Support MessageGroupId on standard SQS queues for fair queues (GH-2886)

[jeremydmiller]

Problem

Closes #2886.

AWS SQS standard queues now support fair queues: setting MessageGroupId on a standard queue improves fairness for multi-tenant workloads so one tenant's backlog doesn't increase dwell time for others.

Wolverine already maps Envelope.GroupId → SQS MessageGroupId, but the mapping was gated behind IsFifoQueue (queue names ending in .fifo), so standard queues never received a MessageGroupId even when the envelope had a group id. That made it hard to use SQS fair queues through Wolverine without custom transport code.

Solution

Per the issue's recommended option, an opt-in, per-endpoint EnableFairQueueMessageGroups(), implemented at the envelope-mapping layer (per maintainer steer):

• ISqsEnvelopeMapper.DetermineGroupId(Envelope) — a new default interface method returning Envelope.GroupId. Non-breaking for all existing mappers (NServiceBus, MassTransit, CloudEvents, RawJson, SNS); custom mappers can override to source the group id from a header, tenant id, etc.
• AmazonSqsSubscriberConfiguration.EnableFairQueueMessageGroups() sets a per-endpoint flag on AmazonSqsQueue. Default off, so existing standard-queue users who set GroupId (e.g. via MessagePartitioning) are unaffected unless they opt in.
• Both send paths (AmazonSqsQueue.SendMessageAsync and OutgoingSqsBatch) consult the mapper and gate on FIFO vs the flag:
  • FIFO — unchanged: always maps MessageGroupId + MessageDeduplicationId.
  • Standard + opt-in — maps MessageGroupId only; no deduplication semantics.

Usage:

opts.PublishMessage<OrderPlaced>()
    .ToSqsQueue("orders")
    .EnableFairQueueMessageGroups();

await bus.PublishAsync(message, new DeliveryOptions { GroupId = tenantId });

Tests

sqs_fair_queue_message_groups (no AWS dependency — exercises the real send mapping via OutgoingSqsBatch.Request): standard queue with the flag off leaves MessageGroupId unset; with it on maps the group id; never sets a deduplication id on a standard queue; FIFO still maps both regardless of the flag; and the fluent config flips the flag. 7/7 passing locally.

Docs

New Fair Queues page under the SQS guide + sidebar entry.

Notes

• AWSSDK.SQS is already at 4.0.2.14; MessageGroupId exists on the request/batch-entry types, so no SDK bump.
• SQS-only; no SNS changes.

🤖 Generated with Claude Code