我有一个长时间运行的 node.js 进程，有时会跳转到 100% CPU 并停止响应请求。最近一次这样做是我将 strace 附加到进程中，这是我看到的:

Process 19523 attached - interrupt to quit
gettimeofday({1394558574, 234192}, NULL) = 0
gettimeofday({1394558574, 235381}, NULL) = 0
gettimeofday({1394558574, 306460}, NULL) = 0
mmap(0x3edab823a000, 2097152, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x3edab823a000
munmap(0x3edab823a000, 811008)          = 0
munmap(0x3edab8400000, 237568)          = 0
mmap(0x3edab8300000, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x3edab8300000
gettimeofday({1394558574, 316435}, NULL) = 0
gettimeofday({1394558574, 316576}, NULL) = 0
gettimeofday({1394558574, 316677}, NULL) = 0
gettimeofday({1394558574, 316775}, NULL) = 0
gettimeofday({1394558574, 316879}, NULL) = 0
gettimeofday({1394558574, 316978}, NULL) = 0
gettimeofday({1394558574, 317439}, NULL) = 0
gettimeofday({1394558574, 317537}, NULL) = 0
gettimeofday({1394558574, 318139}, NULL) = 0
gettimeofday({1394558574, 318234}, NULL) = 0
gettimeofday({1394558574, 318343}, NULL) = 0
gettimeofday({1394558574, 318437}, NULL) = 0
gettimeofday({1394558574, 318530}, NULL) = 0
gettimeofday({1394558574, 318624}, NULL) = 0
gettimeofday({1394558574, 319135}, NULL) = 0
gettimeofday({1394558574, 319648}, NULL) = 0
gettimeofday({1394558574, 319769}, NULL) = 0
gettimeofday({1394558574, 319975}, NULL) = 0
futex(0x7f5b380008c8, FUTEX_WAKE_PRIVATE, 1) = 1
gettimeofday({1394558574, 322266}, NULL) = 0
gettimeofday({1394558574, 322426}, NULL) = 0
gettimeofday({1394558574, 322520}, NULL) = 0
gettimeofday({1394558574, 322759}, NULL) = 0
gettimeofday({1394558574, 322853}, NULL) = 0
gettimeofday({1394558574, 322995}, NULL) = 0
futex(0x7f5b380008c8, FUTEX_WAKE_PRIVATE, 1) = 1
gettimeofday({1394558574, 417614}, NULL) = 0
gettimeofday({1394558575, 386566}, NULL) = 0
gettimeofday({1394558575, 387704}, NULL) = 0
gettimeofday({1394558575, 463410}, NULL) = 0
mmap(0x24cfd260f000, 2097152, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = 0x24cfd260f000
munmap(0x24cfd260f000, 987136)          = 0
munmap(0x24cfd2800000, 61440)           = 0
mmap(0x24cfd2700000, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x24cfd2700000

这是很多 gettimeofday 调用，仅此而已!什么可能导致 node.js 像这样卡住？

更新:我从旧版本的 node.js 升级到了 10.29(我认为)，然后就消失了。我刚刚升级到 10.33，问题又回来了。这次我在调试它方面取得了更多进展。第一条:

$ sudo strace -p 11812 -c
Process 11812 attached - interrupt to quit
Process 11812 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00    0.000192           0      2780           gettimeofday
  0.00    0.000000           0      1390           getrusage
  0.00    0.000000           0        31           futex
  0.00    0.000000           0      1390           clock_gettime
------ ----------- ----------- --------- --------- ----------------
100.00    0.000192                  5591           total

来自 Node.js: How to attach to a running process and to debug the server with a console?我发现了将 Node 调试器附加到正在运行的进程，这就是我得到的地方:

$ sudo kill -s SIGUSR1 11812
$ sudo node debug -p 11812
connecting... ok
break in timers.js:79
  77 }
  78
  79 function listOnTimeout() {
  80   var msecs = this.msecs;
  81   var list = this;
debug> bt
#0 timers.js:79:23

所以看起来它肯定与计时器有关，但我不知道如何进一步向上移动堆栈以找出问题在我的代码中被触发的位置。

最佳答案

我的猜测是有人手动实现了阻塞“setTimeout”。如果有人不想释放对主 JS 线程的控制以防止潜在的竞争条件，则可能会发生这种情况。

出于显而易见的原因，这对于生产代码来说是一种不好的做法，但我有时会在调试中使用它来强制异步进程以特定顺序执行。

你可以找这样的傻事:

var mockAsyncFunction = function (cb) {
    setTimeout(function () {
        cb(null, 'dummy_result')
    }, 5000);
};

var myResult = null;
mockAsyncFunction(function (err, result) {
    myResult = result;
});
var timeOut = 10000; // timeout in 10 sec.
var timeStart = new Date().getTime();


while (1) {
    if (new Date().getTime() - timeStart > 10000) {
        break;
    }
}
console.log('DONE');

或者更邪恶的 nextTick 递归，例如:

var timeStart = new Date().getTime();

var recurseUntilDone = function () {
    if (new Date().getTime() - timeStart < 10000) {
        process.nextTick(recurseUntilDone);
    } else {
        console.log('Done recursing');
    }
};

recurseUntilDone();

关于javascript - Node.js 100% CPU - gettimeofday 调用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22343562/