From 5b3935e95f79d6d6c5ec4ac6932630862f366f0f Mon Sep 17 00:00:00 2001
From: Dmitry Simonenko <pmwkaa@gmail.com>
Date: Fri, 9 Jun 2017 15:49:55 +0300
Subject: [PATCH] odissey: do discard optimistically and only for new clients

---
 src/od_backend.c  | 21 +++++++++++----------
 src/od_backend.h  |  1 +
 src/od_frontend.c | 11 +++++++++++
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/src/od_backend.c b/src/od_backend.c
index 8af8f1de..49a58614 100644
--- a/src/od_backend.c
+++ b/src/od_backend.c
@@ -484,19 +484,20 @@ int od_backend_reset(od_server_t *server)
 		}
 	}
 
-	/* send reset query */
-	if (route->scheme->discard) {
-		char query_reset[] = "DISCARD ALL";
-		rc = od_backend_query(server, "reset", query_reset,
-		                      sizeof(query_reset));
-		if (rc == -1)
-			goto error;
-	}
-
-	/* ready to use */
+	/* ready to use (yet maybe discard is required) */
 	return  1;
 drop:
 	return  0;
 error:
 	return -1;
 }
+
+int od_backend_discard(od_server_t *server)
+{
+	od_instance_t *instance = server->system->instance;
+	char query_discard[] = "DISCARD ALL";
+	od_debug_server(&instance->log, server->id, "discard",
+	                "%s", query_discard);
+	return od_backend_query(server, "reset", query_discard,
+	                        sizeof(query_discard));
+}
diff --git a/src/od_backend.h b/src/od_backend.h
index 05613b82..29fff112 100644
--- a/src/od_backend.h
+++ b/src/od_backend.h
@@ -15,5 +15,6 @@ int  od_backend_terminate(od_server_t*);
 int  od_backend_reset(od_server_t*);
 int  od_backend_ready(od_server_t*, uint8_t*, int);
 int  od_backend_configure(od_server_t*, so_bestartup_t*);
+int  od_backend_discard(od_server_t*);
 
 #endif /* OD_BACKEND_H */
diff --git a/src/od_frontend.c b/src/od_frontend.c
index d7ef60d5..73283db5 100644
--- a/src/od_frontend.c
+++ b/src/od_frontend.c
@@ -298,6 +298,17 @@ od_frontend_main(od_client_t *client)
 				                "previously owned, no need to reconfigure S%" PRIu64,
 				                server->id);
 			} else {
+				/* discard last server configuration, unless
+				 * server has been just connected. */
+				od_route_t *route = client->route;
+				if (route->scheme->discard) {
+				    if (server->last_client_id != UINT64_MAX) {
+						rc = od_backend_discard(client->server);
+						if (rc == -1)
+							return OD_RS_ESERVER_CONFIGURE;
+					}
+				}
+				/* set client parameters */
 				rc = od_backend_configure(client->server, &client->startup);
 				if (rc == -1)
 					return OD_RS_ESERVER_CONFIGURE;