Add the ability to "pre-warm" Wasm engines.

include/proxy-wasm/v8.h

@@ -21,6 +21,7 @@
 
 namespace proxy_wasm {
 
+bool initV8Engine();
 std::unique_ptr<WasmVm> createV8Vm();
 
 } // namespace proxy_wasm

include/proxy-wasm/wamr.h

@@ -21,6 +21,7 @@
 
 namespace proxy_wasm {
 
+bool initWamrEngine();
 std::unique_ptr<WasmVm> createWamrVm();
 
 } // namespace proxy_wasm

include/proxy-wasm/wasmtime.h

@@ -18,6 +18,7 @@
 
 namespace proxy_wasm {
 
+bool initWasmtimeEngine();
 std::unique_ptr<WasmVm> createWasmtimeVm();
 
 } // namespace proxy_wasm

src/v8/v8.cc

@@ -709,6 +709,8 @@ std::string V8::getFailMessage(std::string_view function_name, wasm::own<wasm::T
 
 } // namespace v8
 
+bool initV8Engine() { return v8::engine() != nullptr; }
+
 std::unique_ptr<WasmVm> createV8Vm() { return std::make_unique<v8::V8>(); }
 
 } // namespace proxy_wasm

src/wamr/wamr.cc

@@ -644,6 +644,8 @@ void Wamr::getModuleFunctionImpl(std::string_view function_name,
 
 } // namespace wamr
 
+bool initWamrEngine() { return wamr::engine() != nullptr; }
+
 std::unique_ptr<WasmVm> createWamrVm() { return std::make_unique<wamr::Wamr>(); }
 
 } // namespace proxy_wasm

src/wasmtime/wasmtime.cc

@@ -694,6 +694,8 @@ void Wasmtime::getModuleFunctionImpl(std::string_view function_name,
 
 } // namespace wasmtime
 
+bool initWasmtimeEngine() { return wasmtime::engine() != nullptr; }
+
 std::unique_ptr<WasmVm> createWasmtimeVm() { return std::make_unique<wasmtime::Wasmtime>(); }
 
 } // namespace proxy_wasm

test/wasm_vm_test.cc

@@ -30,6 +30,46 @@ INSTANTIATE_TEST_SUITE_P(WasmEngines, TestVm, testing::ValuesIn(getWasmEngines()
                            return info.param;
                          });
 
+TEST_P(TestVm, Init) {
+  std::chrono::time_point<std::chrono::steady_clock> time2;
+
+  auto time1 = std::chrono::steady_clock::now();
+  if (engine_ == "v8") {
+#if defined(PROXY_WASM_HOST_ENGINE_V8)
+    EXPECT_TRUE(proxy_wasm::initV8Engine());
+    time2 = std::chrono::steady_clock::now();
+    EXPECT_TRUE(proxy_wasm::initV8Engine());
+#endif
+  } else if (engine_ == "wamr") {
+#if defined(PROXY_WASM_HOST_ENGINE_WAMR)
+    EXPECT_TRUE(proxy_wasm::initWamrEngine());
+    time2 = std::chrono::steady_clock::now();
+    EXPECT_TRUE(proxy_wasm::initWamrEngine());
+#endif
+  } else if (engine_ == "wasmtime") {
+#if defined(PROXY_WASM_HOST_ENGINE_WASMTIME)
+    EXPECT_TRUE(proxy_wasm::initWasmtimeEngine());
+    time2 = std::chrono::steady_clock::now();
+    EXPECT_TRUE(proxy_wasm::initWasmtimeEngine());
+#endif
+  } else {
+    return;
+  }
+  auto time3 = std::chrono::steady_clock::now();
+
+  auto cold = std::chrono::duration_cast<std::chrono::nanoseconds>(time2 - time1).count();
+  auto warm = std::chrono::duration_cast<std::chrono::nanoseconds>(time3 - time2).count();
+
+  std::cout << "\"cold\" engine time: " << cold << "ns" << std::endl;
+  std::cout << "\"warm\" engine time: " << warm << "ns" << std::endl;
+
+  // Verify that getting a "warm" engine takes less than 10us.
+  EXPECT_LE(warm, 10000);
+
+  // Verify that getting a "warm" engine takes at least 50x less time than getting a "cold" one.
+  EXPECT_LE(warm * 50, cold);
+}
+
 TEST_P(TestVm, Basic) {
   if (engine_ == "wamr") {
     EXPECT_EQ(vm_->cloneable(), proxy_wasm::Cloneable::NotCloneable);