import {MapWithTTL} from 'app/common/AsyncCreate'; import * as version from 'app/common/version'; import {DocStatus, DocWorkerInfo, IDocWorkerMap} from 'app/server/lib/DocWorkerMap'; import * as log from 'app/server/lib/log'; import {checkPermitKey, formatPermitKey, Permit} from 'app/server/lib/Permit'; import {promisifyAll} from 'bluebird'; import mapValues = require('lodash/mapValues'); import {createClient, Multi, RedisClient} from 'redis'; import * as Redlock from 'redlock'; import * as uuidv4 from 'uuid/v4'; promisifyAll(RedisClient.prototype); promisifyAll(Multi.prototype); // Max time for which we will hold a lock, by default. In milliseconds. const LOCK_TIMEOUT = 3000; // How long do checksums stored in redis last. In milliseconds. // Should be long enough to allow S3 to reach consistency with very high probability. // Consistency failures shorter than this interval will be detectable, failures longer // than this interval will not be detectable. const CHECKSUM_TTL_MSEC = 24 * 60 * 60 * 1000; // 24 hours // How long do permits stored in redis last, in milliseconds. const PERMIT_TTL_MSEC = 1 * 60 * 1000; // 1 minute class DummyDocWorkerMap implements IDocWorkerMap { private _worker?: DocWorkerInfo; private _available: boolean = false; private _permits = new MapWithTTL(PERMIT_TTL_MSEC); private _elections = new MapWithTTL(1); // default ttl never used public async getDocWorker(docId: string) { if (!this._worker) { throw new Error('no workers'); } return {docMD5: 'unknown', docWorker: this._worker, isActive: true}; } public async assignDocWorker(docId: string) { if (!this._worker || !this._available) { throw new Error('no workers'); } return {docMD5: 'unknown', docWorker: this._worker, isActive: true}; } public async getDocWorkerOrAssign(docId: string, workerId: string): Promise { if (!this._worker || !this._available) { throw new Error('no workers'); } if (this._worker.id !== workerId) { throw new Error('worker not known'); } return {docMD5: 'unknown', docWorker: this._worker, isActive: true}; } public async updateDocStatus(docId: string, checksum: string) { // nothing to do } public async addWorker(info: DocWorkerInfo): Promise { this._worker = info; } public async removeWorker(workerId: string): Promise { this._worker = undefined; } public async setWorkerAvailability(workerId: string, available: boolean): Promise { this._available = available; } public async releaseAssignment(workerId: string, docId: string): Promise { // nothing to do } public async getAssignments(workerId: string): Promise { return []; } public async setPermit(permit: Permit): Promise { const key = formatPermitKey(uuidv4()); this._permits.set(key, JSON.stringify(permit)); return key; } public async getPermit(key: string): Promise { const result = this._permits.get(key); return result ? JSON.parse(result) : null; } public async removePermit(key: string): Promise { this._permits.delete(key); } public async close(): Promise { this._permits.clear(); this._elections.clear(); } public async getElection(name: string, durationInMs: number): Promise { if (this._elections.get(name)) { return null; } const key = uuidv4(); this._elections.setWithCustomTTL(name, key, durationInMs); return key; } public async removeElection(name: string, electionKey: string): Promise { if (this._elections.get(name) === electionKey) { this._elections.delete(name); } } public async updateChecksum(family: string, key: string, checksum: string) { // nothing to do } public async getChecksum(family: string, key: string) { return null; } public async getWorkerGroup(workerId: string): Promise { return null; } public async getDocGroup(docId: string): Promise { return null; } } /** * Manage the relationship between document and workers. Backed by Redis. * Can also assign workers to "groups" for serving particular documents. * Keys used: * workers - the set of known active workers, identified by workerId * workers-available - the set of workers available for assignment (a subset of the workers set) * workers-available-{group} - the set of workers available for a given group * worker-{workerId} - a hash of contact information for a worker * worker-{workerId}-docs - a set of docs assigned to a worker, identified by docId * worker-{workerId}-group - if set, marks the worker as serving a particular group * doc-${docId} - a hash containing (JSON serialized) DocStatus fields, other than docMD5. * doc-${docId}-checksum - the docs docMD5, or 'null' if docMD5 is null * doc-${docId}-group - if set, marks the doc as to be served by workers in a given group * workers-lock - a lock used when working with the list of workers * groups - a hash from groupIds (arbitrary strings) to desired number of workers in group * elections-${deployment} - a hash, from groupId to a (serialized json) list of worker ids * * Assignments of documents to workers can end abruptly at any time. Clients * should be prepared to retry if a worker is not responding or denies that a document * is assigned to it. * * If the groups key is set, workers assign themselves to groupIds to * fill the counts specified in groups (in order of groupIds), and * once those are exhausted, get assigned to the special group * "default". */ export class DocWorkerMap implements IDocWorkerMap { private _client: RedisClient; private _clients: RedisClient[]; private _redlock: Redlock; // Optional deploymentKey argument supplies a key unique to the deployment (this is important // for maintaining groups across redeployments only) constructor(_clients?: RedisClient[], private _deploymentKey?: string, private _options?: { permitMsec?: number }) { this._deploymentKey = this._deploymentKey || version.version; this._clients = _clients || [createClient(process.env.REDIS_URL)]; this._redlock = new Redlock(this._clients); this._client = this._clients[0]!; } public async addWorker(info: DocWorkerInfo): Promise { log.info(`DocWorkerMap.addWorker ${info.id}`); const lock = await this._redlock.lock('workers-lock', LOCK_TIMEOUT); try { // Make a worker-{workerId} key with contact info. await this._client.hmsetAsync(`worker-${info.id}`, info); // Add this worker to set of workers (but don't make it available for work yet). await this._client.saddAsync('workers', info.id); if (info.group) { // Accept work only for a specific group. // Do not accept work not associated with the specified group. await this._client.setAsync(`worker-${info.id}-group`, info.group); } else { // Figure out if worker should belong to a group via elections. // Be careful: elections happen within a single deployment, so are somewhat // unintuitive in behavior. For example, if a document is assigned to a group // but there is no worker available for that group, it may open on any worker. // And if a worker is assigned to a group, it may still end up assigned work // not associated with that group if it is the only worker available. const groups = await this._client.hgetallAsync('groups'); if (groups) { const elections = await this._client.hgetallAsync(`elections-${this._deploymentKey}`) || {}; for (const group of Object.keys(groups).sort()) { const count = parseInt(groups[group], 10) || 0; if (count < 1) { continue; } const elected: string[] = JSON.parse(elections[group] || '[]'); if (elected.length >= count) { continue; } elected.push(info.id); await this._client.setAsync(`worker-${info.id}-group`, group); await this._client.hsetAsync(`elections-${this._deploymentKey}`, group, JSON.stringify(elected)); break; } } } } finally { await lock.unlock(); } } public async removeWorker(workerId: string): Promise { log.info(`DocWorkerMap.removeWorker ${workerId}`); const lock = await this._redlock.lock('workers-lock', LOCK_TIMEOUT); try { // Drop out of available set first. await this._client.sremAsync('workers-available', workerId); const group = await this._client.getAsync(`worker-${workerId}-group`) || 'default'; await this._client.sremAsync(`workers-available-${group}`, workerId); // At this point, this worker should no longer be receiving new doc assignments, though // clients may still be directed to the worker. // If we were elected for anything, back out. const elections = await this._client.hgetallAsync(`elections-${this._deploymentKey}`); if (elections) { if (group in elections) { const elected: string[] = JSON.parse(elections[group]); const newElected = elected.filter(worker => worker !== workerId); if (elected.length !== newElected.length) { if (newElected.length > 0) { await this._client.hsetAsync(`elections-${this._deploymentKey}`, group, JSON.stringify(newElected)); } else { await this._client.hdelAsync(`elections-${this._deploymentKey}`, group); delete elections[group]; } } // We're the last one involved in elections - remove the key entirely. if (Object.keys(elected).length === 0) { await this._client.delAsync(`elections-${this._deploymentKey}`); } } } // Now, we start removing the assignments. const assignments = await this._client.smembersAsync(`worker-${workerId}-docs`); if (assignments) { const op = this._client.multi(); for (const doc of assignments) { op.del(`doc-${doc}`); } await op.execAsync(); } // Now remove worker-{workerId}* keys. await this._client.delAsync(`worker-${workerId}-docs`); await this._client.delAsync(`worker-${workerId}-group`); await this._client.delAsync(`worker-${workerId}`); // Forget about this worker completely. await this._client.sremAsync('workers', workerId); } finally { await lock.unlock(); } } public async setWorkerAvailability(workerId: string, available: boolean): Promise { log.info(`DocWorkerMap.setWorkerAvailability ${workerId} ${available}`); const group = await this._client.getAsync(`worker-${workerId}-group`) || 'default'; if (available) { const docWorker = await this._client.hgetallAsync(`worker-${workerId}`) as DocWorkerInfo|null; if (!docWorker) { throw new Error('no doc worker contact info available'); } await this._client.saddAsync(`workers-available-${group}`, workerId); // If we're not assigned exclusively to a group, add this worker also to the general // pool of workers. if (!docWorker.group) { await this._client.saddAsync('workers-available', workerId); } } else { await this._client.sremAsync('workers-available', workerId); await this._client.sremAsync(`workers-available-${group}`, workerId); } } public async releaseAssignment(workerId: string, docId: string): Promise { const op = this._client.multi(); op.del(`doc-${docId}`); op.srem(`worker-${workerId}-docs`, docId); await op.execAsync(); } public async getAssignments(workerId: string): Promise { return this._client.smembersAsync(`worker-${workerId}-docs`); } /** * Defined by IDocWorkerMap. * * Looks up which DocWorker is responsible for this docId. * Responsibility could change at any time after this call, so it * should be treated as a hint, and clients should be prepared to be * refused and need to retry. */ public async getDocWorker(docId: string): Promise { // Fetch the various elements that go into making a DocStatus const props = await this._client.multi() .hgetall(`doc-${docId}`) .get(`doc-${docId}-checksum`) .execAsync() as [{[key: string]: any}|null, string|null]|null; if (!props) { return null; } // If there is no worker, return null. An alternative would be to modify // DocStatus so that it is possible for it to not have a worker assignment. if (!props[0]) { return null; } // Fields are JSON encoded since redis cannot store them directly. const doc = mapValues(props[0], (val) => JSON.parse(val)); // Redis cannot store a null value, so we encode it as 'null', which does // not match any possible MD5. doc.docMD5 = props[1] === 'null' ? null : props[1]; // Ok, we have a valid DocStatus at this point. return doc as DocStatus; } /** * * Defined by IDocWorkerMap. * * Assigns a DocWorker to this docId if one is not yet assigned. * Note that the assignment could be unmade at any time after this * call if the worker dies, is brought down, or for other potential * reasons in the future such as migration of individual documents * between workers. * * A preferred doc worker can be specified, which will be assigned * if no assignment is already made. * * For the special docId "import", return a potential assignment. * It will be up to the doc worker to assign the eventually * created document, if desired. * */ public async assignDocWorker(docId: string, workerId?: string): Promise { if (docId === 'import') { const lock = await this._redlock.lock(`workers-lock`, LOCK_TIMEOUT); try { const _workerId = await this._client.srandmemberAsync(`workers-available-default`); if (!_workerId) { throw new Error('no doc worker available'); } const docWorker = await this._client.hgetallAsync(`worker-${_workerId}`) as DocWorkerInfo|null; if (!docWorker) { throw new Error('no doc worker contact info available'); } return { docMD5: null, docWorker, isActive: false }; } finally { await lock.unlock(); } } // Check if a DocWorker is already assigned; if so return result immediately // without locking. let docStatus = await this.getDocWorker(docId); if (docStatus) { return docStatus; } // No assignment yet, so let's lock and set an assignment up. const lock = await this._redlock.lock(`workers-lock`, LOCK_TIMEOUT); try { // Now that we've locked, recheck that the worker hasn't been reassigned // in the meantime. Return immediately if it has. docStatus = await this.getDocWorker(docId); if (docStatus) { return docStatus; } if (!workerId) { // Check if document has a preferred worker group set. const group = await this._client.getAsync(`doc-${docId}-group`) || 'default'; // Let's start off by assigning documents to available workers randomly. // TODO: use a smarter algorithm. workerId = await this._client.srandmemberAsync(`workers-available-${group}`) || undefined; if (!workerId) { // No workers available in the desired worker group. Rather than refusing to // open the document, we fall back on assigning a worker from any of the workers // available, regardless of grouping. // This limits the impact of operational misconfiguration (bad redis setup, // or not starting enough workers). It has the downside of potentially disguising // problems, so we log a warning. log.warn(`DocWorkerMap.assignDocWorker ${docId} found no workers for group ${group}`); workerId = await this._client.srandmemberAsync('workers-available') || undefined; } if (!workerId) { throw new Error('no doc workers available'); } } else { if (!await this._client.sismemberAsync('workers-available', workerId)) { throw new Error(`worker ${workerId} not known or not available`); } } // Look up how to contact the worker. const docWorker = await this._client.hgetallAsync(`worker-${workerId}`) as DocWorkerInfo|null; if (!docWorker) { throw new Error('no doc worker contact info available'); } // We can now construct a DocStatus. const newDocStatus = {docMD5: null, docWorker, isActive: true}; // We add the assignment to worker-{workerId}-docs and save doc-{docId}. const result = await this._client.multi() .sadd(`worker-${workerId}-docs`, docId) .hmset(`doc-${docId}`, { docWorker: JSON.stringify(docWorker), // redis can't store nested objects, strings only isActive: JSON.stringify(true) // redis can't store booleans, strings only }) .setex(`doc-${docId}-checksum`, CHECKSUM_TTL_MSEC / 1000.0, 'null') .execAsync(); if (!result) { throw new Error('failed to store new assignment'); } return newDocStatus; } finally { await lock.unlock(); } } /** * * Defined by IDocWorkerMap. * * Assigns a specific DocWorker to this docId if one is not yet assigned. * */ public async getDocWorkerOrAssign(docId: string, workerId: string): Promise { return this.assignDocWorker(docId, workerId); } public async updateDocStatus(docId: string, checksum: string): Promise { return this.updateChecksum('doc', docId, checksum); } public async updateChecksum(family: string, key: string, checksum: string) { await this._client.setexAsync(`${family}-${key}-checksum`, CHECKSUM_TTL_MSEC / 1000.0, checksum); } public async getChecksum(family: string, key: string) { const checksum = await this._client.getAsync(`${family}-${key}-checksum`); return checksum === 'null' ? null : checksum; } public async setPermit(permit: Permit): Promise { const key = formatPermitKey(uuidv4()); const duration = (this._options && this._options.permitMsec) || PERMIT_TTL_MSEC; // seems like only integer seconds are supported? await this._client.setexAsync(key, Math.ceil(duration / 1000.0), JSON.stringify(permit)); return key; } public async getPermit(key: string): Promise { if (!checkPermitKey(key)) { throw new Error('permit could not be read'); } const result = await this._client.getAsync(key); return result && JSON.parse(result); } public async removePermit(key: string): Promise { if (!checkPermitKey(key)) { throw new Error('permit could not be read'); } await this._client.delAsync(key); } public async close(): Promise { for (const cli of this._clients || []) { await cli.quitAsync(); } } public async getElection(name: string, durationInMs: number): Promise { // Could use "set nx" for election, but redis docs don't encourage that any more, // favoring redlock: // https://redis.io/commands/setnx#design-pattern-locking-with-codesetnxcode const redisKey = `nomination-${name}`; const lock = await this._redlock.lock(`${redisKey}-lock`, LOCK_TIMEOUT); try { if (await this._client.getAsync(redisKey) !== null) { return null; } const electionKey = uuidv4(); // seems like only integer seconds are supported? await this._client.setexAsync(redisKey, Math.ceil(durationInMs / 1000.0), electionKey); return electionKey; } finally { await lock.unlock(); } } public async removeElection(name: string, electionKey: string): Promise { const redisKey = `nomination-${name}`; const lock = await this._redlock.lock(`${redisKey}-lock`, LOCK_TIMEOUT); try { const current = await this._client.getAsync(redisKey); if (current === electionKey) { await this._client.delAsync(redisKey); } else if (current !== null) { throw new Error('could not remove election'); } } finally { await lock.unlock(); } } public async getWorkerGroup(workerId: string): Promise { return this._client.getAsync(`worker-${workerId}-group`); } public async getDocGroup(docId: string): Promise { return this._client.getAsync(`doc-${docId}-group`); } } // If we don't have redis available and use a DummyDocWorker, it should be a singleton. let dummyDocWorkerMap: DummyDocWorkerMap|null = null; export function getDocWorkerMap(): IDocWorkerMap { if (process.env.REDIS_URL) { return new DocWorkerMap(); } else { dummyDocWorkerMap = dummyDocWorkerMap || new DummyDocWorkerMap(); return dummyDocWorkerMap; } }