wait for all streams to finish - stream a directory of files

问题

I'm using client.upload in pkgcloud to upload a directory of files. What's the best way to execute a callback after all the streams have finished? Is there a built-in way to register each stream's "finish" event and execute a callback after they have all fired?

var filesToUpload = fs.readdirSync("./local_path"); // will make this async

for(let file of filesToUpload) {
    var writeStream = client.upload({
        container: "mycontainer,
        remote: file
    });
    // seems like i should register finish events with something
    writeStream.on("finish", registerThisWithSomething);
    fs.createReadStream("./local_path/" + file).pipe(writeStream);
}

回答1:

One way to do it, is to generate a Promise task for each upload, then utilizing Promise.all().

Assuming you are using ES6, the code would look something like this:

const uploadTasks = filesToUpload.map((file) => new Promise((resolve, reject) => {
    var writeStream = client.upload({
        container: "mycontainer,
        remote: file
    });
    // seems like i should register finish events with something
    writeStream.on("finish", resolve);
    fs.createReadStream("./local_path/" + file).pipe(writeStream);
});

Promise.all(uploadTasks)
  .then(() => { console.log('All uploads completed.'); });

Alternatively, if you have access to async / await - you can utilize this. For example:

const uploadFile = (file) => new Promise((resolve, reject) => {
  const writeStream = client.upload({
    container: "mycontainer,
    remote: file
  });
  writeStream.on("finish", resolve);
  fs.createReadStream("./local_path/" + file).pipe(writeStream);
}

const uploadFiles = async (files) => {
  for(let file of files) {
    await uploadFile(file);
  }
}

await uploadFiles(filesToUpload);
console.log('All uploads completed.');

回答2:

Take a look at NodeDir，which has methods like readFilesStream / promiseFiles etc.

来源：https://stackoverflow.com/questions/37229725/wait-for-all-streams-to-finish-stream-a-directory-of-files

标签

node.js

node-streams