@brandon.cs/bnjs

JsResolver Proof Of Concept

Playground repo to prototype JsResolvers

Project Setup

1. Install project dependencies

yarn install

2. If you want to use a private RPC provider,
   • Copy .env_example to init your own .env file

cp .env_example .env

• Complete your .env file with your private settings

Write a Js Resolver

• Create a new file in src/resolvers
• Register your resolver main function using JsResolverSdk.onChecker
• Example:

import { JsResolverSdk, JsResolverContext } from "../lib";
import { Contract, ethers } from "ethers";
import axios from "axios";

const ORACLE_ABI = [
  "function lastUpdated() external view returns(uint256)",
  "function updatePrice(uint256)",
];

JsResolverSdk.onChecker(async (context: JsResolverContext) => {
  const { userArgs, gelatoArgs, secrets } = context;

  // Use default ethers provider or your own using secrets api key
  console.log('ChainId:', context.gelatoArgs.chainId)
  const rpcProvider = ethers.getDefaultProvider(context.gelatoArgs.chainId, {
    alchemy: await secrets.get("ALCHEMY_ID"),
  });

  // Retrieve Last oracle update time
  const oracleAddress = "0x6a3c82330164822A8a39C7C0224D20DB35DD030a";
  const oracle = new Contract(oracleAddress, ORACLE_ABI, rpcProvider);
  const lastUpdated = parseInt(await oracle.lastUpdated());
  console.log(`Last oracle update: ${lastUpdated}`);

  // Check if it's ready for a new update
  const nextUpdateTime = lastUpdated + 300; // 5 min
  const timestamp = gelatoArgs.blockTime;
  console.log(`Next oracle update: ${nextUpdateTime}`);
  if (timestamp < nextUpdateTime) {
    return { canExec: false, message: `Time not elapsed` };
  }

  // Get current price on coingecko
  const currency = "ethereum";
  const priceData = await axios.get(
    `https://api.coingecko.com/api/v3/simple/price?ids=${currency}&vs_currencies=usd`
  );
  const price = Math.floor(priceData.data[currency].usd);
  console.log(`Updating price: ${price}`);

  // Return execution call data
  return {
    canExec: true,
    callData: oracle.interface.encodeFunctionData("updatePrice", [price]),
  };
});

• create your resolver schema.json to specify your runtime configuration:

{
  "jsResolverVersion": "1.0.0",
  "runtime": "node-18",
  "memory": 128, 
  "timeout": 60,
  "userArgs": {}
}

Test your resolver

• Use yarn test FILENAME command to test your resolver

• Options:

  • --show-logs Show internal Resolver logs
  • --runtime=thread|docker Use thread if you don't have dockerset up locally (default: docker)
  • --debug Show Runtime debug messages
  • --user-args=[key]:[value] Set your Resolver user args

• Example: yarn test src/resolvers/index.ts --show-logs --runtime=thread

• Output:

  JsResolver Build result:
  ✓ File: ./.tmp/resolver.cjs
  ✓ File size: 1.70mb
  ✓ Build time: 109.93ms
  
  JsResolver running logs:
  > ChainId: 5
  > Last oracle update: 1665512172
  > Next oracle update: 1665512472
  > Updating price: 1586
  
  JsResolver Result:
  ✓ Return value: {
    canExec: true,
    callData: '0x8d6cc56d0000000000000000000000000000000000000000000000000000000000000632'
  }
  
  JsResolver Runtime stats:
  ✓ Duration: 5.41s
  ✓ Memory: 57.77mb
  

Upload / fetch Js Resolver

Use yarn upload FILENAME command to upload your resolver.

> yarn upload ./src/resolvers/index.ts

## Use User arguments
1. Declare your expected `userArgs` in you schema, accepted types are 'string', 'number' or 'float':
```json
{
  "jsResolverVersion": "1.0.0",
  "runtime": "node-18",
  "memory": 128, 
  "timeout": 60,
  "userArgs": {
    "currency": "string",
    "oracle": "string"
  }
}

2. Access your userArgs from the JsResolver context:

JsResolverSdk.onChecker(async (context: JsResolverContext) => {
  const { userArgs, gelatoArgs, secrets } = context;

  // User args:
  console.log('Currency:', userArgs.currency)
  console.log('Oracle:', userArgs.oracle)
  
});

1. Pass user-args to the CLI to test your resolver:

yarn test src/resolvers/oracle/index.ts --show-logs --user-args=currency:ethereum --user-args=oracle:0x6a3c82330164822A8a39C7C0224D20DB35DD030a

Benchmark / Load testing

• Use yarn benchmark FILENAME command to run a test load

• Options:

  • all test command options
  • --load=100 configure the number of resolver you want to run for your load test (default: 10)
  • --pool=10 configure the pool size, ie max number of concurrent worker (default: 10)

• Example: yarn benchmark src/resolvers/index.ts --load=100 --pool=10

• Output:

  Benchmark result:
  - nb success: 100/100
  - duration: 64s
  

Failure tests

Some example failing file to test error handling

• Syntax error in the resolver:

  • Run: yarn test src/resolvers/fails/syntax-error.js
  • Result:

  JsResolver building...
  ✘ [ERROR] Could not resolve "nothing"
  
      src/resolvers/fails/syntax-error.js:1:30:
        1 │ import { JsResolverSdk } from "nothing";
          ╵                               ~~~~~~~~~
  
    You can mark the path "nothing" as external to exclude it from the bundle, which will remove this
    error.
  
  
  JsResolver Build result:
  ✗ Error: Build failed with 1 error:
  src/resolvers/fails/syntax-error.js:1:30: ERROR: Could not resolve "nothing"
  

• No checker function registered in the resolver:

  • Run: yarn test src/resolvers/fails/not-registered.ts
  • Result:

  JsResolver Result:
  ✗ Error: JsResolver start-up timeout (5s)
  Make sure you registered your checker function correctly in your script.
  

• Resolver run out of memory:

  • Run: yarn test src/resolvers/fails/escape-memory.ts
  • Result

  JsResolver Result:
  ✗ Error: JsResolver sandbox exited with code=137
  
  JsResolver Runtime stats:
  ✓ Duration: 1.91s
  ✗ Memory: 31.97mb
  

• Resolver exceed timeout:

  • Run: yarn test src/resolvers/fails/escape-timeout.ts
  • Result:

  JsResolver Result:
  ✗ Error: JsResolver exceed execution timeout (10s)
  
  JsResolver Runtime stats:
  ✗ Duration: 10.97s
  ✓ Memory: 25.34mb
  

• Resolver ends without returning result:

  • Run: yarn test src/resolvers/fails/no-result.js
  • Result:

  JsResolver Result:
  ✗ Error: JsResolver exited without returning result