/stakehound

Primary LanguageTypeScript

StakeHound Challenge

Goal

The goal of this application is to continuously listen for transactions of the ETH token on the Ethereum blockchain (Ropsten) going to a specified address, and perform a set of actions for every incoming transaction.

Installation and Running

This application requires Node.js to run.

Install the dependencies and start the server:

$ npm update
$ nodemon @param1 @param2 @param3

where:

@param1 = 'watch' address to listen for incoming transactions. It must be a valid address (0x...)

@param2 = 'custody' address to transfer ETH tokens. It must be a valid address (0x...)

@param3 = time interval in seconds to fetch the incoming transactions to the 'watch address'. It will be 60 seconds by default if no value is defined by parameter.

Execution example:

$ nodemon 0xb5bE4d2510294d0BA77214F26F704d2956a99072 0xc350d1EA93258BC789CEc0FbE283Dc0BA5f5A899 5

The output files will be stored in src/out:

  • MINT.txt with the following content: MIND [amount] [sender_address]

  • SEND.txt with the following content: SEND [amount] [custody_address]

Testing

In order to launch the tests:

$ npm test

At the time of writing, 9 tests have been performed in 1,7s:

  • Test Suites: 1 passed, 1 total
  • Tests: 8 passed, 8 total
  • Snapshots: 0 total
  • Time: 1.723 s, estimated 2 s

Technical Considerations

  • In order to listen for incoming transactions, a 'setInterval' is executed every N seconds:

    setInterval(function () { manageTX() }, params.timer);

  • The application will be always up & running execept if the URL for fetching transactions gives an 404 error.

  • If the application stops due to any unforeseen event (server down, atomic bomb, space invaders...), all transactions will be retrieved from block 0 when restarting the app; therefore, files MINT.txt and SEND.txt will be recreated including any transaction between the downtime period and the current date.

    • Depending on the services that listen for changes in files MINT.txt and SEND.txt, it might be recommended to have a log to track all transactions already handled in order to avoid any potential double processing when the two files are recreated.

  • In order to ensure the application availability, it is highly recommended to use a process manager such as 'pm2' to launch the process in background and restart it in case the server reboots:

$ npm i pm2 -g
$ pm2 start nodemon --name "stakehound deamon"
$ pm2 startup
$ pm2 save

Identified Enhancements

  • If the application is launched in background, all 'console.log' should be replaced by logging errors and warnings into files to further analysis.
  • The tests cover a set of overall cases, but a few more are probably recommended (e.g.: mocking fs.createWriteStream)
  • Verify the address checksum with web3.toChecksumAddress(address);

Conclusion

It's been a great challenge!! Looking forward for new ones 😃