Implement Watch method in health check service.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/proto/grpc/health/v1/health.proto b/src/proto/grpc/health/v1/health.proto
index 4b4677b8a4..38843ff1e7 100644
--- a/src/proto/grpc/health/v1/health.proto
+++ b/src/proto/grpc/health/v1/health.proto
@@ -34,10 +34,30 @@ message HealthCheckResponse {
     UNKNOWN = 0;
     SERVING = 1;
     NOT_SERVING = 2;
+    SERVICE_UNKNOWN = 3;  // Used only by the Watch method.
   }
   ServingStatus status = 1;
 }
 
 service Health {
+  // If the requested service is unknown, the call will fail with status
+  // NOT_FOUND.
   rpc Check(HealthCheckRequest) returns (HealthCheckResponse);
+
+  // Performs a watch for the serving status of the requested service.
+  // The server will immediately send back a message indicating the current
+  // serving status.  It will then subsequently send a new message whenever
+  // the service's serving status changes.
+  //
+  // If the requested service is unknown when the call is received, the
+  // server will send a message setting the serving status to
+  // SERVICE_UNKNOWN but will *not* terminate the call.  If at some
+  // future point, the serving status of the service becomes known, the
+  // server will send a new message with the service's serving status.
+  //
+  // If the call terminates with status UNIMPLEMENTED, then clients
+  // should assume this method is not supported and should not retry the
+  // call.  If the call terminates with any other status (including OK),
+  // clients should retry the call with appropriate exponential backoff.
+  rpc Watch(HealthCheckRequest) returns (stream HealthCheckResponse);
 }