Per-channel outbound rate limiting for Slack Web API calls.

Slack limits chat.postMessage to roughly one message per second per channel; bursts beyond that get 429s and dropped messages. This module fronts outbound calls with one lightweight GenServer per channel (see Slink.Rate.Channel), each draining a FIFO queue no faster than the configured interval. Different channels drain concurrently.

Calls are fire-and-forget: failures are logged, not returned. Use Slink.API directly if you need the response.

Configuration

• config :slink, :rate_interval_ms, 1_000 — minimum gap between sends on a single channel (default 1000ms).
• config :slink, :rate_max_queue, 1_000 — per-channel queue cap; beyond it the oldest queued messages are dropped (default 1000).
• config :slink, :rate_idle_stop_ms, 600_000 — a channel worker with nothing to do for this long stops itself (default 10 minutes), so posting to many channels doesn't accumulate idle workers.

:rate_mode and :rate_sender also exist but are internal test seams (set by Slink.Testing.run/3): :sync performs sends inline with no pacing, no queue bound and swallowed errors. Never set them in production.