Documentation
Utilities
Transports

Transports

The @ponder/utils package exports two new Viem Transports, loadBalance and rateLimit.

These Transports are useful for managing the RPC request workloads that Ponder apps commonly encounter.

Load balance

The loadBalance Transport distributes requests across a list of inner Transports in a simple round-robin scheme.

Usage

import { loadBalance } from "@ponder/utils";
import { createPublicClient, fallback, http, webSocket } from "viem";
import { mainnet } from "viem/chains";
 
const client = createPublicClient({
  chain: mainnet,
  transport: loadBalance([
    http("https://cloudflare-eth.com"),
    http("https://eth-mainnet.public.blastapi.io"),
    webSocket("wss://ethereum-rpc.publicnode.com"),
    rateLimit(http("https://rpc.ankr.com/eth"), { requestsPerSecond: 5 }),
  ]),
});

Usage in Ponder

For convenience, @ponder/core re-exports loadBalance from @ponder/utils.

ponder.config.ts
import { createConfig, loadBalance } from "@ponder/core";
import { http } from "viem";
 
export default createConfig({
  networks: {
    mainnet: {
      chainId: 1,
      transport: loadBalance([
        http("https://cloudflare-eth.com"),
        http("https://eth-mainnet.public.blastapi.io"),
        webSocket("wss://ethereum-rpc.publicnode.com"),
        rateLimit(http("https://rpc.ankr.com/eth"), { requestsPerSecond: 5 }),
      ]),
    },
  },
  contracts: {
    // ...
  },
});

Parameters

Transports

Type: Transport[] (required)

A list of Transports to load balance requests across.

Rate limit

The rateLimit Transport limits the number of requests per second submitted to an inner Transport using a first-in-first-out queue.

Usage

import { rateLimit } from "@ponder/utils";
import { createPublicClient, fallback, http } from "viem";
import { mainnet } from "viem/chains";
 
const client = createPublicClient({
  chain: mainnet,
  transport: rateLimit(http("https://eth-mainnet.g.alchemy.com/v2/..."), {
    requestsPerSecond: 25,
  }),
});

Usage in Ponder

For convenience, @ponder/core re-exports rateLimit from @ponder/utils.

ponder.config.ts
import { createConfig, rateLimit } from "@ponder/core";
import { http } from "viem";
 
export default createConfig({
  networks: {
    mainnet: {
      chainId: 1,
      transport: rateLimit(http(process.env.PONDER_RPC_URL_1), {
        requestsPerSecond: 25,
      }),
    },
  },
  contracts: {
    // ...
  },
});

Parameters

Transport

Type: Transport (required)

An inner transport to rate limit.

requestsPerSecond

Type: number (required)

browser

Type: boolean (default: true)

If false, the internal queue will use the Node.js-specific process.nextTick() API to schedule requests. This leads to more predictable behavior in Node.js, but is not available in the browser.

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