- update: tell consul to use docker dns to resolve CNAME addresses

- add: load balancer for consul services
- update: dns lookup to now return the service address
- update: docker consul to the latest version

utils/src/lib.rs

@@ -3,3 +3,4 @@ pub mod null_string;
 pub mod redis_cache;
 pub mod service_discovery;
 pub mod signal_handler;
+pub mod multi_service_load_balancer;

utils/src/multi_service_load_balancer.rs

@@ -0,0 +1,135 @@
+use std::collections::HashMap;
+use std::net::SocketAddr;
+use std::sync::{Arc, Mutex};
+use rand::seq::SliceRandom;
+use crate::service_discovery::get_service_endpoints_by_dns;
+
+pub enum LoadBalancingStrategy {
+  Random,
+  RoundRobin,
+}
+
+// Service identifier
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct ServiceId {
+  pub name: String,
+  pub protocol: String,
+}
+
+impl ServiceId {
+  pub fn new(name: &str, protocol: &str) -> Self {
+    ServiceId {
+      name: name.to_string(),
+      protocol: protocol.to_string(),
+    }
+  }
+}
+
+// Per-service state
+struct ServiceState {
+  endpoints: Vec<SocketAddr>,
+  current_index: usize,
+}
+
+impl ServiceState {
+  fn new(endpoints: Vec<SocketAddr>) -> Self {
+    ServiceState {
+      endpoints,
+      current_index: 0,
+    }
+  }
+
+  fn get_endpoint(&mut self, strategy: &LoadBalancingStrategy) -> Option<SocketAddr> {
+    if self.endpoints.is_empty() {
+      return None;
+    }
+
+    match strategy {
+      LoadBalancingStrategy::Random => {
+        let mut rng = rand::thread_rng();
+        self.endpoints.choose(&mut rng).copied()
+      }
+      LoadBalancingStrategy::RoundRobin => {
+        let endpoint = self.endpoints[self.current_index].clone();
+        self.current_index = (self.current_index + 1) % self.endpoints.len();
+        Some(endpoint)
+      }
+    }
+  }
+}
+
+pub struct MultiServiceLoadBalancer {
+  consul_url: String,
+  strategy: LoadBalancingStrategy,
+  services: Arc<Mutex<HashMap<ServiceId, ServiceState>>>,
+}
+
+impl MultiServiceLoadBalancer {
+  pub fn new(consul_url: &str, strategy: LoadBalancingStrategy) -> Self {
+    MultiServiceLoadBalancer {
+      consul_url: consul_url.to_string(),
+      strategy,
+      services: Arc::new(Mutex::new(HashMap::new())),
+    }
+  }
+
+  pub async fn get_endpoint(
+    &self,
+    service_name: &str,
+    service_protocol: &str,
+  ) -> Result<Option<SocketAddr>, Box<dyn std::error::Error>> {
+    let service_id = ServiceId::new(service_name, service_protocol);
+
+    // Try to get an endpoint from the cache first
+    {
+      let mut services = self.services.lock().unwrap();
+      if let Some(service_state) = services.get_mut(&service_id) {
+        if let Some(endpoint) = service_state.get_endpoint(&self.strategy) {
+          return Ok(Some(endpoint));
+        }
+      }
+    }
+
+    // If we don't have endpoints or they're all unavailable, refresh them
+    self.refresh_service_endpoints(service_name, service_protocol).await?;
+
+    // Try again after refresh
+    let mut services = self.services.lock().unwrap();
+    if let Some(service_state) = services.get_mut(&service_id) {
+      return Ok(service_state.get_endpoint(&self.strategy));
+    }
+
+    Ok(None)
+  }
+
+  pub async fn refresh_service_endpoints(
+    &self,
+    service_name: &str,
+    service_protocol: &str,
+  ) -> Result<(), Box<dyn std::error::Error>> {
+    let endpoints = get_service_endpoints_by_dns(
+      &self.consul_url,
+      service_protocol,
+      service_name,
+    ).await?;
+
+    let service_id = ServiceId::new(service_name, service_protocol);
+    let mut services = self.services.lock().unwrap();
+
+    services.insert(service_id, ServiceState::new(endpoints));
+    Ok(())
+  }
+
+  pub async fn refresh_all_services(&self) -> Result<(), Box<dyn std::error::Error>> {
+    let service_ids: Vec<ServiceId> = {
+      let services = self.services.lock().unwrap();
+      services.keys().cloned().collect()
+    };
+
+    for service_id in service_ids {
+      self.refresh_service_endpoints(&service_id.name, &service_id.protocol).await?;
+    }
+
+    Ok(())
+  }
+}

utils/src/service_discovery.rs

@@ -3,6 +3,7 @@ use hickory_resolver::{Resolver, TokioAsyncResolver};
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::net::SocketAddr;
+use std::str::FromStr;
 use tokio::runtime::Runtime;
 use tracing::log::debug;
 
@@ -17,12 +18,12 @@ pub async fn get_service_endpoints_by_dns(consul_url: &str, service_protocol: &s
     let srv_record = resolver.srv_lookup(&srv_name).await?;
 
     let mut endpoints = Vec::new();
-    debug!("service records: {:?}", srv_record);
     for record in srv_record {
         let hostname = record.target();
-        debug!("hostname: {:?}", hostname);
-
-        // endpoints.push(SocketAddr::new(, record.port()));
+        let lookup_responses = resolver.lookup_ip(hostname.to_string()).await?;
+        for response in lookup_responses {
+            endpoints.push(SocketAddr::from_str(&format!("{}:{}", &response.to_string(), record.port()))?);
+        }
     }
 
     Ok(endpoints)