File

+
−-- mod_storage_multi
+
−
+
−local storagemanager = require"core.storagemanager";
+
−local backends = module:get_option_array(module.name); -- TODO better name?
+
−
+
−-- TODO migrate data "upwards"
+
−
+
−-- one → one successful write is success
+
−-- all → all backends must report success
+
−-- majority → majority of backends must report success
+
−local policy = module:get_option_string(module.name.."_policy", "all");
+
−
+
−local keyval_store = {};
+
−keyval_store.__index = keyval_store;
+
−
+
−function keyval_store:get(username)
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−	local backends = self.backends;
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−	local data, err;
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−	for i = 1, #backends do
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−		module:log("debug", "%s:%s:get(%q)", tostring(backends[i].get), backends[i]._store, username);
+
−		data, err = backends[i]:get(username);
+
−		if err then
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−			module:log("error", tostring(err));
+
−		elseif not data then
+
−			module:log("debug", "No data returned");
+
−		else
+
−			module:log("debug", "Data returned");
+
−			return data, err;
+
−		end
+
−	end
+
−end
+
−
+
−-- This is where it gets complicated
+
−function keyval_store:set(username, data)
+
−	local backends = self.backends;
+
−	local ok, err, backend;
+
−	local all, one, oks = true, false, 0;
+
−	for i = 1, #backends do
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−		backend = backends[i];
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−		module:log("debug", "%s:%s:set(%q)", tostring(backends[i].get), backends[i].store, username);
+
−		ok, err = backend:set(username, data);
+
−		if not ok then
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−			module:log("error", "Error in storage driver %s: %s", backend.name, tostring(err));
+
−		else
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−			oks = oks + 1;
+
−		end
+
−		one = one or ok; -- At least one successful write
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−		all = all and ok; -- All successful
+
−	end
+
−	if policy == "all" then
+
−		return all, err
+
−	elseif policy == "majority" then
+
−		return oks > (#backends/2), err;
+
−	end
+
−	-- elseif policy == "one" then
+
−	return one, err;
+
−end
+
−
+
−local stores = {
+
−	keyval = keyval_store;
+
−}
+
−
+
−local driver = {};
+
−
+
−function driver:open(store, typ)
+
−	local store_mt = stores[typ or "keyval"];
+
−	if store_mt then
+
−		local my_backends = {};
+
−		local driver, opened
+
−		for i = 1, #backends do
+
−			 driver = storagemanager.load_driver(module.host, backends[i]);
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−			 opened = driver:open(store, typ);
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−			 my_backends[i] = assert(driver:open(store, typ));
+
−			 my_backends[i]._store = store;
+
−		end
+
−		return setmetatable({ backends = my_backends }, store_mt);
+
−	end
+
−	return nil, "unsupported-store";
+
−end
+
−
+
−module:provides("storage", driver);