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Validator-Set-Tutorial-4.md

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Visualize misbehaviours

Now that we have two validators responsible for creating blocks on the network, we need to make sure they perform their task. Misbehaviour reporting is implemented in the contracts we've deployed, and it will allow any other validator to report misbehaviour as well as the users of the network such as Alice to see which node misbehaved.

1. Let Node0 be down

Let's shut down Node0 for a moment and see what happens for Alice. In this case I've shut it down at block #1001:

2018-09-30 19:21:00  Imported #1000 0xfae7…79a5 (0 txs, 0.00 Mgas, 0 ms, 0.57 KiB)
2018-09-30 19:21:05  Imported #1001 0xb5fd…e938 (0 txs, 0.00 Mgas, 0 ms, 0.57 KiB)
2018-09-30 19:21:07     1/25 peers   174 KiB chain 192 KiB db 0 bytes queue 21 KiB sync  RPC:  0 conn,    4 req/s,   64 µs
2018-09-30 19:21:15  Imported #1002 0xe083…0799 (0 txs, 0.00 Mgas, 0 ms, 0.57 KiB)
2018-09-30 19:21:25  Imported #1003 0xd185…58c4 (1 txs, 0.03 Mgas, 0 ms, 0.74 KiB)
2018-09-30 19:21:35  Imported #1004 0xd043…f833 (0 txs, 0.00 Mgas, 0 ms, 0.57 KiB)

Having a look at the block time, it went from every 5sec to every 10sec. This is expected as Node0 misses his turn and does not issue blocks anymore.

In the same time, having a look at Node1's console output shows the following:

2018-09-30 19:21:05  Imported #1001 0xb5fd…e938 (0 txs, 0.00 Mgas, 1 ms, 0.57 KiB)
2018-09-30 19:21:15  Reported benign validator misbehaviour 0xa292…d64a
2018-09-30 19:21:15  Imported #1002 0xe083…0799 (0 txs, 0.00 Mgas, 0 ms, 0.57 KiB)
2018-09-30 19:21:25  Reported benign validator misbehaviour 0xa292…d64a
2018-09-30 19:21:25  Transaction mined (hash 0x696a3876a68e129d82aa7c4ce67fae824a571ca9b0c6da522c7b854910595986)
2018-09-30 19:21:25  Imported #1003 0xd185…58c4 (1 txs, 0.03 Mgas, 0 ms, 0.74 KiB)
2018-09-30 19:21:30     1/25 peers   100 KiB chain 192 KiB db 0 bytes queue 17 KiB sync  RPC:  0 conn,    0 req/s,    0 µs

Node1 expected to receive a block from Node0, and as this did not happen, Node1 will report misbehaviours by sending a transaction to call ReportBenign function on RelaySet contract with the proof.

2. Track misbehaviours in a Dapp

The contract is emitting events for each misbehaviour. In Aura, there are currently two types of misbehaviours recognised and reported as stated in the specifications. It means that any user such as Alice can track the nodes misbehaving.

  • a benign misbehaviour is when a validator does not issue a block.
  • a malicious misbehaviour is when a validator tries to create a fork and issues two different blocks for a given step.

In this tutorial, we will track both but will only test the benign ones. To monitor the events from the contract, use the following javascript code saved in a file called watchEvent.js. It is based on web3.js. You will need to install web3.js library with npm.

"use strict";

const Web3 = require("web3");

const LOCAL_WS = "ws://localhost:8546";
let provider = new Web3.providers.WebsocketProvider(LOCAL_WS);
const web3 = new Web3(provider);

const log = (...args) => console.log(new Date(), ...args);
const error = (...args) => console.error(new Date(), ...args);

provider.on("error", error => error("WS error", error));
provider.on("end", error => {
  error("WS connection closed.");
});

const relayedOwnedSetAddress = "0x3D6f28e83e31bc475dEf77A0F01ECEDe4FBe2d22";
const from = "0x12db1ee91481573302f63ebf3d735820081c68a2";


(async () => {
  var relayedOwnedSetABI=[{"constant": true,"inputs": [],"name": "recentBlocks","outputs": [{"name": "","type": "uint256"}],"payable": false,"stateMutability": "view","type": "function"},{"constant": true,"inputs": [],"name": "getPending","outputs": [{"name": "","type": "address[]"}],"payable": false,"stateMutability": "view","type": "function"},{"constant": false,"inputs": [{"name": "_new","type": "address"}],"name": "setOwner","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": false,"inputs": [{"name": "_validator","type": "address"}],"name": "removeValidator","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": false,"inputs": [{"name": "_validator","type": "address"}],"name": "addValidator","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": false,"inputs": [{"name": "_reporter","type": "address"},{"name": "_validator","type": "address"},{"name": "_blockNumber","type": "uint256"},{"name": "_proof","type": "bytes"}],"name": "relayReportMalicious","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": false,"inputs": [],"name": "finalizeChange","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": false,"inputs": [{"name": "_recentBlocks","type": "uint256"}],"name": "setRecentBlocks","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": true,"inputs": [],"name": "owner","outputs": [{"name": "","type": "address"}],"payable": false,"stateMutability": "view","type": "function"},{"constant": true,"inputs": [],"name": "relaySet","outputs": [{"name": "","type": "address"}],"payable": false,"stateMutability": "view","type": "function"},{"constant": true,"inputs": [],"name": "finalized","outputs": [{"name": "","type": "bool"}],"payable": false,"stateMutability": "view","type": "function"},{"constant": true,"inputs": [],"name": "getValidators","outputs": [{"name": "","type": "address[]"}],"payable": false,"stateMutability": "view","type": "function"},{"constant": false,"inputs": [{"name": "_relaySet","type": "address"}],"name": "setRelay","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"constant": false,"inputs": [{"name": "_reporter","type": "address"},{"name": "_validator","type": "address"},{"name": "_blockNumber","type": "uint256"}],"name": "relayReportBenign","outputs": [],"payable": false,"stateMutability": "nonpayable","type": "function"},{"inputs": [{"name": "_relaySet","type": "address"},{"name": "_initial","type": "address[]"}],"payable": false,"stateMutability": "nonpayable","type": "constructor"},{"anonymous": false,"inputs": [{"indexed": false,"name": "currentSet","type": "address[]"}],"name": "ChangeFinalized","type": "event"},{"anonymous": false,"inputs": [{"indexed": true,"name": "reporter","type": "address"},{"indexed": true,"name": "reported","type": "address"},{"indexed": true,"name": "malicious","type": "bool"}],"name": "Report","type": "event"},{"anonymous": false,"inputs": [{"indexed": true,"name": "old","type": "address"},{"indexed": true,"name": "current","type": "address"}],"name": "NewOwner","type": "event"}]
  let relayedOwnedSet = new web3.eth.Contract(relayedOwnedSetABI, relayedOwnedSetAddress);
  relayedOwnedSet.events.Report()
    .on('data', event => {
      var isMalicious = (typeof(event.malicious)=="undefined" || event.malicious )? "no" : "yes" ;
      log("Reporter: " + event.returnValues.reporter + " Reported: " + event.returnValues.reported + " Malicious: "+ isMalicious);
    })
    .on('error', error => error("Report listener error", error));
})();

This code initiates a WebSockets connection to Alice's node and listens to the events emitted by the RelayedOwnedSet contract. As Node0 is currently offline, we can see that Node1 0x3278..3179E is sending reports about benign (non malicious) misbehaviors regarding Node0 0xA292..d64A. These are sent every 10sec:

$ node watchEvents.js
2018-09-30T17:57:55.025Z 'Reporter: 0x32784591C38Bf8aA081e96Ba4DB462BD73a3179E Reported: 0xA2922fEc00bb29FE13D68E87F64b9Ad1719Ed64A Malicious:  no'
2018-09-30T17:58:15.093Z 'Reporter: 0x32784591C38Bf8aA081e96Ba4DB462BD73a3179E Reported: 0xA2922fEc00bb29FE13D68E87F64b9Ad1719Ed64A Malicious:  no'

| ← Part 3 - Hardfork to use the Validator Set contract |