feat: expose creation of HealthService and HealthReporter

tonic-health/src/server.rs

@@ -37,7 +37,8 @@ pub struct HealthReporter {
 }
 
 impl HealthReporter {
-    fn new() -> Self {
+    /// Create a new HealthReporter with an initial service (named ""), corresponding to overall server health
+    pub fn new() -> Self {
         // According to the gRPC Health Check specification, the empty service "" corresponds to the overall server health
         let server_status = ("".to_string(), watch::channel(ServingStatus::Serving));
 
@@ -97,6 +98,12 @@ impl HealthReporter {
     }
 }
 
+impl Default for HealthReporter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 /// A service providing implementations of gRPC health checking protocol.
 #[derive(Debug)]
 pub struct HealthService {
@@ -108,6 +115,11 @@ impl HealthService {
         HealthService { statuses: services }
     }
 
+    /// Create a HealthService, carrying across the statuses from an existing HealthReporter
+    pub fn from_health_reporter(health_reporter: HealthReporter) -> Self {
+        Self::new(health_reporter.statuses)
+    }
+
     async fn service_health(&self, service_name: &str) -> Option<ServingStatus> {
         let reader = self.statuses.read().await;
         reader.get(service_name).map(|p| *p.1.borrow())