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async_hooks: simplify fatalError #14051

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async_hooks: simplify fatalError #14051

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17aafd7
async_hooks: simplify fatalError
AndreasMadsen Jul 3, 2017
278b163
[squash] use try finally, for better stack traces
AndreasMadsen Jul 3, 2017
610d365
[squash] ensure that uncaughtException listeners are removed
AndreasMadsen Jul 3, 2017
1d3f69b
[squash] async_hooks c++ already have a try finally for each hook
AndreasMadsen Jul 3, 2017
527a4f6
[squash] add frindly comment explaining _events interaction
AndreasMadsen Jul 3, 2017
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108 changes: 54 additions & 54 deletions lib/async_hooks.js
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Original file line number Diff line number Diff line change
Expand Up @@ -60,19 +60,13 @@ async_wrap.setupHooks({ init,
destroy: emitDestroyN });

// Used to fatally abort the process if a callback throws.
function fatalError(e) {
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@refack refack Jul 3, 2017 •
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Why is everyone trying to kill this 😨
I like it as a way to bail from a callback or a Promise.catch
Ref: #13839 (comment)

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Just because it is useful for Promise.catch doesn't mean that is useful here.

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Probably. I'll copy it to test/common/

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Letting an error bubble with try {} finally {} have always been the standard way of handling throws.

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Except what async_hooks is doing isn't standard. This is a guard to prevent an abort from C++ if it detects stack corruption that can likely result from the user try catching/Promise wrapping the call, and to get useful core dumps. It also doesn't follow how this is handled in C++ (https://github.com/nodejs/node/blob/v8.1.3/src/env-inl.h#L144-L160). I'm a big -1 on this.

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By "exporting FatalException" do you mean expose it to JS?

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@trevnorris trevnorris Jul 3, 2017 •
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If anything I'd like to export the code in Environment::AsyncHooks::pop_ids() and use that as the uniform way to exit the process.

EDIT: Except it should show a JS stack instead of a C++ stack.

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By "exporting FatalException" do you mean expose it to JS?

Yes. At the very least I would like a unified way of making a fatal exception. Currently, there are a couple of different implementations floating around in nodecore. It makes things like --abort-on-uncaught-exception difficult to test.

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@AndreasMadsen

At the very least I would like a unified way of making a fatal exception.

Sounds good to me.

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So area this is currently a WIP?

if (typeof e.stack === 'string') {
process._rawDebug(e.stack);
} else {
const o = { message: e };
Error.captureStackTrace(o, fatalError);
process._rawDebug(o.stack);
}
if (process.execArgv.some(
(e) => /^--abort[_-]on[_-]uncaught[_-]exception$/.test(e))) {
process.abort();
}
process.exit(1);
// This is JavaScript version of the ClearFatalExceptionHandlers function
// in C++.
function clearFatalExceptionHandlers(e) {
process.domain = undefined;
// Don't use removeAllListeners in case there is a removeListener listener
// that would revert it.
process._events.uncaughtException = undefined;
}


Expand Down Expand Up @@ -334,7 +328,14 @@ function emitInitS(asyncId, type, triggerAsyncId, resource) {
if (!Number.isSafeInteger(triggerAsyncId) || triggerAsyncId < 0)
throw new RangeError('triggerAsyncId must be an unsigned integer');

init(asyncId, type, triggerAsyncId, resource);
// Remove prepear for a fatal exception in case an error occurred
var didThrow = true;
try {
init(asyncId, type, triggerAsyncId, resource);
didThrow = false;
} finally {
if (didThrow) clearFatalExceptionHandlers();
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I'm not sure it's correct to move this line from the N variant to the S variant?

}

// Isn't null if hooks were added/removed while the hooks were running.
if (tmp_active_hooks_array !== null) {
Expand All @@ -345,15 +346,10 @@ function emitInitS(asyncId, type, triggerAsyncId, resource) {

function emitBeforeN(asyncId) {
processing_hook = true;
// Use a single try/catch for all hook to avoid setting up one per iteration.
try {
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][before_symbol] === 'function') {
active_hooks_array[i][before_symbol](asyncId);
}
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][before_symbol] === 'function') {
active_hooks_array[i][before_symbol](asyncId);
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Allowing an exception to bubble then be handled by a Promise or similar means that it's possible that not all hook callbacks execute, but users that have those unexecuted callbacks won't know that it hasn't been called. Consider the following:

const map = new Map();
createHook({
  before(id) { map.set(id, /* some object */) },
  after(id) { map.delete(id) },
}).enable();

You've just introduced a vector for a memory leak.

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BTW If you're touching this you could use for...of (supposed to be tiny bit faster on TF&I)
Ref: #13419 (comment)

}
} catch (e) {
fatalError(e);
}
processing_hook = false;

Expand All @@ -371,31 +367,37 @@ function emitBeforeS(asyncId, triggerAsyncId = asyncId) {

// Validate the ids.
if (asyncId < 0 || triggerAsyncId < 0) {
fatalError('before(): asyncId or triggerAsyncId is less than zero ' +
`(asyncId: ${asyncId}, triggerAsyncId: ${triggerAsyncId})`);
clearFatalExceptionHandlers();
throw new Error(
'before(): asyncId or triggerAsyncId is less than zero ' +
`(asyncId: ${asyncId}, triggerAsyncId: ${triggerAsyncId})`
);
}

pushAsyncIds(asyncId, triggerAsyncId);

if (async_hook_fields[kBefore] === 0)
return;
emitBeforeN(asyncId);

// Remove prepear for a fatal exception in case an error occurred
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s/prepear/prepare

var didThrow = true;
try {
emitBeforeN(asyncId);
didThrow = false;
} finally {
if (didThrow) clearFatalExceptionHandlers();
}
}


// Called from native. The asyncId stack handling is taken care of there before
// this is called.
function emitAfterN(asyncId) {
processing_hook = true;
// Use a single try/catch for all hook to avoid setting up one per iteration.
try {
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][after_symbol] === 'function') {
active_hooks_array[i][after_symbol](asyncId);
}
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][after_symbol] === 'function') {
active_hooks_array[i][after_symbol](asyncId);
}
} catch (e) {
fatalError(e);
}
processing_hook = false;

Expand All @@ -409,8 +411,16 @@ function emitAfterN(asyncId) {
// kIdStackIndex. But what happens if the user doesn't have both before and
// after callbacks.
function emitAfterS(asyncId) {
if (async_hook_fields[kAfter] > 0)
emitAfterN(asyncId);
if (async_hook_fields[kAfter] > 0) {
// Remove prepear for a fatal exception in case an error occurred
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s/prepear/prepare

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@AndreasMadsen is the comment a TODO? Otherwise I'm not sure I understand what It means.

var didThrow = true;
try {
emitAfterN(asyncId);
didThrow = false;
} finally {
if (didThrow) clearFatalExceptionHandlers();
}
}

popAsyncIds(asyncId);
}
Expand All @@ -427,15 +437,10 @@ function emitDestroyS(asyncId) {

function emitDestroyN(asyncId) {
processing_hook = true;
// Use a single try/catch for all hook to avoid setting up one per iteration.
try {
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][destroy_symbol] === 'function') {
active_hooks_array[i][destroy_symbol](asyncId);
}
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][destroy_symbol] === 'function') {
active_hooks_array[i][destroy_symbol](asyncId);
}
} catch (e) {
fatalError(e);
}
processing_hook = false;

Expand All @@ -460,18 +465,13 @@ function emitDestroyN(asyncId) {
// exceptions.
function init(asyncId, type, triggerAsyncId, resource) {
processing_hook = true;
// Use a single try/catch for all hook to avoid setting up one per iteration.
try {
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][init_symbol] === 'function') {
active_hooks_array[i][init_symbol](
asyncId, type, triggerAsyncId,
resource
);
}
for (var i = 0; i < active_hooks_array.length; i++) {
if (typeof active_hooks_array[i][init_symbol] === 'function') {
active_hooks_array[i][init_symbol](
asyncId, type, triggerAsyncId,
resource
);
}
} catch (e) {
fatalError(e);
}
processing_hook = false;
}
Expand Down
10 changes: 7 additions & 3 deletions test/async-hooks/test-callback-error.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,10 @@ const async_hooks = require('async_hooks');
const initHooks = require('./init-hooks');

const arg = process.argv[2];
if (arg) {
process.on('uncaughtException', common.mustNotCall());
}

switch (arg) {
case 'test_init_callback':
initHooks({
Expand Down Expand Up @@ -50,7 +54,7 @@ assert.ok(!arg);
console.time('end case 1');
const child = spawnSync(process.execPath, [__filename, 'test_init_callback']);
assert.ifError(child.error);
const test_init_first_line = child.stderr.toString().split(/[\r\n]+/g)[0];
const test_init_first_line = child.stderr.toString().split(/[\r\n]+/g)[3];
assert.strictEqual(test_init_first_line, 'Error: test_init_callback');
assert.strictEqual(child.status, 1);
console.timeEnd('end case 1');
Expand All @@ -61,7 +65,7 @@ assert.ok(!arg);
console.time('end case 2');
const child = spawnSync(process.execPath, [__filename, 'test_callback']);
assert.ifError(child.error);
const test_callback_first_line = child.stderr.toString().split(/[\r\n]+/g)[0];
const test_callback_first_line = child.stderr.toString().split(/[\r\n]+/g)[3];
assert.strictEqual(test_callback_first_line, 'Error: test_callback');
assert.strictEqual(child.status, 1);
console.timeEnd('end case 2');
Expand Down Expand Up @@ -115,6 +119,6 @@ assert.ok(!arg);
assert.strictEqual(stdout, '');
const firstLineStderr = stderr.split(/[\r\n]+/g)[0].trim();
assert.strictEqual(firstLineStderr, 'Error: test_callback_abort');
console.timeEnd('end case 3');
});
console.timeEnd('end case 3');
}
4 changes: 2 additions & 2 deletions test/async-hooks/test-emit-before-after.js
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Expand Up @@ -16,13 +16,13 @@ switch (process.argv[2]) {
}

const c1 = spawnSync(process.execPath, [__filename, 'test_invalid_async_id']);
assert.strictEqual(c1.stderr.toString().split(/[\r\n]+/g)[0],
assert.strictEqual(c1.stderr.toString().split(/[\r\n]+/g)[3],
'Error: before(): asyncId or triggerAsyncId is less than ' +
'zero (asyncId: -1, triggerAsyncId: -1)');
assert.strictEqual(c1.status, 1);

const c2 = spawnSync(process.execPath, [__filename, 'test_invalid_trigger_id']);
assert.strictEqual(c2.stderr.toString().split(/[\r\n]+/g)[0],
assert.strictEqual(c2.stderr.toString().split(/[\r\n]+/g)[3],
'Error: before(): asyncId or triggerAsyncId is less than ' +
'zero (asyncId: 1, triggerAsyncId: -1)');
assert.strictEqual(c2.status, 1);
Expand Down