1 files changed, 59 insertions, 0 deletions
diff --git a/src/common/config_cacher.h b/src/common/config_cacher.h
new file mode 100644
index 000000000..a84bad08e
--- /dev/null
+++ b/src/common/config_cacher.h
@@ -0,0 +1,59 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#ifndef CEPH_CONFIG_CACHER_H
+#define CEPH_CONFIG_CACHER_H
+
+#include "common/config_obs.h"
+#include "common/config.h"
+
+template <typename ValueT>
+class md_config_cacher_t : public md_config_obs_t {
+  ConfigProxy& conf;
+  const char* const option_name;
+  std::atomic<ValueT> value_cache;
+
+  const char** get_tracked_conf_keys() const override {
+    const static char* keys[] = { option_name, nullptr };
+    return keys;
+  }
+
+  void handle_conf_change(const ConfigProxy& conf,
+                          const std::set<std::string>& changed) override {
+    if (changed.count(option_name)) {
+      value_cache.store(conf.get_val<ValueT>(option_name));
+    }
+  }
+
+public:
+  md_config_cacher_t(ConfigProxy& conf,
+                     const char* const option_name)
+    : conf(conf),
+      option_name(option_name) {
+    conf.add_observer(this);
+    std::atomic_init(&value_cache,
+                     conf.get_val<ValueT>(option_name));
+  }
+
+  ~md_config_cacher_t() {
+    conf.remove_observer(this);
+  }
+
+  operator ValueT() const {
+    return value_cache.load();
+  }
+};
+
+#endif // CEPH_CONFIG_CACHER_H
+