Deprecation of compose.GetState, Use compose.ProcessState instead

[hi-pender]

To enhance execution efficiency and concurrency safety in Eino Graph's runner engine, we're removing compose.GetState effective immediately. This change is necessary due to fundamental differences in our execution models:

Background

Eino's runner supports two distinct execution modes:

1. Pregel Mode
   Requires explicit SuperStep synchronization for vertex computation scheduling
2. DAG Mode
   Designed for true parallel execution without step synchronization

The Problem

During initial implementation, DAG mode reused parts of the Pregel runner, inadvertently inheriting its SuperStep model. This creates artificial synchronization barriers that:

• Prevent true concurrent path execution
• Introduce unnecessary latency in DAG workflows

So we'll remove DAG's SuperStep, and it'll cause concurrency safety issues with compose.GetState

Solution

We're removing the non-concurrency-safe compose.GetState and eliminating SuperStep artifacts from DAG execution. All implementations must migrate to the replacement API:

// Use this instead:
err := compose.ProcessState(ctx, func(context.Context, s *State) error) {
    // do something with state in a concurrency-safe way
})

Key Benefits

• ✅ True parallel execution for DAG workflows
• ⚡️ Eliminated artificial synchronization barriers
• 🛡️ Guaranteed concurrency safety

Migration Timeline

1. Immediate: Stop using compose.GetState in new code
2. Next release: Complete removal in v0.4.0

Actions Required

Replace all instances of:

oldState := compose.GetState(ctx)

with:

err := compose.ProcessState(ctx, func(context.Context, s *State) error) {
    // do something with state in a concurrency-safe way
})