Table of Contents

EF Core Outbox Concurrency Validation

Issue: #311.

This page documents the repeatable validation path for EF Core-backed governance outbox persistence and provider-neutral drain behavior under concurrent writes, retry handling, and drain-worker contention.

The goal is evidence, not a production throughput guarantee. These tests run against SQLite in shared in-memory mode so they remain CI-friendly while still exercising EF Core relational persistence and separate host-owned DbContext instances.

What the validation covers

The validation lives in:

tests/AsiBackbone.EntityFrameworkCore.Tests/EfCoreOutboxConcurrencyValidationTests.cs

The test class covers three focused scenarios:

Scenario Evidence produced Boundary confirmed
Concurrent writers Multiple host-owned EF Core contexts enqueue outbox entries and append lifecycle records against the same relational store. Local outbox and lifecycle evidence is preserved under concurrent write pressure.
Concurrent drain-worker contention Two drain instances can reach the same pending entry before either saves final delivery state. The current provider-neutral drain is selection-based, not claim-based, so hosts still need a single active worker, partitioning, provider idempotency, or host-owned claim/lease behavior for production multi-worker deployments.
Retryable transient failure A simulated downstream failure is persisted as retryable outbox state with retry timing and retry count evidence. Transient provider failures do not erase local outbox records and can be queried later as retry-ready work.

How to run locally

Run the EF Core test project from the repository root:

dotnet test ./tests/AsiBackbone.EntityFrameworkCore.Tests/AsiBackbone.EntityFrameworkCore.Tests.csproj --configuration Release

To run only the concurrency validation tests:

dotnet test ./tests/AsiBackbone.EntityFrameworkCore.Tests/AsiBackbone.EntityFrameworkCore.Tests.csproj --configuration Release --filter FullyQualifiedName~EfCoreOutboxConcurrencyValidationTests

Expected interpretation

Passing tests support the following bounded claims:

  • EF Core-backed outbox entries and lifecycle records can be preserved by concurrent host-owned contexts in the tested relational path.
  • Retryable downstream failures can be persisted and later queried as retry-ready outbox records.
  • The current provider-neutral drain can expose the same pending entry to more than one worker when workers read before either one saves final state.

Do not interpret these tests as proof of exactly-once delivery, universal throughput, production distributed locking, or provider-side idempotency. The current outbox APIs do not claim, lease, lock, or hide rows before emission.

Production guidance retained by the evidence

For production multi-replica hosts, continue to prefer one of these patterns:

  • one active drain worker per durable outbox partition;
  • partitioned workers with disjoint selection criteria;
  • a host-owned claim/lease design before provider emission;
  • provider-side idempotency using stable envelope or outbox identifiers.

The validation deliberately backs the current reliability story without overstating the package boundary.

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