From 234641ccf49b64f3a8d135b20bf634ba5ce9174a Mon Sep 17 00:00:00 2001
From: Tobias Lindahl <tobias@happihacking.com>
Date: Tue, 26 Oct 2021 09:54:41 +0200
Subject: [PATCH] refactor(persistent_sessions): don't start session sup when
 disabled

---
 apps/emqx/src/emqx_persistent_session_sup.erl | 38 +++++++++----------
 apps/emqx/src/emqx_sup.erl                    |  3 +-
 2 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/apps/emqx/src/emqx_persistent_session_sup.erl b/apps/emqx/src/emqx_persistent_session_sup.erl
index ddb72bf11..1a1c5df5f 100644
--- a/apps/emqx/src/emqx_persistent_session_sup.erl
+++ b/apps/emqx/src/emqx_persistent_session_sup.erl
@@ -26,29 +26,29 @@ start_link() ->
     supervisor:start_link({local, ?MODULE}, ?MODULE, []).
 
 init([]) ->
-    case emqx_persistent_session:is_store_enabled() of
-        false ->
-            {ok, {{one_for_all, 0, 1}, []}};
-        true ->
-            %% We want this supervisor to own the table for restarts
-            SessionTab = emqx_session_router:create_init_tab(),
+    %% We want this supervisor to own the table for restarts
+    SessionTab = emqx_session_router:create_init_tab(),
 
-            %% Resume worker sup
-            ResumeSup = #{id => router_worker_sup,
-                          start => {emqx_session_router_worker_sup, start_link, [SessionTab]},
-                          restart => permanent,
-                          shutdown => 2000,
-                          type => supervisor,
-                          modules => [emqx_session_router_worker_sup]},
+    %% Resume worker sup
+    ResumeSup = #{id => router_worker_sup,
+                  start => {emqx_session_router_worker_sup, start_link, [SessionTab]},
+                  restart => permanent,
+                  shutdown => 2000,
+                  type => supervisor,
+                  modules => [emqx_session_router_worker_sup]},
 
-            SessionRouterPool = emqx_pool_sup:spec(session_router_pool,
-                                                   [session_router_pool, hash,
-                                                    {emqx_session_router, start_link, []}]),
+    SessionRouterPool = emqx_pool_sup:spec(session_router_pool,
+                                           [session_router_pool, hash,
+                                            {emqx_session_router, start_link, []}]),
 
-            GCWorker = child_spec(emqx_persistent_session_gc, worker),
+    GCWorker = child_spec(emqx_persistent_session_gc, worker),
 
-            {ok, {{one_for_all, 0, 1}, [ResumeSup, SessionRouterPool, GCWorker]}}
-    end.
+    Spec = #{ strategy  => one_for_all
+            , intensity => 0
+            , period    => 1
+            },
+
+    {ok, {Spec, [ResumeSup, SessionRouterPool, GCWorker]}}.
 
 child_spec(Mod, worker) ->
     #{id => Mod,
diff --git a/apps/emqx/src/emqx_sup.erl b/apps/emqx/src/emqx_sup.erl
index 432bc15c7..9c8af33d6 100644
--- a/apps/emqx/src/emqx_sup.erl
+++ b/apps/emqx/src/emqx_sup.erl
@@ -68,7 +68,8 @@ init([]) ->
     SessionSup = child_spec(emqx_persistent_session_sup, supervisor),
     CMSup = child_spec(emqx_cm_sup, supervisor),
     SysSup = child_spec(emqx_sys_sup, supervisor),
-    Children = [KernelSup, SessionSup] ++
+    Children = [KernelSup] ++
+               [SessionSup || emqx_persistent_session:is_store_enabled()] ++
                [RouterSup || emqx_boot:is_enabled(router)] ++
                [BrokerSup || emqx_boot:is_enabled(broker)] ++
                [CMSup || emqx_boot:is_enabled(broker)] ++