Public channels

Public channels are broadcast feeds: anyone can subscribe, no token required.

./bin/parsec channels open public:webapp.system.status
echo '{"msg":"deploy started"}' | ./bin/parsec publish public:webapp.system.status
./bin/parsec subscribe public:webapp.system.status

The visibility prefix public: is what unlocks the no-auth subscribe path. The grammar is documented in naming; anything not matching public:<app>.<domain>[.<id>][.<topic>] is rejected by channels.ParseName before the manager ever sees it.

Lifecycle

Public channels move between three states:

The transition from open to closed happens during the manager’s periodic sweep — every 30 seconds by default. A closed channel can be reopened with another channels open call, which resets last_active and emits a fresh opened event.

TTL semantics

Public channels have an inactivity TTL: any Publish (or explicit Touch) resets the clock. The default is 30 minutes; override with --ttl 2h on channels open. Two important properties:

• Closed public channels are not removed. The record stays in the manager so an operator can reopen it without losing the name.
• Closed public channels do not kick subscribers. They simply refuse new ones. This matches the “fade out” intent of a public feed — the broadcaster has stopped, but the people already listening can finish what they’re hearing.

See TTL and expiry for the full lifecycle diagram and how it differs from private.

History

Centrifuge keeps a per-channel history buffer so a late subscriber can catch up. The defaults: 100 publications, 5-minute retention. These are broker-side knobs configured at boot via broker.Options:

• HistorySize — bound on retained publications per channel
• PublicHistoryTTL — how long publications stay in history

Both default to safe single-node values. Embedders who need different windows set them through parsec.Options.BrokerOptions.

Delete

Public channels do not auto-delete (only private does). You explicitly remove one with:

./bin/parsec channels delete public:webapp.system.status

Delete is final. The manager flips the record to deleted, the broker unsubscribes every connected client, and the name becomes unusable — even reopening it returns PARSEC_CHANNEL_NOT_FOUND. Create a new channel under a different name (or wait for the manager state to be wiped on restart).

Typical use

• System status feeds: public:<app>.system.status
• Org-wide counters: public:scoreboard.counter.<metric>
• Maintenance announcements: public:<app>.broadcast.maintenance

Anything that should reach an authenticated population belongs in a private channel instead.