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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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88 changes: 42 additions & 46 deletions lib/async_hooks.js
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Original file line number Diff line number Diff line change
Expand Up @@ -326,7 +326,14 @@ 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 @@ -337,17 +344,10 @@ function emitInitS(asyncId, type, triggerAsyncId, resource) {

function emitBeforeN(asyncId) {
processing_hook = true;
var didThrow = 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)

}
didThrow = false;
} finally {
if (didThrow) clearFatalExceptionHandlers();
}
processing_hook = false;

Expand Down Expand Up @@ -376,25 +376,26 @@ function emitBeforeS(asyncId, triggerAsyncId = asyncId) {

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;
var didThrow = 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);
}
didThrow = false;
} catch (e) {
if (didThrow) clearFatalExceptionHandlers();
}
processing_hook = false;

Expand All @@ -408,8 +409,16 @@ 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 @@ -426,17 +435,10 @@ function emitDestroyS(asyncId) {

function emitDestroyN(asyncId) {
processing_hook = true;
var didThrow = 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);
}
didThrow = false;
} finally {
if (didThrow) clearFatalExceptionHandlers();
}
processing_hook = false;

Expand All @@ -461,19 +463,13 @@ function emitDestroyN(asyncId) {
// exceptions.
function init(asyncId, type, triggerAsyncId, resource) {
processing_hook = true;
var didThrow = 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
);
}
} finally {
if (didThrow) clearFatalExceptionHandlers();
}
processing_hook = false;
}
Expand Down