fs: add WriteStream.prototype.fsync #28513
Description
Right now it's pretty complicated to intermix fs.fsync() calls with ws.write() calls, to the point that you lose most of the benefits of using fs.WriteStream. Example:
const fs = require('fs');
const ws = fs.createWriteStream('test.txt');
ws.write('important data', () => {
fs.fsync(ws.fd, () => {
// only now is it safe again to call ws.write()
ws.write('more important data', () => {
fs.fsync(ws.fd, () => { /* etc. */ });
});
});
});It would be exceedingly helpful if fs.WriteStream grew a .fsync() method that preserves order with respect to writes so that the following example works like I would expect it to:
const ws = require('fs').createWriteStream('test.txt');
ws.write('important data');
ws.fsync();
ws.write('more important data');
ws.fsync();It's not quite impossible to accomplish the above today but it's not very ergonomic. Here is an async/await example:
const util = require('util');
const fs = require('fs');
const ws = fs.createWriteStream('test.txt');
ws.once('open', (fd) => go(fd));
async function go(fd) {
const write = util.promisify(ws.write.bind(ws));
const fsync = util.promisify(fs.fsync.bind(null, fd));
await write('important data');
await fsync();
await write('more important data');
await fsync();
}I don't know, the fact that you need to know about the 'open' event doesn't give me warm fuzzies. Proper synchronization is important enough that I feel it merits a place in core.