@yipsec/kdns

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5.636z"/></symbol><symbol id="menu-icon" viewBox="0 0 24 24"><path fill="none" d="M0 0h24v24H0z"/><path d="M3 4h18v2H3V4zm0 7h18v2H3v-2zm0 7h18v2H3v-2z"/></symbol></defs></svg></head><body data-theme="dark"><div class="sidebar-container"><div class="sidebar" id="sidebar"><div class="sidebar-items-container"><div class="sidebar-section-title with-arrow" data-isopen="false" id="sidebar-modules"><div>Modules</div><svg><use xlink:href="#down-icon"></use></svg></div><div class="sidebar-section-children-container"><div class="sidebar-section-children"><a href="module-kdns_bucket.html">kdns/bucket</a></div><div class="sidebar-section-children"><a href="module-kdns_constants.html">kdns/constants</a></div><div class="sidebar-section-children"><a href="module-kdns_contacts.html">kdns/contacts</a></div><div class="sidebar-section-children"><a href="module-kdns_keys.html">kdns/keys</a></div><div class="sidebar-section-children"><a href="module-kdns_node.html">kdns/node</a></div><div class="sidebar-section-children"><a href="module-kdns_protocol.html">kdns/protocol</a></div><div class="sidebar-section-children"><a href="module-kdns_router.html">kdns/router</a></div></div><div class="sidebar-section-title with-arrow" data-isopen="false" id="sidebar-classes"><div>Classes</div><svg><use xlink:href="#down-icon"></use></svg></div><div class="sidebar-section-children-container"><div class="sidebar-section-children"><a href="module-kdns_bucket-Bucket.html">Bucket</a></div><div class="sidebar-section-children"><a href="module-kdns_contacts-Contact.html">Contact</a></div><div class="sidebar-section-children"><a href="module-kdns_contacts-ContactList.html">ContactList</a></div><div class="sidebar-section-children"><a href="module-kdns_node-Node.html">Node</a></div><div class="sidebar-section-children"><a href="module-kdns_protocol-Protocol.html">Protocol</a></div><div class="sidebar-section-children"><a href="module-kdns_router-Router.html">Router</a></div></div><div class="sidebar-section-title with-arrow" data-isopen="false" id="sidebar-events"><div>Events</div><svg><use xlink:href="#down-icon"></use></svg></div><div class="sidebar-section-children-container"><div class="sidebar-section-children"><a href="module-kdns_node-Node.html#event:message_queued">message_queued</a></div><div class="sidebar-section-children"><a href="module-kdns_node-Node.html#event:storage_delete">storage_delete</a></div><div class="sidebar-section-children"><a href="module-kdns_node-Node.html#event:storage_expire">storage_expire</a></div><div class="sidebar-section-children"><a href="module-kdns_node-Node.html#event:storage_replicate">storage_replicate</a></div><div class="sidebar-section-children"><a href="module-kdns_protocol-Protocol.html#event:storage_get">storage_get</a></div><div class="sidebar-section-children"><a href="module-kdns_protocol-Protocol.html#event:storage_put">storage_put</a></div><div class="sidebar-section-children"><a href="module-kdns_router-Router.html#event:contact_added">contact_added</a></div><div class="sidebar-section-children"><a href="module-kdns_router-Router.html#event:contact_deleted">contact_deleted</a></div></div></div></div></div><div class="navbar-container" id="VuAckcnZhf"><nav class="navbar"><div class="navbar-left-items"></div><div class="navbar-right-items"><div class="navbar-right-item"><button class="icon-button search-button" aria-label="open-search"><svg><use xlink:href="#search-icon"></use></svg></button></div><div class="navbar-right-item"><button class="icon-button theme-toggle" aria-label="toggle-theme"><svg><use class="theme-svg-use" xlink:href="#light-theme-icon"></use></svg></button></div><div class="navbar-right-item"><button class="icon-button font-size" aria-label="change-font-size"><svg><use xlink:href="#font-size-icon"></use></svg></button></div></div><nav></nav></nav></div><div class="toc-container"><div class="toc-content"><span class="bold">On this page</span><div id="eed4d2a0bfd64539bb9df78095dec881"></div></div></div><div class="body-wrapper"><div class="main-content"><div class="main-wrapper"><section id="source-page" class="source-page"><header><h1 id="title" class="has-anchor">node.js</h1></header><article><pre class="prettyprint source lang-js"><code>/** * * @module kdns/node */ 'use strict'; const { Writable: WritableStream } = require('node:stream'); const { EventEmitter } = require('node:events'); const constants = require('./constants'); const keys = require('./keys'); const { Protocol } = require('./protocol'); const { Contact, ContactList } = require('./contact'); const { Router } = require('./router'); /** * Shuffles an array in place. * @param {array} array - Array to shuffle * @returns {array} */ function knuthShuffle(array) { let currentIndex = array.length; let temporaryValue; let randomIndex; while (0 !== currentIndex) { randomIndex = Math.floor(Math.random() * currentIndex); currentIndex -= 1; temporaryValue = array[currentIndex]; array[currentIndex] = array[randomIndex]; array[randomIndex] = temporaryValue; } return array; } module.exports.knuthShuffle = knuthShuffle; /** * Wraps the supplied function in a pseudo-random length timeout to help * prevent convoy effects. These occur when a number of processes need to use * a resource in turn. There is a tendency for such bursts of activity to * drift towards synchronization, which can be disasterous. In Kademlia all * nodes are requird to republish their contents every hour (T_REPLICATE). A * convoy effect might lead to this being synchronized across the network, * which would appear to users as the network dying every hour. The default * timeout will be between 0 and 30 minutes unless specified. * @param {function} func - Function to wrap to execution later * @param {number} [maxtime] - Maximum timeout * @returns {function} */ function preventConvoy(func, timeout) { return function() { let t = Math.ceil( Math.random() * (typeof timeout !== 'number' ? 1.8e+6 : timeout) ); return setTimeout(func, t); }; }; module.exports.preventConvoy = preventConvoy; /** * Reads objects from a {@link module:kdns/node~ReadableStore} and if an * item should be replicated, performs an iterative store operation. * @typedef {WritableStream<module:kdns/node~StoredItem>} ReplicatorStream * @property {boolean} objectMode */ /** * Reads objects from a {@link module:kdns/node~ReadableStore} and if an * item should be expired, requests deletion. * @fires module:kdns/node~Node#storage_delete * @typedef {WritableStream<module:kdns/node~StoredItem>} ExpirationStream * @property {boolean} objectMode - true */ /** * Stream consumed by {@link module:kdns/node~ReplicatorStream} and * {@link module:kdns/node~ReplicatorStream}. * @typedef {ReadableStream<module:kdns/node~StoredItem>} ReadableStore * @property {boolean} objectMode - true */ /** * Format of a storage entry. * @typedef {Object} StoredItem * @property {buffer} blob - Raw bytes for the stored item * @property {object} meta - Metadata needed for replication and expiration * @property {Date} meta.timestamp - The time this item was stored * @property {string} meta.publisher - {@link module:kdns/contacts~Contact} fingerprint that stored this item */ class Node extends EventEmitter { /** * RPC message is queued for you to send. This is implementation * specific based on how you want to handle networking. This event * contains all the data necessary for you to handle transport. * @event module:kdns/node~Node#message_queued * @param {string} method - RPC method name to call * @param {array<string|object|number|boolean|Stream>} params - Arguments to pass the method call * @param {module:kdns/contacts~Contact} target - Contact address information * @param {module:kdns/protocol~HandlerResponse} respond - Resolves the message response */ /** * Indicates that you may delete the item stored by the key. This is * triggered most likely by the expiration routine. * @event module:kdns/node~Node#storage_delete * @param {string} key - Key of storage item to delete * @param {module:kdns/protocol~HandlerResponse} respond - Resolves the delete request */ /** * Replication routine has started. A writable stream is provided. Only * items requiring replication will be replicated. * @event module:kdns/node~Node#storage_replicate * @param {module:kdns/node~ReplicatorStream} replicator - Reads from a {@link module:kdns/node~ReadableStore} */ /** * Expiration routine has started. A writable stream is provided. Only * items requiring expiration will be requested for deletion. * @event module:kdns/node~Node#storage_expire * @param {module:kdns/node~ExpirationStream} expirator - Reads from a {@link module:kdns/node~ReadableStore} */ /** * Overridable options passed to {@link Node}. * @typedef {Object} NodeOptions * @property {module:kdns/router~Router} router * @property {module:kdns/protocol~Protocol} protocol */ /** * Kademlia protocol implementation. Creates an interface for orchestrating * a Kademlia network and extending it. * @constructor * @extends EventEmitter * @param {module:kdns/contacts~Contact} contact - Address and fingerprint of this node * @param {module:kdns/node~NodeOptions} [options] - Internal overrides */ constructor(contact, options = {}) { super(); this._lookups = new Map(); // NB: Track the last lookup time for buckets this._pings = new Map(); // NB: Track the last ping time for contacts this.events = new EventEmitter(); this.contact = contact || new Contact(); this.identity = Buffer.from(this.contact.fingerprint, 'hex') this.router = options.router || new Router(this.identity); this.protocol = options.protocol || new Protocol(this.router); setInterval( preventConvoy(() => this.refresh(0)), constants.T_REFRESH ); setInterval( preventConvoy(() => this.replicate(() => this.expire())), constants.T_REPLICATE ); this.router.events .on('contact_added', (fingerprint) => this.events.emit('contact_added', fingerprint)) .on('contact_deleted', (fingerprint) => this.events.emit('contact_deleted', fingerprint)); this.protocol.events .on('storage_put', (k, v, r) => this.events.emit('storage_put', k, v, r)) .on('storage_get', (k, r) => this.events.emit('storage_get', k, r)) } /** * Inserts the given contact into the routing table and uses it to perform * a {@link Node#iterativeFindNode} for this node's identity, * then refreshes all buckets further than it's closest neighbor, which will * be in the occupied bucket with the lowest index * @param {module:kdns/contacts~Contact} peer - Peer to bootstrap from * @returns {Promise<undefined>} */ join(peer) { return this._join(peer); } /** * @private */ _join(contact) { const identity = contact.fingerprint; return new Promise(async (resolve, reject) => { this.router.addContactByNodeId(identity, contact); try { await this.iterativeFindNode(this.identity.toString('hex')); await this.refresh(this.router.getClosestBucket() + 1); } catch (e) { return reject(e); } resolve(); }); } /** * Sends a PING message to the supplied contact, resolves with latency. * @param {module:kdns/contacts~Contact} peer - Peer to PING * @fires module:kdns/node~Node#message_queued * @returns {Promise<number>} */ ping(contact) { return this._ping(contact); } /** * @private */ _ping(contact) { return new Promise((resolve, reject) => { const start = Date.now(); contact = new Contact(contact.address, contact.fingerprint); this.events.emit('message_queued', 'PING', [this.contact], contact, (err) => { if (err) { return reject(err); } resolve(Date.now() - start); }); }); } /** * @private */ _createStorageItem(value) { if (typeof value === 'string') { value = Buffer.from(value); } else if (Buffer.isBuffer(value)) { // noop } else if (typeof value === 'object') { const keys = Object.keys(value); const meta = Object.keys(value.meta); const alreadyHasMetadata = keys.includes('blob') && meta.includes('publisher') && meta.includes('timestamp'); if (alreadyHasMetadata) { value.meta.timestamp = Date.now(); value.meta.publisher = value.meta.publisher.toString('hex'); return value; } } return { blob: value, meta: { timestamp: Date.now(), publisher: this.identity.toString('hex') } }; } /** * Performs a lookup to collect K contacts nearest to the given key, * sending a STORE message to each of them. Note that if there is a * protocol/validation error, you will not receive it as a rejection. * Be sure to also check that stored > 0 as part of error handling here. * @param {buffer|string} key - Key to store data under * @param {module:kdns/node~StoredItem|Buffer} value - Value to store by key * @fires module:kdns/node~Node#message_queued * @returns {Promise<number>} */ iterativeStore(key, value) { return this._iterativeStore(key, value); } /** * @private */ _iterativeStore(key, value) { return new Promise(async (resolve, reject) => { key = key.toString('hex'); let stored = 0; const _wrapStore = (key, item, target) => { return new Promise((resolve, reject) => { target = new Contact(target.address, target.fingerprint); this.events.emit('message_queued', 'STORE', [key, item, this.contact], target, (e) => { if (e) { return reject(e); } resolve(); }); }); }; const dispatchStoreRpcs = async (iterator) => { for (const [, target] of iterator) { try { await _wrapStore(key, this._createStorageItem(value), target); } catch (err) { continue; } stored++; } }; const contacts = await this.iterativeFindNode(key); const entries = contacts.entries(); const workers = new Array(constants.ALPHA).fill(entries).map(dispatchStoreRpcs); await Promise.allSettled(workers); if (stored === 0) { return reject(new Error('Failed to stored entry with peers')); } resolve(stored); }); } /** * Basic kademlia lookup operation that builds a set of K contacts closest * to the given key * @param {buffer|string} key - Reference key for node lookup * @fires module:kdns/node~Node#message_queued * @returns {Promise<module:kdns/contacts~Contact[]>} */ iterativeFindNode(key) { key = key.toString('hex'); return new Promise((resolve, reject) => { this._iterativeFind('FIND_NODE', key).then(contacts => { for (let i = 0; i < contacts.length; i++) { this.router.addContactByNodeId(contacts[i].fingerprint, new Contact(contacts[i].address, contacts[i].fingerprint)); } resolve(contacts.map(c => new Contact(c.address, c.fingerprint))); }, reject); }); } /** * Kademlia search operation that is conducted as a node lookup and builds * a list of K closest contacts. If at any time during the lookup the value * is returned, the search is abandoned. If no value is found, the K closest * contacts are returned. Upon success, we must store the value at the * nearest node seen during the search that did not return the value. * @param {buffer|string} key - Key for value lookup * @fires module:kdns/node~Node#message_queued * @returns {Promise<module:kdns/contacts~Contact[]|module:kdns/node~StoredItem>} */ iterativeFindValue(key) { key = key.toString('hex'); return this._iterativeFind('FIND_VALUE', key); } /** * Performs a scan of the storage adapter and performs * republishing/replication of items stored. Items that we did not publish * ourselves get republished every T_REPLICATE. Items we did publish get * republished every T_REPUBLISH. * @fires module:kdns/node~Node#storage_replicate * @returns {undefined} */ replicate() { this.events.emit('storage_replicate', this._replicate()); } /** * @private */ _replicate() { const self = this; const now = Date.now(); const replicateStream = new WritableStream({ objectMode: true, write: maybeReplicate }); function maybeReplicate({ hash, meta, blob }, enc, next) { const isPublisher = meta.publisher === self.identity.toString('hex'); const republishDue = (meta.timestamp + constants.T_REPUBLISH) <= now; const replicateDue = (meta.timestamp + constants.T_REPLICATE) <= now; const shouldRepublish = isPublisher && republishDue; const shouldReplicate = !isPublisher && replicateDue; if (shouldReplicate || shouldRepublish) { return self.iterativeStore(hash, { meta, blob }, next); } next(); } return replicateStream; } /** * Items expire T_EXPIRE seconds after the original publication. All items * are assigned an expiration time which is "exponentially inversely * proportional to the number of nodes between the current node and the node * whose ID is closest to the key", where this number is "inferred from the * bucket structure of the current node". * @fires module:kdns/node~Node#storage_expire * @returns {undefined} */ expire() { this.events.emit('storage_expire', this._expire()); } /** * @private */ _expire() { const self = this; const now = Date.now(); const expireStream = new WritableStream({ objectMode: true, write: maybeExpire }); function maybeExpire({ hash, meta, blob }, enc, next) { if ((meta.timestamp + constants.T_EXPIRE) <= now) { self.events.emit('storage_delete', hash); } next(); } return expireStream; } /** * If no node lookups have been performed in any given bucket's range for * T_REFRESH, the node selects a random number in that range and does a * refresh, an iterativeFindNode using that number as key. * @param {number} startIndex - bucket index to start refresh from * @returns {Promise<undefined>} */ refresh(startIndex = 0) { return this._refresh(startIndex); } /** * @private */ _refresh(startIndex) { let now = Date.now(); let indices = [ ...this.router.entries() ].slice(startIndex).map((entry) => entry[0]); // NB: We want to avoid high churn during refresh and prevent further // NB: refreshes if lookups in the next bucket do not return any new // NB: contacts. To do this we will shuffle the bucket indexes we are // NB: going to check and only continue to refresh if new contacts were // NB: discovered in the last MAX_UNIMPROVED_REFRESHES consecutive lookups. let results = new Set(), consecutiveUnimprovedLookups = 0; function isDiscoveringNewContacts() { return consecutiveUnimprovedLookups < constants.MAX_UNIMPROVED_REFRESHES; } return new Promise(async (resolve, reject) => { indices = knuthShuffle(indices); for (let i = 0; i < indices.length; i++) { let index = indices[i]; if (!isDiscoveringNewContacts()) { return resolve(); } const lastBucketLookup = this._lookups.get(index) || 0; const needsRefresh = lastBucketLookup + constants.T_REFRESH <= now; if (needsRefresh) { let contacts; try { contacts = await this.iterativeFindNode( keys.getRandomBufferInBucketRange(this.identity, index) .toString('hex') ); for (let i = 0; i < contacts.length; i++) { try { await this._updateContact(contacts[i]); } catch (e) {} } } catch (e) { return reject(e); } let discoveredNewContacts = false; for (let contact of contacts) { if (!results.has(contact.fingerprint)) { discoveredNewContacts = true; consecutiveUnimprovedLookups = 0; results.add(contact.fingerprint); } } if (!discoveredNewContacts) { consecutiveUnimprovedLookups++; } } } resolve(); }); } /** * Builds a list of closest contacts for a particular RPC * @private */ _iterativeFind(method, key) { return new Promise((resolve) => { let shortlist = new ContactList(key, [ ...this.router.getClosestContactsToKey(key, constants.ALPHA) ].map(([,c]) => { return new Contact(c.address, c.fingerprint) })); let closest = shortlist.closest; this._lookups.set(keys.getBucketIndex(this.identity, key), Date.now()); const _wrapFindRpc = (contact) => { return new Promise((resolve, reject) => { contact = new Contact(contact.address, contact.fingerprint); this.events.emit('message_queued', method, [key, this.contact], contact, (err, result) => { if (err) { return reject(err); } if (method === 'FIND_NODE') { result = result.map((n) => { const c = new Contact(n.address, n.fingerprint); return c; }); resolve(result); } else if (method === 'FIND_VALUE') { resolve(result); } }); }); }; const iterativeLookup = async (selection, continueLookup = true) => { if (!selection.length) { return resolve(shortlist.active.slice(0, constants.K)); } for (let i = 0; i < selection.length; i++) { const contact = selection[i]; // NB: mark this node as contacted so as to avoid repeats shortlist.contacted(contact); let result; try { result = await _wrapFindRpc(contact); } catch (e) { continue; } // NB: mark this node as active to include it in any return values shortlist.responded(contact); // NB: If the result is a contact/node list, just keep track of it // NB: Otherwise, do not proceed with iteration, just callback if (Array.isArray(result) || method !== 'FIND_VALUE') { const added = shortlist.add(Array.isArray(result) ? result : []); // NB: If it wasn't in the shortlist, we haven't added to the // NB: routing table, so do that now. for (let i = 0; i < added.length; i++) { await this._updateContact(added[i]); } continue; } // NB: If we did get an item back, get the closest node we contacted // NB: who is missing the value and store a copy with them const closestMissingValue = new Contact(shortlist.active[0].address, shortlist.active[0].fingerprint); if (closestMissingValue) { this.events.emit('message_queued', 'STORE', [ key, this._createStorageItem(result), this.contact ], closestMissingValue, () => null); } // NB: we found a value, so stop searching return resolve(result, contact); } // NB: If we have reached at least K active nodes, or haven't found a // NB: closer node, even on our finishing trip, return to the caller // NB: the K closest active nodes. if (shortlist.active.length >= constants.K || (closest[0] === shortlist.closest[0] && !continueLookup) ) { return resolve(shortlist.active.slice(0, constants.K)); } // NB: we haven't discovered a closer node, call k uncalled nodes and // NB: finish up if (closest[0] === shortlist.closest[0]) { return iterativeLookup( shortlist.uncontacted.slice(0, constants.K), false ); } closest = shortlist.closest; // NB: continue the lookup with ALPHA close, uncontacted nodes iterativeLookup(shortlist.uncontacted.slice(0, constants.ALPHA), true); }; iterativeLookup( shortlist.uncontacted.slice(0, constants.ALPHA), true ); }); } /** * Worker for updating contact in a routing table bucket * @private */ _updateContact(_contact) { const contact = new Contact(_contact.address, _contact.fingerprint); const identity = contact.fingerprint.toString('hex'); if (identity === this.identity.toString('hex')) { return Promise.resolve(); } const now = Date.now(); const reset = 600000; const [, bucket, contactIndex] = this.router.addContactByNodeId( identity, contact ); const [headId, headContact] = bucket.head; const lastPing = this._pings.get(headId); if (contactIndex !== -1) { return Promise.resolve(); } if (lastPing && lastPing.responded && lastPing.timestamp > (now - reset)) { return Promise.resolve(); } return new Promise((resolve, reject) => { this.ping(headContact).then(() => { this._pings.set(headId, { timestamp: Date.now(), responded: true }); resolve(); }, (e) => { this._pings.set(headId, { timestamp: Date.now(), responded: false }); this.router.removeContactByNodeId(headId); this.router.addContactByNodeId(identity, contact); reject(e); }); }); } } module.exports.Node = Node; </code></pre></article></section></div></div></div><div class="search-container" id="PkfLWpAbet" style="display:none"><div class="wrapper" id="iCxFxjkHbP"><button class="icon-button search-close-button" id="VjLlGakifb" aria-label="close search"><svg><use xlink:href="#close-icon"></use></svg></button><div class="search-box-c"><svg><use xlink:href="#search-icon"></use></svg> <input type="text" id="vpcKVYIppa" class="search-input" placeholder="Search..." autofocus></div><div class="search-result-c" id="fWwVHRuDuN"><span 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