127.0.0.1:6188/one/
+// curl 127.0.0.1:6188/two/
+fn main() {
+    let mut my_server = Server::new(None).unwrap();
+    my_server.bootstrap();
+
+    // build multiple clusters
+    let cluster_one = build_cluster_service::<RoundRobin>(&["1.1.1.1:443", "127.0.0.1:343"]);
+    let cluster_two = build_cluster_service::<RoundRobin>(&["1.0.0.1:443", "127.0.0.2:343"]);
+
+    let router = Router {
+        cluster_one: cluster_one.task(),
+        cluster_two: cluster_two.task(),
+    };
+    let mut router_service = http_proxy_service(&my_server.configuration, router);
+    router_service.add_tcp("0.0.0.0:6188");
+
+    my_server.add_service(router_service);
+    my_server.add_service(cluster_one);
+    my_server.add_service(cluster_two);
+
+    my_server.run_forever();
+}