如何在第一次失敗後停止async.queue？

Question

我想在發生第一個任務錯誤後停止執行我的async.queue。我需要在併發限制的同時執行幾個類似的操作，但在第一個錯誤之後停止所有的操作。我該怎麼做，或者我應該使用什麼？

Answer 1

假設你發出了5個並行函數，每個函數都需要5秒。在3秒內，功能1失敗。那你怎麼能停止其餘的執行呢？

這取決於這些函數的作用，您可以使用setInterval進行輪詢。但是，如果你的問題是如何阻止進一步的任務被推入隊列。你可以這樣做：

q.push(tasks, function (err) { 
    if (err && !called) { 
     //Will prevent async to push more tasks to the queue, however please note that 
     //whatever pushed to the queue, it will be processed anyway. 
     q.kill(); 

     //This will not allow double calling for the final callback 
     called = true; 


     //This the main process callback, the final callback 
     main(err, results); 
    } 
    }); 

這裏一個完整的工作示例：GitHub的頁面上

var async = require('async'); 

/* 
    This function is the actual work you are trying to do. 
    Please note for example if you are running child processes 
    here, by doing q.kill you will not stop the execution 
    of those processes, so you need actually to keep track the 
    spawned processed and then kill them when you call q.kill 
    in 'pushCb' function. In-case of just long running function, 
    you may poll using setInterval 
*/ 
function worker(task, wcb) { 
    setTimeout(function workerTimeout() { 
    if (task === 11 || task === 12 || task === 3) { 
     return wcb('error in processing ' + task); 
    } 

    wcb(null, task + ' got processed'); 

    }, Math.floor(Math.random() * 100)); 
} 


/* 
    This function that will push the tasks to async.queue, 
    and then hand them to your worker function 
*/ 
function process(tasks, concurrency, pcb) { 
    var results = [], called = false; 

    var q = async.queue(function qWorker(task, qcb) { 

    worker(task, function wcb(err, data) { 
     if (err) { 
     return qcb(err); //Here how we propagate error to qcb 
     } 

     results.push(data); 

     qcb(); 
    }); 

    }, concurrency); 

/* 
    The trick is in this function, note that checking q.tasks.length 
    does not work q.kill introduced in async 0.7.0, it is just setting 
    the drain function to null and the tasks length to zero 
*/ 
    q.push(tasks, function qcb(err) { 
    if (err && !called) { 
     q.kill(); 
     called = true; 
     pcb(err, results); 
    } 
    }); 

    q.drain = function drainCb() { 
    pcb(null, results); 
    } 
} 

var tasks = []; 
var concurrency = 10; 

for (var i = 1; i <= 20; i += 1) { 
    tasks.push(i); 
} 

process(tasks, concurrency, function pcb(err, results) { 
    console.log(results); 

    if (err) { 
    return console.log(err); 
    } 

    console.log('done'); 
}); 

Answer 2

異步文檔過期或不正確，同時檢查（）方法我通過async.queue返回隊列對象沒有看到方法kill（）。

儘管如此，還是有一種解決方法。隊列對象具有屬性任務，這是一個數組，簡單地將一個引用賦給一個空數組對我來說確實是個訣竅。

queue.push(someTasks, function (err) { 

    if (err) queue.tasks = []; 

});