node.js - 如何设置可写高水位线？

Question

我在选项中发现为 readable stream 设置高水位线:fs.createReadStream(path[, options])

但找不到 writeable stream 的高水位线选项

那么创建可写流时如何设置呢？

Answer 1

尽管 fs.createWriteStream 上没有记录它，但 stream.Writable可以采用:highWaterMark 作为选项。

fs.createWriteStream('out', { highWaterMark: 32000 });

console.log(stream._writableState.highWaterMark); // 32000

并实际测试它是否正常工作:

const lowHWStream = fs.createWriteStream('low', { highWaterMark: 1 });
const highHWStream = fs.createWriteStream('high', { highWaterMark: 32000 });

console.log(lowHWStream.write('a')); // false
console.log(highHWStream.write('a')); // true

The return value is true if the internal buffer is less than the highWaterMark configured when the stream was created after admitting chunk. If false is returned, further attempts to write data to the stream should stop until the 'drain' event is emitted.

Checking the source code ，您可以看到传递给 createWriteStream 的选项被传递给 stream.Writable