From 948887668e0e61ea16204c8602e421f0f5451165 Mon Sep 17 00:00:00 2001
From: Diana Parra Corbacho <dparracorbac@vmware.com>
Date: Tue, 11 Oct 2022 09:18:31 +0200
Subject: [PATCH] khepri_cluster: Accept `machine_config` in Ra server config

It is now possible to pass state machine arguments in the Ra server
config. This is handy to e.g. set the snapshot interval:

    RaServerConfig = #{cluster_name => StoreId,
                       machine_config => #{snapshot_interval => 10000}},
    khepri:start(RaSystem, RaServerConfig).
---
 src/khepri_cluster.erl | 10 ++++--
 test/cluster_SUITE.erl | 70 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/src/khepri_cluster.erl b/src/khepri_cluster.erl
index da94dfee..9a2f0e62 100644
--- a/src/khepri_cluster.erl
+++ b/src/khepri_cluster.erl
@@ -1118,8 +1118,14 @@ complete_ra_server_config(#{cluster_name := StoreId,
                       end,
 
     UId = ra:new_uid(ra_lib:to_binary(StoreId)),
-    MachineConfig = #{store_id => StoreId,
-                      member => Member},
+    MachineConfig0 = case RaServerConfig of
+                         #{machine_config := MachineConfig00} ->
+                             MachineConfig00;
+                         _ ->
+                             #{}
+                     end,
+    MachineConfig = MachineConfig0#{store_id => StoreId,
+                                    member => Member},
     Machine = {module, khepri_machine, MachineConfig},
     RaServerConfig2#{uid => UId,
                      log_init_args => #{uid => UId},
diff --git a/test/cluster_SUITE.erl b/test/cluster_SUITE.erl
index 2385f308..9d345061 100644
--- a/test/cluster_SUITE.erl
+++ b/test/cluster_SUITE.erl
@@ -13,6 +13,7 @@
 
 -include("include/khepri.hrl").
 -include("src/khepri_error.hrl").
+-include("src/khepri_machine.hrl").
 
 -export([all/0,
          groups/0,
@@ -39,7 +40,8 @@
          can_use_default_store_on_single_node/1,
          can_start_store_in_specified_data_dir_on_single_node/1,
          handle_leader_down_on_three_node_cluster_command/1,
-         handle_leader_down_on_three_node_cluster_response/1]).
+         handle_leader_down_on_three_node_cluster_response/1,
+         can_set_snapshot_interval/1]).
 
 all() ->
     [can_start_a_single_node,
@@ -56,7 +58,8 @@ all() ->
      can_use_default_store_on_single_node,
      can_start_store_in_specified_data_dir_on_single_node,
      handle_leader_down_on_three_node_cluster_command,
-     handle_leader_down_on_three_node_cluster_response].
+     handle_leader_down_on_three_node_cluster_response,
+     can_set_snapshot_interval].
 
 groups() ->
     [].
@@ -80,7 +83,8 @@ init_per_testcase(Testcase, Config)
        Testcase =:= can_restart_a_single_node_with_ra_server_config orelse
        Testcase =:= fail_to_start_with_bad_ra_server_config orelse
        Testcase =:= initial_members_are_ignored orelse
-       Testcase =:= fail_to_join_non_existing_node ->
+       Testcase =:= fail_to_join_non_existing_node orelse
+       Testcase =:= can_set_snapshot_interval ->
     setup_node(),
     {ok, _} = application:ensure_all_started(khepri),
     Props = helpers:start_ra_system(Testcase),
@@ -1091,6 +1095,66 @@ can_start_store_in_specified_data_dir_on_single_node(_Config) ->
     helpers:remove_store_dir(DataDir),
     ?assertNot(filelib:is_dir(DataDir)).
 
+can_set_snapshot_interval(Config) ->
+    Node = node(),
+    #{Node := #{ra_system := RaSystem}} = ?config(ra_system_props, Config),
+    StoreId = RaSystem,
+
+    ct:pal("Start database"),
+    RaServerConfig = #{cluster_name => StoreId,
+                       machine_config => #{snapshot_interval => 3}},
+    ?assertEqual(
+       {ok, StoreId},
+       khepri:start(RaSystem, RaServerConfig)),
+
+    ct:pal("Verify applied command count is 0"),
+    ?assertEqual(
+       #{},
+       khepri_machine:process_query(
+         StoreId,
+         fun(#khepri_machine{metrics = Metrics}) -> Metrics end,
+         #{})),
+
+    ct:pal("Use database after starting it"),
+    ?assertEqual(ok, khepri:put(StoreId, [foo], value1)),
+
+    ct:pal("Verify applied command count is 1"),
+    ?assertEqual(
+       #{applied_command_count => 1},
+       khepri_machine:process_query(
+         StoreId,
+         fun(#khepri_machine{metrics = Metrics}) -> Metrics end,
+         #{})),
+
+    ct:pal("Use database after starting it"),
+    ?assertEqual(ok, khepri:put(StoreId, [foo], value1)),
+
+    ct:pal("Verify applied command count is 2"),
+    ?assertEqual(
+       #{applied_command_count => 2},
+       khepri_machine:process_query(
+         StoreId,
+         fun(#khepri_machine{metrics = Metrics}) -> Metrics end,
+         #{})),
+
+    ct:pal("Use database after starting it"),
+    ?assertEqual(ok, khepri:put(StoreId, [foo], value1)),
+
+    ct:pal("Verify applied command count is 0"),
+    ?assertEqual(
+       #{},
+       khepri_machine:process_query(
+         StoreId,
+         fun(#khepri_machine{metrics = Metrics}) -> Metrics end,
+         #{})),
+
+    ct:pal("Stop database"),
+    ?assertEqual(
+       ok,
+       khepri:stop(StoreId)),
+
+    ok.
+
 %% -------------------------------------------------------------------
 %% Internal functions
 %% -------------------------------------------------------------------