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Engelschall <rse@engelschall.com> ** ** Permission is hereby granted, free of charge, to any person obtaining ** a copy of this software and associated documentation files (the ** "Software"), to deal in the Software without restriction, including ** without limitation the rights to use, copy, modify, merge, publish, ** distribute, sublicense, and/or sell copies of the Software, and to ** permit persons to whom the Software is furnished to do so, subject to ** the following conditions: ** ** The above copyright notice and this permission notice shall be included ** in all copies or substantial portions of the Software. ** ** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, ** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF ** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. ** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY ** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, ** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE ** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ /* built-in requirements */ import { Readable } from "node:stream" /* external requirements */ import type { IClientPublishOptions, IClientSubscribeOptions } from "mqtt" import { nanoid } from "nanoid" /* internal requirements */ import { CreditGate, ReadableTee, sendBufferAsChunks, sendStreamAsChunks, makeMutuallyExclusiveFields } from "./mqtt-plus-util" import { run, Spool, ensureError } from "./mqtt-plus-error" import type { SourceFetchRequest, SourceFetchResponse, SourceFetchChunk, SourceFetchCredit } from "./mqtt-plus-msg" import type { APISchema, SourceKeys, Registration } from "./mqtt-plus-api" import type { WithInfo, InfoSource } from "./mqtt-plus-info" import { ServiceTrait } from "./mqtt-plus-service" import type { AuthOption } from "./mqtt-plus-auth" /* Source Fetch Trait */ export class SourceTrait<T extends APISchema = APISchema> extends ServiceTrait<T> { /* source state */ private sourceCreditGates = new Map<string, CreditGate>() private sourceControllers = new Map<string, AbortController>() private sourceSpools = new Map<string, Spool>() /* destroy source trait */ override async destroy () { for (const controller of this.sourceControllers.values()) controller.abort(new Error("source destroyed")) for (const gate of this.sourceCreditGates.values()) gate.abort() for (const spool of this.sourceSpools.values()) await spool.unroll() this.sourceSpools.clear() this.sourceControllers.clear() this.sourceCreditGates.clear() await super.destroy() } /* establish a source (for fetch requests) */ async source<K extends SourceKeys<T> & string> ( name: K, callback: WithInfo<T[K], InfoSource> ): Promise<Registration> async source<K extends SourceKeys<T> & string> ( config: { name: K, callback: WithInfo<T[K], InfoSource>, options?: Partial<IClientSubscribeOptions>, share?: string, auth?: AuthOption } ): Promise<Registration> async source<K extends SourceKeys<T> & string> ( nameOrConfig: K | { name: K, callback: WithInfo<T[K], InfoSource>, options?: Partial<IClientSubscribeOptions>, share?: string, auth?: AuthOption }, ...args: any[] ): Promise<Registration> { /* determine actual parameters */ let name: K let callback: WithInfo<T[K], InfoSource> let options: Partial<IClientSubscribeOptions> = {} let share = this.options.share let auth: AuthOption | undefined if (typeof nameOrConfig === "object" && nameOrConfig !== null && "name" in nameOrConfig) { /* object-based API */ name = nameOrConfig.name callback = nameOrConfig.callback options = nameOrConfig.options ?? {} share = nameOrConfig.share ?? this.options.share auth = nameOrConfig.auth } else { /* positional API */ name = nameOrConfig callback = args[0] } /* sanity check callback */ if (typeof callback !== "function") throw new Error("source: callback argument is required and must be a function") /* create a resource spool */ const spool = new Spool() /* sanity check situation */ if (this.onRequest.has(`source-fetch-request:${name}`)) throw new Error(`source: source "${name}" already registered`) /* generate the corresponding MQTT topics for broadcast and direct use */ const topicS = share !== "" ? `$share/${share}/${name}` : name const topicReqB = this.options.topicMake(topicS, "source-fetch-request") const topicReqD = this.options.topicMake(name, "source-fetch-request", this.options.id) /* remember the registration */ this.onRequest.set(`source-fetch-request:${name}`, async (request: SourceFetchRequest, topicName: string) => { /* check receiver */ if (request.receiver && request.receiver !== this.options.id) return /* determine information */ const requestId = request.id const params = request.params ?? [] const sender = request.sender if (sender === undefined || sender === "") throw new Error("invalid request: missing sender") const receiver = request.receiver const abortController = new AbortController() if (this.sourceControllers.has(requestId)) throw new Error(`source: duplicate request id "${requestId}"`) this.sourceControllers.set(requestId, abortController) const abortSignal = abortController.signal const info: InfoSource = { sender, signal: abortSignal } if (receiver) info.receiver = receiver if (request.meta) info.meta = request.meta /* generate corresponding MQTT topic (single topic for all responses) */ const responseTopic = this.options.topicMake(name, "source-fetch-response", sender) const sourceNameMismatchError = (kind: string, actualName: string) => new Error(`${kind} name mismatch (expected "${name}", got "${actualName}")`) /* callback for sending the ack/nak response */ const sendResponse = async (error?: string) => { const metaStore = this.metaStore(info.meta) const response = this.msg.makeSourceFetchResponse(requestId, name, error, this.options.id, sender, metaStore) const message = this.codec.encode(response) await this.publishToTopic(responseTopic, message, { qos: options.qos ?? 2 }) } /* create a resource spool for request cleanup */ const reqSpool = new Spool() if (this.sourceSpools.has(requestId)) throw new Error(`source: duplicate request id "${requestId}"`) this.sourceSpools.set(requestId, reqSpool) reqSpool.roll(() => { this.sourceSpools.delete(requestId) }) reqSpool.roll(() => { this.onResponse.delete(`source-fetch-credit:${requestId}`) this.sourceControllers.delete(requestId) }) /* ensure stream gets destroyed on abort */ abortSignal.addEventListener("abort", () => { if (info.stream instanceof Readable && !info.stream.destroyed) info.stream.destroy(ensureError(abortSignal.reason)) }, { once: true }) const abortPromise = new Promise<never>((_resolve, reject) => { const onAbort = () => { reject(ensureError(abortSignal.reason)) } if (abortSignal.aborted) onAbort() else abortSignal.addEventListener("abort", onAbort, { once: true }) reqSpool.roll(() => { abortSignal.removeEventListener("abort", onAbort) }) }) /* utility functions for timeout management */ const sourceTimerId = `source-fetch-send:${requestId}` const refreshSourceTimeout = () => { if (abortSignal.aborted) return this.timerRefresh(sourceTimerId, () => { const error = new Error(`source fetch "${name}" timed out`) abortController.abort(error) const gate = this.sourceCreditGates.get(requestId) if (gate !== undefined) { gate.abort() this.sourceCreditGates.delete(requestId) } reqSpool.unroll() }) } const clearSourceTimeout = () => this.timerClear(sourceTimerId) refreshSourceTimeout() reqSpool.roll(() => { clearSourceTimeout() }) /* callback for creating and sending a chunk message */ const sendChunk = async ( chunk: Uint8Array | undefined, error: string | undefined, final: boolean ): Promise<void> => { refreshSourceTimeout() const chunkMsg = this.msg.makeSourceFetchChunk(requestId, name, chunk, error, final, this.options.id, sender) const message = this.codec.encode(chunkMsg) await this.publishToTopic(responseTopic, message, { qos: options.qos ?? 2 }) } /* call the handler callback */ let ackSent = false let creditGate: CreditGate | undefined let cancelledByFetcher = false try { if (topicName !== request.name) throw new Error(`source name mismatch (topic: "${topicName}", payload: "${request.name}")`) if (auth) info.authenticated = await this.authenticated(sender, request.auth, auth) if (info.authenticated !== undefined && !info.authenticated) throw new Error(`source "${name}" failed authentication`) /* handle credit-based flow control (if credit provided in request) */ const initialCredit = request.credit creditGate = (initialCredit !== undefined && initialCredit > 0) ? new CreditGate(initialCredit) : undefined if (creditGate) { this.sourceCreditGates.set(requestId, creditGate) reqSpool.roll(() => { creditGate!.abort() this.sourceCreditGates.delete(requestId) }) } /* register credit/cancel handler (unconditional for cancel support) */ this.onResponse.set(`source-fetch-credit:${requestId}`, (creditParsed: SourceFetchCredit) => { if (creditParsed.name !== name) { abortController.abort(sourceNameMismatchError("source credit", creditParsed.name)) return } if (creditParsed.sender === undefined || creditParsed.sender === "") { abortController.abort(new Error(`source credit for "${name}" missing sender`)) return } if (creditParsed.sender !== sender) return if (creditParsed.credit === 0) { /* cancel signal from fetcher */ cancelledByFetcher = true abortController.abort(new Error(`source fetch "${name}" cancelled by fetcher`)) return } if (creditGate) { creditGate.replenish(creditParsed.credit) refreshSourceTimeout() } }) await Promise.race([ Promise.resolve(callback(...params, info)), abortPromise ]) /* check for valid data source */ if (!(info.stream instanceof Readable) && !(info.buffer instanceof Promise) && !(info.buffer instanceof Uint8Array)) throw new Error("handler did not provide data via info.stream or info.buffer fields") if (info.stream instanceof Readable && (info.buffer instanceof Promise || info.buffer instanceof Uint8Array)) throw new Error("handler has set both info.stream and info.buffer fields") /* send ack response */ await sendResponse() ackSent = true /* dispatch according to data type */ if (info.stream instanceof Readable) /* handle Readable stream result */ await sendStreamAsChunks(info.stream, this.options.chunkSize, sendChunk, creditGate, abortSignal) else if (info.buffer instanceof Promise || info.buffer instanceof Uint8Array) { /* handle Buffer result */ const buffer = (info.buffer instanceof Promise) ? await Promise.race([ info.buffer, abortPromise ]) : info.buffer await sendBufferAsChunks(buffer, this.options.chunkSize, sendChunk, creditGate, abortSignal) } } catch (err: unknown) { /* cleanup stream resource (if provided by handler) */ const error = ensureError(err, `handler for source "${name}" failed`) abortController.abort(error) /* on explicit fetcher cancellation, abort silently without emitting error responses */ if (!cancelledByFetcher) { /* send error as nak response or as error chunk */ this.error(error) if (ackSent) await sendChunk(undefined, error.message, true).catch(() => {}) else await sendResponse(error.message).catch(() => {}) } } finally { /* cleanup resources */ await reqSpool.unroll() } }) spool.roll(() => { this.onRequest.delete(`source-fetch-request:${name}`) }) /* subscribe to MQTT topics */ await this.subscribeTopicAndSpool(spool, topicReqB, options) await this.subscribeTopicAndSpool(spool, topicReqD, options) /* provide a registration for subsequent destruction */ return this.makeRegistration(spool, "source", name, `source-fetch-request:${name}`) } /* fetch source */ async fetch<K extends SourceKeys<T> & string> ( name: K, ...params: Parameters<T[K]> ): Promise<{ stream: Readable, buffer: Promise<Uint8Array>, meta: Promise<Record<string, any> | undefined> }> async fetch<K extends SourceKeys<T> & string> ( config: { name: K, params: Parameters<T[K]>, receiver?: string, options?: IClientPublishOptions, meta?: Record<string, any> } ): Promise<{ stream: Readable, buffer: Promise<Uint8Array>, meta: Promise<Record<string, any> | undefined> }> async fetch<K extends SourceKeys<T> & string> ( nameOrConfig: K | { name: K, params: Parameters<T[K]>, receiver?: string, options?: IClientPublishOptions, meta?: Record<string, any> }, ...args: any[] ): Promise<{ stream: Readable, buffer: Promise<Uint8Array>, meta: Promise<Record<string, any> | undefined> }> { /* determine actual parameters */ let name: K let params: Parameters<T[K]> let receiver: string | undefined let options: IClientPublishOptions = {} let meta: Record<string, any> | undefined if (typeof nameOrConfig === "object" && nameOrConfig !== null && "name" in nameOrConfig) { /* object-based API */ name = nameOrConfig.name params = nameOrConfig.params receiver = nameOrConfig.receiver options = nameOrConfig.options ?? {} meta = nameOrConfig.meta } else { /* positional API */ name = nameOrConfig params = args as Parameters<T[K]> } /* create a resource spool */ const spool = new Spool() /* generate unique request id */ let requestId = nanoid() while ( this.onResponse.has(`source-fetch-response:${requestId}`) || this.onResponse.has(`source-fetch-chunk:${requestId}`)) requestId = nanoid() /* subscribe to single response topic (for ack/nak and data chunks) */ const responseTopic = this.options.topicMake(name, "source-fetch-response", this.options.id) const sourceNameMismatchError = (kind: string, actualName: string) => new Error(`${kind} name mismatch (expected "${name}", got "${actualName}")`) await this.subscribeTopicAndSpool(spool, responseTopic, { qos: options.qos ?? 2 }) /* credit-based flow control state */ const chunkCredit = this.options.chunkCredit const maxBufferedBytes = chunkCredit > 0 ? chunkCredit * this.options.chunkSize : 16 * 1024 let chunksReceived = 0 let creditGranted = chunkCredit let responderId = receiver let responseAcked = false let streamEnded = false /* lock the responder for this communication */ const lockResponder = (kind: string, sender?: string): boolean => { if (sender === undefined || sender === "") { streamEnded = true const error = new Error(`received ${kind} without sender`) metaReject(error) stream?.destroy(error) spool.unroll() return false } if (responderId === undefined) responderId = sender else if (sender !== responderId) return false return true } /* create promise for meta (resolved on first chunk) */ let metaResolve!: (value: Record<string, any> | undefined) => void let metaReject!: (reason?: any) => void const metaP = new Promise<Record<string, any> | undefined>((resolve, reject) => { metaResolve = resolve metaReject = reject }) metaP.catch(() => {}) /* avoid unhandled promise rejection */ spool.roll(() => { metaResolve(undefined) }) /* define timer */ const timerId = `source-fetch-recv:${requestId}` let stream: ReadableTee | undefined = undefined const refreshTimeout = () => { if (streamEnded || (stream && stream.destroyed)) return this.timerRefresh(timerId, () => { const error = new Error("communication timeout") metaReject(error) stream?.destroy(error) }) } spool.roll(() => { this.timerClear(timerId) }) /* establish a readable for buffering received chunks */ stream = new ReadableTee({ highWaterMark: maxBufferedBytes, read: (_size) => { if (chunkCredit <= 0 || streamEnded) return const targetId = responderId if (!targetId) return const outstanding = creditGranted - chunksReceived const freeBytes = Math.max(0, maxBufferedBytes - (stream?.readableLength ?? 0)) const freeChunks = Math.floor(freeBytes / this.options.chunkSize) const creditToGrant = Math.max(0, freeChunks - outstanding) if (creditToGrant > 0) { creditGranted += creditToGrant const creditMsg = this.msg.makeSourceFetchCredit(requestId, name, creditToGrant, this.options.id, targetId) const encoded = this.codec.encode(creditMsg) const creditTopic = this.options.topicMake(name, "source-fetch-request", targetId) this.publishToTopic(creditTopic, encoded, { qos: options.qos ?? 2 }).catch((err: Error) => { this.error(err, `sending credit for fetch "${name}" failed`) }) refreshTimeout() } } }) stream.once("error", () => {}) /* prevent unhandled error exception */ /* create promise for eagerly collecting stream chunks */ const buffer = stream.buffer /* start timeout handler */ refreshTimeout() /* ensure resources are released if consumer aborts stream early */ let cancelled = false const cancelAndUnroll = () => { if (!cancelled && !streamEnded) { cancelled = true const targetId = responderId if (targetId) { const cancelMsg = this.msg.makeSourceFetchCredit(requestId, name, 0, this.options.id, targetId) const encoded = this.codec.encode(cancelMsg) const cancelTopic = this.options.topicMake(name, "source-fetch-request", targetId) this.publishToTopic(cancelTopic, encoded, { qos: options.qos ?? 2 }).catch(() => {}) } } if (!streamEnded) metaReject(new Error("stream aborted")) spool.unroll() } stream.once("close", cancelAndUnroll) stream.once("error", cancelAndUnroll) /* register response dispatch callback (ack/nak) */ this.onResponse.set(`source-fetch-response:${requestId}`, (response: SourceFetchResponse) => { if (streamEnded) return if (response.name !== name) { streamEnded = true const error = sourceNameMismatchError("source response", response.name) metaReject(error) stream.destroy(error) spool.unroll() return } if (!lockResponder("source response", response.sender)) return if (response.error) { streamEnded = true const error = new Error(response.error) metaReject(error) stream.destroy(error) spool.unroll() } else { responseAcked = true metaResolve(response.meta) refreshTimeout() } }) /* register chunk dispatch callback (data chunks) */ this.onResponse.set(`source-fetch-chunk:${requestId}`, (response: SourceFetchChunk) => { if (streamEnded) return if (response.name !== name) { streamEnded = true const error = sourceNameMismatchError("source chunk", response.name) metaReject(error) stream.destroy(error) spool.unroll() return } if (!lockResponder("source chunk", response.sender)) return if (!responseAcked) { streamEnded = true const error = new Error("received source chunk before source response acknowledgement") metaReject(error) stream.destroy(error) spool.unroll() return } if (response.error) { streamEnded = true const error = new Error(response.error) metaReject(error) stream.destroy(error) spool.unroll() } else { refreshTimeout() if (response.chunk !== undefined) { if (chunkCredit > 0 && chunksReceived >= creditGranted) { streamEnded = true const error = new Error("flow control violation") metaReject(error) stream.destroy(error) spool.unroll() return } chunksReceived++ if (!stream.destroyed) stream.push(response.chunk) } if (response.final) { streamEnded = true if (!stream.destroyed) stream.push(null) spool.unroll() } } }) spool.roll(() => { this.onResponse.delete(`source-fetch-response:${requestId}`) this.onResponse.delete(`source-fetch-chunk:${requestId}`) }) /* generate encoded message */ const auth = this.authenticate() const metaStore = this.metaStore(meta) const credit = chunkCredit > 0 ? chunkCredit : undefined const request = this.msg.makeSourceFetchRequest(requestId, name, params, this.options.id, receiver, auth, metaStore, credit) const message = this.codec.encode(request) /* generate corresponding MQTT topic */ const topic = this.options.topicMake(name, "source-fetch-request", receiver) /* publish message to MQTT topic (no spool passed to run() — on failure, stream.destroy() triggers cleanup via the stream's "close"/"error" handlers above) */ run(`publish fetch request as MQTT message to topic "${topic}"`, () => this.publishToTopic(topic, message, { qos: 2, ...options }) ).catch((err: unknown) => { const error = ensureError(err) metaReject(error) stream.destroy(error) }) /* produce result */ const result = { stream, buffer, meta: metaP } makeMutuallyExclusiveFields(result, "stream", "buffer", (field) => { if (field === "stream") stream.stopCollecting() else if (field === "buffer") stream.resume() /* drain readable side */ }) return result } } |