feat(outbox): single-commit connection sharing for consumer writes - #39
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asawicki merged 2 commits intoJun 28, 2026
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…ommit writes Expose the database connection the transactional outbox middleware pins for the in-flight message via a new public IOutboxConnectionAccessor. A consumer DbContext can use that same connection so its business write commits single-phase with the buffered outbox messages and the inbox processed marker — one physical connection, one enlistment — instead of opening a second connection and forcing System.Transactions to escalate to a two-phase (prepared) commit. A single-phase commit is faster (no PREPARE/COMMIT PREPARED round-trip and fsync per message) and removes the PostgreSQL max_prepared_transactions requirement. Verified end-to-end against PostgreSQL with max_prepared_transactions=0: the OrderedConsumers sample processes every message with zero "55000: prepared transactions are disabled" errors and creates no prepared transactions, while per-key ordering and inbox deduplication remain intact. - TransactionalOutboxMiddleware publishes its pinned DbConnection on an AsyncLocal for the duration of the consume operation and clears it on completion, so a consumer resolved in its own DI scope (same async flow) can share it. - OutboxConnectionAccessor (internal) reads it; registered as a singleton by AddBareWireOutbox. - OrderedConsumers sample shares the outbox connection instead of opening its own. - EF package README leads with the single-commit pattern and a working example; 2PC is documented as the fallback. samples/README re-points the 2PC note to TransactionalOutbox and InboxDeduplication, which still rely on it.
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June 28, 2026 15:18
… InboxDeduplication; drop 2PC Apply the single-commit connection-sharing pattern to the remaining outbox samples whose consumers persist business state during consume: TransactionalOutbox (TransferConsumer updates the Transfer row) and InboxDeduplication (Email/Audit consumers append a NotificationLog). Each now binds its DbContext to the connection the outbox middleware pinned for the in-flight message (IOutboxConnectionAccessor), so the business write commits single-phase with the outbox/inbox writes instead of opening a second connection and escalating to a two-phase (prepared) commit. With every outbox sample sharing the connection, no sample needs prepared transactions: the Aspire AppHost no longer sets max_prepared_transactions and the standalone-run instructions drop the -c max_prepared_transactions=100 flag. PostgreSQL runs with its default (2PC disabled). Verified end-to-end against PostgreSQL with max_prepared_transactions=0: - TransactionalOutbox: 3 transfers all reach Completed, zero "55000" errors, no prepared transactions. - InboxDeduplication: 2 payments produce 4 NotificationLogs (Audit=2, Email=2), zero "55000" errors.
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