1 files changed, 148 insertions, 0 deletions
diff --git a/src/rocksdb/db/write_controller.h b/src/rocksdb/db/write_controller.h
new file mode 100644
index 000000000..bcead165b
--- /dev/null
+++ b/src/rocksdb/db/write_controller.h
@@ -0,0 +1,148 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <stdint.h>
+
+#include <atomic>
+#include <memory>
+
+#include "rocksdb/rate_limiter.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class SystemClock;
+class WriteControllerToken;
+
+// WriteController is controlling write stalls in our write code-path. Write
+// stalls happen when compaction can't keep up with write rate.
+// All of the methods here (including WriteControllerToken's destructors) need
+// to be called while holding DB mutex
+class WriteController {
+ public:
+  explicit WriteController(uint64_t _delayed_write_rate = 1024u * 1024u * 32u,
+                           int64_t low_pri_rate_bytes_per_sec = 1024 * 1024)
+      : total_stopped_(0),
+        total_delayed_(0),
+        total_compaction_pressure_(0),
+        credit_in_bytes_(0),
+        next_refill_time_(0),
+        low_pri_rate_limiter_(
+            NewGenericRateLimiter(low_pri_rate_bytes_per_sec)) {
+    set_max_delayed_write_rate(_delayed_write_rate);
+  }
+  ~WriteController() = default;
+
+  // When an actor (column family) requests a stop token, all writes will be
+  // stopped until the stop token is released (deleted)
+  std::unique_ptr<WriteControllerToken> GetStopToken();
+  // When an actor (column family) requests a delay token, total delay for all
+  // writes to the DB will be controlled under the delayed write rate. Every
+  // write needs to call GetDelay() with number of bytes writing to the DB,
+  // which returns number of microseconds to sleep.
+  std::unique_ptr<WriteControllerToken> GetDelayToken(
+      uint64_t delayed_write_rate);
+  // When an actor (column family) requests a moderate token, compaction
+  // threads will be increased
+  std::unique_ptr<WriteControllerToken> GetCompactionPressureToken();
+
+  // these three metods are querying the state of the WriteController
+  bool IsStopped() const;
+  bool NeedsDelay() const { return total_delayed_.load() > 0; }
+  bool NeedSpeedupCompaction() const {
+    return IsStopped() || NeedsDelay() || total_compaction_pressure_.load() > 0;
+  }
+  // return how many microseconds the caller needs to sleep after the call
+  // num_bytes: how many number of bytes to put into the DB.
+  // Prerequisite: DB mutex held.
+  uint64_t GetDelay(SystemClock* clock, uint64_t num_bytes);
+  void set_delayed_write_rate(uint64_t write_rate) {
+    // avoid divide 0
+    if (write_rate == 0) {
+      write_rate = 1u;
+    } else if (write_rate > max_delayed_write_rate()) {
+      write_rate = max_delayed_write_rate();
+    }
+    delayed_write_rate_ = write_rate;
+  }
+
+  void set_max_delayed_write_rate(uint64_t write_rate) {
+    // avoid divide 0
+    if (write_rate == 0) {
+      write_rate = 1u;
+    }
+    max_delayed_write_rate_ = write_rate;
+    // update delayed_write_rate_ as well
+    delayed_write_rate_ = write_rate;
+  }
+
+  uint64_t delayed_write_rate() const { return delayed_write_rate_; }
+
+  uint64_t max_delayed_write_rate() const { return max_delayed_write_rate_; }
+
+  RateLimiter* low_pri_rate_limiter() { return low_pri_rate_limiter_.get(); }
+
+ private:
+  uint64_t NowMicrosMonotonic(SystemClock* clock);
+
+  friend class WriteControllerToken;
+  friend class StopWriteToken;
+  friend class DelayWriteToken;
+  friend class CompactionPressureToken;
+
+  std::atomic<int> total_stopped_;
+  std::atomic<int> total_delayed_;
+  std::atomic<int> total_compaction_pressure_;
+
+  // Number of bytes allowed to write without delay
+  uint64_t credit_in_bytes_;
+  // Next time that we can add more credit of bytes
+  uint64_t next_refill_time_;
+  // Write rate set when initialization or by `DBImpl::SetDBOptions`
+  uint64_t max_delayed_write_rate_;
+  // Current write rate (bytes / second)
+  uint64_t delayed_write_rate_;
+
+  std::unique_ptr<RateLimiter> low_pri_rate_limiter_;
+};
+
+class WriteControllerToken {
+ public:
+  explicit WriteControllerToken(WriteController* controller)
+      : controller_(controller) {}
+  virtual ~WriteControllerToken() {}
+
+ protected:
+  WriteController* controller_;
+
+ private:
+  // no copying allowed
+  WriteControllerToken(const WriteControllerToken&) = delete;
+  void operator=(const WriteControllerToken&) = delete;
+};
+
+class StopWriteToken : public WriteControllerToken {
+ public:
+  explicit StopWriteToken(WriteController* controller)
+      : WriteControllerToken(controller) {}
+  virtual ~StopWriteToken();
+};
+
+class DelayWriteToken : public WriteControllerToken {
+ public:
+  explicit DelayWriteToken(WriteController* controller)
+      : WriteControllerToken(controller) {}
+  virtual ~DelayWriteToken();
+};
+
+class CompactionPressureToken : public WriteControllerToken {
+ public:
+  explicit CompactionPressureToken(WriteController* controller)
+      : WriteControllerToken(controller) {}
+  virtual ~CompactionPressureToken();
+};
+
+}  // namespace ROCKSDB_NAMESPACE