ircd: Support read-only and write-avoid modes via conf item / command line.

construct/construct.cc

@@ -34,6 +34,8 @@ bool nodirect;
 bool noaio;
 bool no6;
 bool norun;
+bool read_only;
+bool write_avoid;
 const char *execute;
 lgetopt opts[] =
 {
@@ -52,6 +54,8 @@ lgetopt opts[] =
 	{ "noaio",      &noaio,         lgetopt::BOOL,    "Disable the AIO interface in favor of traditional syscalls. " },
 	{ "no6",        &no6,           lgetopt::BOOL,    "Disable IPv6 operations" },
 	{ "norun",      &norun,         lgetopt::BOOL,    "[debug & testing only] Initialize but never run the event loop." },
+	{ "ro",         &read_only,     lgetopt::BOOL,    "Read-only mode. No writes to database allowed." },
+	{ "wa",         &write_avoid,   lgetopt::BOOL,    "Like read-only mode, but writes permitted if triggered." },
 	{ nullptr,      nullptr,        lgetopt::STRING,  nullptr },
 };
 
@@ -257,6 +261,13 @@ enable_coredumps()
 void
 applyargs()
 {
+	if(read_only)
+		ircd::read_only.set("true");
+
+	// read_only implies write_avoid.
+	if(write_avoid || read_only)
+		ircd::write_avoid.set("true");
+
 	if(debugmode)
 		ircd::debugmode.set("true");
 	else

include/ircd/ircd.h

@@ -74,4 +74,6 @@ namespace ircd
 
 	extern conf::item<bool> restart;
 	extern conf::item<bool> debugmode;
+	extern conf::item<bool> read_only;
+	extern conf::item<bool> write_avoid;
 }

ircd/db.cc

@@ -183,7 +183,12 @@ try
 		fs::path(fs::DB)
 	};
 
-	if(fs::mkdir(dbdir))
+	if(!fs::is_dir(dbdir) && (ircd::read_only || ircd::write_avoid))
+		log::warning
+		{
+			log, "Not creating database directory `%s' in read-only/write-avoid mode.", dbdir
+		};
+	else if(fs::mkdir(dbdir))
 		log::notice
 		{
 			log, "Created new database directory at `%s'", dbdir
@@ -964,7 +969,7 @@ try
 }
 ,read_only
 {
-	false
+	ircd::read_only
 }
 ,env
 {
@@ -1213,7 +1218,7 @@ try
 
 	// If the directory does not exist, though rocksdb will create it, we can
 	// avoid scaring the user with an error log message if we just do that..
-	if(opts->create_if_missing && !fs::is_dir(path))
+	if(opts->create_if_missing && !fs::is_dir(path) && !ircd::write_avoid)
 		fs::mkdir(path);
 
 	// Announce attempt before usual point where exceptions are thrown
@@ -1225,6 +1230,14 @@ try
 		columns.size()
 	};
 
+	if(read_only)
+		log::warning
+		{
+			log, "Database \"%s\" @ `%s' will be opened in read-only mode.",
+			this->name,
+			path,
+		};
+
 	// Open DB into ptr
 	rocksdb::DB *ptr;
 	if(read_only)
@@ -7285,14 +7298,14 @@ ircd::db::make_dbopts(std::string optstr,
 	// RocksDB doesn't parse a read_only option, so we allow that to be added
 	// to open the database as read_only and then remove that from the string.
 	if(read_only)
-		*read_only = optstr_find_and_remove(optstr, "read_only=true;"s);
+		*read_only |= optstr_find_and_remove(optstr, "read_only=true;"s);
 	else
 		optstr_find_and_remove(optstr, "read_only=true;"s);
 
 	// We also allow the user to specify fsck=true to run a repair operation on
 	// the db. This may be expensive to do by default every startup.
 	if(fsck)
-		*fsck = optstr_find_and_remove(optstr, "fsck=true;"s);
+		*fsck |= optstr_find_and_remove(optstr, "fsck=true;"s);
 	else
 		optstr_find_and_remove(optstr, "fsck=true;"s);
 

ircd/ircd.cc

@@ -17,6 +17,22 @@ namespace ircd
 	void main() noexcept;
 }
 
+decltype(ircd::write_avoid)
+ircd::write_avoid
+{
+	{ "name",     "ircd.write_avoid"  },
+	{ "default",  false               },
+	{ "persist",  false               },
+};
+
+decltype(ircd::read_only)
+ircd::read_only
+{
+	{ "name",     "ircd.read_only"  },
+	{ "default",  false             },
+	{ "persist",  false             },
+};
+
 decltype(ircd::debugmode)
 ircd::debugmode
 {

ircd/logger.cc

@@ -109,6 +109,9 @@ ircd::log::init()
 	if(!ircd::debugmode)
 		console_disable(level::DEBUG);
 
+	if(ircd::write_avoid)
+		return;
+
 	mkdir();
 }
 

ircd/m.cc

@@ -48,7 +48,8 @@ try
 	std::make_unique<modules>()
 }
 {
-	presence::set(me, "online", me_online_status_msg);
+	if(!ircd::write_avoid)
+		presence::set(me, "online", me_online_status_msg);
 
 	if(room::state::disable_history)
 		log::warning
@@ -83,7 +84,7 @@ noexcept try
 {
 	m::sync::pool.join();
 
-	if(!std::current_exception())
+	if(!std::uncaught_exceptions() && !ircd::write_avoid)
 		presence::set(me, "offline", me_offline_status_msg);
 }
 catch(const m::error &e)

ircd/sodium.cc

@@ -121,7 +121,7 @@ try
 		reinterpret_cast<char *>(key.get()), SK_SZ
 	};
 
-	if(!fs::exists(filename))
+	if(!fs::exists(filename) && !ircd::write_avoid)
 	{
 		throw_on_error
 		{

modules/s_keys.cc

@@ -90,7 +90,7 @@ init_my_tls_crt()
 		fs::path_string(certificate_path_parts)
 	};
 
-	if(!fs::exists(private_key_file))
+	if(!fs::exists(private_key_file) && !ircd::write_avoid)
 	{
 		log::warning
 		{
@@ -121,7 +121,7 @@ init_my_tls_crt()
 */
 
 	const json::object config{};
-	if(!fs::exists(cert_file))
+	if(!fs::exists(cert_file) && !ircd::write_avoid)
 	{
 		const json::object &certificate
 		{
@@ -248,7 +248,7 @@ init_my_ed25519()
 		})
 	};
 
-	if(fs::exists(sk_file))
+	if(fs::exists(sk_file) || ircd::write_avoid)
 		log::info
 		{
 			m::log, "Using ed25519 secret key @ `%s'", sk_file