Make outbox, inbox, and scheduling workers idempotent on start

[alisan3]

The Mocha message-bus hosted workers were not idempotent on start. StartAsync
checked _task for null and then assigned it as two separate steps, so:

• A second StartAsync call threw InvalidOperationException instead of being a no-op.
• Concurrent calls could both pass the guard and each create a background loop (and,
  for the Postgres workers, an NpgsqlDataSource), leaking the orphaned loop/connection
  that StopAsync could never dispose.

Changes

Made StartAsync/StopAsync idempotent and thread-safe in:

• PostgresMessageBusOutboxWorker
• ScheduledMessageWorker
• MessageBusInboxWorker

Each now guards lifecycle state with a lock: a repeat StartAsync is a no-op (no throw),
and StopAsync atomically claims the task before disposing it (outside the lock) so a
single caller owns disposal and resources can't leak.

Tests

Added StartAsync_Should_NotThrow_When_CalledMultipleTimes for each worker, plus a new
SchedulingServiceRegistrationTests. All pass on net8.0/net9.0/net10.0.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds idempotent, thread-safe IHostedService start/stop behavior for Mocha background workers and expands test coverage to validate service registration and repeated StartAsync calls.

Changes:

• Added new DI registration tests for Postgres scheduling worker.
• Added tests ensuring StartAsync can be called multiple times for inbox/outbox/scheduling workers.
• Updated inbox/outbox/scheduling workers to make StartAsync a no-op when already started and to make stop/start transitions thread-safe via locking.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Mocha/test/Mocha.EntityFrameworkCore.Postgres.Tests/SchedulingServiceRegistrationTests.cs	New tests for scheduling worker DI registration and repeated StartAsync.
src/Mocha/test/Mocha.EntityFrameworkCore.Postgres.Tests/OutboxServiceRegistrationTests.cs	Adds repeated StartAsync test for Postgres outbox worker.
src/Mocha/test/Mocha.EntityFrameworkCore.Postgres.Tests/InboxServiceRegistrationTests.cs	Adds repeated StartAsync test for inbox worker.
src/Mocha/src/Mocha.Inbox/MessageBusInboxWorker.cs	Makes StartAsync idempotent and synchronizes start/stop via a lock.
src/Mocha/src/Mocha.EntityFrameworkCore.Postgres/Scheduling/ScheduledMessageWorker.cs	Makes StartAsync idempotent and synchronizes start/stop via a lock.
src/Mocha/src/Mocha.EntityFrameworkCore.Postgres/Outbox/MessageBusOutboxWorker.cs	Makes StartAsync idempotent and synchronizes start/stop via a lock.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

src/Mocha/src/Mocha.Inbox/MessageBusInboxWorker.cs:1

• The XML docs no longer mention the previous behavior (throwing on a second start), but they also don’t describe the new behavior. Please update the StartAsync documentation to explicitly state that repeated calls are a no-op (idempotent) so callers/tests aren’t relying on undocumented behavior.

using Microsoft.Extensions.Hosting;

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.