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refactor(sdk): Remove CancelableGenerator #2867

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Merged
teogeb merged 2 commits into from
Nov 11, 2024
Merged

refactor(sdk): Remove CancelableGenerator #2867

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9498d6f
rm CancelableGenerator
teogeb Nov 11, 2024
f2e6d62
rm pTimeout
teogeb Nov 11, 2024
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195 changes: 0 additions & 195 deletions packages/sdk/src/utils/iterators.ts
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Original file line number Diff line number Diff line change
@@ -1,11 +1,5 @@
import Emitter from 'events'
import pMemoize from 'p-memoize'
import { MaybeAsync } from '../types'

import { AggregatedError } from './AggregatedError'
import { pTimeout } from './promises'
import { Defer } from '@streamr/utils'

export interface ICancelable {
cancel(err?: Error): Promise<void>
isCancelled: () => boolean
Expand Down Expand Up @@ -133,195 +127,6 @@ export function iteratorFinally<T>(
)
}

async function endGenerator(gtr: AsyncGenerator, error?: Error) {
return error
? gtr.throw(error).catch(() => {}) // ignore err
: gtr.return(undefined)
}

function canCancel<T extends object>(gtr: MaybeCancelable<T>): gtr is Cancelable<T> {
return (
gtr
&& 'cancel' in gtr && typeof gtr.cancel === 'function'
&& typeof gtr.isCancelled === 'function'
&& !gtr.isCancelled()
)
}

async function cancelGenerator<T extends object>(gtr: MaybeCancelable<T>, error?: Error) {
if (!canCancel(gtr)) { return }
await gtr.cancel(error)
}

const endGeneratorTimeout = pMemoize(async (gtr, error, timeout = 250) => {
await pTimeout(endGenerator(gtr, error), {
timeout,
rejectOnTimeout: false,
})

if (canCancel(gtr)) {
await cancelGenerator(gtr, error)
}
}, {
cache: new WeakMap(),
cachePromiseRejection: true,
})

/**
* Creates a generator that can be cancelled and perform optional final cleanup.
* const [cancal, generator] = CancelableGenerator(iterable, onFinally)
*/
export function CancelableGenerator<T>(
iterable: MaybeCancelable<AsyncIterable<T> | AsyncGenerator<T>>,
onFinally: OnFinallyFn = () => {},
{ timeout = 250 } = {}
): Cancelable<AsyncGenerator<T, any, unknown>> {
let cancelled = false
let finalCalled = false
let error: Error | AggregatedError | undefined

const cancelSignal = new Emitter()
const onDone = new Defer<undefined>()

let iterator: AsyncIterator<T>

async function cancelIterable(err?: Error) {
// cancel inner if has cancel
await cancelGenerator(iterable, err)
await cancelGenerator(iterator, err)
}

function collectErrors(value?: Error | AggregatedError) {
if (!value || value === error) { return }

if (!error) {
error = value
return
}

error = 'extend' in error
? error.extend(value, value.message)
: new AggregatedError([value, error], value.message)
}

function resolveCancel(value?: Error) {
if (value instanceof Error) {
collectErrors(value)
}

if (error) {
cancelSignal.emit('cancel', error)
} else {
cancelSignal.emit('cancel', value)
}
}

const cancel = (gtr: MaybeCancelable<AsyncGenerator<T>>) => async (value: Error) => {
if (cancelled || finalCalled) {
// prevent recursion
return onDone
}

cancelled = true
resolveCancel(value)

// need to make sure we don't try return inside final otherwise we end up deadlocked
await endGeneratorTimeout(gtr, error, timeout)
return onDone
}

let pendingNext = 0

async function* CancelableGeneratorFn() {
// manually iterate
iterator = iterable[Symbol.asyncIterator]()

try {
yield* {
// each next() races against cancel signal
next: async () => {
pendingNext += 1
cancelSignal.setMaxListeners(pendingNext)
// NOTE:
// Very easy to create a memleak here.
// Using a shared promise with Promise.race
// between loop iterations prevents data from being GC'ed.
// Create new per-loop promise and resolve using an event emitter.
const cancelPromise = new Defer<{ value: undefined, done: true }>()
const onCancel = (v?: Error) => {
if (v instanceof Error) {
cancelPromise.reject(v)
} else {
cancelPromise.resolve({ value: undefined, done: true })
}
}

cancelSignal.once('cancel', onCancel)
return Promise.race([
iterator.next(),
cancelPromise,
]).finally(() => {
pendingNext -= 1
cancelSignal.setMaxListeners(pendingNext)
cancelSignal.off('cancel', onCancel)
})
},
async throw(err: Error): Promise<{ value: T, done: true }> {
cancelSignal.removeAllListeners()
await endGeneratorTimeout(iterator, err, timeout)
throw err
},
async return(v?: T) {
cancelSignal.removeAllListeners()
await endGeneratorTimeout(iterator, error, timeout)
return {
value: v,
done: true,
}
},
[Symbol.asyncIterator]() {
return this
},
}
} finally {
cancelSignal.removeAllListeners()
// try end iterator
if (iterator) {
await endGeneratorTimeout(iterator, error, timeout)
}
}
}
const c = CancelableGeneratorFn()
const cancelableGenerator = iteratorFinally(c, async (err) => {
finalCalled = true
try {
// cancel inner if has cancel
await cancelIterable(err ?? error)
await onFinally(err ?? error)
} finally {
onDone.resolve(undefined)
}

// error whole generator, for await of will reject.
if (error) {
throw error
}

return onDone
}) as AsyncGenerator<T>

const cancelFn = cancel(cancelableGenerator)

Object.assign(cancelableGenerator, {
cancel: cancelFn,
timeout,
isCancelled: () => cancelled,
isDone: () => finalCalled,
})

return cancelableGenerator as Cancelable<typeof cancelableGenerator>
}

export const nextValue = async <T>(source: AsyncIterator<T>): Promise<T | undefined> => {
const item = source.next()
return (await item).value
Expand Down
67 changes: 1 addition & 66 deletions packages/sdk/src/utils/promises.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
import pLimit from 'p-limit'
import pThrottle from 'p-throttle'
import { Defer, wait } from '@streamr/utils'
import { wait } from '@streamr/utils'
import { MaybeAsync } from '../types'

/**
Expand Down Expand Up @@ -112,71 +112,6 @@ export class TimeoutError extends Error {
}
}

/**
* Takes a promise and a timeout and an optional message for timeout errors.
* Returns a promise that rejects when timeout expires, or when promise settles, whichever comes first.
*
* Invoke with positional arguments for timeout & message:
* await pTimeout(promise, timeout, message)
*
* or using an options object for timeout, message & rejectOnTimeout:
*
* await pTimeout(promise, { timeout, message, rejectOnTimeout })
*
* message and rejectOnTimeout are optional.
*/

interface pTimeoutOpts {
timeout?: number
message?: string
rejectOnTimeout?: boolean
}

type pTimeoutArgs = [timeout?: number, message?: string] | [pTimeoutOpts]

export async function pTimeout<T>(promise: Promise<T>, ...args: pTimeoutArgs): Promise<T | undefined> {
let opts: pTimeoutOpts = {}
if (args[0] && typeof args[0] === 'object') {
[opts] = args
} else {
[opts.timeout, opts.message] = args
}

const { timeout = 0, message = '', rejectOnTimeout = true } = opts

if (typeof timeout !== 'number') {
throw new Error(`timeout must be a number, got ${timeout}`)
}

let timedOut = false
const p = new Defer<undefined>()
const t = setTimeout(() => {
timedOut = true
if (rejectOnTimeout) {
p.reject(new TimeoutError(message, timeout))
} else {
p.resolve(undefined)
}
}, timeout)
p.catch(() => {})

return Promise.race([
Promise.resolve(promise).catch((err) => {
clearTimeout(t)
if (timedOut) {
// ignore errors after timeout
return undefined
}

throw err
}),
p
]).finally(() => {
clearTimeout(t)
p.resolve(undefined)
})
}

// TODO use streamr-test-utils#waitForCondition instead (when streamr-test-utils is no longer a test-only dependency)
/**
* Wait until a condition is true
Expand Down
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