[PATCH] replication: downstream status reporting in box.info

[Serge Petrenko]

Start showing downstream status for relays in "follow" state.
Also refactor lbox_pushrelay to unify code for different relay
states.

Closes #3904
---
https://github.com/tarantool/tarantool/issues/3904
https://github.com/tarantool/tarantool/tree/sp/gh-3904-downstream-status

 src/box/lua/info.c               | 46 ++++++++++++++++++--------------
 test/replication/status.result   |  4 +++
 test/replication/status.test.lua |  1 +
 3 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/src/box/lua/info.c b/src/box/lua/info.c
index f1950deeb..70672f271 100644
--- a/src/box/lua/info.c
+++ b/src/box/lua/info.c
@@ -115,9 +115,31 @@ static void
 lbox_pushrelay(lua_State *L, struct relay *relay)
 {
 	lua_newtable(L);
-	lua_pushstring(L, "vclock");
-	lbox_pushvclock(L, relay_vclock(relay));
-	lua_settable(L, -3);
+	lua_pushstring(L, "status");
+
+	switch(relay_get_state(relay)) {
+	case RELAY_FOLLOW:
+		lua_pushstring(L, "follow");
+		lua_settable(L, -3);
+		lua_pushstring(L, "vclock");
+		lbox_pushvclock(L, relay_vclock(relay));
+		lua_settable(L, -3);
+		break;
+	case RELAY_STOPPED:
+	{
+		lua_pushstring(L, "stopped");
+		lua_settable(L, -3);
+
+		struct error *e = diag_last_error(relay_get_diag(relay));
+		if (e != NULL) {
+			lua_pushstring(L, "message");
+			lua_pushstring(L, e->errmsg);
+			lua_settable(L, -3);
+		}
+		break;
+	}
+	default: unreachable();
+	}
 }
 
 static void
@@ -147,25 +169,9 @@ lbox_pushreplica(lua_State *L, struct replica *replica)
 		lua_settable(L, -3);
 	}
 
-	if (relay_get_state(relay) == RELAY_FOLLOW) {
+	if (relay_get_state(relay) != RELAY_OFF) {
 		lua_pushstring(L, "downstream");
 		lbox_pushrelay(L, relay);
-		lua_settable(L, -3);
-	} else if (relay_get_state(relay) == RELAY_STOPPED) {
-		lua_pushstring(L, "downstream");
-
-		lua_newtable(L);
-		lua_pushstring(L, "status");
-		lua_pushstring(L, "stopped");
-		lua_settable(L, -3);
-
-		struct error *e = diag_last_error(relay_get_diag(relay));
-		if (e != NULL) {
-			lua_pushstring(L, "message");
-			lua_pushstring(L, e->errmsg);
-			lua_settable(L, -3);
-		}
-
 		lua_settable(L, -3);
 	}
 }
diff --git a/test/replication/status.result b/test/replication/status.result
index 9e69f2478..a408d7eb2 100644
--- a/test/replication/status.result
+++ b/test/replication/status.result
@@ -172,6 +172,10 @@ replica.upstream == nil
 ---
 - true
 ...
+replica.downstream.status == 'follow'
+---
+- true
+...
 replica.downstream.vclock[master_id] == box.info.vclock[master_id]
 ---
 - true
diff --git a/test/replication/status.test.lua b/test/replication/status.test.lua
index cfdf6acdb..8a82fe9ae 100644
--- a/test/replication/status.test.lua
+++ b/test/replication/status.test.lua
@@ -64,6 +64,7 @@ replica.uuid == box.space._cluster:get(replica_id)[2]
 -- replica.lsn == box.info.vclock[replica_id]
 replica.lsn == 0
 replica.upstream == nil
+replica.downstream.status == 'follow'
 replica.downstream.vclock[master_id] == box.info.vclock[master_id]
 replica.downstream.vclock[replica_id] == box.info.vclock[replica_id]
 
-- 
2.17.2 (Apple Git-113)