Javascript Async 并行调用不相关的回调
Javascript Async calls unrelated callback in parallel
当使用不依赖于 async
库的第三方库时,以某种方式处理结果回调中的错误会调用一个并行任务中的任意回调。
例如
var async = require('async'),
bloomjs = require('bloom-js');
var client = new bloomjs.Client({url: "http://localhost:3005/api"});
async.parallel([function (cb) {
console.log('callback1');
client.find('usgov.hhs.npi', '1558490003', function (err, results) {
console.log('callback2');
if (err) return cb(err);
cb(results);
});
}], function (err, results) {
console.log('callback3');
throw "hello";
if(err) return console.dir(err);
console.dir(results);
});
生成输出
callback1
callback2
callback3
callback2
/Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:30
if (called) throw new Error("Callback was already called.");
^
Error: Callback was already called.
at /Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:30:31
at /Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:251:21
at /Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:575:34
at /Users/untoldone/Source/async-demo/demo.js:9:21
at /Users/untoldone/Source/async-demo/node_modules/bloom-js/src/bloom.js:117:18
at IncomingMessage.<anonymous> (/Users/untoldone/Source/async-demo/node_modules/bloom-js/src/bloom.js:219:22)
at IncomingMessage.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16
at process._tickCallback (node.js:415:13)
callback2 似乎以某种方式被用来处理 callback3 中的异常。但是考虑到 bloomjs
从不使用 async
库,我不知道这怎么可能。想法?
我怀疑在bloomjs.Client.find
里面,回调代码包含这样的东西:
try {
callback(false, result);
} catch (e) {
callback(e, result);
}
所以当你的回调抛出 hello
错误时,这会被上面的代码捕获,并重新调用 client.find
回调。这将再次调用 cb()
,但 async.js
检测到此循环并发出自己的错误信号。
当使用不依赖于 async
库的第三方库时,以某种方式处理结果回调中的错误会调用一个并行任务中的任意回调。
例如
var async = require('async'),
bloomjs = require('bloom-js');
var client = new bloomjs.Client({url: "http://localhost:3005/api"});
async.parallel([function (cb) {
console.log('callback1');
client.find('usgov.hhs.npi', '1558490003', function (err, results) {
console.log('callback2');
if (err) return cb(err);
cb(results);
});
}], function (err, results) {
console.log('callback3');
throw "hello";
if(err) return console.dir(err);
console.dir(results);
});
生成输出
callback1
callback2
callback3
callback2
/Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:30
if (called) throw new Error("Callback was already called.");
^
Error: Callback was already called.
at /Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:30:31
at /Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:251:21
at /Users/untoldone/Source/async-demo/node_modules/async/lib/async.js:575:34
at /Users/untoldone/Source/async-demo/demo.js:9:21
at /Users/untoldone/Source/async-demo/node_modules/bloom-js/src/bloom.js:117:18
at IncomingMessage.<anonymous> (/Users/untoldone/Source/async-demo/node_modules/bloom-js/src/bloom.js:219:22)
at IncomingMessage.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16
at process._tickCallback (node.js:415:13)
callback2 似乎以某种方式被用来处理 callback3 中的异常。但是考虑到 bloomjs
从不使用 async
库,我不知道这怎么可能。想法?
我怀疑在bloomjs.Client.find
里面,回调代码包含这样的东西:
try {
callback(false, result);
} catch (e) {
callback(e, result);
}
所以当你的回调抛出 hello
错误时,这会被上面的代码捕获,并重新调用 client.find
回调。这将再次调用 cb()
,但 async.js
检测到此循环并发出自己的错误信号。