durable-isolates

The replay kernel behind durable-workflows, built on iso4.

Run a program in a sandbox and make chosen operations durable. Their results live in a cache you persist, so a run can pause, survive a restart, and continue later. Resume is always the same move: run it again with the cache you saved.

Node >= 26, ESM only.

Install

pnpm add durable-isolates

@iso4/sandbox is a peer you provide. @iso4/fetch is optional, for a durable HTTP capability.

Features

• Durable by key. A completed operation is answered from the cache and never runs twice. A fresh one runs for real.
• Pause and continue. A host global can pause the whole run; continue by running again with the saved cache. No value is ever injected from outside.
• Nested scopes, sequential or parallel. Group work with boundary(key, fn); nested keys stay isolated per branch, even under Promise.all.
• You own storage. The kernel keeps nothing. It hands back a cache, you persist it and pass it back next time.

Quick start

import { durableIsolates } from 'durable-isolates'

const di = durableIsolates()
const runner = await di.prepare({
  modules: {
    reports: {
      shim: `
        import { durableCall, nextKey } from 'durable-isolates:internal'
        export const load = id => durableCall(nextKey('load'), 'load', id)
      `,
    },
  },
})

let cache = {}
const r = await runner.execute({
  code: `import { load } from 'reports'; export default await load('r-1')`,
  cache,
  globals: { load: (id) => db.reports.get(id) },
}).result

if (r.outcome === 'completed')
  console.log(r.result)
cache = r.cache // persist, then hand back next time

License

MIT