Listen for operations of a deployed contract

Question

Coming from an ethereum web3 background, I'm accustomed to listening for a contract's events to figure out when things happen in my contract and react accordingly in the application.

I'm looking for ways to do something similar with a tezos node and smart contract. Since there currently isn't any equivalent of emitting events on tezos, I was hoping there would be some way to get a list of operations for my contract KT1 address -- but that doesn't seem possible looking at the tezos-node RPC and taquito docs.

I've seen some tools like tzindex which seem like overkill for the problem I'm trying to solve. Looks like it can handle a contract's operations but it stores them historically and for all contracts on the chain.

The only thing that seems reasonable to me is to roll my own 'operation listener' to hear each block, and process/handle any operation if it involves my contract's address.

Is it possible to do this or something similar with a library like taquito? Is there another tool, option, or strategy that I'm missing?

Answer 1

After working with @taquito/rpc for a little while and having success there I also discovered in the main @taquito/taquito package there's some useful things you can subscribe to on the stream. A simple example to listen for new block hashes:

const tezos = new TezosToolkit("http://localhost:8732");
const blockSub = tezos.stream.subscribe("head");
blockSub.on("data", data => {
    console.log(data);
});

There's also something for listening to filtered operations, eg. at a contract's address:

tezos.stream.subscribeOperation({destination: 'KT1...'});

Answer 2

First, note that there is work in progress to implement on-chain events for Tezos: TZIP and MR.

At the moment however, I don't think you have a choice other than using an indexer. In addition to tzindex that you mentioned, there is also Nomadic Labs Tezos indexer.