Add osiris:get_stat/1 API

To get the first and committed offset from any member of a stream

Author: kjnilsson

src/osiris.erl

@@ -25,7 +25,8 @@
          start_writer/1,
          start_replica/2,
          delete_cluster/1,
-         configure_logger/1]).
+         configure_logger/1,
+         get_stats/1]).
 
 %% holds static or rarely changing fields
 -record(cfg, {}).
@@ -273,3 +274,12 @@ start_replicas(Config, [Node | Nodes], ReplicaPids) ->
 configure_logger(Module) ->
     persistent_term:put('$osiris_logger', Module).
 
+-spec get_stats(pid()) -> #{committed_chunk_id => integer(),
+                            first_chunk_id => integer()}.
+get_stats(Pid)
+    when node(Pid) =:= node() ->
+    {ok, #{offset_ref := ORef}} = gen:call(Pid, '$gen_call', get_reader_context),
+    #{committed_chunk_id => atomics:get(ORef, 1),
+      first_chunk_id => atomics:get(ORef, 2)};
+get_stats(Pid) when is_pid(Pid) ->
+    erpc:call(node(Pid), ?MODULE, ?FUNCTION_NAME, [Pid]).

test/osiris_SUITE.erl

@@ -636,12 +636,11 @@ cluster_restart(Config) ->
 
     timer:sleep(1),
     RangesBeforeRecovery =
-    [ erpc:call(node(P),
-                fun () ->
-                        {ok, #{offset_ref := ORef}} = gen:call(P, '$gen_call', get_reader_context),
-                        {atomics:get(ORef, 2), atomics:get(ORef, 1)}
-                end)
-      || P <- [Leader, Replica1, Replica2]],
+    [begin
+         #{committed_chunk_id := E,
+           first_chunk_id := S} = osiris:get_stats(P),
+         {S, E}
+     end || P <- [Leader, Replica1, Replica2]],
 
     ?assertEqual([{0,0}, {0,0}, {0,0}], RangesBeforeRecovery),
 
@@ -655,12 +654,11 @@ cluster_restart(Config) ->
     %% get all log ranges after recovery for each member and validate they are all
     %% the same
     RangesAfterRecovery =
-    [ erpc:call(node(P),
-                fun () ->
-                        {ok, #{offset_ref := ORef}} = gen:call(P, '$gen_call', get_reader_context),
-                        {atomics:get(ORef, 2), atomics:get(ORef, 1)}
-                end)
-      || P <- [Leader1, ReplicaPid1, ReplicaPid2]],
+    [begin
+         #{committed_chunk_id := E,
+           first_chunk_id := S} = osiris:get_stats(P),
+         {S, E}
+     end || P <- [Leader1, ReplicaPid1, ReplicaPid2]],
     ?assertEqual([{0,0}, {0,0}, {0,0}], RangesAfterRecovery),
     ct:pal("~p ~p", [RangesBeforeRecovery, RangesAfterRecovery]),
     ok = validate_log_offset_reader(Leader1, [{0, <<"before-restart">>}]),