Add prep_stop callback

src/classy.erl

@@ -32,9 +32,11 @@ This MFA can contain calls to various @code{classy:on_...} functions.
         , the_cluster/0
         , node_sets/0
         , prep_stop/0
+        , prep_stop/1
         ]).
 
 -export([ on_node_init/2
+        , on_prep_stop/2
         , on_create_cluster/2
         , on_create_site/2
         , on_peer_connection_change/2
@@ -286,6 +288,13 @@ node_of_site(Site, OnlyConnected) ->
       {error, {unknown_node, Site}}
   end.
 
+-doc """
+Equivalent to @code{prep_stop(shutdown)}.
+""".
+-spec prep_stop() -> ok.
+prep_stop() ->
+  prep_stop(shutdown).
+
 -doc """
 This function can be called before the Erlang node shuts down.
 
@@ -294,8 +303,9 @@ without blocking the application controller.
 
 This is helpful if changing the run level involves stopping or starting OTP applications.
 """.
--spec prep_stop() -> ok.
-prep_stop() ->
+-spec prep_stop(term()) -> ok.
+prep_stop(Reason) ->
+  classy_node:prep_stop(Reason),
   classy_sup:prep_stop().
 
 %%--------------------------------------------------------------------------------
@@ -501,6 +511,16 @@ and can be used to override the default cluster and site initialization logic.
 on_node_init(Hook, Prio) ->
   classy_hook:insert(?on_node_init, Hook, Prio).
 
+-doc """
+Register a hook that is executed before shutting down business applications.
+
+It is called before classy application starts the shutdown procedure,
+as well when the site leaves a cluster or heals from a network partition.
+""".
+-spec on_prep_stop(fun((_Reason) -> _), classy_hook:prio()) -> classy_hook:hook().
+on_prep_stop(Hook, Prio) ->
+  classy_hook:insert(?on_prep_stop, Hook, Prio).
+
 -doc """
 This callback is executed once per cluster by the site that originally creates the cluster.
 """.

src/classy_hook.erl

@@ -230,6 +230,7 @@ safe_apply(HookPoint, Fun, Args) ->
           #{ reason    => Err
            , hook      => Fun
            , hookpoint => HookPoint
+           , args      => Args
            }),
       error
   end.

src/classy_internal.hrl

@@ -25,6 +25,7 @@
 -define(min_hook_prio, -?max_hook_prio).
 
 -define(on_node_init, on_node_init).
+-define(on_prep_stop, on_prep_stop).
 -define(on_create_cluster, on_create_cluster).
 -define(on_create_site, on_create_site).
 -define(on_peer_connection_status_change, on_peer_connection_status_change).

src/classy_lib.erl

@@ -107,7 +107,11 @@ safe_apply(Module, Function, Args) ->
 -doc """
 Apply a function in a separate process with a timeout.
 """.
--spec safe_apply_with_timeout(callback(), timeout()) -> {ok, term()} | wrapped_exception() | {error, timeout}.
+-spec safe_apply_with_timeout(callback(), timeout()) ->
+        {ok, term()} |
+        wrapped_exception() |
+        {error, {timeout, Info}} when
+    Info :: list() | undefined.
 safe_apply_with_timeout(Callback, Timeout) ->
   {Pid, MRef} = spawn_monitor(
                   fun() ->
@@ -117,9 +121,10 @@ safe_apply_with_timeout(Callback, Timeout) ->
     {'DOWN', MRef, process, Pid, Reason} ->
       Reason
   after Timeout ->
+      Info = process_info(Pid, [current_stacktrace]),
       demonitor(MRef, [flush]),
       exit(Pid, kill),
-      {error, timeout}
+      {error, {timeout, Info}}
   end.
 
 -doc """

src/classy_node.erl

@@ -20,6 +20,7 @@ Management of the local site and node.
         , peer_info/0
         , node_of_site/2
         , n_restarts/1
+        , prep_stop/1
         ]).
 
 %% behavior callbacks:
@@ -290,7 +291,7 @@ terminate(Reason, _S) ->
          }),
   classy_table:flush(?globals),
   classy_table:flush(?site_info),
-  sync_set_run_level(?stopped),
+  prep_stop(shutdown, infinity),
   persistent_term:erase(?pt_node_sets),
   persistent_term:erase(?pt_site_sets),
   persistent_term:erase(?pt_site),
@@ -346,6 +347,10 @@ notify_mem_deltas(Cluster, Deltas) ->
                     , data    = Deltas
                     }).
 
+-doc false.
+prep_stop(Reason) ->
+  classy_hook:foreach(?on_prep_stop, [Reason]).
+
 %%================================================================================
 %% Internal functions
 %%================================================================================
@@ -460,7 +465,7 @@ do_join_node(Node, Cluster, Remote, MemData, JoinIntent, S0) ->
   end.
 
 on_leave(S = #s{cluster = Cluster, site = Local}, Intent) ->
-  sync_set_run_level(?stopped),
+  prep_stop(leave, infinity),
   %% Sync with the business apps:
   classy_table:delete(?globals, ?the_cluster),
   classy_hook:foreach(?on_post_kick, [Cluster, Local, Intent]),
@@ -570,8 +575,9 @@ start_old_clusters(Site) ->
     end,
     classy_membership:known_clusters(Site)).
 
-sync_set_run_level(Level) ->
-  classy_rl_changer:set_sync(Level, infinity).
+prep_stop(Reason, Timeout) ->
+  prep_stop(Reason),
+  classy_rl_changer:set_sync(?stopped, Timeout).
 
 the_cluster() ->
   case classy_table:lookup(?globals, ?the_cluster) of
@@ -620,7 +626,7 @@ apply_deltas_with_effects(Deltas, S0 = #s{cluster = Cluster, site = Local}) ->
 
 -spec on_remote_restart(#s{}) -> {ok, #s{}}.
 on_remote_restart(S) ->
-  classy_rl_changer:set_sync(?stopped, 120_000),
+  prep_stop(remote_restart, 120_000),
   {ok, adjust_run_level(S)}.
 
 -spec import_deltas(#{classy:site() => classy_membership:update()}, #s{}) ->

test/classy_SUITE.erl

@@ -405,18 +405,18 @@ t_061_run_level_timeouts(_) ->
        ?assertMatch(
           [ %% Advance:
             #{f := ?stopped, t := ?single}
-          , #{?snk_kind := ?classy_hook_failure, reason := {error, timeout}}
+          , #{?snk_kind := ?classy_hook_failure, reason := {error, {timeout, _}}}
           , #{f := ?single, t := ?cluster}
-          , #{?snk_kind := ?classy_hook_failure, reason := {error, timeout}}
+          , #{?snk_kind := ?classy_hook_failure, reason := {error, {timeout, _}}}
           , #{f := ?cluster, t := ?quorum}
-          , #{?snk_kind := ?classy_hook_failure, reason := {error, timeout}}
+          , #{?snk_kind := ?classy_hook_failure, reason := {error, {timeout, _}}}
             %% Retard:
           , #{f := ?quorum, t := ?cluster}
-          , #{?snk_kind := ?classy_hook_failure, reason := {error, timeout}}
+          , #{?snk_kind := ?classy_hook_failure, reason := {error, {timeout, _}}}
           , #{f := ?cluster, t := ?single}
-          , #{?snk_kind := ?classy_hook_failure, reason := {error, timeout}}
+          , #{?snk_kind := ?classy_hook_failure, reason := {error, {timeout, _}}}
           , #{f := ?single, t := ?stopped}
-          , #{?snk_kind := ?classy_hook_failure, reason := {error, timeout}}
+          , #{?snk_kind := ?classy_hook_failure, reason := {error, {timeout, _}}}
           ],
           Events3)
      end,