How to Build a \"tail -f\" Generator in Go with an Efficient Sleep-Based Approach?

"Tail -f"-like Generator in Go

This article discusses the creation of a "tail -f"-like generator in Go, which allows for real-time monitoring of a file's last lines. The initial Go implementation involved an asynchronous call with a goroutine continuously reading from the file. However, a more idiomatic approach is recommended using a wrapper around a reader that sleeps on EOF.

Improved Implementation:

The suggested improvement involves creating a tailReader struct that implements the io.ReadCloser interface. This reader sleeps when encountering an EOF, allowing for continuous monitoring without continuous polling.

<code class="go">type tailReader struct {
    io.ReadCloser
}

func (t tailReader) Read(b []byte) (int, error) {
    for {
        n, err := t.ReadCloser.Read(b)
        if n > 0 {
            return n, nil
        } else if err != io.EOF {
            return n, err
        }
        time.Sleep(10 * time.Millisecond)
    }
}</code>

To create a tailReader, use newTailReader(fileName). This reader can be used with any provider that accepts an io.Reader, such as bufio.Scanner or json.NewDecoder.

Advantages:

This method offers several advantages over the goroutine approach:

• Easier Shutdown: Simply close the file to terminate the operation.
• Compatibility: The reader can be integrated seamlessly with many existing packages that support io.Reader.
• Adjustable Sleep Time: The sleep delay can be optimized based on performance requirements and latency tolerance.

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