Add src/hyperkitty_sup.erl

src/hyperkitty_sup.erl

@@ -0,0 +1,74 @@
+%%%-------------------------------------------------------------------
+%%% @doc HK-CORE :: root supervisor.
+%%%
+%%% Implements the `<otp_architecture>' hierarchy exactly:
+%%%
+%%%   hyperkitty_sup
+%%%     +-- hk_event_sup       (started first: everything else can publish immediately)
+%%%     +-- hk_messaging_sup
+%%%     +-- hk_browser_sup
+%%%     +-- hk_agent_sup
+%%%     +-- hk_search_sup
+%%%     +-- hk_api_sup         (started after every plane it exposes)
+%%%     +-- hk_frontend_sup
+%%%
+%%% `rest_for_one': if an earlier-listed subsystem crashes, every
+%%% subsystem *after* it in this list is restarted too, because they
+%%% may depend on it (e.g. `hk_api_sup' talks to all of `hk_browser_sup',
+%%% `hk_agent_sup', `hk_search_sup', `hk_messaging_sup', and
+%%% `hk_event_sup'; if `hk_event_sup' restarts, callers that publish
+%%% events don't get an error, but every listener that had subscribed
+%%% to the old `hk_event_bus' has silently lost that subscription and
+%%% must resubscribe -- `hk_api_sup' restarting alongside it forces
+%%% every open WebSocket to reconnect and pick that back up, rather
+%%% than leaving the frontend silently stale). Subsystems listed
+%%% *before* the one that crashed are left running, so a browser
+%%% crash never disturbs messaging or the event log, and an agent
+%%% crash never disturbs the browser plane.
+%%%
+%%% `intensity'/`period' are a modest bump over OTP's typical default
+%%% (3/5) to 8/10. The real defense against a mid-tree supervisor's
+%%% *nested* children not having released their registered names yet
+%%% (see `hk_sup_util' -- every registered-name `start_link/0' in
+%%% this application waits for the old holder to actually die and
+%%% retries once, rather than surfacing that transient race as a
+%%% start error) lives in `hk_sup_util:start_link_retry/1', not in
+%%% this number; this headroom just tolerates the occasional
+%%% legitimate extra restart without weakening the check's real
+%%% purpose of catching a genuinely crash-looping child.
+%%% @end
+%%%-------------------------------------------------------------------
+-module(hyperkitty_sup).
+-behaviour(supervisor).
+
+-export([start_link/0]).
+-export([init/1]).
+
+-define(SERVER, ?MODULE).
+
+start_link() ->
+    supervisor:start_link({local, ?SERVER}, ?MODULE, []).
+
+init([]) ->
+    SupFlags = #{strategy => rest_for_one, intensity => 8, period => 10},
+    ChildSpecs = [
+        sup_child(hk_event_sup),
+        sup_child(hk_messaging_sup),
+        sup_child(hk_browser_sup),
+        sup_child(hk_agent_sup),
+        sup_child(hk_search_sup),
+        worker_child(hk_health),
+        sup_child(hk_api_sup),
+        sup_child(hk_frontend_sup)
+    ],
+    {ok, {SupFlags, ChildSpecs}}.
+
+%%% internal
+
+sup_child(Mod) ->
+    #{id => Mod, start => {Mod, start_link, []}, restart => permanent,
+      shutdown => infinity, type => supervisor, modules => [Mod]}.
+
+worker_child(Mod) ->
+    #{id => Mod, start => {Mod, start_link, []}, restart => permanent,
+      shutdown => 5000, type => worker, modules => [Mod]}.