0.6.30 • Public • Published


A Nostr RelayPool implementation in TypeScript using library as a dependency.

Its main goal is to make it simpler to build a client on top of it than just a dumb RelayPool implementation.

It's used by:

(Add yourself here :) )


  • Merging filters: separate filters with the same type of query (like asking for different authors with the same kinds) are automatically merged for every subscription request to decrease the number of filters, as the server usually handles it better.
  • Deleting empty filters: filters with no possible match are deleted, and subscription is not even created if there would be no valid event.
  • Duplicate events from cache / different relays are parsed / verified / emitted only once
  • If an event with kind 0 / 3 is emitted, older events with the same author and kind are not emitted. The last emitted event with that kind and author is always the freshest.
  • Delayed subscriptions allow clients to request data from different components, and let the RelayPool implementation merge, deduplicate, prioritize, cache these requests and split the replies to send to each subscription from the clients. It needs lots of testing and optimizations to get it to production level, but prototyping is important at this stage.
  • Compute smallest created_at (for continuing subscriptions on relays). When continuing a subscription, just pass the specific relay.
  • Run RelayPool in Web worker for smooth scrolling
  • Delete signatures (off by default)
  • Caching events (off by default): every event searched by id or event of Metadata or Contacts kind are cached in memory. Returning cached data can be turned off for each filter
  • Automatically close subscriptions (optional)
  • Automatically select relays by getting write relays from indexing servers
  • Getting metadata / contacts from indexing servers and cache them.
  • Automatically reconnect to servers (optional)


npm i nostr-relaypool

Installation for use in NodeJS

npm i nostr-relaypool ws


import {RelayPool} from "nostr-relaypool";

let relays = [

let relayPool = new RelayPool(relays);

let unsub = relayPool.subscribe(
      authors: [
      kinds: [0],
      authors: [
      relay: "wss://",
  (event, isAfterEose, relayURL) => {
    console.log(event, isAfterEose, relayURL);
  (events, relayURL) => {
    console.log(events, relayURL);

relayPool.onerror((err, relayUrl) => {
  console.log("RelayPool error", err, " from relay ", relayUrl);
relayPool.onnotice((relayUrl, notice) => {
  console.log("RelayPool notice", notice, " from relay ", relayUrl);

Web worker support (not all functionality is supported yet, but feel free to add, it's easy):

import { RelayPoolWorker } from 'nostr-relaypool';

const worker = new Worker(
  new URL('./node_modules/nostr-relaypool/lib/nostr-relaypool.worker.js', document.location.href)
const relayPool = new RelayPoolWorker(worker);

API documentation:

RelayPool(relays:string[] = [], options:{useEventCache?: boolean, logSubscriptions?: boolean,
          deleteSignatures?: boolean, skipVerification?: boolean,
          autoReconnect?: boolean} = {})

RelayPool constructor connects to the given relays, but it doesn't determine which relays are used for specific subscriptions.

It caches all events and returns filtering id and 0 / 3 kinds with requested pubkeys from cache.


  • useEventCache: turns on caching of all events. WARNING: This makes memory grow without limit.
  • logSubscriptions: turns on logging subscriptions. 1 entry per RelayPool subscription, and it can help clients significantly
  • deleteSignatures: delete signatures for events
  • skipVerification: skip event signature verification
  • autoReconnect: aggressively reconnect automatically (not suggested for clients)

 RelayPool::subscribe(filters: Filter & {relay?: string, noCache?: boolean},
                      relays: string[] | undefined,
                      onEvent: (event: Event, isAfterEose: boolean,
                          relayURL: string | undefined) => void,
                      maxDelayms?: number,
                      onEose?: (relayURL, minCreatedAt) => void,
                      options: {
                        allowDuplicateEvents?: boolean,
                        allowOlderEvents?: boolean,
                        logAllEvents?: boolean,
                        unsubscribeOnEose: boolean,
                        defaultRelays?: string[]} = {}
              ) : () => void

Creates a subscription to a list of filters and sends them to a pool of relays if new data is required from those relays.

  • filters:

    If the relay property of a filter is set, that filter will be requested only from that relay. Filters that don't have relay set will be sent to the relays passed inside the relays parameter. There will be at most 1 subscription created for each relay even if it's passed multiple times in relay / relays.

    The implementation finds filters in the subscriptions that only differ in 1 key and merges them both on RelayPool level and Relay level. The merging algorithm is linear in input size (not accidental O(n^2)). It also removes empty filters that are guaranteed to not match any events.

    noCache inside a filter instructs relayPool to never return cached results for that specific filter, but get them from a subscription. (maybe refresh or revalidate would be a better name, but noCache was selected as it's defined in the Cache-Control header of the HTTP standard). It may only be useful if kinds 0, 3 are requested.

    If no real work would be done by a relay (all filters are satisfied from cache or empty) the subscription will not be sent (but the cached events will be provided instantly using the onEvent callback).

  • relays: Events for filters that have no relay field set will be requested from all the specified relays.

    If relays is not set and authors is set for all filters, RelayPool will get write relays for all authors in the subscription and send the subscription to those relays.

  • onEvent:

    Other RelayPool implementations allow calling onevent multiple times on a Subscription class, which was the original design in this library as well, but since caching is implemented, it's safer API design to pass onevent inside the subscribe call.

    Events that are read from the cache will be called back immediately with relayURL === undefined.

    isAfterEose is true if the event was recieved from a relay after the EOSE message. isAfterEose is always false for cached events.

  • maxDelayms: Adding maxDelay option delays sending subscription requests, batching them and matching them after the events come back.

It's called maxDelay instead of delay, as subscribing with a maxDelay of 100ms and later subscribing with infinity time will reset the timer to 100ms delay.

The first implementation uses matchFilter (O(n^2)) for redistributing events that can be easily optimized if the abstraction is successful.

If it's used, the returned function doesn't do anything. It can't be used together with onEose.

  • onEose: called for each EOSE event received from a relay. Can't be used together with maxDelayms

    minCreatedAt contains the smallest created_at seen or Infinity if there were no events in the subscription.

  • options:

    • allowDuplicateEvents: by default duplicate events with the same id are filtered out. This option removes duplicate event filtering.

    • allowOlderEvents: if a subscription emitted an event with kind 0 or 3 (metadata / contacts), it doesn't allow emitting older events by default. This option overrides that filter.

    • logAllEvents: Log all events that are sent back to separate subscriptions. It can be a lot of events, so this option is only advised for application development, especially debugging.

    • unsubscribeOnEose: The most important option to use for past events with different queries (for example subscribing when the ids are known). the number of subscriptions on relays are limited, this option closes subscription on each relay when the relay sends EOSE event.

    • defaultRelays: if relays is undefined, sometimes no writeRelays can be found for the authors in the filters. In that case the subscription falls back to these passed defaultRelays

    • dontSendOtherFilters: other filters may have timeouts, but this subscription may be sent instantly, in this case this option can be used (for example for that doesn't have limits).

Return value:

Returns a function that stops sending more data with the onEvent callback. When all virtual subscriptions are unsubscribed, an unsubscribe request is sent to all relays.

 RelayPool::sendSubscriptions(onEose?: (events, relayURL) => void) : () => void

Sends subscriptions queued up with delayed subscriptions. It can be used after all subscriptions are requested (with some delay or Infinite delay).

  async getEventById(id: string, relays: string[], maxDelayms: number) : Promise<Event>

Gets one event by event id. Many similar subscriptions should be batched together. It is useful inside a component when many components are rendered.

Other API functions:

RelayPool::publish(event: Event, relays: string[])

RelayPool::onnotice(cb: (url: string, msg: string) => void)

RelayPool::onerror(cb: (url: string, msg: string) => void)

RelayPool::setWriteRelaysForPubKey(pubkey: string, writeRelays: string[])

    event: Event,
    onEvent: OnEvent,
    maxDelayms?: number,
    onEose?: OnEose,
    options: SubscriptionOptions = {}
  ): () => void

RelayPool::fetchAndCacheMetadata(pubkey: string): Promise<Event>

    event: Event,
    onEvent: OnEvent,
    maxDelayms?: number,
    onEose?: OnEose,
    options: SubscriptionOptions = {}
  ): () => void

RelayPool::setCachedMetadata(pubkey: string, metadata: Event)


Telegram: @AdamRitter


DEPRECIATED: Experimental API wrapper for RelayPool

All these are depreciated as they are not too useful abstractions in practice.

This is the first taste of an API wrapper that makes RelayPool easier to use. It's experimental (many methods haven't been tested at all) and subject to change significantly.

The first parameter is OnEvent, last parameter is always maxDelayms, and the middle parameter is limit if it's needed.

An unsubscribe function is returned, although it's not implemented yet.

 RelayPool::subscribeEventObject(filters: Filter & {relay?: string, noCache?: boolean},
                      relays: string[] | undefined,
                      onEventObject: (eventObject: EventObject, isAfterEose: boolean,
                          relayURL: string | undefined) => void,
                      maxDelayms?: number,
                      onEose?: (relayURL, minCreatedAt) => void,
                      options: {allowDuplicateEvents?: boolean, allowOlderEvents?: boolean,
                          logAllEvents?: boolean, unsubscribeOnEose: boolean} = {}
              ) : () => void

const pubkey =
const relays = [
const relayPool = new RelayPool();
const author = new Author(relayPool, relays, pubkey);
author.metaData(console.log, 0);
author.follows(console.log, 0);
author.followers(console.log, 0);
author.subscribe([{kinds: [Kind.Contacts]}], console.log, 0);
author.allEvents(console.log, 5, 0);
author.referenced(console.log, 5, 0);
author.followers(console.log, 50, 0);
author.sentAndRecievedDMs(console.log, 50, 0);
author.text(console.log, 10, 0);

new Author(relayPool: RelayPool, relays: string[], pubkey: string)

Author::metaData(cb: (event: EventObject) => void, maxDelayms: number): () => void

Author::subscribe(filters: Filter[], cb: OnEvent, maxDelayms: number): () => void

Author::followsPubkeys(cb: (pubkeys: string[]) => void, maxDelayms: number): () => void

Author::follows(cb: (authors: Author[]) => void, maxDelayms: number): () => void

Author::allEvents(cb: OnEventObject, limit = 100, maxDelayms: number): () => void

Author::referenced(cb: OnEventObject, limit = 100, maxDelayms: number): () => void

Author::followers(cb: OnEventObject, limit = 100, maxDelayms: number): () => void

Author::sentAndRecievedDMs(cb: OnEventObject, limit = 100, maxDelayms: number): () => void

Author::text(cb: OnEventObject, limit = 100, maxDelayms: number): () => void

collect(onEvents: (events: Event[]) => void): OnEvent  // Keeps events array sorted by created_at

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