Put Bunny in front of the station

A station streaming video to more than about 500 viewers needs a CDN (ADR-0017). At the default quality each viewer takes about 1 Mbit/s, so 500 viewers are about 500 Mbit/s of upload, more than most homes and many servers have to spare, before chat, guests and listeners. The studio app says so: when video is on, more than about 500 are connected and the station has no CDN or edges configured (steering.edges), desk.audience shows a warning. The count is of listeners on the station’s stream, the nearest figure the control plane has; it does not yet count video viewers apart.

Bunny is the CDN this documentation names and tests for live HLS and for large archive downloads. Nothing in WeaveSignal is Bunny-specific: the HLS output and the archive are plain files that any pull CDN can serve, and a self-run edge pool can stand beside it or instead of it. Bunny Standard costs about 0.01 USD per GB in Europe and North America (report 18): about 4.4 to 8.8 USD per programme hour for 2,000 to 4,000 viewers, against 0.8 to 1.4 USD for a self-run pool (ADR-0051).

Audio listeners need no CDN at the expected audience: 2,000 listeners at 96 kbit/s are about 200 Mbit/s, which one server or a couple of relays carry.

Before you start

• The station’s HLS origin running (the control plane serves the desk’s HLS at /hls/, with video on) and published through its reverse proxy, such as https://station.example/hls/.
• A Bunny account.

Make a pull zone

1. In Bunny’s dashboard, add a pull zone whose origin is the station’s public address, https://station.example.
2. Note the zone’s host name. Optionally, give it your own name, such as cdn.station.example, with Bunny’s certificate.
3. Let the zone follow the origin’s cache headers: the control plane marks playlists no-cache and segments public, max-age=30 (the edge image, for its part, caches playlists for a second and segments for a minute).
4. Turn on request coalescing if the zone offers it, so a new segment reaches the station once per Bunny node, as proxy_cache_lock does on a self-run edge.
5. Turn on the zone’s CORS headers for m3u8, m4s and mp4 files. The player fetches from the zone across origins, and the control plane sends no Access-Control-Allow-Origin on /hls/ itself.

Check it:

curl -si https://cdn.station.example/hls/live.m3u8

Send viewers to Bunny

With Bunny alone, point the player at the zone in control.toml and restart the control plane:

[join]
hls_url = "https://cdn.station.example/hls"

The player then fetches every playlist and segment from Bunny, and its page allows that address. The Compose bundle and the Cloudron package write control.toml themselves and have no setting for hls_url or steering yet: on the Compose bundle, add the lines to the control entry under configs: in deploy/compose/compose.yaml and start the bundle again; the Cloudron package cannot take them. The studio app’s warning above looks at steering.edges only, so it still shows with Bunny set this way.

Steer viewers to Bunny with content steering

With content steering, add the zone as a pathway instead. As the default CDN, give it a weight like any edge:

[[steering.edges]]
pathway = "bunny"
host = "cdn.station.example"

With a self-run pool for event nights, keep Bunny after the pool instead, so it carries viewers only when the edges fail:

[[steering.edges]]
pathway = "bunny"
host = "cdn.station.example"
weight = 0

A pathway without check_url is never checked and always counted up; Bunny’s own nodes fail over among themselves. The station’s own player page does not follow a steered pathway to another host yet (its Content-Security-Policy allows only the station and hls_url), so steering serves players on other pages and apps. Every setting is in Content steering.

Archive downloads

A second pull zone over the episode files (/media/episodes/) can carry a new episode’s first day of downloads. The feeds do not yet take a CDN address for their enclosures, so today that zone serves only links you hand out yourself.

Known limits

• Steering through Bunny has not been tested against Bunny itself: planned.
• Pathway clones are in hls.js 1.7.3’s content-steering code (read, not yet run in a browser); whether Safari’s own player follows them has not been tested.