From 85b2bde3dd9a3b30def867eb2cda656ebd352b0c Mon Sep 17 00:00:00 2001
From: Siying Dong <siying.d@fb.com>
Date: Fri, 12 Apr 2019 10:55:14 -0700
Subject: [PATCH] Still implement StatisticsImpl::measureTime() (#5181)

Summary:
Since Statistics::measureTime() is deprecated, StatisticsImpl::measureTime() is not implemented. We realized that users might have a wrapped Statistics implementation in which measureTime() is implemented as forwarded to StatisticsImpl, and causes assert failure. In order to make the change less intrusive, we implement StatisticsImpl::measureTime(). We will revisit whether we need to remove it after several releases.

Also, add a test to make sure that a Statistics implementation using the old interface still works.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5181

Differential Revision: D14907089

Pulled By: siying

fbshipit-source-id: 29b6202fd04e30ed6f6adcaeb1000e87f10d1e1a
---
 db/db_test2.cc          | 42 +++++++++++++++++++++++++++++++++++++++++
 monitoring/statistics.h |  7 +++++++
 2 files changed, 49 insertions(+)

diff --git a/db/db_test2.cc b/db/db_test2.cc
index 37382b2b8..388d3ccf5 100644
--- a/db/db_test2.cc
+++ b/db/db_test2.cc
@@ -3696,6 +3696,48 @@ TEST_F(DBTest2, MultiDBParallelOpenTest) {
 }
 #endif  // OS_WIN
 
+namespace {
+class DummyOldStats : public Statistics {
+ public:
+  uint64_t getTickerCount(uint32_t /*ticker_type*/) const override { return 0; }
+  void recordTick(uint32_t /* ticker_type */, uint64_t /* count */) override {
+    num_rt++;
+  }
+  void setTickerCount(uint32_t /*ticker_type*/, uint64_t /*count*/) override {}
+  uint64_t getAndResetTickerCount(uint32_t /*ticker_type*/) override {
+    return 0;
+  }
+  void measureTime(uint32_t /*histogram_type*/, uint64_t /*count*/) override {
+    num_mt++;
+  }
+  void histogramData(uint32_t /*histogram_type*/,
+                     rocksdb::HistogramData* const /*data*/) const override {}
+  std::string getHistogramString(uint32_t /*type*/) const override {
+    return "";
+  }
+  bool HistEnabledForType(uint32_t /*type*/) const override { return false; }
+  std::string ToString() const override { return ""; }
+  int num_rt = 0;
+  int num_mt = 0;
+};
+}  // namespace
+
+TEST_F(DBTest2, OldStatsInterface) {
+  DummyOldStats* dos = new DummyOldStats();
+  std::shared_ptr<Statistics> stats(dos);
+  Options options = CurrentOptions();
+  options.create_if_missing = true;
+  options.statistics = stats;
+  Reopen(options);
+
+  Put("foo", "bar");
+  ASSERT_EQ("bar", Get("foo"));
+  ASSERT_OK(Flush());
+  ASSERT_EQ("bar", Get("foo"));
+
+  ASSERT_GT(dos->num_rt, 0);
+  ASSERT_GT(dos->num_mt, 0);
+}
 }  // namespace rocksdb
 
 int main(int argc, char** argv) {
diff --git a/monitoring/statistics.h b/monitoring/statistics.h
index fac01205f..952bf8cb4 100644
--- a/monitoring/statistics.h
+++ b/monitoring/statistics.h
@@ -53,6 +53,13 @@ class StatisticsImpl : public Statistics {
   virtual void setTickerCount(uint32_t ticker_type, uint64_t count) override;
   virtual uint64_t getAndResetTickerCount(uint32_t ticker_type) override;
   virtual void recordTick(uint32_t ticker_type, uint64_t count) override;
+  // The function is implemented for now for backward compatibility reason.
+  // In case a user explictly calls it, for example, they may have a wrapped
+  // Statistics object, passing the call to recordTick() into here, nothing
+  // will break.
+  void measureTime(uint32_t histogramType, uint64_t time) override {
+    recordInHistogram(histogramType, time);
+  }
   virtual void recordInHistogram(uint32_t histogram_type,
                                  uint64_t value) override;