--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_storage_multi/mod_storage_multi.lua Thu Aug 21 23:14:55 2014 +0200
@@ -0,0 +1,81 @@
+-- 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)
+ local backends = self.backends;
+ local data, err;
+ for i = 1, #backends do
+ module:log("debug", "%s:%s:get(%q)", tostring(backends[i].get), backends[i]._store, username);
+ data, err = backends[i]:get(username);
+ if err then
+ 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
+ backend = backends[i];
+ 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
+ module:log("error", "Error in storage driver %s: %s", backend.name, tostring(err));
+ else
+ oks = oks + 1;
+ end
+ one = one or ok; -- At least one successful write
+ 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]);
+ opened = driver:open(store, typ);
+ 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);