Table of Contents

Vehicle Fleet Simulator

A simulated vehicle fleet that streams structured telemetry events over gRPC. Imported into this repo to drive the WAL benchmarks for Orleans.Lattice and Orleans.Lattice.Replication (see benchmark, whose silo reuses the simulator's projects unmodified), and as the foundation for a future sample that bridges the simulator's event stream into a Lattice tree.

samples/VehicleFleetSimulator (this folder)

Status

  • Independent. The simulator does not currently depend on Orleans.Lattice or Orleans.Lattice.Replication. It is its own multi-project Orleans application with its own VehicleFleetSimulator.slnx. Building or running it has no impact on the lattice library and vice versa.
  • Imported as-is. The source is a near-verbatim copy of the upstream simulator. The only modification on import was the addition of [assembly: CollectionBehavior(DisableTestParallelization = true)] in tests/VehicleFleetSimulator.Tests/ClusterFixture.cs to remove an xUnit collection-parallelism flake under load. See "Test parallelism" below.
  • Forward-looking. A future sample (likely samples/VehicleFleetSimulator.LatticeBridge/ or similar) will subscribe to the simulator's gRPC telemetry stream and project events into a Lattice tree, exercising replication WAL throughput end-to-end.

What it does

The simulator stands up a four-tier local stack:

Tier Project Purpose
Storage Azurite (container) Backing store for Orleans clustering and the reminder table. Grain state is held in memory, and there are no Orleans streams.
Silo VehicleFleetSimulator.Silo Hosts vehicle grains, the city graph, and the fan-out telemetry sink. Each vehicle ticks on a grain timer; a fleet wake reminder reactivates the vehicles after a silo restart.
API VehicleFleetSimulator.Api ASP.NET Core gRPC + gRPC-Web frontend. Streams telemetry to subscribers; accepts admin commands.
UI VehicleFleetSimulator.Ui Blazor WebAssembly dashboard - live map, simulation-speed slider, fleet controls.

A pluggable ITelemetrySink lets the silo route events to fan-out grains or a null sink; the benchmark silo (benchmark/host/Bench.Silo) swaps in a Lattice-backed sink (benchmark/host/Bench.Sink) through the same seam. VehicleSimulator advances each vehicle along a city graph; FuelModel and SpeedModel are pure functions over each tick. Routes are generated on demand by RouteGenerator. All vehicle state is grain-resident; Azurite holds only Orleans plumbing.

Running it

The full stack runs under Docker Compose:

./samples/VehicleFleetSimulator/run.ps1

The script wipes the Azurite volume, builds any stale images, and starts Azurite + Silo + API + UI in detached mode. UI is served on http://localhost:8090. The API serves its REST admin surface and gRPC-Web (the transport the UI uses) over HTTP/1.1 on http://localhost:8080, and native HTTP/2 gRPC on http://localhost:8081.

./samples/VehicleFleetSimulator/run.ps1 -Down

Tears the stack down and removes the Azurite volume.

Test parallelism

tests/VehicleFleetSimulator.Tests shares a single Orleans TestCluster across collection-bound tests. Six pure-unit-test classes carry no [Collection] attribute and were running in parallel with the cluster-fixture tests by default - that races StreamSubscriberOrderTests against its 15s telemetry-collection budget under load. The on-import patch:

[assembly: CollectionBehavior(DisableTestParallelization = true)]

is added to ClusterFixture.cs. The whole suite runs in ~4s single-threaded, so there's no observable cost. CI's samples-only fast path (see .github/workflows/ci.yml) discovers this test project automatically and runs it after building the slnx.