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'use strict';
const {
ObjectKeys,
SafeMap,
SafeSet,
Symbol,
} = primordials;
const { trace } = internalBinding('trace_events');
const async_wrap = internalBinding('async_wrap');
const async_hooks = require('async_hooks');
// Use small letters such that chrome://tracing groups by the name.
// The behavior is not only useful but the same as the events emitted using
// the specific C++ macros.
const kBeforeEvent = 'b'.charCodeAt(0);
const kEndEvent = 'e'.charCodeAt(0);
const kTraceEventCategory = 'node,node.async_hooks';
const kEnabled = Symbol('enabled');
// It is faster to emit traceEvents directly from C++. Thus, this happens
// in async_wrap.cc. However, events emitted from the JavaScript API or the
// Embedder C++ API can't be emitted from async_wrap.cc. Thus they are
// emitted using the JavaScript API. To prevent emitting the same event
// twice the async_wrap.Providers list is used to filter the events.
const nativeProviders = new SafeSet(ObjectKeys(async_wrap.Providers));
const typeMemory = new SafeMap();
function createHook() {
// In traceEvents it is not only the id but also the name that needs to be
// repeated. Since async_hooks doesn't expose the provider type in the
// non-init events, use a map to manually map the asyncId to the type name.
const hook = async_hooks.createHook({
init(asyncId, type, triggerAsyncId, resource) {
if (nativeProviders.has(type)) return;
typeMemory.set(asyncId, type);
trace(kBeforeEvent, kTraceEventCategory,
type, asyncId,
{
triggerAsyncId,
executionAsyncId: async_hooks.executionAsyncId()
});
},
before(asyncId) {
const type = typeMemory.get(asyncId);
if (type === undefined) return;
trace(kBeforeEvent, kTraceEventCategory, `${type}_CALLBACK`, asyncId);
},
after(asyncId) {
const type = typeMemory.get(asyncId);
if (type === undefined) return;
trace(kEndEvent, kTraceEventCategory, `${type}_CALLBACK`, asyncId);
},
destroy(asyncId) {
const type = typeMemory.get(asyncId);
if (type === undefined) return;
trace(kEndEvent, kTraceEventCategory, type, asyncId);
// Cleanup asyncId to type map
typeMemory.delete(asyncId);
}
});
return {
enable() {
if (this[kEnabled])
return;
this[kEnabled] = true;
hook.enable();
},
disable() {
if (!this[kEnabled])
return;
this[kEnabled] = false;
hook.disable();
typeMemory.clear();
}
};
}
exports.createHook = createHook;
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