[christopherread]

Combines five reviewed PRs into one, so master gets a single merge and NuGet a single release, and adds a fix for #103. Each original PR is one commit here, in order; the originals will be closed in favour of this one.

Fixes #74, fixes #76, fixes #77, fixes #78, fixes #79, fixes #103.

Commits

1. Run broker-backed transport tests in CI (was Run broker-backed transport tests in CI #82)
   • CI starts RabbitMQ, NATS and Kafka as service containers and runs their Category=Explicit tests, using the xUnit v3 syntax.
   • NetMQ's tests stay out for now: they lose their first messages on CI runners (NetMQ: first messages lost before subscribers connect (slow joiner) #102).
2. Official ActiveMQ Classic image in the examples (was Use the official ActiveMQ Classic image in the examples #83): apache/activemq-classic:6.2.0 with admin/admin connection credentials.
3. Deprecate Obvs.Serialization.MessagePack (was Deprecate Obvs.Serialization.MessagePack (MsgPack.Cli) #96): [Obsolete] warnings pointing to Obvs.Serialization.MessagePack-CSharp. ⚠️ A package owner still has to mark the package deprecated on nuget.org.
4. NEST → Elastic.Clients.Elasticsearch 9.5.3 (was Port Obvs.Monitoring.ElasticSearch from NEST to Elastic.Clients.Elasticsearch #98). ⚠️ Breaking: ElasticsearchClient replaces IElasticClient, and NodePool replaces IConnectionPool. Index names and document fields are unchanged.
5. NATS.Client 1.1.8 → NATS.Net (NATS.Client.Core 3.3.1) (was Port Obvs.NATS from NATS.Client to NATS.Net #99). ⚠️ Breaking only for direct MessageSource and MessagePublisher use (INatsConnection instead of Lazy<IConnection>). The fluent configuration and wire format are unchanged.
6. Kafka subscribe fix (Kafka: messages published straight after subscribing can be missed #103), test first.
   • Bug: Subscribe returned before Kafka assigned partitions, and "latest" was only resolved later. So messages published straight after subscribing were skipped.
   • Fix: Subscribe now waits, for up to 30 seconds, for partition assignment. The assignment handler fixes each partition's start offset there and then: the group's committed offset, or else the current end of the log.
   • CI: the broker warm-up added in Run broker-backed transport tests in CI #82 to hide this problem is removed; only the test topic is created up front.

Resolving #99 with #98 needed small conflict fixes: both changed adjacent lines in Directory.Packages.props (the Elastic line is now in alphabetical order), and #99's NATS test met #101's cancellation-token change. The library code for #96, #98 and #99 is identical to their reviewed PRs.

Testing

• Locally:
  • Full rebuild with 0 warnings; 129 unit tests pass.
  • Kafka, against a fresh local broker with no warm-up: without the fix, both Kafka tests fail every time (3/3 runs); with it, both pass every time (3/3).
  • The new test, TestMessagePublishedStraightAfterSubscribingIsReceived, publishes immediately after subscribing. The existing TestSendAndReceiveMessage also failed without the warm-up, even after its 2-second wait.
• CI: the commit with only the new test failed exactly as expected, with both Kafka tests failing. The final run is below.

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