Effect.fn stack frames keep the call's arguments alive in forked fibers

Chiusa
  • Qualcosa non va?
#9,877 0 commenti 0 reazioni 0 assegnatari Vedi su GitHub

I maintainer di solito rispondono entro 1 giorno

Una pull request collegata è già stata integrata.

  • #9878 di @Hona — integrata

Valutazione

Difficoltà
2/5
Tempo stimato
1-3 ore
Idoneità per principianti
25/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
node.js, typescript
Ambito
performance

Direzione di ricerca

Investigate makeFn in packages/effect/src/internal/effect.ts where the stack frame closure captures arguments. Run the provided Node repro to observe retained. A fix moves frame building to a helper outside the traced function; expected outcome is collected and open PR #9878 already implements it.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

What is the problem?

An Effect.fn call's stack frame keeps every argument of that call alive. A fiber forked inside the call inherits the frame through CurrentStackFrame, so the arguments of every traced call above it stay reachable for as long as that fiber lives, long after the calls have returned.

Reproduction

Run with Node against [email protected]:

import { Effect, Fiber } from "effect"
import { setFlagsFromString } from "node:v8"
import { runInNewContext } from "node:vm"

setFlagsFromString("--expose_gc")
const gc = runInNewContext("gc") as () => void

const start = Effect.fn("start")(function*(input: { payload: string }) {
  yield* Effect.annotateCurrentSpan("payload", input.payload.length)
  return yield* Effect.forkDetach(Effect.never)
})

let reference: WeakRef<object> | undefined
const fiber = await (async () => {
  const input = { payload: "x".repeat(1024) }
  reference = new WeakRef(input)
  return Effect.runPromise(start(input))
})()
for (let i = 0; i < 8; i++) {
  await new Promise((resolve) => setTimeout(resolve, 0))
  gc()
}
console.log(reference!.deref() ? "retained" : "collected")
await Effect.runPromise(Fiber.interrupt(fiber))
Result
Expected collected: start has returned and nothing references input
Actual retained
Effect.fnUntraced collected

Bun shows the same behaviour.

Cause

makeFn in packages/effect/src/internal/effect.ts builds the frame inside the traced function:

return defineFunctionLength(body.length, function(this: any, ...args: Array<any>) {
  let result = suspend(() => {
    const iter = body.apply(this, arguments) // closes over `arguments`
    ...
  })
  ...
  return updateService(result, CurrentStackFrame, (prev) => ({
    name,
    stack: callError ? fnStackCleaner(() => callError.stack) : constUndefined, // same scope
    parent: { name: definitionName, stack: definitionStack, parent: prev }
  }))
})

The stack closure only reads callError. Engines allocate one context per scope, though, and this scope also holds arguments, which the suspend thunk uses. So the frame's stack closure keeps the whole arguments object alive:

flowchart LR
  F["forked fiber"] --> C["context: CurrentStackFrame"]
  C --> S["frame.stack closure"]
  S --> A["scope: arguments"]
  A --> I["every call argument"]
Impact

We found this in a production heap snapshot of a long-running server (opencode). 152 fibers that outlive their calls kept the frame chain … < SessionRunner.runStep, for example:

  • watchers and plugin services first started inside a request;
  • background job notifiers.

runStep receives the full loaded conversation as its first argument, so those fibers kept 117 MB of message history (including base64 screenshots) alive indefinitely.

Proposed fix

Build the frame in a helper outside the traced function, so the closure's context holds only name, callError and the definition frame. PR: https://github.com/Effect-TS/effect/pull/9878

Lingua principale
TypeScript
Stelle
16.7k
Fork
808
Merge medio
11h 31m
PR unite (30g)
834

Preparare l'ambiente

Questo progetto non fornisce container di sviluppo, Dockerfile né guida per i contributori, quindi l'ambiente è a tuo carico: parti dal suo README e consulta la nostra guida al primo contributo per i passaggi generali.

Come iniziare

  1. Leggi tutta la issue e poi la guida ai contributi del progetto.
  2. Commenta sulla issue per dire che te ne occupi tu — evita che due persone facciano lo stesso lavoro.
  3. Fai un fork del repository e lavora su un branch.
  4. Apri una pull request che faccia riferimento al numero della issue.

Altre issue di Effect-TS/effect

Tutte le issue di Effect-TS/effect

Issue simili

Altre issue su TypeScript

Ricevi le nuove issue nella tua casella

Un breve riepilogo di issue GitHub adatte ai principianti.