请教 async 并发限制的问题
使用async流程控制库在什么情况下需要限制并发量？ 并发数(limit参数)通常根据什么来定？
5 回复
async.eachLimit = function (arr, limit, iterator, callback) {
var fn = _eachLimit(limit);
fn.apply(null, [arr, iterator, callback]);
};
async.forEachLimit = async.eachLimit;
var _eachLimit = function (limit) {
return function (arr, iterator, callback) {
callback = callback || function () {};
if (!arr.length || limit <= 0) {
return callback();
}
var completed = 0;
var started = 0;
var running = 0;
(function replenish () {
if (completed >= arr.length) {
return callback();
}
while (running < limit && started < arr.length) {
started += 1;
running += 1;
iterator(arr[started - 1], function (err) {
if (err) {
callback(err);
callback = function () {};
}
else {
completed += 1;
running -= 1;
if (completed >= arr.length) {
callback();
}
else {
replenish();
}
}
});
}
})();
};
};
```
