Add a semaphore to limit concurrent t.me access

[nDmitry]

Summary by CodeRabbit

• Chores
  • Enhanced scraper efficiency by implementing request concurrency limiting to prevent resource exhaustion and improve overall system stability.

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📥 Commits

Reviewing files that changed from the base of the PR and between bd43b84 and d7996ed.

📒 Files selected for processing (1)

• internal/feed/scraper.go

Walkthrough

The scraper now enforces concurrent request limits using a semaphore mechanism capped at 3 simultaneous requests. A new semaphore type with acquire and release methods was introduced, integrated into the Scraper struct, and initialized during instantiation to control HTTP visit concurrency.

Changes

Cohort / File(s)	Summary
Concurrency limiting mechanism internal/feed/scraper.go	Added new semaphore type with constructor and acquire/release methods; Scraper struct now includes unexported sema field; NewDefaultScraper initializes semaphore with limit of 3 concurrent requests; HTTP visit operations wrapped with semaphore acquire/release calls.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A scraper hops with grace so fine,
With three requests in sync—divine!
The semaphore stands guard with care,
No congestion in the air! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a semaphore to limit concurrent requests to t.me (Telegram), which is exactly what the code changes implement.

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Actionable comments posted: 0

🧹 Nitpick comments (1)

internal/feed/scraper.go (1)

23-37: Consider adding context support to acquire to prevent goroutine leaks.

The current acquire() blocks unconditionally. If a caller's context is cancelled while waiting for the semaphore, the goroutine will block forever, potentially causing leaks under cancellation scenarios.

♻️ Suggested context-aware acquire

-func (s *semaphore) acquire() {
-	s.c <- struct{}{}
+func (s *semaphore) acquire(ctx context.Context) error {
+	select {
+	case s.c <- struct{}{}:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	}
 }

Then update the call site in Scrape:

-	s.sema.acquire()
-	defer s.sema.release()
-
-	if err := c.Visit(channel.URL); err != nil {
+	if err := s.sema.acquire(ctx); err != nil {
+		return nil, fmt.Errorf("could not acquire semaphore: %w", err)
+	}
+	defer s.sema.release()
+
+	if err := c.Visit(channel.URL); err != nil {

📜 Review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 6dd19a3 and bd43b84.

📒 Files selected for processing (1)

• internal/feed/scraper.go

🔇 Additional comments (3)

internal/feed/scraper.go (3)

21-22: LGTM!

Reasonable concurrency limit constant.

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39-51: LGTM!

Clean integration of the semaphore into the Scraper struct with proper initialization.

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95-100: Good use of defer for release.

The placement correctly limits concurrent Visit calls, and defer ensures the semaphore is released on all exit paths including errors.