MB-48047:[BP] Prevent socket close on clusterEncryptionLevel

change

When clusterEncryptionLevel changes from strict to other setting or vice
versa we restart web server.
On occasion the web server is restarted prior to settings API response.

Backports change related to MB-47663.

Reviewed-on: http://review.couchbase.org/c/ns_server/+/159808

Change-Id: I283d8419b923640a5479f92bc8196704c064db81
Reviewed-on: http://review.couchbase.org/c/ns_server/+/164952
Tested-by: Abhijeeth Nuthan <[email protected]>
Reviewed-by: Timofey Barmin <[email protected]>
Well-Formed: Restriction Checker

Author: anuthan

src/menelaus_web_settings.erl

@@ -319,6 +319,9 @@ handle_post(Type, Req) ->
     handle_post(Type, [], Req).
 
 handle_post(Type, Keys, Req) ->
+    %% NOTE: due to a potential restart we need to protect
+    %%       ourselves from 'death signal' of parent
+    erlang:process_flag(trap_exit, true),
     case parse_post_data(conf(Type), Keys, mochiweb_request:recv_body(Req),
                          fun is_allowed_setting/1) of
         {ok, ToSet} ->
@@ -332,7 +335,8 @@ handle_post(Type, Keys, Req) ->
             end;
         {error, Errors} ->
             reply_json(Req, {struct, [{errors, Errors}]}, 400)
-    end.
+    end,
+    erlang:exit(normal).
 
 set_keys_in_txn(Cfg, SetFn, ToSet) ->
     {NewCfg, AuditProps} =