Best practice for Provider instances for multiple and different types of block chain requests

[cdesch]

I was wondering what the best practice is in terms of using the ethers provider as either a singleton (or persistent instance) in a module or to create a new instance every time a request is made. For example, for a provider that is listening for block events with something like provider.on('block', async (blockNumber) => { it makes sense to use a single instance like the following:

import { ethers } from 'ethers';
import { NETWORK_ADDRESS, NETWORK_ADDRESS_WS } from './config';
import logger from './logger';

// Create the new provider
const provider = new ethers.providers.JsonRpcProvider(NETWORK_ADDRESS);

/**
 * Get the network provider
 * @return {ethers.provider} network provider
 */
export const getNetworkProvider = () => {
  return provider;
};

But let's say that our application also has an express endpoint that can query balances through something like await provider.getBalance(address); or sign and send a transaction with a signer like:

const provider = getNetworkProvider();
const wallet = new ethers.Wallet(senderPrivateKey, provider);
const tx = {
  ...
};
// Send transaction
return wallet.sendTransaction(tx);

Is it easier/harder to have create a new instance of the provider for these operations with const provider = new ethers.providers.JsonRpcProvider(NETWORK_ADDRESS); or use the ethers.getDefaultProvider(NETWORK_ADDRESS); each time?

It seems like that in situations where using you're performing event monitoring in the blockchain for blocks, transactions and contracts, the single persistent connection via one provider is the right answer. So, for the other types of queries should I be creating new instance of a provider each time? Or is there some magic inside the provider that is occurring where what I'm describing doesn't matter and everything can be done through one provider regardless?

Also, does the ethers.getDefaultProvider(NETWORK_ADDRESS) function return a new instance provider each time it is called or a shared instance? e.g.

const myProvider = ethers.getDefaultProvider(NETWORK_ADDRESS);

[zemse]

Is it easier/harder to have create a new instance of the provider for these operations with const provider = new ethers.providers.JsonRpcProvider(NETWORK_ADDRESS); or use the ethers.getDefaultProvider(NETWORK_ADDRESS); each time?

When you pass a network address to ethers.getDefaultProvider, it gives you a JsonRpcProvider, both are the same thing. Also if you already have an ethers provider, but want a provider with a different network address, you have to create a new provider. This should be fine but if that causes a performance issue to you, you may have to use a lower level API through ethers.utils.fetchJson for making JSON RPC calls to a network address.