ircd::conf: Add feature to toggle whether conf item is persisted in a db.

include/ircd/conf.h

@@ -51,6 +51,7 @@ namespace ircd::conf
 	extern callbacks<void (item<> &)> on_init;
 
 	bool exists(const string_view &key);
+	bool persists(const string_view &key);
 	string_view get(const string_view &key, const mutable_buffer &out);
 	bool set(const string_view &key, const string_view &value);
 	bool set(std::nothrow_t, const string_view &key, const string_view &value);

ircd/conf.cc

@@ -125,6 +125,21 @@ catch(const std::out_of_range &e)
 	};
 }
 
+bool
+ircd::conf::persists(const string_view &key)
+try
+{
+	const auto &item(*items.at(key));
+	return item.feature.get("persist", true);
+}
+catch(const std::out_of_range &e)
+{
+	throw not_found
+	{
+		"Conf item '%s' is not available", key
+	};
+}
+
 bool
 ircd::conf::exists(const string_view &key)
 {

ircd/db.cc

@@ -336,6 +336,7 @@ ircd::db::open_check
 {
 	{ "name",     "ircd.db.open.check"  },
 	{ "default",  false                 },
+	{ "persist",  false                 },
 };
 
 /// Conf item determines the recovery mode to use when opening any database.
@@ -365,6 +366,7 @@ ircd::db::open_recover
 {
 	{ "name",     "ircd.db.open.recover"  },
 	{ "default",  "absolute"              },
+	{ "persist",  false                   },
 };
 
 void

ircd/fs.cc

@@ -981,6 +981,7 @@ ircd::fs::aio::enable
 {
 	{ "name",     "ircd.fs.aio.enable"  },
 	{ "default",  true                  },
+	{ "persist",  false                 },
 };
 
 /// Global stats structure
@@ -1049,6 +1050,7 @@ ircd::fs::fd::opts::direct_io_enable
 {
 	{ "name",     "ircd.fs.fd.direct_io_enable"  },
 	{ "default",  true                           },
+	{ "persist",  false                          },
 };
 
 #ifdef __linux__

ircd/ircd.cc

@@ -22,6 +22,7 @@ ircd::debugmode
 {
 	{ "name",     "ircd.debugmode"  },
 	{ "default",  false             },
+	{ "persist",  false             },
 };
 
 /// Sets up the IRCd and its main context, then returns without blocking.

ircd/mods.cc

@@ -23,6 +23,7 @@ ircd::mods::enable
 {
 	{ "name",     "ircd.mods.enable"  },
 	{ "default",  true                },
+	{ "persist",  false               },
 };
 
 decltype(ircd::mods::autoload)
@@ -30,6 +31,7 @@ ircd::mods::autoload
 {
 	{ "name",     "ircd.mods.autoload"  },
 	{ "default",  true                  },
+	{ "persist",  false                 },
 };
 
 //

ircd/net.cc

@@ -896,6 +896,7 @@ ircd::net::listen
 {
 	{ "name",     "ircd.net.listen" },
 	{ "default",  true              },
+	{ "persist",  false             },
 };
 
 //

modules/s_conf.cc

@@ -132,6 +132,11 @@ noexcept try
 	if(runlevel == runlevel::START && !conf::exists(key))
 		return;
 
+	// Conf items marked with a persist=false property are not read from
+	// the conf room into the item, even if the value exists in the room.
+	if(conf::exists(key) && !conf::persists(key))
+		return;
+
 	log::debug
 	{
 		"Updating conf [%s] => %s", key, value
@@ -247,13 +252,7 @@ create_conf_room(const m::event &,
                  m::vm::eval &)
 {
 	m::create(conf_room_id, m::me.user_id);
-
-	for(const auto &p : conf::items)
-	{
-		const auto &key{p.first};
-		const auto &item{p.second}; assert(item);
-		create_conf_item(key, *item);
-	}
+	rehash_conf({}, true);
 }
 
 const m::hookfn<m::vm::eval &>
@@ -283,6 +282,13 @@ rehash_conf(const string_view &prefix,
 			continue;
 
 		const auto &item{p.second}; assert(item);
+
+		// Conf items marked with a persist=false property are not written
+		// to the conf room.
+		if(!item->feature.get("persist", true))
+			continue;
+
+		// Use the `existing` argument to toggle a force-overwrite
 		if(!existing)
 			if(state.has("ircd.conf.item", key))
 				continue;