Future.wait()不能没有光纤(在等待Meteor.method中的另一个未来时) [英] Future.wait() can't wait without a fiber (while waiting on another future in Meteor.method)

问题描述

在Meteor中，我正在编写一个方法，该方法将必须检查特定文件的某个路径的子目录. 首先，我想只列出Meteor中的子目录，然后我child_process.exec一个简单的bash脚本，列出自上次执行以来添加的文件.

In Meteor, I'm writing a method that will have to check a certain path's subdirectories for new files. I first would like to just list the subdirectories within Meteor after which I child_process.exec a simple bash script that lists files added since the last time it executed.

我在使目录发现异步(Error: Can't wait without a fiber)时遇到一些问题.我已经编写了一个同步版本，但是同时具有fs.readdir和fs.stat而不是它们的同步替代选项可以让我捕获错误.

I'm having some issues getting the directory discovery to be async (Error: Can't wait without a fiber). I've written a synchronous version but having both fs.readdir and fs.stat in stead of their synchronous alternatives allows me to catch errors.

代码如下:

function listDirs(dir, isDir){

    var future1 = new Future();fs.readdir(dir, function(err, files){

            if (err)
                throw new Meteor.error(500, "Error listing files", err);

            var dirs = _.map(files, function(file){

                var future2 = new Future();
                var resolve2 = future2.resolver();

                fs.stat(dir+file, function(err, stats){

                    if (err)
                        throw new Meteor.error(500, "Error statting files", err);

                    if (stats.isDirectory() == isDir && file.charAt(0) !== '.')
                        resolve2(err, file);

                });

                return future2;

            });

            Future.wait(dirs);

            //var result = _.invoke(dirs, 'get');

            future1['return'](_.compact(dirs));
        });

        return future1.wait();
    }

错误Error: Can't wait without a fiber与future2有关. 当我注释掉Future.wait(dirs)时，服务器不再崩溃，但这与我试图解决此问题有关. :/

The error Error: Can't wait without a fiber has to do with future2. When I comment out Future.wait(dirs) the server doesn't crash anymore, but that's about as far as I got in trying to solve this. :/

我在方法的另一部分中使用的另一个_.map函数在期货上运行良好. (另请参阅 https://gist.github.com/possibilities/3443021 我从中找到了灵感)

Another _.map function I use in another part of the method works fine with futures. (see also https://gist.github.com/possibilities/3443021 where I found my inspiration)

推荐答案

将回调包装到Meteor.bindEnvironment中，例如:

Wrap your callback into Meteor.bindEnvironment, example:

fs.readdir(dir, Meteor.bindEnvironment(function (err, res) {
    if (err) future.throw(err);
    future.return(res);
}, function (err) { console.log("couldn't wrap the callback"); });

Meteor.bindEnvironment做很多事情，其中​​之一是确保回调在Fibre中运行.

Meteor.bindEnvironment does a lot of things and one of them is to make sure callback is running in a Fiber.

另一种可能有用的是var funcSync = Meteor._wrapAsync(func)，它利用期货并允许以同步方式调用函数(但它仍然是异步的).

Another thing that could be helpful is var funcSync = Meteor._wrapAsync(func) which utilizes futures and allows use to call a function in synchronous style (but it is still async).

如果您想了解更多信息，请观看有关突发事件的视频: https://www.eventedmind.com/posts/meteor-dynamic-scoping-with-environment-variables

Watch these videos on evented mind if you want to know more: https://www.eventedmind.com/posts/meteor-dynamic-scoping-with-environment-variables https://www.eventedmind.com/posts/meteor-what-is-meteor-bindenvironment

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