1 files changed, 43 insertions, 0 deletions
diff --git a/src/crimson/common/throttle.h b/src/crimson/common/throttle.h
new file mode 100644
index 000000000..2998cb5f8
--- /dev/null
+++ b/src/crimson/common/throttle.h
@@ -0,0 +1,43 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:nil -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include <seastar/core/condition-variable.hh>
+// pull seastar::timer<...>::timer definitions. FIX SEASTAR or reactor.hh
+// is obligatory and should be included everywhere?
+#include <seastar/core/reactor.hh>
+
+#include "common/ThrottleInterface.h"
+
+namespace crimson::common {
+
+class Throttle final : public ThrottleInterface {
+  size_t max = 0;
+  size_t count = 0;
+  size_t pending = 0;
+  // we cannot change the "count" of seastar::semaphore after it is created,
+  // so use condition_variable instead.
+  seastar::condition_variable on_free_slots;
+public:
+  explicit Throttle(size_t m)
+    : max(m)
+  {}
+  int64_t take(int64_t c = 1) override;
+  int64_t put(int64_t c = 1) override;
+  seastar::future<> get(size_t c);
+  size_t get_current() const {
+    return count;
+  }
+  size_t get_max() const {
+    return max;
+  }
+  size_t get_pending() const {
+    return pending;
+  }
+  void reset_max(size_t m);
+private:
+  bool _should_wait(size_t c) const;
+};
+
+} // namespace crimson::common