Print metrics for blackbox tests

It was overcounting

Bench.cpp

@@ -358,7 +358,30 @@ void benchWorstCaseForRadixRangeRead() {
   // }
 }
 
+void benchMetrics() {
+  ankerl::nanobench::Bench bench;
+  ConflictSet cs{0};
+
+  int count;
+  ConflictSet::MetricsV1 *m;
+  cs.getMetricsV1(&m, &count);
+  bench.batch(count);
+  bench.run("fetch metric", [&]() {
+    for (int i = 0; i < count; ++i) {
+      m[i].getValue();
+    }
+  });
+}
+
+void benchCreateAndDestroy() {
+  ankerl::nanobench::Bench bench;
+
+  bench.run("create and destroy", [&]() { ConflictSet cs{0}; });
+}
+
 int main(void) {
   benchConflictSet();
   benchWorstCaseForRadixRangeRead();
+  benchMetrics();
+  benchCreateAndDestroy();
 }

CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.18)
 project(
   conflict-set
-  VERSION 0.0.8
+  VERSION 0.0.9
   DESCRIPTION
     "A data structure for optimistic concurrency control on ranges of bitwise-lexicographically-ordered keys."
   HOMEPAGE_URL "https://git.weaselab.dev/weaselab/conflict-set"
@@ -60,6 +60,8 @@ cmake_pop_check_state()
 option(USE_SIMD_FALLBACK
        "Use fallback implementations of functions that use SIMD" OFF)
 
+option(DISABLE_TSAN "Disable TSAN" OFF)
+
 # This is encouraged according to
 # https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq
 include_directories(SYSTEM ${CMAKE_CURRENT_SOURCE_DIR}/third_party/valgrind)
@@ -245,7 +247,7 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
   endforeach()
 
   # tsan tests
-  if(NOT CMAKE_CROSSCOMPILING AND NOT CMAKE_BUILD_TYPE STREQUAL Debug)
+  if(NOT CMAKE_CROSSCOMPILING AND NOT DISABLE_TSAN)
     add_executable(tsan_driver ConflictSet.cpp FuzzTestDriver.cpp)
     target_compile_options(tsan_driver PRIVATE ${TEST_FLAGS} -fsanitize=thread)
     target_link_options(tsan_driver PRIVATE -fsanitize=thread)

ConflictSet.cpp

@@ -29,6 +29,7 @@ limitations under the License.
 #include <span>
 #include <string>
 #include <string_view>
+#include <sys/time.h>
 #include <type_traits>
 #include <utility>
 
@@ -546,7 +547,48 @@ static_assert(kBytesPerKey - sizeof(Node0) >= kMinNodeSurplus);
 
 constexpr int64_t kFreeListMaxMemory = 1 << 20;
 
+struct Metric {
+  Metric *prev;
+  const char *name;
+  const char *help;
+  ConflictSet::MetricsV1::Type type;
+  std::atomic<double> value;
+
+protected:
+  Metric(ConflictSet::Impl *impl, const char *name, const char *help,
+         ConflictSet::MetricsV1::Type type);
+};
+
+struct Gauge : private Metric {
+  Gauge(ConflictSet::Impl *impl, const char *name, const char *help)
+      : Metric(impl, name, help, ConflictSet::MetricsV1::Gauge) {}
+
+  void set(double value) {
+    this->value.store(value, std::memory_order_relaxed);
+  }
+};
+
+struct Counter : private Metric {
+  Counter(ConflictSet::Impl *impl, const char *name, const char *help)
+      : Metric(impl, name, help, ConflictSet::MetricsV1::Counter) {}
+  // Expensive. Accumulate locally and then call add instead of repeatedly
+  // calling add.
+  void add(double value) {
+    assert(value >= 0);
+    static_assert(std::atomic<double>::is_always_lock_free);
+    double old = this->value.load(std::memory_order_relaxed);
+    for (;;) {
+      double newVal = old + value;
+      if (this->value.compare_exchange_weak(old, newVal,
+                                            std::memory_order_relaxed)) {
+        break;
+      }
+    }
+  }
+};
+
 template <class T> struct BoundedFreeListAllocator {
+
   static_assert(sizeof(T) >= sizeof(void *));
   static_assert(std::derived_from<T, Node>);
   static_assert(std::is_trivial_v<T>);
@@ -1670,17 +1712,30 @@ struct SearchStepWise {
   }
 };
 
+thread_local double point_read_accum = 0;
+thread_local double prefix_read_accum = 0;
+thread_local double range_read_accum = 0;
+thread_local double point_read_short_circuit_accum = 0;
+thread_local double prefix_read_short_circuit_accum = 0;
+thread_local double range_read_short_circuit_accum = 0;
+thread_local double point_read_iterations_accum = 0;
+thread_local double prefix_read_iterations_accum = 0;
+thread_local double range_read_iterations_accum = 0;
+thread_local double range_read_node_scan_accum = 0;
+
 // Logically this is the same as performing firstGeq and then checking against
 // point or range version according to cmp, but this version short circuits as
 // soon as it can prove that there's no conflict.
 bool checkPointRead(Node *n, const std::span<const uint8_t> key,
                     InternalVersionT readVersion, ConflictSet::Impl *impl) {
+  ++point_read_accum;
 #if DEBUG_VERBOSE && !defined(NDEBUG)
   fprintf(stderr, "Check point read: %s\n", printable(key).c_str());
 #endif
   auto remaining = key;
-  for (;;) {
+  for (;; ++point_read_iterations_accum) {
     if (maxVersion(n, impl) <= readVersion) {
+      ++point_read_short_circuit_accum;
       return true;
     }
     if (remaining.size() == 0) {
@@ -1752,17 +1807,19 @@ downLeftSpine:
 // short circuits as soon as it can prove that there's no conflict.
 bool checkPrefixRead(Node *n, const std::span<const uint8_t> key,
                      InternalVersionT readVersion, ConflictSet::Impl *impl) {
+  ++prefix_read_accum;
 #if DEBUG_VERBOSE && !defined(NDEBUG)
   fprintf(stderr, "Check prefix read: %s\n", printable(key).c_str());
 #endif
   auto remaining = key;
-  for (;;) {
+  for (;; ++prefix_read_iterations_accum) {
     auto m = maxVersion(n, impl);
     if (remaining.size() == 0) {
       return m <= readVersion;
     }
 
     if (m <= readVersion) {
+      ++prefix_read_short_circuit_accum;
       return true;
     }
 
@@ -1993,6 +2050,7 @@ scan16(const InternalVersionT *vs, int begin, int end,
 template <bool kAVX512>
 bool checkMaxBetweenExclusive(Node *n, int begin, int end,
                               InternalVersionT readVersion) {
+  ++range_read_node_scan_accum;
   assume(-1 <= begin);
   assume(begin <= 256);
   assume(-1 <= end);
@@ -2601,13 +2659,16 @@ bool checkRangeReadImpl(Node *n, std::span<const uint8_t> begin,
     return checkPrefixRead(n, begin, readVersion, impl);
   }
 
+  ++range_read_accum;
+
   SearchStepWise search{n, begin.subspan(0, lcp)};
   Arena arena;
-  for (;;) {
+  for (;; ++range_read_iterations_accum) {
     assert(getSearchPath(arena, search.n) <=>
                begin.subspan(0, lcp - search.remaining.size()) ==
            0);
     if (maxVersion(search.n, impl) <= readVersion) {
+      ++range_read_short_circuit_accum;
       return true;
     }
     if (search.step()) {
@@ -2648,18 +2709,21 @@ bool checkRangeReadImpl(Node *n, std::span<const uint8_t> begin,
     bool leftDone = checkRangeLeftSide.step();
     bool rightDone = checkRangeRightSide.step();
     if (!leftDone && !rightDone) {
+      range_read_iterations_accum += 2;
       continue;
     }
     if (leftDone && rightDone) {
       break;
     } else if (leftDone) {
-      while (!checkRangeRightSide.step())
-        ;
+      while (!checkRangeRightSide.step()) {
+        ++range_read_iterations_accum;
+      }
       break;
     } else {
       assert(rightDone);
-      while (!checkRangeLeftSide.step())
-        ;
+      while (!checkRangeLeftSide.step()) {
+        ++range_read_iterations_accum;
+      }
     }
     break;
   }
@@ -3004,11 +3068,22 @@ Node *firstGeqPhysical(Node *n, const std::span<const uint8_t> key) {
   }
 }
 
+#define MEASURE_CHECK_CPU_TIME 0
+
 struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
 
   void check(const ReadRange *reads, Result *result, int count) {
+#if MEASURE_CHECK_CPU_TIME
+    timespec ts_begin;
+    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts_begin);
+#endif
+    int commits_accum = 0;
+    int conflicts_accum = 0;
+    int too_olds_accum = 0;
+    double check_byte_accum = 0;
     for (int i = 0; i < count; ++i) {
       const auto &r = reads[i];
+      check_byte_accum += r.begin.len + r.end.len;
       auto begin = std::span<const uint8_t>(r.begin.p, r.begin.len);
       auto end = std::span<const uint8_t>(r.end.p, r.end.len);
       assert(oldestVersionFullPrecision >=
@@ -3022,7 +3097,38 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
                                   InternalVersionT(reads[i].readVersion), this))
               ? Commit
               : Conflict;
+      commits_accum += result[i] == Commit;
+      conflicts_accum += result[i] == Conflict;
+      too_olds_accum += result[i] == TooOld;
     }
+    point_read_total.add(std::exchange(point_read_accum, 0));
+    prefix_read_total.add(std::exchange(prefix_read_accum, 0));
+    range_read_total.add(std::exchange(range_read_accum, 0));
+    range_read_node_scan_total.add(
+        std::exchange(range_read_node_scan_accum, 0));
+    point_read_short_circuit_total.add(
+        std::exchange(point_read_short_circuit_accum, 0));
+    prefix_read_short_circuit_total.add(
+        std::exchange(prefix_read_short_circuit_accum, 0));
+    range_read_short_circuit_total.add(
+        std::exchange(range_read_short_circuit_accum, 0));
+    point_read_iterations_total.add(
+        std::exchange(point_read_iterations_accum, 0));
+    prefix_read_iterations_total.add(
+        std::exchange(prefix_read_iterations_accum, 0));
+    range_read_iterations_total.add(
+        std::exchange(range_read_iterations_accum, 0));
+    commits_total.add(commits_accum);
+    conflicts_total.add(conflicts_accum);
+    too_olds_total.add(too_olds_accum);
+    check_bytes_total.add(check_byte_accum);
+#if MEASURE_CHECK_CPU_TIME
+    timespec ts_end;
+    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts_end);
+    check_cpu_seconds_total.add(
+        std::max<double>(0, (ts_end.tv_nsec * 1e-9 + ts_end.tv_sec) -
+                                (ts_begin.tv_nsec * 1e-9 + ts_begin.tv_sec)));
+#endif
   }
 
   void addWrites(const WriteRange *writes, int count, int64_t writeVersion) {
@@ -3056,6 +3162,8 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
                       this);
       }
     }
+
+    memory_bytes.set(totalBytes);
   }
 
   // Spends up to `fuel` gc'ing, and returns its unused fuel. Reclaims memory
@@ -3070,8 +3178,12 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
       rootMaxVersion = std::max(rootMaxVersion, oldestVersion);
       n = nextPhysical(n);
     }
-    for (; fuel > 0 && n != nullptr; --fuel) {
+    for (; fuel > 0 && n != nullptr;) {
       rezero(n, oldestVersion);
+      // The "make sure gc keeps up with writes" calculations assume that we're
+      // scanning key by key, not node by node. Make sure we only spend fuel
+      // when there's a logical entry.
+      fuel -= n->entryPresent;
       if (n->entryPresent && std::max(n->entry.pointVersion,
                                       n->entry.rangeVersion) <= oldestVersion) {
         // Any transaction n would have prevented from committing is
@@ -3121,6 +3233,8 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     }
 #endif
     keyUpdates = gcScanStep(keyUpdates);
+
+    memory_bytes.set(totalBytes);
   }
 
   int64_t getBytes() const { return totalBytes; }
@@ -3156,8 +3270,14 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     // Intentionally not resetting totalBytes
   }
 
-  explicit Impl(int64_t oldestVersion) { init(oldestVersion); }
-  ~Impl() { destroyTree(root); }
+  explicit Impl(int64_t oldestVersion) {
+    init(oldestVersion);
+    initMetrics();
+  }
+  ~Impl() {
+    destroyTree(root);
+    safe_free(metrics, metricsCount * sizeof(metrics[0]));
+  }
 
   NodeAllocators allocators;
 
@@ -3173,8 +3293,77 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   int64_t oldestVersionAtGcBegin;
   int64_t newestVersionFullPrecision;
   int64_t totalBytes = 0;
+
+  MetricsV1 *metrics;
+  int metricsCount = 0;
+  void initMetrics() {
+    metrics = (MetricsV1 *)safe_malloc(metricsCount * sizeof(metrics[0]));
+    for (auto [i, m] = std::make_tuple(metricsCount - 1, metricList); i >= 0;
+         --i, m = m->prev) {
+      metrics[i].name = m->name;
+      metrics[i].help = m->help;
+      metrics[i].p = m;
+      metrics[i].type = m->type;
+    }
+  }
+
+  Metric *metricList = nullptr;
+
+#define GAUGE(name, help)                                                      \
+  Gauge name { this, #name, help }
+#define COUNTER(name, help)                                                    \
+  Counter name { this, #name, help }
+  // ==================== METRICS DEFINITIONS ====================
+  GAUGE(memory_bytes, "Total number of bytes in use");
+  COUNTER(point_read_total, "Total number of point reads checked");
+  COUNTER(point_read_short_circuit_total,
+          "Total number of point reads that did not require a full search to "
+          "check");
+  COUNTER(point_read_iterations_total,
+          "Total number of iterations of the main loop for point read checks");
+  COUNTER(prefix_read_total, "Total number of prefix reads checked");
+  COUNTER(prefix_read_short_circuit_total,
+          "Total number of prefix reads that did not require a full search to "
+          "check");
+  COUNTER(prefix_read_iterations_total,
+          "Total number of iterations of the main loop for prefix read checks");
+  COUNTER(range_read_total, "Total number of range reads checked");
+  COUNTER(range_read_short_circuit_total,
+          "Total number of range reads that did not require a full search to "
+          "check");
+  COUNTER(range_read_iterations_total,
+          "Total number of iterations of the main loops for range read checks");
+  COUNTER(range_read_node_scan_total,
+          "Total number of scans of individual nodes while "
+          "checking a range read");
+  COUNTER(commits_total,
+          "Total number of checks where the result is \"commit\"");
+  COUNTER(conflicts_total,
+          "Total number of checks where the result is \"conflict\"");
+  COUNTER(too_olds_total,
+          "Total number of checks where the result is \"too old\"");
+  COUNTER(check_bytes_total, "Total number of key bytes checked");
+#if MEASURE_CHECK_CPU_TIME
+  COUNTER(check_cpu_seconds_total,
+          "Total cpu seconds spent in a call to check");
+#endif
+  // ==================== END METRICS DEFINITIONS ====================
+#undef GAUGE
+#undef COUNTER
+
+  void getMetricsV1(MetricsV1 **metrics, int *count) {
+    *metrics = this->metrics;
+    *count = metricsCount;
+  }
 };
 
+Metric::Metric(ConflictSet::Impl *impl, const char *name, const char *help,
+               ConflictSet::MetricsV1::Type type)
+    : prev(std::exchange(impl->metricList, this)), name(name), help(help),
+      type(type), value(0) {
+  ++impl->metricsCount;
+}
+
 InternalVersionT maxVersion(Node *n, ConflictSet::Impl *impl) {
   int index = n->parentsIndex;
   n = n->parent;
@@ -3304,6 +3493,15 @@ void internal_destroy(ConflictSet::Impl *impl) {
 
 int64_t internal_getBytes(ConflictSet::Impl *impl) { return impl->getBytes(); }
 
+void internal_getMetricsV1(ConflictSet::Impl *impl,
+                           ConflictSet::MetricsV1 **metrics, int *count) {
+  impl->getMetricsV1(metrics, count);
+}
+
+double internal_getMetricValue(const ConflictSet::MetricsV1 *metric) {
+  return ((Metric *)metric->p)->value.load(std::memory_order_relaxed);
+}
+
 // ==================== END IMPLEMENTATION ====================
 
 // GCOVR_EXCL_START
@@ -3388,6 +3586,14 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
 
 int64_t ConflictSet::getBytes() const { return internal_getBytes(impl); }
 
+void ConflictSet::getMetricsV1(MetricsV1 **metrics, int *count) const {
+  return internal_getMetricsV1(impl, metrics, count);
+}
+
+double ConflictSet::MetricsV1::getValue() const {
+  return internal_getMetricValue(this);
+}
+
 ConflictSet::ConflictSet(int64_t oldestVersion)
     : impl(internal_create(oldestVersion)) {}
 
@@ -3443,6 +3649,7 @@ static_assert(std::is_standard_layout_v<ConflictSet::Result>);
 static_assert(std::is_standard_layout_v<ConflictSet::Key>);
 static_assert(std::is_standard_layout_v<ConflictSet::ReadRange>);
 static_assert(std::is_standard_layout_v<ConflictSet::WriteRange>);
+static_assert(std::is_standard_layout_v<ConflictSet::MetricsV1>);
 
 namespace {
 

Internal.h

@@ -702,17 +702,36 @@ template <class ConflictSetImpl> struct TestDriver {
         }
       }
 
+      oldestVersion +=
+          arbitrary.bounded(10) ? arbitrary.bounded(10) : arbitrary.next();
+      oldestVersion = std::min(oldestVersion, writeVersion);
+
+#ifdef THREAD_TEST
+      std::latch ready{1};
+      std::thread thread2{[&]() {
+        ready.count_down();
+        ConflictSet::MetricsV1 *m;
+        int count;
+        cs.getMetricsV1(&m, &count);
+        for (int i = 0; i < count; ++i) {
+          m[i].getValue();
+        }
+      }};
+      ready.wait();
+#endif
+
       CALLGRIND_START_INSTRUMENTATION;
       cs.addWrites(writes, numPointWrites + numRangeWrites, v);
       CALLGRIND_STOP_INSTRUMENTATION;
 
       refImpl.addWrites(writes, numPointWrites + numRangeWrites, v);
 
-      oldestVersion +=
-          arbitrary.bounded(10) ? arbitrary.bounded(10) : arbitrary.next();
-      oldestVersion = std::min(oldestVersion, writeVersion);
       cs.setOldestVersion(oldestVersion);
       refImpl.setOldestVersion(oldestVersion);
+
+#ifdef THREAD_TEST
+      thread2.join();
+#endif
     }
     {
       int numPointReads = arbitrary.bounded(100);
@@ -785,7 +804,15 @@ template <class ConflictSetImpl> struct TestDriver {
       std::latch ready{1};
       std::thread thread2{[&]() {
         ready.count_down();
+        // Call all const methods
         cs.check(reads, results3, numPointReads + numRangeReads);
+        cs.getBytes();
+        ConflictSet::MetricsV1 *m;
+        int count;
+        cs.getMetricsV1(&m, &count);
+        for (int i = 0; i < count; ++i) {
+          m[i].getValue();
+        }
       }};
       ready.wait();
 #endif
@@ -794,6 +821,15 @@ template <class ConflictSetImpl> struct TestDriver {
       cs.check(reads, results1, numPointReads + numRangeReads);
       CALLGRIND_STOP_INSTRUMENTATION;
 
+      // Call remaining const methods
+      cs.getBytes();
+      ConflictSet::MetricsV1 *m;
+      int count;
+      cs.getMetricsV1(&m, &count);
+      for (int i = 0; i < count; ++i) {
+        m[i].getValue();
+      }
+
       refImpl.check(reads, results2, numPointReads + numRangeReads);
 
       auto compareResults = [reads](ConflictSet::Result *results1,

Jenkinsfile

@@ -48,6 +48,17 @@ pipeline {
                 recordIssues(tools: [clang()])
             }
         }
+        stage('Debug') {
+            agent {
+                dockerfile {
+                    args '-v /home/jenkins/ccache:/ccache'
+                    reuseNode true
+                }
+            }
+            steps {
+                CleanBuildAndTest("-DCMAKE_BUILD_TYPE=Debug")
+            }
+        }
         stage('SIMD fallback') {
             agent {
                 dockerfile {
@@ -106,7 +117,7 @@ pipeline {
                 }
             }
             steps {
-                CleanBuildAndTest("-DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DCMAKE_C_FLAGS=--coverage -DCMAKE_CXX_FLAGS=--coverage -DCMAKE_BUILD_TYPE=Debug")
+                CleanBuildAndTest("-DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DCMAKE_C_FLAGS=--coverage -DCMAKE_CXX_FLAGS=--coverage -DCMAKE_BUILD_TYPE=Debug -DDISABLE_TSAN=ON")
                 sh '''
                 gcovr -f ConflictSet.cpp --cobertura > build/coverage.xml
                 '''

RealDataBench.cpp

@@ -129,6 +129,16 @@ int main(int argc, const char **argv) {
     close(fd);
   }
 
+  ConflictSet::MetricsV1 *metrics;
+  int metricsCount;
+  cs.getMetricsV1(&metrics, &metricsCount);
+  for (int i = 0; i < metricsCount; ++i) {
+    printf("# HELP %s %s\n", metrics[i].name, metrics[i].help);
+    printf("# TYPE %s %s\n", metrics[i].name,
+           metrics[i].type == metrics[i].Counter ? "counter" : "gauge");
+    printf("%s %g\n", metrics[i].name, metrics[i].getValue());
+  }
+
   printf("Check: %g seconds, %g MB/s, Add: %g seconds, %g MB/s, Gc ratio: "
          "%g%%, Peak idle memory: %g\n",
          checkTime, checkBytes / checkTime * 1e-6, addTime,

SkipList.cpp

@@ -42,7 +42,7 @@ std::span<const uint8_t> copyToArena(Arena &arena,
 }
 
 using Version = int64_t;
-#define force_inline __attribute__((always_inline))
+#define force_inline inline __attribute__((always_inline))
 using StringRef = std::span<const uint8_t>;
 
 struct KeyRangeRef {
@@ -861,6 +861,16 @@ void internal_destroy(ConflictSet::Impl *impl) {
 
 int64_t internal_getBytes(ConflictSet::Impl *impl) { return impl->totalBytes; }
 
+void internal_getMetricsV1(ConflictSet::Impl *impl,
+                           ConflictSet::MetricsV1 **metrics, int *count) {
+  *metrics = nullptr;
+  *count = 0;
+}
+
+double internal_getMetricValue(const ConflictSet::MetricsV1 *metric) {
+  return 0;
+}
+
 void ConflictSet::check(const ReadRange *reads, Result *results,
                         int count) const {
   internal_check(impl, reads, results, count);
@@ -877,6 +887,14 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
 
 int64_t ConflictSet::getBytes() const { return internal_getBytes(impl); }
 
+void ConflictSet::getMetricsV1(MetricsV1 **metrics, int *count) const {
+  return internal_getMetricsV1(impl, metrics, count);
+}
+
+double ConflictSet::MetricsV1::getValue() const {
+  return internal_getMetricValue(this);
+}
+
 ConflictSet::ConflictSet(int64_t oldestVersion)
     : impl(internal_create(oldestVersion)) {}
 

TestDriver.cpp

@@ -15,5 +15,18 @@ int main(int argc, char **argv) {
     if (!driver.ok) {
       abort();
     }
+
+    ConflictSet::MetricsV1 *metrics;
+    int metricsCount;
+    driver.cs.getMetricsV1(&metrics, &metricsCount);
+    printf("#################### METRICS FOR %s ####################\n",
+           argv[i]);
+    for (int i = 0; i < metricsCount; ++i) {
+      printf("# HELP %s %s\n", metrics[i].name, metrics[i].help);
+      printf("# TYPE %s %s\n", metrics[i].name,
+             metrics[i].type == metrics[i].Counter ? "counter" : "gauge");
+      printf("%s %g\n", metrics[i].name, metrics[i].getValue());
+    }
+    puts("");
   }
 }

aarch64-symbol-imports.txt

@@ -1,3 +1,5 @@
+__aarch64_cas8_relax
+__getauxval@GLIBC_2.17
 __stack_chk_fail@GLIBC_2.17
 __stack_chk_guard@GLIBC_2.17
 abort@GLIBC_2.17

apple-symbol-exports.txt

@@ -13,5 +13,7 @@ __ZN8weaselab11ConflictSetC2Ex
 __ZN8weaselab11ConflictSetD1Ev
 __ZN8weaselab11ConflictSetD2Ev
 __ZN8weaselab11ConflictSetaSEOS0_
+__ZNK8weaselab11ConflictSet12getMetricsV1EPPNS0_9MetricsV1EPi
 __ZNK8weaselab11ConflictSet5checkEPKNS0_9ReadRangeEPNS0_6ResultEi
 __ZNK8weaselab11ConflictSet8getBytesEv
+__ZNK8weaselab11ConflictSet9MetricsV18getValueEv

conflict_set_cxx_api_test.cpp

@@ -1,6 +1,7 @@
 #include "ConflictSet.h"
 
 #include <cassert>
+#include <cstdio>
 
 using namespace weaselab;
 
@@ -21,4 +22,14 @@ int main(void) {
   assert(result == ConflictSet::Conflict);
   int64_t bytes = cs.getBytes();
   assert(bytes > 0);
+
+  ConflictSet::MetricsV1 *metrics;
+  int metricsCount;
+  cs.getMetricsV1(&metrics, &metricsCount);
+  for (int i = 0; i < metricsCount; ++i) {
+    printf("# HELP %s %s\n", metrics[i].name, metrics[i].help);
+    printf("# TYPE %s %s\n", metrics[i].name,
+           metrics[i].type == metrics[i].Counter ? "counter" : "gauge");
+    printf("%s %g\n", metrics[i].name, metrics[i].getValue());
+  }
 }

include/ConflictSet.h

@@ -88,6 +88,35 @@ struct __attribute__((__visibility__("default"))) ConflictSet {
   /** Returns the total bytes in use by this ConflictSet */
   int64_t getBytes() const;
 
+  /** Experimental! */
+  struct MetricsV1 {
+    /** A null-terminated string with static lifetime. Identifies this metric.
+     * Matches the regex [a-zA-Z_:][a-zA-Z0-9_:]*
+     */
+    const char *name;
+    /** A null-terminated string with static lifetime. Describes this metric.
+     * May contain any sequence of UTF-8 characters, but the backslash and the
+     * line feed characters are escaped as \\ and \n, respectively.
+     */
+    const char *help;
+    /** Counters are >= 0 and non-decreasing. Gauges are any value. */
+    enum Type { Counter, Gauge } type;
+    /** Get the most up-to-date (best effort) value for this metric.
+     * Thread-safe. */
+    double getValue() const;
+    /** @private */
+    void *p;
+  };
+
+  /** Experimental! Store a pointer to an array of MetricsV1 (owned by the
+   * ConflictSet) to `*metrics`, and its length to `*count`. This function makes
+   * no guarantees about the contents of the metrics (e.g. names, help text, and
+   * the meaning of values). A correct implementation is free to return nonsense
+   * or nothing at all. Not intended to be inspected programmatically. Only
+   * intended to be plumbed along to e.g. Prometheus. Callers may repeatedly
+   * call `getValue` on the metrics they're interested in. */
+  void getMetricsV1(MetricsV1 **metrics, int *count) const;
+
 #if __cplusplus > 199711L
   ConflictSet(ConflictSet &&) noexcept;
   ConflictSet &operator=(ConflictSet &&) noexcept;

symbol-exports.txt

@@ -6,12 +6,14 @@ ConflictSet_getBytes
 ConflictSet_setOldestVersion
 _ZN8weaselab11ConflictSet16setOldestVersionEl
 _ZN8weaselab11ConflictSet9addWritesEPKNS0_10WriteRangeEil
-_ZN8weaselab11ConflictSetaSEOS0_
-_ZN8weaselab11ConflictSetC1El
 _ZN8weaselab11ConflictSetC1EOS0_
-_ZN8weaselab11ConflictSetC2El
+_ZN8weaselab11ConflictSetC1El
 _ZN8weaselab11ConflictSetC2EOS0_
+_ZN8weaselab11ConflictSetC2El
 _ZN8weaselab11ConflictSetD1Ev
 _ZN8weaselab11ConflictSetD2Ev
+_ZN8weaselab11ConflictSetaSEOS0_
+_ZNK8weaselab11ConflictSet12getMetricsV1EPPNS0_9MetricsV1EPi
 _ZNK8weaselab11ConflictSet5checkEPKNS0_9ReadRangeEPNS0_6ResultEi
 _ZNK8weaselab11ConflictSet8getBytesEv
+_ZNK8weaselab11ConflictSet9MetricsV18getValueEv

symbol-imports.txt

@@ -8,4 +8,4 @@ free@GLIBC_2.2.5
 malloc@GLIBC_2.2.5
 memcpy@GLIBC_2.14
 memmove@GLIBC_2.2.5
-memset@GLIBC_2.2.5
+memset@GLIBC_2.2.5