Allow users to specifcy now

Summary:
We are changing the underlying fb303 timeseries to have sub-second buckets. It requires a sub-second clock to reap the benefits. However, there is a small performance regression if we change `now()` when calling `addStatValue` for all ServiceData. This is because of this optimization in the MultilevelTimeseries https://fburl.com/code/904ox41z where it caches sum and count until the clock moves to the next tick. A more granular clock makes this optimization less useful.

In this change, we allow users of ServiceData to specify `now` which defaults to a clock of second granularity to make this change perf neutral.

#buildall

Reviewed By: islamismailov

Differential Revision: D82854336

fbshipit-source-id: 2c3d8ab2c0e91ac4c96ecbd54d7a574a6b6c7872

Author: uvdn7

fb303/BUCK

@@ -190,7 +190,6 @@ cpp_library(
     srcs = ["ServiceData.cpp"],
     modular_headers = True,
     deps = [
-        ":legacy_clock",
         "//fb303/detail:regex_util",
         "//folly:conv",
         "//folly:indestructible",
@@ -202,6 +201,7 @@ cpp_library(
         ":dynamic_counters",
         ":exported_stat_map_impl",
         ":histogram_exporter",
+        ":legacy_clock",
         "//fb303/detail:quantile_stat_map",
         "//folly:chrono",
         "//folly:optional",
@@ -212,8 +212,8 @@ cpp_library(
         "//folly/synchronization:relaxed_atomic",
     ],
     external_deps = [
-        "gflags",
         ("boost", None, "boost_regex"),
+        "gflags",
     ],
 )
 

fb303/ServiceData.cpp

@@ -19,7 +19,6 @@
 #include <stdexcept>
 
 #include <boost/regex.hpp>
-#include <fb303/LegacyClock.h>
 #include <fb303/detail/RegexUtil.h>
 #include <folly/Conv.h>
 #include <folly/Indestructible.h>
@@ -32,10 +31,6 @@ using folly::StringPiece;
 
 namespace facebook::fb303 {
 
-TimePoint get_current_time() {
-  return TimePoint(std::chrono::seconds(get_legacy_stats_time()));
-}
-
 template <typename T>
 static T& as_mutable(T const& t) {
   return const_cast<T&>(t);
@@ -156,29 +151,32 @@ void ServiceData::addStatExports(
   }
 }
 
-void ServiceData::addStatValue(StringPiece key, int64_t value) {
-  statsMap_.addValue(key, get_current_time(), value);
+void ServiceData::addStatValue(StringPiece key, int64_t value, TimePoint now) {
+  statsMap_.addValue(key, now, value);
 }
 
 void ServiceData::addStatValue(
     StringPiece key,
     int64_t value,
-    ExportType exportType) {
-  statsMap_.addValue(key, get_current_time(), value, exportType);
+    ExportType exportType,
+    TimePoint now) {
+  statsMap_.addValue(key, now, value, exportType);
 }
 
 void ServiceData::addStatValue(
     StringPiece key,
     int64_t value,
-    folly::Range<const ExportType*> exportTypes) {
-  statsMap_.addValue(key, get_current_time(), value, exportTypes);
+    folly::Range<const ExportType*> exportTypes,
+    TimePoint now) {
+  statsMap_.addValue(key, now, value, exportTypes);
 }
 
 void ServiceData::addStatValueAggregated(
     StringPiece key,
     int64_t sum,
-    int64_t numSamples) {
-  statsMap_.addValueAggregated(key, get_current_time(), sum, numSamples);
+    int64_t numSamples,
+    TimePoint now) {
+  statsMap_.addValueAggregated(key, now, sum, numSamples);
 }
 
 bool ServiceData::addHistogram(
@@ -267,8 +265,9 @@ void ServiceData::addHistogramValueMult(
 void ServiceData::addHistAndStatValue(
     StringPiece key,
     int64_t value,
-    bool checkContains) {
-  statsMap_.addValue(key, get_current_time(), value);
+    bool checkContains,
+    TimePoint now) {
+  statsMap_.addValue(key, now, value);
 
   if (!checkContains || histMap_.contains(key)) {
     histMap_.addValue(key, get_legacy_stats_time(), value);

fb303/ServiceData.h

@@ -29,6 +29,7 @@
 #include <folly/container/RegexMatchCache.h>
 #include <folly/synchronization/RelaxedAtomic.h>
 
+#include <fb303/LegacyClock.h>
 #include <atomic>
 #include <chrono>
 #include <cinttypes>
@@ -40,6 +41,10 @@
 
 namespace facebook::fb303 {
 
+inline TimePoint get_current_time() {
+  return TimePoint(std::chrono::seconds(get_legacy_stats_time()));
+}
+
 /**
  * ServiceData stores statistics and other information used by most
  * Facebook C++ services.
@@ -233,17 +238,25 @@ class ServiceData {
    * Note that the optional exportType parameter is only used if the
    * stat has not already been added.
    */
-  void addStatValue(folly::StringPiece key, int64_t value = 1);
-  void
-  addStatValue(folly::StringPiece key, int64_t value, ExportType exportType);
+  void addStatValue(
+      folly::StringPiece key,
+      int64_t value = 1,
+      TimePoint now = get_current_time());
+  void addStatValue(
+      folly::StringPiece key,
+      int64_t value,
+      ExportType exportType,
+      TimePoint now = get_current_time());
   void addStatValue(
       folly::StringPiece key,
       int64_t value,
-      folly::Range<const ExportType*> exportType);
+      folly::Range<const ExportType*> exportType,
+      TimePoint now = get_current_time());
   void addStatValueAggregated(
       folly::StringPiece key,
       int64_t sum,
-      int64_t numSamples);
+      int64_t numSamples,
+      TimePoint now = get_current_time());
 
   /**
    * Defines a histogram that can be used via calls to addHistogramValue() and
@@ -399,7 +412,8 @@ class ServiceData {
   [[deprecated]] void addHistAndStatValue(
       folly::StringPiece key,
       int64_t value,
-      bool checkContains = false);
+      bool checkContains = false,
+      TimePoint now = get_current_time());
 
   /**
    * Convenience function for adding the same value to stats and histograms.