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Commit c3abdc5

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joyeecheungRafaelGSS
joyeecheung
authored and
RafaelGSS
committed
src: implement --trace-promises
This patch implements a debugging flag that dumps the current stack trace when a promise is created or resolved. To reduce noise we ignore before and after events (as the execution is less interesting) and use the per-isolate hook to avoid extra JS frames. This flag can assist work in reducing unnecessary promise overhead. PR-URL: #50899 Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io> Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com> Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br> Reviewed-By: Chengzhong Wu <legendecas@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
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‎src/env.cc‎

Copy file name to clipboardExpand all lines: src/env.cc
+58Lines changed: 58 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,7 @@
3030
#include <iostream>
3131
#include <limits>
3232
#include <memory>
33+
#include <optional>
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#include <unordered_map>
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3536
namespace node {
@@ -55,13 +56,16 @@ using v8::Number;
5556
using v8::Object;
5657
using v8::ObjectTemplate;
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using v8::Private;
59+
using v8::Promise;
60+
using v8::PromiseHookType;
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using v8::Script;
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using v8::SnapshotCreator;
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using v8::StackTrace;
6164
using v8::String;
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using v8::Symbol;
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using v8::TracingController;
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using v8::TryCatch;
68+
using v8::Uint32;
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using v8::Undefined;
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using v8::Value;
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using v8::WrapperDescriptor;
@@ -1839,6 +1843,60 @@ void Environment::BuildEmbedderGraph(Isolate* isolate,
18391843
tracker.Track(env);
18401844
}
18411845

1846+
std::optional<uint32_t> GetPromiseId(Environment* env, Local<Promise> promise) {
1847+
Local<Value> id_val;
1848+
if (!promise->GetPrivate(env->context(), env->promise_trace_id())
1849+
.ToLocal(&id_val) ||
1850+
!id_val->IsUint32()) {
1851+
return std::nullopt;
1852+
}
1853+
return id_val.As<Uint32>()->Value();
1854+
}
1855+
1856+
void Environment::TracePromises(PromiseHookType type,
1857+
Local<Promise> promise,
1858+
Local<Value> parent) {
1859+
// We don't care about the execution of promises, just the
1860+
// creation/resolution.
1861+
if (type == PromiseHookType::kBefore || type == PromiseHookType::kAfter) {
1862+
return;
1863+
}
1864+
Isolate* isolate = Isolate::GetCurrent();
1865+
Local<Context> context = isolate->GetCurrentContext();
1866+
Environment* env = Environment::GetCurrent(context);
1867+
if (env == nullptr) return;
1868+
1869+
std::optional<uint32_t> parent_id;
1870+
if (!parent.IsEmpty() && parent->IsPromise()) {
1871+
parent_id = GetPromiseId(env, parent.As<Promise>());
1872+
}
1873+
1874+
uint32_t id = 0;
1875+
std::string action;
1876+
if (type == PromiseHookType::kInit) {
1877+
id = env->trace_promise_id_counter_++;
1878+
promise->SetPrivate(
1879+
context, env->promise_trace_id(), Uint32::New(isolate, id));
1880+
action = "created";
1881+
} else if (type == PromiseHookType::kResolve) {
1882+
auto opt = GetPromiseId(env, promise);
1883+
if (!opt.has_value()) return;
1884+
id = opt.value();
1885+
action = "resolved";
1886+
} else {
1887+
UNREACHABLE();
1888+
}
1889+
1890+
FPrintF(stderr, "[--trace-promises] ");
1891+
if (parent_id.has_value()) {
1892+
FPrintF(stderr, "promise #%d ", parent_id.value());
1893+
}
1894+
FPrintF(stderr, "%s promise #%d\n", action, id);
1895+
// TODO(joyeecheung): we can dump the native stack trace too if the
1896+
// JS stack trace is empty i.e. it may be resolved on the native side.
1897+
PrintCurrentStackTrace(isolate);
1898+
}
1899+
18421900
size_t Environment::NearHeapLimitCallback(void* data,
18431901
size_t current_heap_limit,
18441902
size_t initial_heap_limit) {
Collapse file

‎src/env.h‎

Copy file name to clipboardExpand all lines: src/env.h
+4Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -934,6 +934,9 @@ class Environment : public MemoryRetainer {
934934
inline void RemoveCleanupHook(CleanupQueue::Callback cb, void* arg);
935935
void RunCleanup();
936936

937+
static void TracePromises(v8::PromiseHookType type,
938+
v8::Local<v8::Promise> promise,
939+
v8::Local<v8::Value> parent);
937940
static size_t NearHeapLimitCallback(void* data,
938941
size_t current_heap_limit,
939942
size_t initial_heap_limit);
@@ -1094,6 +1097,7 @@ class Environment : public MemoryRetainer {
10941097
uint32_t module_id_counter_ = 0;
10951098
uint32_t script_id_counter_ = 0;
10961099
uint32_t function_id_counter_ = 0;
1100+
uint32_t trace_promise_id_counter_ = 0;
10971101

10981102
AliasedInt32Array exit_info_;
10991103

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‎src/env_properties.h‎

Copy file name to clipboardExpand all lines: src/env_properties.h
+1Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -28,6 +28,7 @@
2828
V(napi_wrapper, "node:napi:wrapper") \
2929
V(untransferable_object_private_symbol, "node:untransferableObject") \
3030
V(exit_info_private_symbol, "node:exit_info_private_symbol") \
31+
V(promise_trace_id, "node:promise_trace_id") \
3132
V(require_private_symbol, "node:require_private_symbol")
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3334
// Symbols are per-isolate primitives but Environment proxies them
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‎src/node.cc‎

Copy file name to clipboardExpand all lines: src/node.cc
+3Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -264,6 +264,9 @@ void Environment::InitializeDiagnostics() {
264264
env->isolate()->SetAtomicsWaitCallback(nullptr, nullptr);
265265
}, this);
266266
}
267+
if (options_->trace_promises) {
268+
isolate_->SetPromiseHook(TracePromises);
269+
}
267270
}
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269272
static
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‎src/node_errors.cc‎

Copy file name to clipboardExpand all lines: src/node_errors.cc
+7Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -291,6 +291,13 @@ void PrintStackTrace(Isolate* isolate,
291291
PrintToStderrAndFlush(FormatStackTrace(isolate, stack, prefix));
292292
}
293293

294+
void PrintCurrentStackTrace(Isolate* isolate, StackTracePrefix prefix) {
295+
Local<StackTrace> stack;
296+
if (GetCurrentStackTrace(isolate).ToLocal(&stack)) {
297+
PrintStackTrace(isolate, stack, prefix);
298+
}
299+
}
300+
294301
std::string FormatCaughtException(Isolate* isolate,
295302
Local<Context> context,
296303
Local<Value> err,
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‎src/node_internals.h‎

Copy file name to clipboardExpand all lines: src/node_internals.h
+2Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -87,6 +87,8 @@ enum class StackTracePrefix {
8787
kAt, // " at "
8888
kNumber
8989
};
90+
void PrintCurrentStackTrace(v8::Isolate* isolate,
91+
StackTracePrefix prefix = StackTracePrefix::kAt);
9092
void PrintStackTrace(v8::Isolate* isolate,
9193
v8::Local<v8::StackTrace> stack,
9294
StackTracePrefix prefix = StackTracePrefix::kAt);
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‎src/node_options.cc‎

Copy file name to clipboardExpand all lines: src/node_options.cc
+4Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -672,6 +672,10 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
672672
"show stack traces on process warnings",
673673
&EnvironmentOptions::trace_warnings,
674674
kAllowedInEnvvar);
675+
AddOption("--trace-promises",
676+
"show stack traces on promise initialization and resolution",
677+
&EnvironmentOptions::trace_promises,
678+
kAllowedInEnvvar);
675679
AddOption("--experimental-default-type",
676680
"set module system to use by default",
677681
&EnvironmentOptions::type,
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‎src/node_options.h‎

Copy file name to clipboardExpand all lines: src/node_options.h
+1Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -179,6 +179,7 @@ class EnvironmentOptions : public Options {
179179
bool trace_tls = false;
180180
bool trace_uncaught = false;
181181
bool trace_warnings = false;
182+
bool trace_promises = false;
182183
bool extra_info_on_fatal_exception = true;
183184
std::string unhandled_rejections;
184185
std::vector<std::string> userland_loaders;
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‎test/parallel/test-process-env-allowed-flags-are-documented.js‎

Copy file name to clipboardExpand all lines: test/parallel/test-process-env-allowed-flags-are-documented.js
+2Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -106,6 +106,8 @@ assert(undocumented.delete('--no-node-snapshot'));
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assert(undocumented.delete('--loader'));
107107
assert(undocumented.delete('--verify-base-objects'));
108108
assert(undocumented.delete('--no-verify-base-objects'));
109+
assert(undocumented.delete('--trace-promises'));
110+
assert(undocumented.delete('--no-trace-promises'));
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110112
// Remove negated versions of the flags.
111113
for (const flag of undocumented) {

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