Implement VM/Runtime for actors #147

New Issue

2026-05-15T09:35:42Z

HugoNijhuis commented

2026-05-15 09:35:42 +00:00

Problem

Only interfaces exist for Runtime and VirtualMachine in cluster/types.go and cluster/distributed.go, but no actual implementation. Actors cannot be created, started, stopped, or have their state managed.

Required Components

1. VM Implementation (cluster/vm.go - new)

type VirtualMachine struct {
    actorID   string
    eventStore aether.EventStore
    state     map[string]interface{}
    version   int64
}

Methods needed:

GetID(), GetActorID(), GetState() - already in interface
Start() - replay events to rebuild state
ProcessEvent(event *aether.Event) - apply event to state
Stop() - persist final state
GetVersion() - current event version

2. Runtime Implementation (cluster/runtime.go - new)

type Runtime struct {
    natsConn   *nats.Conn
    eventStore aether.EventStore
    vmRegistry VMRegistry // map[actorID]*VirtualMachine
    config     RuntimeConfig
}

Methods needed:

Start() - initialize and start processing
LoadModel(model eventstorming.Model) - register domain types
SendMessage(message RuntimeMessage) - route to appropriate VM
GetActiveVMs() - return map of active VMs
CreateVM(actorID string) - create new VM instance
StopVM(actorID string) - persist and stop VM

3. Event Processing

Subscribe to actor's event stream
Replay events to build initial state
Apply new events as they arrive
Handle event versions and conflicts

Suggested Design

VM Lifecycle

1. Actor message arrives for actor-123
2. Runtime checks if VM exists for actor-123
3. If not, create VM:
   - Replay events from event store
   - Rebuild state
4. Route message to VM
5. VM processes message -> creates new events
6. Events persisted to event store
7. VM state updated

State Management

State derived from event replay
No separate state store needed
Can snapshot periodically for performance
Version conflict handling using existing EventStore

Implementation Steps

Create VM struct in cluster/vm.go
Implement event replay to rebuild state
Create Runtime in cluster/runtime.go
Register Runtime with cluster via SetVMProvider
Implement message processing - validate against model
Add version conflict handling using existing EventStore
Write tests - mock event store, test state transitions

File Structure

cluster/
├── vm.go              # VirtualMachine implementation
├── runtime.go         # Runtime implementation
├── vm_test.go         # VM tests
├── runtime_test.go    # Runtime tests
└── integration_test.go # Integration tests

Acceptance Criteria

VM can be created with actor ID
VM replays events to build state
VM processes events and updates state
VM persists current version
Runtime can create/stop VMs
Runtime manages VM registry
Integration test with NATS and JetStream

## Problem Only interfaces exist for `Runtime` and `VirtualMachine` in `cluster/types.go` and `cluster/distributed.go`, but no actual implementation. Actors cannot be created, started, stopped, or have their state managed. ## Required Components ### 1. VM Implementation (cluster/vm.go - new) ```go type VirtualMachine struct { actorID string eventStore aether.EventStore state map[string]interface{} version int64 } ``` Methods needed: - `GetID()`, `GetActorID()`, `GetState()` - already in interface - `Start()` - replay events to rebuild state - `ProcessEvent(event *aether.Event)` - apply event to state - `Stop()` - persist final state - `GetVersion()` - current event version ### 2. Runtime Implementation (cluster/runtime.go - new) ```go type Runtime struct { natsConn *nats.Conn eventStore aether.EventStore vmRegistry VMRegistry // map[actorID]*VirtualMachine config RuntimeConfig } ``` Methods needed: - `Start()` - initialize and start processing - `LoadModel(model eventstorming.Model)` - register domain types - `SendMessage(message RuntimeMessage)` - route to appropriate VM - `GetActiveVMs()` - return map of active VMs - `CreateVM(actorID string)` - create new VM instance - `StopVM(actorID string)` - persist and stop VM ### 3. Event Processing - Subscribe to actor's event stream - Replay events to build initial state - Apply new events as they arrive - Handle event versions and conflicts ## Suggested Design ### VM Lifecycle ``` 1. Actor message arrives for actor-123 2. Runtime checks if VM exists for actor-123 3. If not, create VM: - Replay events from event store - Rebuild state 4. Route message to VM 5. VM processes message -> creates new events 6. Events persisted to event store 7. VM state updated ``` ### State Management - State derived from event replay - No separate state store needed - Can snapshot periodically for performance - Version conflict handling using existing EventStore ## Implementation Steps 1. **Create VM struct** in `cluster/vm.go` 2. **Implement event replay** to rebuild state 3. **Create Runtime** in `cluster/runtime.go` 4. **Register Runtime with cluster** via `SetVMProvider` 5. **Implement message processing** - validate against model 6. **Add version conflict handling** using existing EventStore 7. **Write tests** - mock event store, test state transitions ## File Structure ``` cluster/ ├── vm.go # VirtualMachine implementation ├── runtime.go # Runtime implementation ├── vm_test.go # VM tests ├── runtime_test.go # Runtime tests └── integration_test.go # Integration tests ``` ## Acceptance Criteria - [ ] VM can be created with actor ID - [ ] VM replays events to build state - [ ] VM processes events and updates state - [ ] VM persists current version - [ ] Runtime can create/stop VMs - [ ] Runtime manages VM registry - [ ] Integration test with NATS and JetStream

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Reference: flowmade-one/aether#147