Asynchronous 如何取消/中止Dart中的区域?
我有一个http web服务器,试图检测长时间运行的请求并中止它们。以下代码在超时时成功返回到客户端,但异步区域仍继续运行到完成我如何才能真正杀死请求处理程序?Asynchronous 如何取消/中止Dart中的区域?,asynchronous,dart,future,zone,dart-shelf,Asynchronous,Dart,Future,Zone,Dart Shelf,我有一个http web服务器,试图检测长时间运行的请求并中止它们。以下代码在超时时成功返回到客户端,但异步区域仍继续运行到完成我如何才能真正杀死请求处理程序? var zone = runZoned(() { var timer = new Timer(new Duration(seconds: Config.longRequestTimeoutSeconds), () { if (!completer.isCompleted) { // -- not already comple
var zone = runZoned(() {
var timer = new Timer(new Duration(seconds: Config.longRequestTimeoutSeconds), () {
if (!completer.isCompleted) { // -- not already completed
log.severe('request timed out');
// TODO: This successfully responds to the client early, but it does nothing to abort the zone/handler that is already running.
// Even though the client will never see the result (and won't have to wait for it), the zone/handler will continue to run to completion as normal.
// TODO: Find a way to kill/abort/cancel the zone
completer.complete(new shelf.Response(HttpStatus.SERVICE_UNAVAILABLE, body: 'The server timed out while processing the request'));
}
});
return innerHandler(request) // -- handle request as normal (this may consist of several async futures within)
.then((shelf.Response response) {
timer.cancel(); // -- prevent the timeout intercept
if (!completer.isCompleted) { // -- not already completed (not timed out)
completer.complete(response);
}
})
.catchError(completer.completeError);
});
除了代码本身,没有任何东西可以杀死正在运行的代码。如果您希望代码是可中断的,您需要某种方式来告诉它,并且代码本身需要终止(可能是抛出错误)。在这种情况下,
innerHandler
需要能够在请求时中断自身。如果不是你的代码,那就不可能了
您可以编写一个区域,在设置标志时停止异步事件的执行(通过修改zone.run
等),但您必须非常小心—如果您开始丢弃异步事件,它可能永远不会到达异步块并释放资源。因此,不建议将其作为一种通用解决方案,仅适用于愿意手动管理资源的非常谨慎的人员