Tx-server only availably locally - how to run a lite node?

[ameeuw]

Hi everybody. So far I have been using lotion locally to develop my application. I recently deployed it to two EC2 instances and found out two things:

The express tx-server is run with 'localhost' as host and therefore only available on the host itself. Now that I need to have clients sending transactions and not being full validator nodes I have two options:

1) Run the tx-server openly on a port for clients to send their transactions to the lotion application. (probably a security issue) 2) Run a lite node on the client side and submit transactions via a local tx-server (currently not working for me)

I have tried to run a lite node but have not been successful. It seems that the supercop module is crashing. Is there a step that I have to include other than running lotion as lite and giving it the GCI as a target?

As I actually have all the information (genesis etc.) from the chain - is there a way to run a light client without utilising the GCI and the bittorrent magic behind it?

Is opening a tx-server to the 'public' and using it as an end-point for my clients a wrong pattern?

Thank you very much.

[keppel]

hey Arne! great question, the docs are a bit behind on this one.

you can skip the GCI / bittorrent magic like this:

let { connect } = require('lotion')

let genesis = require('./genesis.json')
let ip = '159.89.140.7'
let tendermintPort = '41763'
let nodes = [  `ws://${ip}:${tendermintPort}` ] 

async function main() {
  let { state } = await connect(null, { genesis, nodes })
  console.log(await state) // { count: 0 }
}

main()

running a lite node with the same http interface as a local full node used to be supported, and the http servers used to listen publicly by default. I changed this because it encouraged people to build apps that blindly trust full nodes they didn't control, and there are very few situations where that's a good idea.

by using the connect() API, all the tendermint headers get verified in JavaScript, and the client verifies a merkle proof of the queried part of the state to make sure the full node can't send you back an invalid response.

hope that helps :)

[ameeuw]

Thank you - I will try it as soon as I find the time.

[ameeuw]

Hey @keppel - I tried setting it up like you suggested. The script keeps on failing as it can't parse a json. I found something I cannot quite make sense of (index.js line:313)

getState: async function(path = '') {
    let queryResponse = await axios.get(
        `${fullNodeRpcAddress}/abci_query?path="${path}"`
    )
    let resp = queryResponse.data.result.response
    resp.height = Number(resp.height)
    let proof = parse(Buffer.from(resp.proof, 'hex').toString())
    await waitForHeight(resp.height, lc)
    let rootHash = appHashByHeight[resp.height].toLowerCase()
    let verifiedValue = merk.verify(rootHash, proof, path)
    return verifiedValue
}

The code tries to compute the appHash from the height and tries to get the proof via the abci. It is then trying to parse the resp.proof as a hex encoded JSON. The proof however only includes a number and the JSON including the state is only within the resp.value.

Am I missing something completely?

By the way: its really nice some serious development is going on in this repo! I support you wherever I can.

[keppel]

I think your full node might be running an older version of Lotion

[ameeuw]

Yep that seemed to be one issue.. now that I updated them I am running into the problem that the response from the abci query only yields this:

{ code: 2,
  index: '0',
  key: '',
  value: '',
  proof: '',
  height: 0,
  log: 'invalid query: Cannot read property \'key\' of null' }

It seems like the abci_query with path=' ' does not yield any proper response. Am I missing something again?

[keppel]

hey Arne, are you still getting this? can you post the code that you're using to do this query? is the client also on the latest version of Lotion?

[SaifRehman]

facing the same issue

[keppel]

ok, this should be fixed in v0.1.15.

[ameeuw]

Yep - works for me. Thanks so much for your effort.

[SaifRehman]

@ameeuw how did you fix it? I am facing issue to run access lotiontx port on a container