View Source Changelog

v0.1.4 - 2026-09-06

Concurrent fan-out: each flush delivers to remote nodes in parallel (one task per node via a Task.Supervisor), so a flush costs the slowest single round-trip instead of the sum of all of them. On by default and engaging at 2+ remote peers; disable with config :echo_pubsub, concurrent_flush: false.
Guides: docs/how-it-works.md (cursor internals, flush decision, failure scenarios, duplicate handling); README rewritten with "When to use it", "Caveats", and the run-alongside-Phoenix.PubSub setup.

The producer GenServer state is now a typed struct with a documented t() (compile-time-only typed_struct dependency), replacing the raw map.

Bidirectional fault injection for simulating a network partition. Previously only the worker rejected incoming batches; the producer now also short-circuits outgoing sends under an injected fault, so a partitioned node neither receives nor emits. Both directions keep the at-least-once/replay semantics - messages stay buffered and replay in order on recovery, and holding the fault long enough overflows the sender's own ring buffer, delivering {:cursor_expired, node} to the peer.

Centralized the compile-time fault switch in a single EchoPubSub.FaultInjection module (ok?/0), shared by the producer and worker instead of each carrying its own gate and duplicated code paths. A consuming app opts in with config :echo_pubsub, :enable_fault_injection, true (e.g. for demos).
Dropped the unused :sleep fault mode and removed leftover dbg/1 calls from the worker; the :fault_injection flag is now effectively boolean (:ok delivers, anything else rejects).

Detect ring-buffer expiry on the flush path, not just on node (re)join. When a remote node lagged far enough that its unacked messages were overwritten (e.g. during a sustained failure with replay), the producer would replay overwritten slots - silently delivering wrong/duplicated messages and breaking the "no gaps" guarantee. It now emits [:echo_pubsub, :buffer, :expired] and sends {:cursor_expired, node} instead. An expired node is resumed at the current write cursor so it is not re-expired on every subsequent flush.
Ack and retry the {:cursor_expired, node} notice like a normal batch. It was previously a raw GenServer.call: an unreachable peer at expiry time crashed the producer (losing the buffer and every node's read cursor), and the lagging node's cursor was advanced even if the notice never arrived - a silent gap. The cursor now only advances once the peer acks, and a failed notice is retried on the next flush.
Skip flushing a node that is already caught up, avoiding a spurious empty batch that the worker rejected as a bad message (triggering a needless retry).
Guard the capacity-warning calculation against a zero-sized buffer.

Moved the test-only failure-injection hook out of the production worker code path. It is now compiled in only under Mix.env() == :test and reads config :echo_pubsub, :fault_injection (previously the generic :msg/:val read on every batch in production).

Stop duplicating messages on the broadcasting node. Local delivery is handled by Phoenix.PubSub dispatch, so the producer now only forwards to remote nodes and advances the local read cursor itself.

Batched inter-node delivery: messages are accumulated and flushed on a timer instead of being sent one-by-one. Controlled by :batch_interval (default 200 ms; 0 flushes immediately).
Automatic replay of undelivered messages: when a remote node rejects, times out, or fails a batch, the producer keeps the messages buffered and schedules a retry flush.
New configuration options, settable per PubSub name via the supervisor or Application config (opts take precedence): :batch_interval, :call_timeout (default 5000 ms), :capacity_warning_threshold (default 0.4), and :capacity_warning_interval (default 60 s).
Buffer capacity warnings: a throttled Logger.warning is emitted once the buffer fill ratio crosses :capacity_warning_threshold.
Telemetry events: [:phoenix_pubsub_buffered, :buffer, :flush], [..., :buffer, :expired], [..., :buffer, :capacity_warning], [..., :sync, :failure], and [..., :retry, :scheduled].

Renamed the OTP application from :phoenix_pubsub_buffered to :distributed_pubsub.
Added :telemetry ~> 1.0 dependency.