Live Cache for Decentraweb

One of the main features of Decentraweb is resolving domain names to Ethereum addresses and addresses to names. Normally, this is done by querying the Ethereum blockchain. In some cases, this can be slow, especially with batch operations. This package allows you to create Redis cache that will be updated automatically by listening on conract events.

Installation

npm install --save @decentraweb/dweb-live-cache
#OR
yarn add @decentraweb/dweb-live-cache

Instantiating the cache

To start using the cache, you need to instantiate it. The cache is a class that takes 3 parameters:

1. provider - an instance of ethers.js provider
2. redisUrl - a URL to the Redis server
3. keyPrefix - refix that will be added to all Redis keys

import { DWEBIndex } from '@decentraweb/dweb-live-cache';
const provider = new providers.WebSocketProvider('wss://example.com/0000000000000000000000000000000', 'mainnet');
const dwebIndex = new DWEBIndex(provider, 'redis://localhost:6379', 'dweb-cache');

Seeding the cache

When starting new cache instance, you need to pre-populate it with initial data. This can be done by calling seed method:

import { DWEBIndex } from '@decentraweb/dweb-live-cache';
const provider = new providers.WebSocketProvider(WS_URL, ETH_NETWORK);
const dwebIndex = new DWEBIndex(provider, REDIS_URL, REDIS_PREFIX);
await dwebIndex.seedCache();

Listening for events

For each cache instance you need to have one process that will listen for events and update the cache. You can run live-cache-service app from our repo or write your own script that will instantiate the cache and call start method:

import { DWEBIndex } from '@decentraweb/dweb-live-cache';
const provider = new providers.WebSocketProvider(WS_URL, ETH_NETWORK);
const dwebIndex = new DWEBIndex(provider, REDIS_URL, REDIS_PREFIX);

dwebIndex.start().then(() => {
  console.log('Started processing eth blocks');
});

Notes:

1. Make sure to have only one listener per cache instance.
2. Receiving events is crucial for cache reliability. So if no block events received for 30 seconds, cache will throw an error as it means that connection to the blockchain is lost.

After calling start, cache will check which block was last processed and will start processing from that block until the latest one. Also cache class will subscribe to block event on contract. On each new block it will query DWEB PublicResolver and DefaultReverseResolver contract events to detect changes in Ethereum address assignment.

Using the cache

To query data, you can create multiple instances of DWEBIndex class. There are 2 main methods:

1. resolveAddress(address: string, forceRefresh?: boolean): Promise<AddressResolution> - to resolve Ethereum address to name
2. resolveName(name: string, forceRefresh?: boolean): Promise<string | null> - to resolve name to Ethereum address forceRefresh parameter is optional and can be used to force class to query the blockchain instead of using cached data.

import { DWEBIndex } from '@decentraweb/dweb-live-cache';
const provider = new providers.WebSocketProvider(WS_URL, ETH_NETWORK);
const dwebIndex = new DWEBIndex(provider, REDIS_URL, REDIS_PREFIX);

const address = await dwebIndex.resolveName('notyourbro');
// returns '0xcB3E45F337Dd3Beeba98F5F9F9A16e9cD152cC86'
const nameResult = await dwebIndex.resolveAddress('0xcB3E45F337Dd3Beeba98F5F9F9A16e9cD152cC86');
// returns { name: 'notyourbro', confirmed: true }

Note: Address to name resolution includes so-called "forward check". When user is creating reverse resolution record for their wallet, they can assign any random name. To confirm that the name is actually owned by the user, we resolve name to Ethereum address and check that it matches the address we are resolving. confirmed flag in result is indicating if forward check was successful.