Changelog

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v0.3.0 (2026-06-17)

Enhancements

  • Transactional callback variants — handle_cast_tx/3, handle_call_tx/4, and handle_info_tx/3 are optional callback variants that receive a tx_ctx() map as their first argument (#{td := tenant(), tuid := tuid()}). When exported, the _tx variant is preferred over the plain variant. The td value is the open backend transaction+directory pair for the current consume cycle, allowing callbacks to read or write arbitrary keys atomically alongside the module-state commit. The new tx_ctx/0 type is exported from dgen_server.

  • lock_timeout option for dgen_server — Sets the maximum milliseconds a distributed lock may be held before other consumers treat it as stale and clear it. Previously a consumer killed (SIGKILL / VM abort) while holding the lock would block all other consumers permanently if no new messages arrived to trigger a re-check. With lock_timeout set, a backstop timer is scheduled whenever a live lock is observed: after the remaining timeout the consumer re-evaluates staleness and clears the lock if the holder has not done so. infinity (the default) preserves the previous behaviour. dgen_registry uses lock_timeout: 6_000.

  • dgen_registry — Experimental. An OTP-compatible process registry backed by the configured storage backend. Implements the four-function {via, dgen_registry, {Name, LogicalName}} contract so standard OTP processes (gen_server, gen_statem, etc.) can be started and addressed by name across an Erlang cluster. Writes and consistent reads go through an elected leader; whereis_name/1 (used by OTP via-tuple routing) is a snapshot read from the local member's in-memory map with no backend round-trip. The leader monitors registered pids and propagates {name_unregistered} to followers on process exit. Start with dgen_registry:start_link(Name, Tenant) and supply a supervisor name as the first argument to start_link/3 to embed it in an existing supervision tree.

    Partition recovery is reliable: each join carries a unique token so stale member_down messages from before a reconnect are discarded rather than undoing the rejoin. Leader transitions during a partition no longer trigger automatic distribution reconnect.

Breaking changes

  • DGenServer renamed to DGen.Server — use DGenServer becomes use DGen.Server; all DGenServer.* call sites become DGen.Server.*. The module now lives at lib/dgen/server.ex.

  • handle_locked/3 → handle_locked/4 — a db_ctx() map is now prepended as the first argument, matching the convention of handle_call_tx/4 and friends. db_ctx() carries #{db := tenant(), tuid := tuid()} where db is the DB-level tenant (not a transaction); use dgen_backend:transactional/2 inside the callback to open explicit transactions. Update all handle_locked implementations to accept the new first argument.

v0.2.0 (2026-04-05)

Enhancements

  • Dead-letter queue — opt-in poison-message handling via the new dead_letter_threshold start option (default infinity, i.e. disabled). When set to a positive integer, messages that crash the consumer that many times are moved to a dead-letter queue (DLQ) stored in FoundationDB instead of being retried indefinitely. For call messages the blocked caller raises {dead_letter, N}. The optional handle_dead_letter/2 callback is invoked when a message is dead-lettered.

  • dgen_server:outbox_cast/1,2 — returns a Cast = fun((Tx, Message) -> ok) closure for enqueuing a cast message atomically within the caller's own FDB transaction. Call it before opening the transaction as a preparatory step; the closure captures the queue directory and identifier internally. Intended for callers already operating directly with a backend transaction who need to compose the enqueue with other writes atomically.

v0.1.0 (2026-02-22)

Initial release.