feat(api-ds): provide more information on nonexistent site leave

apps/emqx_durable_storage/src/emqx_ds_replication_layer_meta.erl

@@ -131,7 +131,7 @@
 -type transition() :: {add | del, site()}.
 
 -type update_cluster_result() ::
-    ok
+    {ok, unchanged | [site()]}
     | {error, {nonexistent_db, emqx_ds:db()}}
     | {error, {nonexistent_sites, [site()]}}
     | {error, {too_few_sites, [site()]}}
@@ -449,7 +449,7 @@ allocate_shards_trans(DB) ->
         Allocation
     ).
 
--spec assign_db_sites_trans(emqx_ds:db(), [site()]) -> ok.
+-spec assign_db_sites_trans(emqx_ds:db(), [site()]) -> {ok, [site()]}.
 assign_db_sites_trans(DB, Sites) ->
     Opts = db_config_trans(DB),
     case [S || S <- Sites, mnesia:read(?NODE_TAB, S, read) == []] of
@@ -466,21 +466,22 @@ assign_db_sites_trans(DB, Sites) ->
     %% 2. Ensure that sites are responsible for roughly the same number of shards.
     Shards = mnesia:match_object(?SHARD_TAB, ?SHARD_PAT({DB, '_'}), write),
     Reallocation = compute_allocation(Shards, Sites, Opts),
-    lists:foreach(
+    ok = lists:foreach(
         fun({Record, ReplicaSet}) ->
             ok = mnesia:write(Record#?SHARD_TAB{target_set = ReplicaSet})
         end,
         Reallocation
-    ).
+    ),
+    {ok, Sites}.
 
--spec modify_db_sites_trans(emqx_ds:db(), [transition()]) -> ok.
+-spec modify_db_sites_trans(emqx_ds:db(), [transition()]) -> {ok, unchanged | [site()]}.
 modify_db_sites_trans(DB, Modifications) ->
     Shards = mnesia:match_object(?SHARD_TAB, ?SHARD_PAT({DB, '_'}), write),
     Sites0 = list_db_target_sites(Shards),
     Sites = lists:foldl(fun apply_transition/2, Sites0, Modifications),
     case Sites of
         Sites0 ->
-            ok;
+            {ok, unchanged};
         _Changed ->
             assign_db_sites_trans(DB, Sites)
     end.

apps/emqx_durable_storage/test/emqx_ds_replication_SUITE.erl

@@ -239,7 +239,7 @@ t_rebalance(Config) ->
             ),
 
             %% Scale down the cluster by removing the first node.
-            ?assertEqual(ok, ds_repl_meta(N1, leave_db_site, [?DB, S1])),
+            ?assertMatch({ok, _}, ds_repl_meta(N1, leave_db_site, [?DB, S1])),
             ct:pal("Transitions (~p -> ~p): ~p~n", [
                 Sites, tl(Sites), emqx_ds_test_helpers:transitions(N1, ?DB)
             ]),
@@ -297,12 +297,12 @@ t_join_leave_errors(Config) ->
     ),
     %% NOTE: Leaving a non-existent site is not an error.
     ?assertEqual(
-        ok,
+        {ok, unchanged},
         ds_repl_meta(N1, leave_db_site, [?DB, <<"NO-MANS-SITE">>])
     ),
 
     %% Should be no-op.
-    ?assertEqual(ok, ds_repl_meta(N1, join_db_site, [?DB, S1])),
+    ?assertEqual({ok, unchanged}, ds_repl_meta(N1, join_db_site, [?DB, S1])),
     ?assertEqual([], emqx_ds_test_helpers:transitions(N1, ?DB)),
 
     %% Impossible to leave the last site.
@@ -312,13 +312,13 @@ t_join_leave_errors(Config) ->
     ),
 
     %% "Move" the DB to the other node.
-    ?assertEqual(ok, ds_repl_meta(N1, join_db_site, [?DB, S2])),
-    ?assertEqual(ok, ds_repl_meta(N2, leave_db_site, [?DB, S1])),
+    ?assertMatch({ok, _}, ds_repl_meta(N1, join_db_site, [?DB, S2])),
+    ?assertMatch({ok, _}, ds_repl_meta(N2, leave_db_site, [?DB, S1])),
     ?assertMatch([_ | _], emqx_ds_test_helpers:transitions(N1, ?DB)),
     ?retry(1000, 10, ?assertEqual([], emqx_ds_test_helpers:transitions(N1, ?DB))),
 
     %% Should be no-op.
-    ?assertEqual(ok, ds_repl_meta(N2, leave_db_site, [?DB, S1])),
+    ?assertMatch({ok, _}, ds_repl_meta(N2, leave_db_site, [?DB, S1])),
     ?assertEqual([], emqx_ds_test_helpers:transitions(N1, ?DB)).
 
 t_rebalance_chaotic_converges(init, Config) ->
@@ -457,7 +457,7 @@ t_rebalance_offline_restarts(Config) ->
 
     %% Shut down N3 and then remove it from the DB.
     ok = emqx_cth_cluster:stop_node(N3),
-    ?assertEqual(ok, ds_repl_meta(N1, leave_db_site, [?DB, S3])),
+    ?assertMatch({ok, _}, ds_repl_meta(N1, leave_db_site, [?DB, S3])),
     Transitions = emqx_ds_test_helpers:transitions(N1, ?DB),
     ct:pal("Transitions: ~p~n", [Transitions]),
 

apps/emqx_durable_storage/test/emqx_ds_test_helpers.erl

@@ -164,8 +164,8 @@ apply_stream(DB, NodeStream0, Stream0, N) ->
         ->
             ?tp(notice, test_apply_operation, #{node => Node, operation => Operation, arg => Arg}),
             %% Apply the transition.
-            ?assertEqual(
-                ok,
+            ?assertMatch(
+                {ok, _},
                 ?ON(
                     Node,
                     emqx_ds_replication_layer_meta:Operation(DB, Arg)

apps/emqx_management/src/emqx_mgmt_api_ds.erl

@@ -323,17 +323,11 @@ get_db(get, #{bindings := #{ds := DB}}) ->
     }).
 
 db_replicas(get, #{bindings := #{ds := DB}}) ->
-    Replicas = lists:flatmap(
-        fun(Shard) ->
-            #{replica_set := RS} = emqx_ds_replication_layer_meta:shard_info(DB, Shard),
-            maps:keys(RS)
-        end,
-        emqx_ds_replication_layer_meta:shards(DB)
-    ),
-    ?OK(lists:usort(Replicas));
+    Replicas = emqx_ds_replication_layer_meta:db_sites(DB),
+    ?OK(Replicas);
 db_replicas(put, #{bindings := #{ds := DB}, body := Sites}) ->
     case update_db_sites(DB, Sites, rest) of
-        ok ->
+        {ok, _} ->
             {202, <<"OK">>};
         {error, Description} ->
             ?BAD_REQUEST(400, Description)
@@ -341,39 +335,43 @@ db_replicas(put, #{bindings := #{ds := DB}, body := Sites}) ->
 
 db_replica(put, #{bindings := #{ds := DB, site := Site}}) ->
     case join(DB, Site, rest) of
-        ok ->
+        {ok, _} ->
             {202, <<"OK">>};
         {error, Description} ->
             ?BAD_REQUEST(400, Description)
     end;
 db_replica(delete, #{bindings := #{ds := DB, site := Site}}) ->
     case leave(DB, Site, rest) of
-        ok ->
+        {ok, Sites} when is_list(Sites) ->
             {202, <<"OK">>};
+        {ok, unchanged} ->
+            ?NOT_FOUND(<<"Site is not part of replica set">>);
         {error, Description} ->
             ?BAD_REQUEST(400, Description)
     end.
 
 -spec update_db_sites(emqx_ds:db(), [emqx_ds_replication_layer_meta:site()], rest | cli) ->
-    ok | {error, binary()}.
+    {ok, [emqx_ds_replication_layer_meta:site()]} | {error, _}.
 update_db_sites(DB, Sites, Via) when is_list(Sites) ->
-    ?SLOG(warning, #{
+    ?SLOG(notice, #{
         msg => "durable_storage_rebalance_request", ds => DB, sites => Sites, via => Via
     }),
     meta_result_to_binary(emqx_ds_replication_layer_meta:assign_db_sites(DB, Sites));
 update_db_sites(_, _, _) ->
     {error, <<"Bad type">>}.
 
--spec join(emqx_ds:db(), emqx_ds_replication_layer_meta:site(), rest | cli) -> ok | {error, _}.
+-spec join(emqx_ds:db(), emqx_ds_replication_layer_meta:site(), rest | cli) ->
+    {ok, unchanged | [emqx_ds_replication_layer_meta:site()]} | {error, _}.
 join(DB, Site, Via) ->
-    ?SLOG(warning, #{
+    ?SLOG(notice, #{
         msg => "durable_storage_join_request", ds => DB, site => Site, via => Via
     }),
     meta_result_to_binary(emqx_ds_replication_layer_meta:join_db_site(DB, Site)).
 
--spec leave(emqx_ds:db(), emqx_ds_replication_layer_meta:site(), rest | cli) -> ok | {error, _}.
+-spec leave(emqx_ds:db(), emqx_ds_replication_layer_meta:site(), rest | cli) ->
+    {ok, unchanged | [emqx_ds_replication_layer_meta:site()]} | {error, _}.
 leave(DB, Site, Via) ->
-    ?SLOG(warning, #{
+    ?SLOG(notice, #{
         msg => "durable_storage_leave_request", ds => DB, site => Site, via => Via
     }),
     meta_result_to_binary(emqx_ds_replication_layer_meta:leave_db_site(DB, Site)).
@@ -468,8 +466,8 @@ list_shards(DB) ->
      || Shard <- emqx_ds_replication_layer_meta:shards(DB)
     ].
 
-meta_result_to_binary(ok) ->
-    ok;
+meta_result_to_binary({ok, Result}) ->
+    {ok, Result};
 meta_result_to_binary({error, {nonexistent_sites, UnknownSites}}) ->
     Msg = ["Unknown sites: " | lists:join(", ", UnknownSites)],
     {error, iolist_to_binary(Msg)};

apps/emqx_management/test/emqx_mgmt_api_ds_SUITE.erl

@@ -174,6 +174,14 @@ t_leave(_) ->
         request_api(delete, Path)
     ).
 
+t_leave_notfound(_) ->
+    Site = "not_part_of_replica_set",
+    Path = api_path(["ds", "storages", "emqx_persistent_message", "replicas", Site]),
+    ?assertMatch(
+        {error, {_, 404, _}},
+        request_api(delete, Path)
+    ).
+
 parse_error({ok, Code, JSON}) ->
     {ok, Code, emqx_utils_json:decode(JSON)};
 parse_error(Err) ->