elasticgrid

Cross-cloud elastic training grid for variable-size workloads, built on iroh-tinker.

elasticgrid is the control plane in front of iroh-tinker's multi-cloud launch layer. It answers two questions:

• How big should this job be right now? A rolling window of training steps (step time, queue time, throughput) feeds a scheduler that grows the job when workers are waiting and shrinks it when the job is comfortably faster than the target, with bounds, a cooldown and a deadline rule.
• Where should the nodes run? A placement plan spreads the nodes over the available providers, respects a spot/on-demand budget, costs the placement and renders it as an iroh-tinker LaunchSpec.

Nothing here provisions anything by itself: the placement is a plan, and iroh-tinker's JobManager executes it.

Install

pip install elasticgrid
pip install -e ".[dev]"           # from a checkout

elasticgrid depends on the public iroh-tinker surface only.

Built on the iroh-tinker public surface

iroh_tinker.AllreduceAlgorithm is not exported from the top-level package; it lives in iroh_tinker.comm. elasticgrid does not depend on it.

CLI

elasticgrid providers                        # the configured grid
elasticgrid plan --nodes 64                 # placement + cost
elasticgrid plan --nodes 64 --max-spot-fraction 0.5
elasticgrid spec --nodes 64 --name my-job   # the iroh-tinker launch spec
elasticgrid simulate --samples steps.json   # what the scheduler would do

Every command accepts --json.

The scale decision

The scheduler reads a window of step samples and applies the rules in order:

1. Never scale on thin evidence. Fewer than min_samples observations means hold.
2. Respect the bounds. The target is clamped to [min_nodes, max_nodes].
3. Honour the cooldown. After a change, wait cooldown_s. Elastic scaling without a cooldown oscillates.
4. Queue-bound means scale up. If 20% or more of the step was spent waiting for a worker, the job needs more workers.
5. Idle means scale down. If the step is well inside target_step_s and nobody is waiting, the current size is more than enough.
6. Do not scale up past the deadline. Workers that cannot finish before the deadline cost money and save nothing.

Every decision carries the signals it was based on, so it can be replayed and reviewed:

{
  "action": "scale_up",
  "current_nodes": 8,
  "target_nodes": 16,
  "reason": "80% of the step was spent waiting for a worker; scaling up 8 -> 16",
  "signals": {"queue_fraction": 0.8, "mean_step_s": 10.0, "...": "..."}
}

The placement

GridPlanner.plan(nodes) returns a placement: how many nodes each provider takes, what it costs per hour, and the ordered infra references that iroh-tinker fails over through.

The policy is explicit:

• providers are filled cheapest first;
• max_spot_fraction caps the share of nodes on spot capacity;
• if the spot budget cannot hold the job, the remaining nodes are placed anyway, because a job that cannot start is worse than a job that breaks the policy;
• the placement is a pure function of (nodes, providers, policy), so the same plan always gives the same answer.

Tests

pip install -e ".[dev]"
pytest

The suite is credential-free: the planner and the scheduler are pure functions and are tested directly.

Layout

src/elasticgrid/
  metrics.py   step samples and the rolling window of signals
  scheduler.py the scale decision (bounds, cooldown, deadline)
  grid.py      providers, placement, cost, launch spec
  cli.py       elasticgrid providers | plan | spec | simulate

Licence

Apache-2.0. elasticgrid is a separate project from iroh-tinker, which stays MIT OR Apache-2.0.