Crate chase

Chase: File following

Chase a file through thick and thin:

• Provide line numbers with each line yielded
• Ability to exit the watch loop programmatically
• Deals with file rotations automatically
• Cross-platform async
• Configurable (which line to start on, delays and retries)
• Easy to use synchronously
• Async modes (incl. support for Future Streams)

Examples

Sync

Here, we enter a synchronous watch loop and use Control::Stop and Control::Continue to decide when we want to exit the loop

let temp_dir = TempDir::new("chase-test-sync-docs").unwrap();
let file_path = temp_dir.path().join("test.log");
let mut chaser = Chaser::new(&file_path);

let mut file_write = OpenOptions::new()
  .write(true)
  .append(true)
  .create(true)
  .open(&file_path)
  .unwrap();

write!(file_write, "Hello, world 1\n").unwrap();
write!(file_write, "Hello, world 2\n").unwrap();
write!(file_write, "Hello, world 3\n").unwrap();

let mut seen = Vec::with_capacity(3);

// This is a synchronous loop; so we need to exit manually
chaser.run(|line, _, _| {
    seen.push(line.to_string());
    if seen.len() < 3 {
        Ok(Control::Continue)
    } else {
        Ok(Control::Stop)
    }
}).unwrap();

assert_eq!(seen, vec!["Hello, world 1".to_string(), "Hello, world 2".to_string(), "Hello, world 3".to_string()]);
drop(file_write);
temp_dir.close().unwrap();

Async

This is how you would use Chase with standard lib Channels, though Future Stream usage, available through a feature, is similar.

In async modes, simply drop the receiving end and the watch loop will stop. Any elements that it tries to send you afterwards will bubble up to you as the Err result of joining the thread, which is the same as how channels normally act.

let temp_dir = TempDir::new("chase-test-lib").unwrap();
let file_path = temp_dir.path().join("test.log");
let chaser = Chaser::new(&file_path);

let mut file_write = OpenOptions::new()
  .write(true)
  .append(true)
  .create(true)
  .open(&file_path)
  .unwrap();

write!(file_write, "Hello, world 1\n").unwrap();
write!(file_write, "Hello, world 2\n").unwrap();

let mut seen = String::new();

let (receiver, _) = chaser.run_channel().unwrap();

seen.push_str(&receiver.recv().unwrap().0);
seen.push_str(&receiver.recv().unwrap().0);

assert_eq!(seen.as_str(), "Hello, world 1Hello, world 2");

write!(file_write, "Hello, world 3\n").unwrap();
seen.push_str(&receiver.recv().unwrap().0);
assert_eq!(seen.as_str(), "Hello, world 1Hello, world 2Hello, world 3");

drop(receiver);
drop(file_write);
temp_dir.close().unwrap();

Structs

Chaser	Your entry point for following a file.
Line
Pos

Enums

ChaseError
Control	When chasing a file synchronously, use this to control when to exit the follow loop.

Constants

DEFAULT_NOT_ROTATED_WAIT_MILLIS
DEFAULT_ROTATION_CHECK_WAIT_MILLIS