feat: live tail mode

[erickzhao]

This PR adds a Live Tail mode that peeks at your local Slack.app log folder. Useful for making your local logs human-readable and filterable, especially when you need to inspect across process types.

[georgexu99]

see above in ipc.ts line 404

we're recursively scanning files here

[georgexu99]

Blocking: This seems unsafe! We should define a file allow list, otherwise we can freely recurse and stream any file content under a given path.

[georgexu99]

Suggested change

	private onFileChange(fullPath: string) {
	if (this.stopped) return;
	const watched = this.watchedFiles.get(fullPath);
	if (!watched) return;
	let newSize: number;
	try {
	newSize = fs.statSync(fullPath).size;
	} catch {
	return;
	}
	if (newSize <= watched.byteOffset) {
	if (newSize < watched.byteOffset) {
	d('File %s was truncated/rotated, resetting', fullPath);
	this.resetFile(watched);
	}
	return;
	}
	this.readIncremental(watched, newSize);
	}
	private onFileChange(fullPath: string) {
	if (this.stopped || !this.watchedFiles.has(fullPath)) return;
	this.dirtyFiles.add(fullPath);
	if (!this.readTimer) {
	this.readTimer = setTimeout(() => this.drainDirty(), 20);
	}
	}
	private drainDirty() {
	this.readTimer = null;
	if (this.stopped) return;
	for (const fullPath of this.dirtyFiles) {
	const watched = this.watchedFiles.get(fullPath);
	if (!watched) continue;
	let newSize: number;
	try {
	newSize = fs.statSync(fullPath).size;
	} catch {
	continue;
	}
	if (newSize <= watched.byteOffset) {
	if (newSize < watched.byteOffset) {
	d('File %s was truncated/rotated, resetting', fullPath);
	this.resetFile(watched);
	}
	continue;
	}
	this.readIncremental(watched, newSize);
	}
	this.dirtyFiles.clear();
	}

[georgexu99]

we can add a 20ms debounce, or even a 50tbh so we aren't creating a new read stream and readline scaffolding on each line, if we're bursting logs we can batch read and write.

[georgexu99]

Suggested change

	private flushTimer: ReturnType<typeof setTimeout> | null = null;
	private flushTimer: ReturnType<typeof setTimeout> | null = null;
	private dirtyFiles = new Set<string>();
	private readTimer: ReturnType<typeof setTimeout> | null = null;
	private stopped = false;

[georgexu99]

see comment about batching read and writes across a debounce below

[georgexu99]

Suggested change

	if (this.flushTimer) {
	if (this.flushTimer) {
	clearTimeout(this.flushTimer);
	this.flushTimer = null;
	}
	if (this.readTimer) {
	clearTimeout(this.readTimer);
	this.readTimer = null;
	}
	this.dirtyFiles.clear();
	this.pendingUpdates = [];

[georgexu99]

cleanup for batching read and writes

[georgexu99]

nit: I'd like to change this into a guard instead, makes for better error logs

[georgexu99]

follow-up: all of our parsing work runs in the main thread, if CE uses these on non-dev machines, i'm not sure if all the regex matching can cause sleuth to lag, I think its a much better architectural decision to treat the file stream like a message queue and move all the reading, decoding and regex matching to a node worker thread instead.