Hyperion Stream Client

Streaming Client for Hyperion History API (v3+)

Usage

Supported Environments

• Node.js v16 and up
  • ES Module
  • CommonJS
• Browsers
  • ES Module - Angular, React and other frameworks
  • UMD

Quick Start

Installing via npm package

npm install @genesisblockid/hyperion-stream-client --save

Importing the client

ESM (Node and Browser):

import {HyperionStreamClient} from "@genesisblockid/hyperion-stream-client";

CommonJs (Node):

const {HyperionStreamClient} = require('@genesisblockid/hyperion-stream-client');

Browser library (served from public Hyperion APIs)

Without installing via npm, you can also load the webpack bundle directly:

<script src="https://<ENDPOINT>/stream-client.js"></script>

Where <ENDPOINT> is the Hyperion API (e.g. https://eos.hyperion.eosrio.io)

For other usages, the bundle is also available at dist/hyperion-stream-client.js

1. Connection

Set up the endpoint that you want to fetch data from:

const client = new HyperionStreamClient({
    endpoint: 'https://example.com',
    debug: true,
    libStream: false
});

https://example.com is the host, from where https://example.com/v2/history/... is served.

• set libStream to true if you want to enable a stream of only irreversible data. Don't forget to attach the handler using the method: setAsyncLibDataHandler(handler: AsyncHandlerFunction)
• set debug to true to print debugging messages

2. Making requests

to ensure the client is connected, requests should be made only after calling the client.connect() method, refer to examples below;

2.1 Action Stream - client.streamActions

client.streamActions(request: StreamActionsRequest): void

• contract - contract account
• action - action name
• account - notified account name
• start_from - start reading on block or on a specific date. 0=disabled means it will read starting from HEAD block.
• read_until - stop reading on block (0=disable) or on a specific date (0=disabled)
• filters - actions filter (more details below)

Notes

• Block number can be either positive or negative - E.g.: 700 (start from block 700)
• In case of negative block number, it will be subtracted from the HEAD - E.g.: -150 (since 150 blocks ago)
• Date format (ISO 8601) - e.g. 2020-01-01T00:00:00.000Z

import {HyperionStreamClient, StreamClientEvents} from "@genesisblockid/hyperion-stream-client";

const client = new HyperionStreamClient({
    endpoint: "http://localhost:1234",
    debug: true,
    libStream: false
});

client.on(StreamClientEvents.LIBUPDATE, (data: EventData) => {
    console.log(data);
});

client.on('connect', () => {
  console.log('connected!');
});

client.setAsyncDataHandler(async (data) => {
    console.log(data);
    // process incoming data, replace with your code
    // await processSomethingHere();
})

await client.connect();

client.streamActions({
  contract: 'vexcore',
  action: 'voteproducer',
  account: '',
  start_from: '2020-03-15T00:00:00.000Z',
  read_until: 0,
  filters: [],
});

2.1.1 Act Data Filters

You can set up filters to refine your stream. Filters should use fields following the Hyperion Action Data Structure, such as:

• act.data.producers (on vexcore::voteproducer)
• @transfer.to (here the @ prefix is required since transfers have special mappings)

Please refer to the mapping definitions to know which data fields are available

For example, to filter the stream for every transfer made to the vex.ramfee account:

client.streamActions({
    contract: 'vex.token',
    action: 'transfer',
    account: 'vexcore',
    start_from: 0,
    read_until: 0,
    filters: [
        {field: '@transfer.to', value: 'vex.ramfee'}
    ],
});

To refine even more your stream, you could add more filters. Remember that adding more filters will result in AND operations. For OR operations setup another request.

2.2 Delta Stream (contract rows) - client.streamDeltas

client.streamDeltas(request: StreamDeltasRequest): void

• code - contract account
• table - table name
• scope - table scope
• payer - ram payer
• start_from - start reading on block or on a specific date. 0=disabled means it will read starting from HEAD block.
• read_until - stop reading on block (0=disable) or on a specific date (0=disabled)

Example:

Referring to the same pattern as the action stream example above, one could also include a delta stream request

client.streamDeltas({
    code: 'vex.token',
    table: '*',
    scope: '',
    payer: '',
    start_from: 0,
    read_until: 0,
});

Note: Delta filters are planned to be implemented soon.

3. Handling Data

Incoming data handler is defined via the client.setAsyncDataHandler(async (data)=> void) method

if you set libStream to true another stream of only irreversible data will be available. Don't forget to attach the handler using the method: setAsyncLibDataHandler(handler: AsyncHandlerFunction)

data object is structured as follows:

• type - action | delta
• mode - live | history
• content - Hyperion Data Structure ( see action index and delta index templates)

client.setAsyncDataHandler(async (data) => {
    console.log(data);
    // process incoming data, replace with your code
    // await processSomethingHere();
})

// irreversible data stream only for when libStream: true on client connection setup
client.setAsyncLibDataHandler(async (data) => {
  console.log(data);
  // process incoming data, replace with your code
  // await processSomethingHere();
})

Useful information about load-balancing multiple Socket.IO servers: https://socket.io/docs/v4/using-multiple-nodes/#NginX-configuration