From 36dcb98b01251724b29aab79ea6f58dfc01c0dc6 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Fri, 6 Dec 2019 23:28:55 +0000
Subject: [PATCH 01/13] Add stats to WASM VMs.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 bazel/external/wee8.genrule_cmd               |  6 +-
 source/extensions/common/wasm/BUILD           |  8 +++
 source/extensions/common/wasm/null/BUILD      |  1 +
 source/extensions/common/wasm/null/null.cc    |  2 +-
 source/extensions/common/wasm/null/null.h     |  2 +-
 source/extensions/common/wasm/null/null_vm.cc |  3 +
 source/extensions/common/wasm/null/null_vm.h  | 15 +++--
 source/extensions/common/wasm/v8/BUILD        |  1 +
 source/extensions/common/wasm/v8/v8.cc        | 36 +++++++++--
 source/extensions/common/wasm/v8/v8.h         |  2 +-
 source/extensions/common/wasm/wasm_vm.cc      |  6 +-
 source/extensions/common/wasm/wasm_vm.h       | 16 +++--
 source/extensions/common/wasm/wasm_vm_base.h  | 63 +++++++++++++++++++
 test/extensions/common/wasm/wasm_vm_test.cc   | 51 +++++++++------
 14 files changed, 169 insertions(+), 43 deletions(-)
 create mode 100644 source/extensions/common/wasm/wasm_vm_base.h

diff --git a/bazel/external/wee8.genrule_cmd b/bazel/external/wee8.genrule_cmd
index 323402b493927..9103dfb4d9fbc 100644
--- a/bazel/external/wee8.genrule_cmd
+++ b/bazel/external/wee8.genrule_cmd
@@ -72,7 +72,11 @@ WEE8_BUILD_ARGS+=" v8_use_external_startup_data=false"
 WEE8_BUILD_ARGS+=" v8_enable_shared_ro_heap=false"
 
 # Build wee8.
-third_party/depot_tools/gn gen out/wee8 --args="$$WEE8_BUILD_ARGS"
+if [[ `uname` == "Darwin" ]]; then
+  buildtools/mac/gn gen out/wee8 --args="$$WEE8_BUILD_ARGS"
+else
+  buildtools/linux64/gn gen out/wee8 --args="$$WEE8_BUILD_ARGS"
+fi
 third_party/depot_tools/ninja -C out/wee8 wee8
 
 # Move compiled library to the expected destinations.
diff --git a/source/extensions/common/wasm/BUILD b/source/extensions/common/wasm/BUILD
index dbc0f83910be8..9333c679421f6 100644
--- a/source/extensions/common/wasm/BUILD
+++ b/source/extensions/common/wasm/BUILD
@@ -25,6 +25,14 @@ envoy_cc_library(
     ],
 )
 
+envoy_cc_library(
+    name = "wasm_vm_base",
+    hdrs = ["wasm_vm_base.h"],
+    deps = [
+        "//source/common/stats:stats_lib",
+    ],
+)
+
 envoy_cc_library(
     name = "wasm_vm_lib",
     srcs = ["wasm_vm.cc"],
diff --git a/source/extensions/common/wasm/null/BUILD b/source/extensions/common/wasm/null/BUILD
index eed8e62d2e49b..6f93952bc9cfc 100644
--- a/source/extensions/common/wasm/null/BUILD
+++ b/source/extensions/common/wasm/null/BUILD
@@ -26,6 +26,7 @@ envoy_cc_library(
         "//external:abseil_node_hash_map",
         "//include/envoy/registry",
         "//source/common/common:assert_lib",
+        "//source/extensions/common/wasm:wasm_vm_base",
         "//source/extensions/common/wasm:wasm_vm_interface",
         "//source/extensions/common/wasm:well_known_names",
     ],
diff --git a/source/extensions/common/wasm/null/null.cc b/source/extensions/common/wasm/null/null.cc
index 185dde60780ab..1a2fc46924331 100644
--- a/source/extensions/common/wasm/null/null.cc
+++ b/source/extensions/common/wasm/null/null.cc
@@ -18,7 +18,7 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-WasmVmPtr createVm() { return std::make_unique<NullVm>(); }
+WasmVmPtr createVm(Stats::ScopeSharedPtr scope) { return std::make_unique<NullVm>(scope); }
 
 } // namespace Null
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/null/null.h b/source/extensions/common/wasm/null/null.h
index 7d88fb356923e..1fab2784f04bc 100644
--- a/source/extensions/common/wasm/null/null.h
+++ b/source/extensions/common/wasm/null/null.h
@@ -11,7 +11,7 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-WasmVmPtr createVm();
+WasmVmPtr createVm(Stats::ScopeSharedPtr scope);
 
 } // namespace Null
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/null/null_vm.cc b/source/extensions/common/wasm/null/null_vm.cc
index d2cb16b994f16..c23d6d7bd0c48 100644
--- a/source/extensions/common/wasm/null/null_vm.cc
+++ b/source/extensions/common/wasm/null/null_vm.cc
@@ -7,6 +7,7 @@
 #include "envoy/registry/registry.h"
 
 #include "common/common/assert.h"
+#include "common/singleton/threadsafe_singleton.h"
 
 #include "extensions/common/wasm/null/null_vm_plugin.h"
 #include "extensions/common/wasm/well_known_names.h"
@@ -17,6 +18,8 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
+ThreadSafeSingleton<VmGlobalStats> global_stats_;
+
 WasmVmPtr NullVm::clone() {
   auto cloned_null_vm = std::make_unique<NullVm>(*this);
   cloned_null_vm->load(plugin_name_, false /* unused */);
diff --git a/source/extensions/common/wasm/null/null_vm.h b/source/extensions/common/wasm/null/null_vm.h
index d23e332bcb77d..64f0e666978e1 100644
--- a/source/extensions/common/wasm/null/null_vm.h
+++ b/source/extensions/common/wasm/null/null_vm.h
@@ -7,8 +7,10 @@
 #include "envoy/registry/registry.h"
 
 #include "common/common/assert.h"
+#include "common/singleton/threadsafe_singleton.h"
 
 #include "extensions/common/wasm/null/null_vm_plugin.h"
+#include "extensions/common/wasm/wasm_vm_base.h"
 #include "extensions/common/wasm/well_known_names.h"
 
 namespace Envoy {
@@ -17,16 +19,21 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
+extern ThreadSafeSingleton<VmGlobalStats> global_stats_;
+
 // The NullVm wraps a C++ WASM plugin which has been compiled with the WASM API
 // and linked directly into the Envoy process. This is useful for development
 // in that it permits the debugger to set breakpoints in both Envoy and the plugin.
-struct NullVm : public WasmVm {
-  NullVm() = default;
-  NullVm(const NullVm& other) : plugin_name_(other.plugin_name_) {}
+struct NullVm : public WasmVmBase {
+  NullVm(Stats::ScopeSharedPtr scope)
+      : WasmVmBase(scope, &global_stats_.get(), WasmRuntimeNames::get().Null) {}
+  NullVm(const NullVm& other)
+      : WasmVmBase(other.scope_, &global_stats_.get(), WasmRuntimeNames::get().Null),
+        plugin_name_(other.plugin_name_) {}
 
   // WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().Null; }
-  bool cloneable() override { return true; };
+  Cloneable cloneable() override { return Cloneable::InstantiatedModule; };
   WasmVmPtr clone() override;
   bool load(const std::string& code, bool allow_precompiled) override;
   void link(absl::string_view debug_name) override;
diff --git a/source/extensions/common/wasm/v8/BUILD b/source/extensions/common/wasm/v8/BUILD
index fb5a473026402..04d0954d1b2cd 100644
--- a/source/extensions/common/wasm/v8/BUILD
+++ b/source/extensions/common/wasm/v8/BUILD
@@ -17,6 +17,7 @@ envoy_cc_library(
     ],
     deps = [
         "//source/common/common:assert_lib",
+        "//source/extensions/common/wasm:wasm_vm_base",
         "//source/extensions/common/wasm:wasm_vm_interface",
         "//source/extensions/common/wasm:well_known_names",
     ],
diff --git a/source/extensions/common/wasm/v8/v8.cc b/source/extensions/common/wasm/v8/v8.cc
index 44e4a46f1989d..e7fbea3620d90 100644
--- a/source/extensions/common/wasm/v8/v8.cc
+++ b/source/extensions/common/wasm/v8/v8.cc
@@ -5,7 +5,9 @@
 #include <vector>
 
 #include "common/common/assert.h"
+#include "common/singleton/threadsafe_singleton.h"
 
+#include "extensions/common/wasm/wasm_vm_base.h"
 #include "extensions/common/wasm/well_known_names.h"
 
 #include "absl/container/flat_hash_map.h"
@@ -18,6 +20,8 @@ namespace Common {
 namespace Wasm {
 namespace V8 {
 
+ThreadSafeSingleton<VmGlobalStats> global_stats_;
+
 wasm::Engine* engine() {
   static const auto engine = wasm::Engine::make();
   return engine.get();
@@ -33,9 +37,10 @@ struct FuncData {
 
 using FuncDataPtr = std::unique_ptr<FuncData>;
 
-class V8 : public WasmVm {
+class V8 : public WasmVmBase {
 public:
-  V8() = default;
+  V8(Stats::ScopeSharedPtr scope)
+      : WasmVmBase(scope, &global_stats_.get(), WasmRuntimeNames::get().V8) {}
 
   // Extensions::Common::Wasm::WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().V8; }
@@ -44,9 +49,8 @@ class V8 : public WasmVm {
   absl::string_view getCustomSection(absl::string_view name) override;
   void link(absl::string_view debug_name) override;
 
-  // V8 is currently not cloneable.
-  bool cloneable() override { return false; }
-  WasmVmPtr clone() override { return nullptr; }
+  Cloneable cloneable() override { return Cloneable::CompiledBytecode; }
+  WasmVmPtr clone() override;
 
   uint64_t getMemorySize() override;
   absl::optional<absl::string_view> getMemory(uint64_t pointer, uint64_t size) override;
@@ -89,6 +93,7 @@ class V8 : public WasmVm {
   wasm::vec<byte_t> source_ = wasm::vec<byte_t>::invalid();
   wasm::own<wasm::Store> store_;
   wasm::own<wasm::Module> module_;
+  wasm::own<wasm::Shared<wasm::Module>> shared_module_;
   wasm::own<wasm::Instance> instance_;
   wasm::own<wasm::Memory> memory_;
   wasm::own<wasm::Table> table_;
@@ -247,9 +252,28 @@ bool V8::load(const std::string& code, bool /* allow_precompiled */) {
   ::memcpy(source_.get(), code.data(), code.size());
 
   module_ = wasm::Module::make(store_.get(), source_);
+  if (module_) {
+    shared_module_ = module_->share();
+    RELEASE_ASSERT(shared_module_ != nullptr, "");
+  }
+
   return module_ != nullptr;
 }
 
+WasmVmPtr V8::clone() {
+  ENVOY_LOG(trace, "clone()");
+  ASSERT(shared_module_ != nullptr);
+
+  auto clone = std::make_unique<V8>(scope_);
+  clone->store_ = wasm::Store::make(engine());
+  RELEASE_ASSERT(clone->store_ != nullptr, "");
+
+  clone->module_ = wasm::Module::obtain(clone->store_.get(), shared_module_.get());
+  RELEASE_ASSERT(clone->module_ != nullptr, "");
+
+  return clone;
+}
+
 absl::string_view V8::getCustomSection(absl::string_view name) {
   ENVOY_LOG(trace, "getCustomSection(\"{}\")", name);
   ASSERT(source_.get() != nullptr);
@@ -562,7 +586,7 @@ void V8::getModuleFunctionImpl(absl::string_view function_name,
   };
 }
 
-WasmVmPtr createVm() { return std::make_unique<V8>(); }
+WasmVmPtr createVm(Stats::ScopeSharedPtr scope) { return std::make_unique<V8>(scope); }
 
 } // namespace V8
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/v8/v8.h b/source/extensions/common/wasm/v8/v8.h
index 3650f190a73c8..1cee4424e8152 100644
--- a/source/extensions/common/wasm/v8/v8.h
+++ b/source/extensions/common/wasm/v8/v8.h
@@ -10,7 +10,7 @@ namespace Common {
 namespace Wasm {
 namespace V8 {
 
-WasmVmPtr createVm();
+WasmVmPtr createVm(Stats::ScopeSharedPtr scope);
 
 } // namespace V8
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/wasm_vm.cc b/source/extensions/common/wasm/wasm_vm.cc
index 34f2745331440..88ee11c60bc0d 100644
--- a/source/extensions/common/wasm/wasm_vm.cc
+++ b/source/extensions/common/wasm/wasm_vm.cc
@@ -14,13 +14,13 @@ namespace Wasm {
 thread_local Envoy::Extensions::Common::Wasm::Context* current_context_ = nullptr;
 thread_local uint32_t effective_context_id_ = 0;
 
-WasmVmPtr createWasmVm(absl::string_view runtime) {
+WasmVmPtr createWasmVm(absl::string_view runtime, Stats::ScopeSharedPtr scope) {
   if (runtime.empty()) {
     throw WasmVmException("Failed to create WASM VM with unspecified runtime.");
   } else if (runtime == WasmRuntimeNames::get().Null) {
-    return Null::createVm();
+    return Null::createVm(scope);
   } else if (runtime == WasmRuntimeNames::get().V8) {
-    return V8::createVm();
+    return V8::createVm(scope);
   } else {
     throw WasmVmException(fmt::format(
         "Failed to create WASM VM using {} runtime. Envoy was compiled without support for it.",
diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index 7cf58ed561550..45e5c08d0a81b 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -3,6 +3,7 @@
 #include <memory>
 
 #include "envoy/common/exception.h"
+#include "envoy/stats/scope.h"
 
 #include "common/common/logger.h"
 
@@ -98,8 +99,7 @@ template <size_t N> using WasmCallWord = std::function<WasmFuncType<N, Word, Con
 
 #define FOR_ALL_WASM_VM_EXPORTS(_f)                                                                \
   _f(WasmCallVoid<0>) _f(WasmCallVoid<1>) _f(WasmCallVoid<2>) _f(WasmCallVoid<3>)                  \
-      _f(WasmCallVoid<4>) _f(WasmCallVoid<5>) _f(WasmCallVoid<8>) _f(WasmCallWord<0>)              \
-          _f(WasmCallWord<1>) _f(WasmCallWord<2>) _f(WasmCallWord<3>)
+      _f(WasmCallVoid<5>) _f(WasmCallWord<1>) _f(WasmCallWord<2>) _f(WasmCallWord<3>)
 
 // Calls out of the WASM VM.
 // 1st arg is always a pointer to raw_context (void*).
@@ -111,6 +111,7 @@ template <size_t N> using WasmCallbackWord = WasmFuncType<N, Word, void*, Word>*
 // Extended with W = Word
 // Z = void, j = uint32_t, l = int64_t, m = uint64_t
 using WasmCallback_WWl = Word (*)(void*, Word, int64_t);
+using WasmCallback_WWlWW = Word (*)(void*, Word, int64_t, Word, Word);
 using WasmCallback_WWm = Word (*)(void*, Word, uint64_t);
 using WasmCallback_dd = double (*)(void*, double);
 
@@ -119,8 +120,11 @@ using WasmCallback_dd = double (*)(void*, double);
       _f(WasmCallbackVoid<4>) _f(WasmCallbackWord<0>) _f(WasmCallbackWord<1>)                      \
           _f(WasmCallbackWord<2>) _f(WasmCallbackWord<3>) _f(WasmCallbackWord<4>)                  \
               _f(WasmCallbackWord<5>) _f(WasmCallbackWord<6>) _f(WasmCallbackWord<7>)              \
-                  _f(WasmCallbackWord<8>) _f(WasmCallbackWord<9>) _f(WasmCallback_WWl)             \
-                      _f(WasmCallback_WWm) _f(WasmCallback_dd)
+                  _f(WasmCallbackWord<8>) _f(WasmCallbackWord<9>) _f(WasmCallbackWord<10>)         \
+                      _f(WasmCallback_WWl) _f(WasmCallback_WWlWW) _f(WasmCallback_WWm)             \
+                          _f(WasmCallback_dd)
+
+enum class Cloneable { NotCloneable, CompiledBytecode, InstantiatedModule };
 
 // Wasm VM instance. Provides the low level WASM interface.
 class WasmVm : public Logger::Loggable<Logger::Id::wasm> {
@@ -143,7 +147,7 @@ class WasmVm : public Logger::Loggable<Logger::Id::wasm> {
    * VM from scratch for each worker.
    * @return true if the VM is cloneable.
    */
-  virtual bool cloneable() PURE;
+  virtual Cloneable cloneable() PURE;
 
   /**
    * Make a worker/thread-specific copy if supported by the underlying VM system (see cloneable()
@@ -287,7 +291,7 @@ struct SaveRestoreContext {
 };
 
 // Create a new low-level WASM VM using runtime of the given type (e.g. "envoy.wasm.runtime.wavm").
-WasmVmPtr createWasmVm(absl::string_view runtime);
+WasmVmPtr createWasmVm(absl::string_view runtime, Stats::ScopeSharedPtr scope);
 
 } // namespace Wasm
 } // namespace Common
diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
new file mode 100644
index 0000000000000..4ad0950ffa72c
--- /dev/null
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -0,0 +1,63 @@
+#pragma once
+
+#include "envoy/stats/scope.h"
+#include "envoy/stats/stats.h"
+#include "envoy/stats/stats_macros.h"
+
+#include "extensions/common/wasm/wasm_vm.h"
+
+#include "absl/strings/str_cat.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace Common {
+namespace Wasm {
+
+/**
+ * Wasm host stats.
+ */
+#define ALL_VM_STATS(COUNTER, GAUGE)                                                               \
+  COUNTER(created)                                                                                 \
+  COUNTER(cloned)                                                                                  \
+  GAUGE(active, NeverImport)
+
+struct VmStats {
+  ALL_VM_STATS(GENERATE_COUNTER_STRUCT, GENERATE_GAUGE_STRUCT)
+};
+
+struct VmGlobalStats {
+  std::atomic<int64_t> active_;
+};
+
+// Wasm VM base instance. Provides common behavior (e.g. Stats).
+class WasmVmBase : public WasmVm {
+public:
+  WasmVmBase(Stats::ScopeSharedPtr scope, VmGlobalStats* global_stats_ptr,
+             absl::string_view runtime)
+      : scope_(scope), global_stats_ptr_(global_stats_ptr),
+        stats_(VmStats{
+            ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, absl::StrCat("wasm_vm.", runtime, ".")),
+                         POOL_GAUGE_PREFIX(*scope_, absl::StrCat("wasm_vm.", runtime, ".")))}),
+        runtime_(std::string(runtime)) {
+    global_stats_ptr_->active_++;
+    stats_.created_.inc();
+    stats_.active_.set(global_stats_ptr_->active_);
+    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, global_stats_ptr_->active_);
+  }
+  virtual ~WasmVmBase() {
+    global_stats_ptr_->active_--;
+    stats_.active_.set(global_stats_ptr_->active_);
+    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, global_stats_ptr_->active_);
+  }
+
+protected:
+  Stats::ScopeSharedPtr scope_;
+  VmGlobalStats* global_stats_ptr_;
+  VmStats stats_;
+  std::string runtime_;
+};
+
+} // namespace Wasm
+} // namespace Common
+} // namespace Extensions
+} // namespace Envoy
diff --git a/test/extensions/common/wasm/wasm_vm_test.cc b/test/extensions/common/wasm/wasm_vm_test.cc
index 1584406c89097..87085a97475ef 100644
--- a/test/extensions/common/wasm/wasm_vm_test.cc
+++ b/test/extensions/common/wasm/wasm_vm_test.cc
@@ -1,5 +1,7 @@
 #include "envoy/registry/registry.h"
 
+#include "common/stats/isolated_store_impl.h"
+
 #include "extensions/common/wasm/null/null_vm_plugin.h"
 #include "extensions/common/wasm/wasm_vm.h"
 
@@ -35,7 +37,7 @@ class PluginFactory : public Null::NullVmPluginFactory {
 };
 
 TestNullVmPlugin* test_null_vm_plugin_ = nullptr;
-REGISTER_FACTORY(PluginFactory, Null::NullVmPluginFactory);
+Envoy::Registry::RegisterFactory<PluginFactory, Null::NullVmPluginFactory> register_;
 
 std::unique_ptr<Null::NullVmPlugin> PluginFactory::create() const {
   auto result = std::make_unique<TestNullVmPlugin>();
@@ -43,29 +45,38 @@ std::unique_ptr<Null::NullVmPlugin> PluginFactory::create() const {
   return result;
 }
 
-TEST(BadVmTest, NoRuntime) {
-  EXPECT_THROW_WITH_MESSAGE(createWasmVm(""), WasmVmException,
+class BaseVmTest : public testing::Test {
+public:
+  BaseVmTest() : scope_(Stats::ScopeSharedPtr(stats_store.createScope("wasm."))) {}
+
+protected:
+  Stats::IsolatedStoreImpl stats_store;
+  Stats::ScopeSharedPtr scope_;
+};
+
+TEST_F(BaseVmTest, NoRuntime) {
+  EXPECT_THROW_WITH_MESSAGE(createWasmVm("", scope_), WasmVmException,
                             "Failed to create WASM VM with unspecified runtime.");
 }
 
-TEST(BadVmTest, BadRuntime) {
-  EXPECT_THROW_WITH_MESSAGE(createWasmVm("envoy.wasm.runtime.invalid"), WasmVmException,
+TEST_F(BaseVmTest, BadRuntime) {
+  EXPECT_THROW_WITH_MESSAGE(createWasmVm("envoy.wasm.runtime.invalid", scope_), WasmVmException,
                             "Failed to create WASM VM using envoy.wasm.runtime.invalid runtime. "
                             "Envoy was compiled without support for it.");
 }
 
-TEST(NullVmTest, NullVmStartup) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.null");
+TEST_F(BaseVmTest, NullVmStartup) {
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.null", scope_);
   EXPECT_TRUE(wasm_vm != nullptr);
   EXPECT_TRUE(wasm_vm->runtime() == "envoy.wasm.runtime.null");
-  EXPECT_TRUE(wasm_vm->cloneable());
+  EXPECT_TRUE(wasm_vm->cloneable() == Cloneable::InstantiatedModule);
   auto wasm_vm_clone = wasm_vm->clone();
   EXPECT_TRUE(wasm_vm_clone != nullptr);
   EXPECT_TRUE(wasm_vm->getCustomSection("user").empty());
 }
 
-TEST(NullVmTest, NullVmMemory) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.null");
+TEST_F(BaseVmTest, NullVmMemory) {
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.null", scope_);
   EXPECT_EQ(wasm_vm->getMemorySize(), std::numeric_limits<uint64_t>::max());
   std::string d = "data";
   auto m = wasm_vm->getMemory(reinterpret_cast<uint64_t>(d.data()), d.size()).value();
@@ -114,26 +125,23 @@ Word bad_pong2(void*, Word) { return 2; }
 // pong() with wrong argument type.
 double bad_pong3(void*, double) { return 3; }
 
-class WasmVmTest : public testing::Test {
+class WasmVmTest : public BaseVmTest {
 public:
   void SetUp() override { g_host_functions = new MockHostFunctions(); }
   void TearDown() override { delete g_host_functions; }
 };
 
 TEST_F(WasmVmTest, V8BadCode) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8");
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8", scope_);
   ASSERT_TRUE(wasm_vm != nullptr);
 
   EXPECT_FALSE(wasm_vm->load("bad code", false));
 }
 
 TEST_F(WasmVmTest, V8Code) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8");
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8", scope_);
   ASSERT_TRUE(wasm_vm != nullptr);
-
   EXPECT_TRUE(wasm_vm->runtime() == "envoy.wasm.runtime.v8");
-  EXPECT_FALSE(wasm_vm->cloneable());
-  EXPECT_TRUE(wasm_vm->clone() == nullptr);
 
   auto code = TestEnvironment::readFileToStringForTest(TestEnvironment::substitute(
       "{{ test_rundir }}/test/extensions/common/wasm/test_data/test_rust.wasm"));
@@ -141,10 +149,13 @@ TEST_F(WasmVmTest, V8Code) {
 
   EXPECT_THAT(wasm_vm->getCustomSection("producers"), HasSubstr("rustc"));
   EXPECT_TRUE(wasm_vm->getCustomSection("emscripten_metadata").empty());
+
+  EXPECT_TRUE(wasm_vm->cloneable() == Cloneable::CompiledBytecode);
+  EXPECT_TRUE(wasm_vm->clone() != nullptr);
 }
 
 TEST_F(WasmVmTest, V8BadHostFunctions) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8");
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8", scope_);
   ASSERT_TRUE(wasm_vm != nullptr);
 
   auto code = TestEnvironment::readFileToStringForTest(TestEnvironment::substitute(
@@ -172,7 +183,7 @@ TEST_F(WasmVmTest, V8BadHostFunctions) {
 }
 
 TEST_F(WasmVmTest, V8BadModuleFunctions) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8");
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8", scope_);
   ASSERT_TRUE(wasm_vm != nullptr);
 
   auto code = TestEnvironment::readFileToStringForTest(TestEnvironment::substitute(
@@ -200,7 +211,7 @@ TEST_F(WasmVmTest, V8BadModuleFunctions) {
 }
 
 TEST_F(WasmVmTest, V8FunctionCalls) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8");
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8", scope_);
   ASSERT_TRUE(wasm_vm != nullptr);
 
   auto code = TestEnvironment::readFileToStringForTest(TestEnvironment::substitute(
@@ -238,7 +249,7 @@ TEST_F(WasmVmTest, V8FunctionCalls) {
 }
 
 TEST_F(WasmVmTest, V8Memory) {
-  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8");
+  auto wasm_vm = createWasmVm("envoy.wasm.runtime.v8", scope_);
   ASSERT_TRUE(wasm_vm != nullptr);
 
   auto code = TestEnvironment::readFileToStringForTest(TestEnvironment::substitute(

From 0ba0bdfffb149bde4b2d64ebf69d04c42d6ebf69 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Thu, 12 Dec 2019 21:50:21 +0000
Subject: [PATCH 02/13] Convert Singleton to a global.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/null/null_vm.cc |  2 +-
 source/extensions/common/wasm/null/null_vm.h  |  6 ++---
 source/extensions/common/wasm/v8/v8.cc        |  5 ++---
 source/extensions/common/wasm/wasm_vm_base.h  | 22 ++++++++-----------
 4 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/source/extensions/common/wasm/null/null_vm.cc b/source/extensions/common/wasm/null/null_vm.cc
index c23d6d7bd0c48..d661c43134946 100644
--- a/source/extensions/common/wasm/null/null_vm.cc
+++ b/source/extensions/common/wasm/null/null_vm.cc
@@ -18,7 +18,7 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-ThreadSafeSingleton<VmGlobalStats> global_stats_;
+std::atomic<int> active_vms_;
 
 WasmVmPtr NullVm::clone() {
   auto cloned_null_vm = std::make_unique<NullVm>(*this);
diff --git a/source/extensions/common/wasm/null/null_vm.h b/source/extensions/common/wasm/null/null_vm.h
index 64f0e666978e1..4c0aae998d71b 100644
--- a/source/extensions/common/wasm/null/null_vm.h
+++ b/source/extensions/common/wasm/null/null_vm.h
@@ -19,16 +19,16 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-extern ThreadSafeSingleton<VmGlobalStats> global_stats_;
+extern std::atomic<int> active_vms_;
 
 // The NullVm wraps a C++ WASM plugin which has been compiled with the WASM API
 // and linked directly into the Envoy process. This is useful for development
 // in that it permits the debugger to set breakpoints in both Envoy and the plugin.
 struct NullVm : public WasmVmBase {
   NullVm(Stats::ScopeSharedPtr scope)
-      : WasmVmBase(scope, &global_stats_.get(), WasmRuntimeNames::get().Null) {}
+      : WasmVmBase(scope, &active_vms_, WasmRuntimeNames::get().Null) {}
   NullVm(const NullVm& other)
-      : WasmVmBase(other.scope_, &global_stats_.get(), WasmRuntimeNames::get().Null),
+      : WasmVmBase(other.scope_, &active_vms_, WasmRuntimeNames::get().Null),
         plugin_name_(other.plugin_name_) {}
 
   // WasmVm
diff --git a/source/extensions/common/wasm/v8/v8.cc b/source/extensions/common/wasm/v8/v8.cc
index e7fbea3620d90..7d54d30d8a174 100644
--- a/source/extensions/common/wasm/v8/v8.cc
+++ b/source/extensions/common/wasm/v8/v8.cc
@@ -20,7 +20,7 @@ namespace Common {
 namespace Wasm {
 namespace V8 {
 
-ThreadSafeSingleton<VmGlobalStats> global_stats_;
+std::atomic<int> active_vms_;
 
 wasm::Engine* engine() {
   static const auto engine = wasm::Engine::make();
@@ -39,8 +39,7 @@ using FuncDataPtr = std::unique_ptr<FuncData>;
 
 class V8 : public WasmVmBase {
 public:
-  V8(Stats::ScopeSharedPtr scope)
-      : WasmVmBase(scope, &global_stats_.get(), WasmRuntimeNames::get().V8) {}
+  V8(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, &active_vms_, WasmRuntimeNames::get().V8) {}
 
   // Extensions::Common::Wasm::WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().V8; }
diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
index 4ad0950ffa72c..7c95099265ecd 100644
--- a/source/extensions/common/wasm/wasm_vm_base.h
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -25,34 +25,30 @@ struct VmStats {
   ALL_VM_STATS(GENERATE_COUNTER_STRUCT, GENERATE_GAUGE_STRUCT)
 };
 
-struct VmGlobalStats {
-  std::atomic<int64_t> active_;
-};
-
 // Wasm VM base instance. Provides common behavior (e.g. Stats).
 class WasmVmBase : public WasmVm {
 public:
-  WasmVmBase(Stats::ScopeSharedPtr scope, VmGlobalStats* global_stats_ptr,
+  WasmVmBase(Stats::ScopeSharedPtr scope, std::atomic<int>* active_vms_ptr,
              absl::string_view runtime)
-      : scope_(scope), global_stats_ptr_(global_stats_ptr),
+      : scope_(scope), active_vms_ptr_(active_vms_ptr),
         stats_(VmStats{
             ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, absl::StrCat("wasm_vm.", runtime, ".")),
                          POOL_GAUGE_PREFIX(*scope_, absl::StrCat("wasm_vm.", runtime, ".")))}),
         runtime_(std::string(runtime)) {
-    global_stats_ptr_->active_++;
     stats_.created_.inc();
-    stats_.active_.set(global_stats_ptr_->active_);
-    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, global_stats_ptr_->active_);
+    (*active_vms_ptr_)++;
+    stats_.active_.set(*active_vms_ptr_);
+    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, *active_vms_ptr_);
   }
   virtual ~WasmVmBase() {
-    global_stats_ptr_->active_--;
-    stats_.active_.set(global_stats_ptr_->active_);
-    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, global_stats_ptr_->active_);
+    (*active_vms_ptr_)--;
+    stats_.active_.set(*active_vms_ptr_);
+    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, *active_vms_ptr_);
   }
 
 protected:
   Stats::ScopeSharedPtr scope_;
-  VmGlobalStats* global_stats_ptr_;
+  std::atomic<int>* active_vms_ptr_;
   VmStats stats_;
   std::string runtime_;
 };

From 80d36f2c2fddeaed498c05748bf2c271dbc8a33a Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Thu, 12 Dec 2019 22:07:17 +0000
Subject: [PATCH 03/13] Address coments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/wasm_vm.h      |  2 +-
 source/extensions/common/wasm/wasm_vm_base.h | 10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index 45e5c08d0a81b..1b90fe988161b 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -145,7 +145,7 @@ class WasmVm : public Logger::Loggable<Logger::Id::wasm> {
    * compilation. Then, if cloning is supported, we clone that VM for each worker, potentially
    * copying and sharing the initialized data structures for efficiency. Otherwise we create an new
    * VM from scratch for each worker.
-   * @return true if the VM is cloneable.
+   * @return one of enum Cloneable with the VMs cloneablity.
    */
   virtual Cloneable cloneable() PURE;
 
diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
index 7c95099265ecd..0a1ab94ee88a2 100644
--- a/source/extensions/common/wasm/wasm_vm_base.h
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -31,9 +31,9 @@ class WasmVmBase : public WasmVm {
   WasmVmBase(Stats::ScopeSharedPtr scope, std::atomic<int>* active_vms_ptr,
              absl::string_view runtime)
       : scope_(scope), active_vms_ptr_(active_vms_ptr),
-        stats_(VmStats{
-            ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, absl::StrCat("wasm_vm.", runtime, ".")),
-                         POOL_GAUGE_PREFIX(*scope_, absl::StrCat("wasm_vm.", runtime, ".")))}),
+        runtime_prefix_(absl::StrCat("wasm_vm.", runtime, ".")),
+        stats_(VmStats{ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, runtime_prefix_),
+                                    POOL_GAUGE_PREFIX(*scope_, runtime_prefix_))}),
         runtime_(std::string(runtime)) {
     stats_.created_.inc();
     (*active_vms_ptr_)++;
@@ -42,6 +42,7 @@ class WasmVmBase : public WasmVm {
   }
   virtual ~WasmVmBase() {
     (*active_vms_ptr_)--;
+    // The stats referrd to by stats_ are resolved by name in the stats system.
     stats_.active_.set(*active_vms_ptr_);
     ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, *active_vms_ptr_);
   }
@@ -49,8 +50,9 @@ class WasmVmBase : public WasmVm {
 protected:
   Stats::ScopeSharedPtr scope_;
   std::atomic<int>* active_vms_ptr_;
+  std::string runtime_prefix_;
   VmStats stats_;
-  std::string runtime_;
+  std::string runtime_; // The runtime e.g. "v8".
 };
 
 } // namespace Wasm

From 766c7d9c7787e4db4a7ab3710ee9c6ea727a6529 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Fri, 13 Dec 2019 19:07:56 +0000
Subject: [PATCH 04/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/null/null_vm.cc |  2 --
 source/extensions/common/wasm/null/null_vm.h  |  7 +++---
 source/extensions/common/wasm/v8/v8.cc        |  6 ++---
 source/extensions/common/wasm/wasm_vm_base.h  | 25 +++++++++++--------
 4 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/source/extensions/common/wasm/null/null_vm.cc b/source/extensions/common/wasm/null/null_vm.cc
index d661c43134946..3dd45ea96069f 100644
--- a/source/extensions/common/wasm/null/null_vm.cc
+++ b/source/extensions/common/wasm/null/null_vm.cc
@@ -18,8 +18,6 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-std::atomic<int> active_vms_;
-
 WasmVmPtr NullVm::clone() {
   auto cloned_null_vm = std::make_unique<NullVm>(*this);
   cloned_null_vm->load(plugin_name_, false /* unused */);
diff --git a/source/extensions/common/wasm/null/null_vm.h b/source/extensions/common/wasm/null/null_vm.h
index 4c0aae998d71b..98fa6b6321165 100644
--- a/source/extensions/common/wasm/null/null_vm.h
+++ b/source/extensions/common/wasm/null/null_vm.h
@@ -19,16 +19,14 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-extern std::atomic<int> active_vms_;
-
 // The NullVm wraps a C++ WASM plugin which has been compiled with the WASM API
 // and linked directly into the Envoy process. This is useful for development
 // in that it permits the debugger to set breakpoints in both Envoy and the plugin.
 struct NullVm : public WasmVmBase {
   NullVm(Stats::ScopeSharedPtr scope)
-      : WasmVmBase(scope, &active_vms_, WasmRuntimeNames::get().Null) {}
+      : WasmVmBase(scope, globalStats(), WasmRuntimeNames::get().Null) {}
   NullVm(const NullVm& other)
-      : WasmVmBase(other.scope_, &active_vms_, WasmRuntimeNames::get().Null),
+      : WasmVmBase(other.scope_, globalStats(), WasmRuntimeNames::get().Null),
         plugin_name_(other.plugin_name_) {}
 
   // WasmVm
@@ -43,6 +41,7 @@ struct NullVm : public WasmVmBase {
   bool setWord(uint64_t pointer, Word data) override;
   bool getWord(uint64_t pointer, Word* data) override;
   absl::string_view getCustomSection(absl::string_view name) override;
+  VmGlobalStats& globalStats() { MUTABLE_CONSTRUCT_ON_FIRST_USE(VmGlobalStats); }
 
 #define _FORWARD_GET_FUNCTION(_T)                                                                  \
   void getFunction(absl::string_view function_name, _T* f) override {                              \
diff --git a/source/extensions/common/wasm/v8/v8.cc b/source/extensions/common/wasm/v8/v8.cc
index 7d54d30d8a174..5213bfc71be5b 100644
--- a/source/extensions/common/wasm/v8/v8.cc
+++ b/source/extensions/common/wasm/v8/v8.cc
@@ -20,8 +20,6 @@ namespace Common {
 namespace Wasm {
 namespace V8 {
 
-std::atomic<int> active_vms_;
-
 wasm::Engine* engine() {
   static const auto engine = wasm::Engine::make();
   return engine.get();
@@ -39,7 +37,7 @@ using FuncDataPtr = std::unique_ptr<FuncData>;
 
 class V8 : public WasmVmBase {
 public:
-  V8(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, &active_vms_, WasmRuntimeNames::get().V8) {}
+  V8(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, globalStats(), WasmRuntimeNames::get().V8) {}
 
   // Extensions::Common::Wasm::WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().V8; }
@@ -89,6 +87,8 @@ class V8 : public WasmVmBase {
   void getModuleFunctionImpl(absl::string_view function_name,
                              std::function<R(Context*, Args...)>* function);
 
+  VmGlobalStats& globalStats() { MUTABLE_CONSTRUCT_ON_FIRST_USE(VmGlobalStats); }
+
   wasm::vec<byte_t> source_ = wasm::vec<byte_t>::invalid();
   wasm::own<wasm::Store> store_;
   wasm::own<wasm::Module> module_;
diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
index 0a1ab94ee88a2..c2e5506decc68 100644
--- a/source/extensions/common/wasm/wasm_vm_base.h
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -25,32 +25,35 @@ struct VmStats {
   ALL_VM_STATS(GENERATE_COUNTER_STRUCT, GENERATE_GAUGE_STRUCT)
 };
 
+struct VmGlobalStats {
+  std::atomic<int> active_vms_{0};
+};
+
 // Wasm VM base instance. Provides common behavior (e.g. Stats).
 class WasmVmBase : public WasmVm {
 public:
-  WasmVmBase(Stats::ScopeSharedPtr scope, std::atomic<int>* active_vms_ptr,
-             absl::string_view runtime)
-      : scope_(scope), active_vms_ptr_(active_vms_ptr),
-        runtime_prefix_(absl::StrCat("wasm_vm.", runtime, ".")),
+  WasmVmBase(Stats::ScopeSharedPtr scope, VmGlobalStats& global_stats, absl::string_view runtime)
+      : scope_(scope), runtime_prefix_(absl::StrCat("wasm_vm.", runtime, ".")),
+        global_stats_(global_stats),
         stats_(VmStats{ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, runtime_prefix_),
                                     POOL_GAUGE_PREFIX(*scope_, runtime_prefix_))}),
         runtime_(std::string(runtime)) {
     stats_.created_.inc();
-    (*active_vms_ptr_)++;
-    stats_.active_.set(*active_vms_ptr_);
-    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, *active_vms_ptr_);
+    auto active = ++global_stats_.active_vms_;
+    stats_.active_.set(active);
+    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, active);
   }
   virtual ~WasmVmBase() {
-    (*active_vms_ptr_)--;
+    auto active = --global_stats_.active_vms_;
     // The stats referrd to by stats_ are resolved by name in the stats system.
-    stats_.active_.set(*active_vms_ptr_);
-    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, *active_vms_ptr_);
+    stats_.active_.set(active);
+    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, active);
   }
 
 protected:
   Stats::ScopeSharedPtr scope_;
-  std::atomic<int>* active_vms_ptr_;
   std::string runtime_prefix_;
+  VmGlobalStats& global_stats_;
   VmStats stats_;
   std::string runtime_; // The runtime e.g. "v8".
 };

From bfefaf416b9ad652758ce909fc90cbcd63c593d6 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Wed, 18 Dec 2019 18:48:43 +0000
Subject: [PATCH 05/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/null/null_vm.h |  7 ++-----
 source/extensions/common/wasm/v8/v8.cc       |  4 +---
 source/extensions/common/wasm/wasm_vm_base.h | 19 +++++--------------
 3 files changed, 8 insertions(+), 22 deletions(-)

diff --git a/source/extensions/common/wasm/null/null_vm.h b/source/extensions/common/wasm/null/null_vm.h
index 98fa6b6321165..6adafd22c0a65 100644
--- a/source/extensions/common/wasm/null/null_vm.h
+++ b/source/extensions/common/wasm/null/null_vm.h
@@ -23,11 +23,9 @@ namespace Null {
 // and linked directly into the Envoy process. This is useful for development
 // in that it permits the debugger to set breakpoints in both Envoy and the plugin.
 struct NullVm : public WasmVmBase {
-  NullVm(Stats::ScopeSharedPtr scope)
-      : WasmVmBase(scope, globalStats(), WasmRuntimeNames::get().Null) {}
+  NullVm(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, WasmRuntimeNames::get().Null) {}
   NullVm(const NullVm& other)
-      : WasmVmBase(other.scope_, globalStats(), WasmRuntimeNames::get().Null),
-        plugin_name_(other.plugin_name_) {}
+      : WasmVmBase(other.scope_, WasmRuntimeNames::get().Null), plugin_name_(other.plugin_name_) {}
 
   // WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().Null; }
@@ -41,7 +39,6 @@ struct NullVm : public WasmVmBase {
   bool setWord(uint64_t pointer, Word data) override;
   bool getWord(uint64_t pointer, Word* data) override;
   absl::string_view getCustomSection(absl::string_view name) override;
-  VmGlobalStats& globalStats() { MUTABLE_CONSTRUCT_ON_FIRST_USE(VmGlobalStats); }
 
 #define _FORWARD_GET_FUNCTION(_T)                                                                  \
   void getFunction(absl::string_view function_name, _T* f) override {                              \
diff --git a/source/extensions/common/wasm/v8/v8.cc b/source/extensions/common/wasm/v8/v8.cc
index 5213bfc71be5b..d54dab9212556 100644
--- a/source/extensions/common/wasm/v8/v8.cc
+++ b/source/extensions/common/wasm/v8/v8.cc
@@ -37,7 +37,7 @@ using FuncDataPtr = std::unique_ptr<FuncData>;
 
 class V8 : public WasmVmBase {
 public:
-  V8(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, globalStats(), WasmRuntimeNames::get().V8) {}
+  V8(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, WasmRuntimeNames::get().V8) {}
 
   // Extensions::Common::Wasm::WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().V8; }
@@ -87,8 +87,6 @@ class V8 : public WasmVmBase {
   void getModuleFunctionImpl(absl::string_view function_name,
                              std::function<R(Context*, Args...)>* function);
 
-  VmGlobalStats& globalStats() { MUTABLE_CONSTRUCT_ON_FIRST_USE(VmGlobalStats); }
-
   wasm::vec<byte_t> source_ = wasm::vec<byte_t>::invalid();
   wasm::own<wasm::Store> store_;
   wasm::own<wasm::Module> module_;
diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
index c2e5506decc68..1ab0506008835 100644
--- a/source/extensions/common/wasm/wasm_vm_base.h
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -25,35 +25,26 @@ struct VmStats {
   ALL_VM_STATS(GENERATE_COUNTER_STRUCT, GENERATE_GAUGE_STRUCT)
 };
 
-struct VmGlobalStats {
-  std::atomic<int> active_vms_{0};
-};
-
 // Wasm VM base instance. Provides common behavior (e.g. Stats).
 class WasmVmBase : public WasmVm {
 public:
-  WasmVmBase(Stats::ScopeSharedPtr scope, VmGlobalStats& global_stats, absl::string_view runtime)
+  WasmVmBase(Stats::ScopeSharedPtr scope, absl::string_view runtime)
       : scope_(scope), runtime_prefix_(absl::StrCat("wasm_vm.", runtime, ".")),
-        global_stats_(global_stats),
         stats_(VmStats{ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, runtime_prefix_),
                                     POOL_GAUGE_PREFIX(*scope_, runtime_prefix_))}),
         runtime_(std::string(runtime)) {
     stats_.created_.inc();
-    auto active = ++global_stats_.active_vms_;
-    stats_.active_.set(active);
-    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, active);
+    stats_.active_.inc();
+    ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, stats_.active_.value());
   }
   virtual ~WasmVmBase() {
-    auto active = --global_stats_.active_vms_;
-    // The stats referrd to by stats_ are resolved by name in the stats system.
-    stats_.active_.set(active);
-    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, active);
+    stats_.active_.dec();
+    ENVOY_LOG(debug, "~WasmVm {} {} remaining active", runtime_, stats_.active_.value());
   }
 
 protected:
   Stats::ScopeSharedPtr scope_;
   std::string runtime_prefix_;
-  VmGlobalStats& global_stats_;
   VmStats stats_;
   std::string runtime_; // The runtime e.g. "v8".
 };

From a3d8030838e4e7e28e008a5e44d89496d25ac7b7 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Thu, 19 Dec 2019 20:40:47 +0000
Subject: [PATCH 06/13] Fix pedantic spelling.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/wasm_vm.h | 2 +-
 tools/spelling_dictionary.txt           | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index 1b90fe988161b..d9dc432c3a54f 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -145,7 +145,7 @@ class WasmVm : public Logger::Loggable<Logger::Id::wasm> {
    * compilation. Then, if cloning is supported, we clone that VM for each worker, potentially
    * copying and sharing the initialized data structures for efficiency. Otherwise we create an new
    * VM from scratch for each worker.
-   * @return one of enum Cloneable with the VMs cloneablity.
+   * @return one of enum Cloneable with the VMs cloneability.
    */
   virtual Cloneable cloneable() PURE;
 
diff --git a/tools/spelling_dictionary.txt b/tools/spelling_dictionary.txt
index de07712e8ae64..3f1fe7766e59e 100644
--- a/tools/spelling_dictionary.txt
+++ b/tools/spelling_dictionary.txt
@@ -408,6 +408,7 @@ ciphersuites
 circllhist
 CITT
 cloneable
+cloneability
 cmd
 cmsghdr
 codebase

From 48bfc76779f4f9497874001d2b8ad2e624c27f99 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Mon, 23 Dec 2019 18:48:49 +0000
Subject: [PATCH 07/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/null/null.cc   | 2 +-
 source/extensions/common/wasm/null/null.h    | 2 +-
 source/extensions/common/wasm/null/null_vm.h | 2 +-
 source/extensions/common/wasm/v8/v8.cc       | 4 ++--
 source/extensions/common/wasm/v8/v8.h        | 2 +-
 source/extensions/common/wasm/wasm_vm.cc     | 2 +-
 source/extensions/common/wasm/wasm_vm.h      | 2 +-
 source/extensions/common/wasm/wasm_vm_base.h | 2 +-
 8 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/source/extensions/common/wasm/null/null.cc b/source/extensions/common/wasm/null/null.cc
index 1a2fc46924331..af2ba77d1dc56 100644
--- a/source/extensions/common/wasm/null/null.cc
+++ b/source/extensions/common/wasm/null/null.cc
@@ -18,7 +18,7 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-WasmVmPtr createVm(Stats::ScopeSharedPtr scope) { return std::make_unique<NullVm>(scope); }
+WasmVmPtr createVm(const Stats::ScopeSharedPtr& scope) { return std::make_unique<NullVm>(scope); }
 
 } // namespace Null
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/null/null.h b/source/extensions/common/wasm/null/null.h
index 1fab2784f04bc..285b13373fbc8 100644
--- a/source/extensions/common/wasm/null/null.h
+++ b/source/extensions/common/wasm/null/null.h
@@ -11,7 +11,7 @@ namespace Common {
 namespace Wasm {
 namespace Null {
 
-WasmVmPtr createVm(Stats::ScopeSharedPtr scope);
+WasmVmPtr createVm(const Stats::ScopeSharedPtr& scope);
 
 } // namespace Null
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/null/null_vm.h b/source/extensions/common/wasm/null/null_vm.h
index 6adafd22c0a65..ca962b2eefd97 100644
--- a/source/extensions/common/wasm/null/null_vm.h
+++ b/source/extensions/common/wasm/null/null_vm.h
@@ -23,7 +23,7 @@ namespace Null {
 // and linked directly into the Envoy process. This is useful for development
 // in that it permits the debugger to set breakpoints in both Envoy and the plugin.
 struct NullVm : public WasmVmBase {
-  NullVm(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, WasmRuntimeNames::get().Null) {}
+  NullVm(const Stats::ScopeSharedPtr& scope) : WasmVmBase(scope, WasmRuntimeNames::get().Null) {}
   NullVm(const NullVm& other)
       : WasmVmBase(other.scope_, WasmRuntimeNames::get().Null), plugin_name_(other.plugin_name_) {}
 
diff --git a/source/extensions/common/wasm/v8/v8.cc b/source/extensions/common/wasm/v8/v8.cc
index d54dab9212556..d83f6e8acde85 100644
--- a/source/extensions/common/wasm/v8/v8.cc
+++ b/source/extensions/common/wasm/v8/v8.cc
@@ -37,7 +37,7 @@ using FuncDataPtr = std::unique_ptr<FuncData>;
 
 class V8 : public WasmVmBase {
 public:
-  V8(Stats::ScopeSharedPtr scope) : WasmVmBase(scope, WasmRuntimeNames::get().V8) {}
+  V8(const Stats::ScopeSharedPtr& scope) : WasmVmBase(scope, WasmRuntimeNames::get().V8) {}
 
   // Extensions::Common::Wasm::WasmVm
   absl::string_view runtime() override { return WasmRuntimeNames::get().V8; }
@@ -583,7 +583,7 @@ void V8::getModuleFunctionImpl(absl::string_view function_name,
   };
 }
 
-WasmVmPtr createVm(Stats::ScopeSharedPtr scope) { return std::make_unique<V8>(scope); }
+WasmVmPtr createVm(const Stats::ScopeSharedPtr& scope) { return std::make_unique<V8>(scope); }
 
 } // namespace V8
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/v8/v8.h b/source/extensions/common/wasm/v8/v8.h
index 1cee4424e8152..a7288f0004a59 100644
--- a/source/extensions/common/wasm/v8/v8.h
+++ b/source/extensions/common/wasm/v8/v8.h
@@ -10,7 +10,7 @@ namespace Common {
 namespace Wasm {
 namespace V8 {
 
-WasmVmPtr createVm(Stats::ScopeSharedPtr scope);
+WasmVmPtr createVm(const Stats::ScopeSharedPtr& scope);
 
 } // namespace V8
 } // namespace Wasm
diff --git a/source/extensions/common/wasm/wasm_vm.cc b/source/extensions/common/wasm/wasm_vm.cc
index 88ee11c60bc0d..9299eceba2d10 100644
--- a/source/extensions/common/wasm/wasm_vm.cc
+++ b/source/extensions/common/wasm/wasm_vm.cc
@@ -14,7 +14,7 @@ namespace Wasm {
 thread_local Envoy::Extensions::Common::Wasm::Context* current_context_ = nullptr;
 thread_local uint32_t effective_context_id_ = 0;
 
-WasmVmPtr createWasmVm(absl::string_view runtime, Stats::ScopeSharedPtr scope) {
+WasmVmPtr createWasmVm(absl::string_view runtime, const Stats::ScopeSharedPtr& scope) {
   if (runtime.empty()) {
     throw WasmVmException("Failed to create WASM VM with unspecified runtime.");
   } else if (runtime == WasmRuntimeNames::get().Null) {
diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index d9dc432c3a54f..a383b95ce7c4d 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -291,7 +291,7 @@ struct SaveRestoreContext {
 };
 
 // Create a new low-level WASM VM using runtime of the given type (e.g. "envoy.wasm.runtime.wavm").
-WasmVmPtr createWasmVm(absl::string_view runtime, Stats::ScopeSharedPtr scope);
+WasmVmPtr createWasmVm(absl::string_view runtime, const Stats::ScopeSharedPtr& scope);
 
 } // namespace Wasm
 } // namespace Common
diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
index 1ab0506008835..4eae2fc0e9240 100644
--- a/source/extensions/common/wasm/wasm_vm_base.h
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -28,7 +28,7 @@ struct VmStats {
 // Wasm VM base instance. Provides common behavior (e.g. Stats).
 class WasmVmBase : public WasmVm {
 public:
-  WasmVmBase(Stats::ScopeSharedPtr scope, absl::string_view runtime)
+  WasmVmBase(const Stats::ScopeSharedPtr& scope, absl::string_view runtime)
       : scope_(scope), runtime_prefix_(absl::StrCat("wasm_vm.", runtime, ".")),
         stats_(VmStats{ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, runtime_prefix_),
                                     POOL_GAUGE_PREFIX(*scope_, runtime_prefix_))}),

From 66cdce03e94d93a695438414bf3e82f64105bbab Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Sat, 28 Dec 2019 17:55:48 +0000
Subject: [PATCH 08/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/wasm_vm_base.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/source/extensions/common/wasm/wasm_vm_base.h b/source/extensions/common/wasm/wasm_vm_base.h
index 4eae2fc0e9240..a709534cba521 100644
--- a/source/extensions/common/wasm/wasm_vm_base.h
+++ b/source/extensions/common/wasm/wasm_vm_base.h
@@ -30,9 +30,9 @@ class WasmVmBase : public WasmVm {
 public:
   WasmVmBase(const Stats::ScopeSharedPtr& scope, absl::string_view runtime)
       : scope_(scope), runtime_prefix_(absl::StrCat("wasm_vm.", runtime, ".")),
+        runtime_(std::string(runtime)),
         stats_(VmStats{ALL_VM_STATS(POOL_COUNTER_PREFIX(*scope_, runtime_prefix_),
-                                    POOL_GAUGE_PREFIX(*scope_, runtime_prefix_))}),
-        runtime_(std::string(runtime)) {
+                                    POOL_GAUGE_PREFIX(*scope_, runtime_prefix_))}) {
     stats_.created_.inc();
     stats_.active_.inc();
     ENVOY_LOG(debug, "WasmVm created {} now active", runtime_, stats_.active_.value());
@@ -43,10 +43,10 @@ class WasmVmBase : public WasmVm {
   }
 
 protected:
-  Stats::ScopeSharedPtr scope_;
-  std::string runtime_prefix_;
+  const Stats::ScopeSharedPtr scope_;
+  const std::string runtime_prefix_;
+  const std::string runtime_; // The runtime e.g. "v8".
   VmStats stats_;
-  std::string runtime_; // The runtime e.g. "v8".
 };
 
 } // namespace Wasm

From 4069f426826934cb6b5f05657a9425f37052dd28 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Sat, 28 Dec 2019 18:01:05 +0000
Subject: [PATCH 09/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/wasm_vm.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index a383b95ce7c4d..94ddae0174b9a 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -124,7 +124,11 @@ using WasmCallback_dd = double (*)(void*, double);
                       _f(WasmCallback_WWl) _f(WasmCallback_WWlWW) _f(WasmCallback_WWm)             \
                           _f(WasmCallback_dd)
 
-enum class Cloneable { NotCloneable, CompiledBytecode, InstantiatedModule };
+enum class Cloneable {
+  NotCloneable,      // VMs can not be cloned and should be created from scratch.
+  CompiledBytecode,  // VMs can be clone with compiled bytecode.
+  InstantiatedModule // VMs can be cloned from an instatiated module.
+};
 
 // Wasm VM instance. Provides the low level WASM interface.
 class WasmVm : public Logger::Loggable<Logger::Id::wasm> {

From 3374ab364f8a11f2c9ce75a19680a880426d746d Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Sat, 28 Dec 2019 18:25:50 +0000
Subject: [PATCH 10/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/wasm_vm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index 94ddae0174b9a..1ef3dd2887795 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -126,7 +126,7 @@ using WasmCallback_dd = double (*)(void*, double);
 
 enum class Cloneable {
   NotCloneable,      // VMs can not be cloned and should be created from scratch.
-  CompiledBytecode,  // VMs can be clone with compiled bytecode.
+  CompiledBytecode,  // VMs can be cloned with compiled bytecode.
   InstantiatedModule // VMs can be cloned from an instatiated module.
 };
 

From 963f3b1066c98c1cdf4d8d99b3a41cce67047474 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Sat, 28 Dec 2019 19:01:45 +0000
Subject: [PATCH 11/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 tools/spelling_dictionary.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/spelling_dictionary.txt b/tools/spelling_dictionary.txt
index 3f1fe7766e59e..f2ac8989e583b 100644
--- a/tools/spelling_dictionary.txt
+++ b/tools/spelling_dictionary.txt
@@ -383,6 +383,7 @@ builtin
 builtins
 bulkstrings
 bursty
+bytecode
 callee
 callsite
 callsites

From bb8dfc05f188e28faabcb187ee3e48c7fb1bc366 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Sat, 28 Dec 2019 21:29:47 +0000
Subject: [PATCH 12/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/wasm_vm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/extensions/common/wasm/wasm_vm.h b/source/extensions/common/wasm/wasm_vm.h
index 1ef3dd2887795..95b43aee47512 100644
--- a/source/extensions/common/wasm/wasm_vm.h
+++ b/source/extensions/common/wasm/wasm_vm.h
@@ -127,7 +127,7 @@ using WasmCallback_dd = double (*)(void*, double);
 enum class Cloneable {
   NotCloneable,      // VMs can not be cloned and should be created from scratch.
   CompiledBytecode,  // VMs can be cloned with compiled bytecode.
-  InstantiatedModule // VMs can be cloned from an instatiated module.
+  InstantiatedModule // VMs can be cloned from an instantiated module.
 };
 
 // Wasm VM instance. Provides the low level WASM interface.

From 4ec423289b88480e3571d0163afb461e9a56d336 Mon Sep 17 00:00:00 2001
From: John Plevyak <jplevyak@gmail.com>
Date: Thu, 9 Jan 2020 23:21:37 +0000
Subject: [PATCH 13/13] Address comments.

Signed-off-by: John Plevyak <jplevyak@gmail.com>
---
 source/extensions/common/wasm/null/null_vm.cc | 1 -
 source/extensions/common/wasm/null/null_vm.h  | 1 -
 source/extensions/common/wasm/v8/v8.cc        | 6 ------
 3 files changed, 8 deletions(-)

diff --git a/source/extensions/common/wasm/null/null_vm.cc b/source/extensions/common/wasm/null/null_vm.cc
index 3dd45ea96069f..d2cb16b994f16 100644
--- a/source/extensions/common/wasm/null/null_vm.cc
+++ b/source/extensions/common/wasm/null/null_vm.cc
@@ -7,7 +7,6 @@
 #include "envoy/registry/registry.h"
 
 #include "common/common/assert.h"
-#include "common/singleton/threadsafe_singleton.h"
 
 #include "extensions/common/wasm/null/null_vm_plugin.h"
 #include "extensions/common/wasm/well_known_names.h"
diff --git a/source/extensions/common/wasm/null/null_vm.h b/source/extensions/common/wasm/null/null_vm.h
index ca962b2eefd97..82da033019723 100644
--- a/source/extensions/common/wasm/null/null_vm.h
+++ b/source/extensions/common/wasm/null/null_vm.h
@@ -7,7 +7,6 @@
 #include "envoy/registry/registry.h"
 
 #include "common/common/assert.h"
-#include "common/singleton/threadsafe_singleton.h"
 
 #include "extensions/common/wasm/null/null_vm_plugin.h"
 #include "extensions/common/wasm/wasm_vm_base.h"
diff --git a/source/extensions/common/wasm/v8/v8.cc b/source/extensions/common/wasm/v8/v8.cc
index d83f6e8acde85..bd158874ba731 100644
--- a/source/extensions/common/wasm/v8/v8.cc
+++ b/source/extensions/common/wasm/v8/v8.cc
@@ -5,7 +5,6 @@
 #include <vector>
 
 #include "common/common/assert.h"
-#include "common/singleton/threadsafe_singleton.h"
 
 #include "extensions/common/wasm/wasm_vm_base.h"
 #include "extensions/common/wasm/well_known_names.h"
@@ -243,7 +242,6 @@ template <typename T, typename U> constexpr T convertValTypesToArgsTuple(const U
 bool V8::load(const std::string& code, bool /* allow_precompiled */) {
   ENVOY_LOG(trace, "load()");
   store_ = wasm::Store::make(engine());
-  RELEASE_ASSERT(store_ != nullptr, "");
 
   source_ = wasm::vec<byte_t>::make_uninitialized(code.size());
   ::memcpy(source_.get(), code.data(), code.size());
@@ -251,7 +249,6 @@ bool V8::load(const std::string& code, bool /* allow_precompiled */) {
   module_ = wasm::Module::make(store_.get(), source_);
   if (module_) {
     shared_module_ = module_->share();
-    RELEASE_ASSERT(shared_module_ != nullptr, "");
   }
 
   return module_ != nullptr;
@@ -263,10 +260,8 @@ WasmVmPtr V8::clone() {
 
   auto clone = std::make_unique<V8>(scope_);
   clone->store_ = wasm::Store::make(engine());
-  RELEASE_ASSERT(clone->store_ != nullptr, "");
 
   clone->module_ = wasm::Module::obtain(clone->store_.get(), shared_module_.get());
-  RELEASE_ASSERT(clone->module_ != nullptr, "");
 
   return clone;
 }
@@ -377,7 +372,6 @@ void V8::link(absl::string_view debug_name) {
   ASSERT(import_types.size() == imports.size());
 
   instance_ = wasm::Instance::make(store_.get(), module_.get(), imports.data());
-  RELEASE_ASSERT(instance_ != nullptr, "");
 
   const auto export_types = module_.get()->exports();
   const auto exports = instance_.get()->exports();