How to use Chainlink Function on Outerbridge

What is Chainlink Function

Chainlink Functions provides your smart contracts with access to a trust-minimized compute infrastructure. Your smart contract sends your code to a Decentralized Oracle Network (DON), and each DON’s oracle runs the same code in a serverless environment.

The DON aggregates all the independent runs and returns the final result to your smart contract. Your code can be anything from simple computation to fetching data from API providers.

Read more on the docs page. If you want to get more ideas, here's the example functions put together by the community.

Why use Outerbridge

Chainlink Function has made developers life easier, allowing us to execute Javascript code from smart contract on-chain. However, there are some caveats:

• ❌ Hassle of reading 3rd party API docs to implement API calls
• ❌ Side effect on building non-idempotent requests, such as sending an email or storing data on the cloud. Since each oracle node runs the same computation in the Off-chain Reporting protocol, it will cause redundant requests such as sending multiple emails or storing the same data multiple times.

Outerbridge was able to solve this by using sticky session-id, everytime an execution is sent, each oracle node will receive the same session-id, allowing Outerbridge to detect if they are sent from the same request, hence preventing multiple redundant requests. More technical implementation can be found from our official Github repo.

Outerbridge currently has 60+ integrations where users can just plug and play without having to code the entire API. Complex workflow involving multiple API providers can be easily built and configured.

• ✅ Prevent multiple redundant calls
• ✅ 60+ API integrations and growing
• ✅ Ability to build complex workflows
• ✅ Open source

In this post, we are going to take a look at how to trigger a workflow in Outerbridge by making a HTTP call using Chainlink Function.

Let's get started 🚀🚀🚀

Step 1: Building Workflow

Here's a simple workflow that is going to send a Discord message and return the message as a response upon completion.

The GOAL is to trigger this workflow using Chainlink Function.

1. Chainlink Function Webhook: Trigger workflow upon receiving the webhook call
2. Discord: Send discord message to channel. (Replace with your channel's webhook URL)
3. NodeJS: Return the message that was posted as final response

Click Deploy to activate the workflow.

Step 2: Trigger workflow using Chainlink Function

We are going to use the forked Chainlink Functions Starter Kit with Hardhat to set up on-chain contracts, test request, and send request to be fulfilled by the Chainlink Functions Decentralized Oracle Network (DON).

1. In a terminal, clone the forked Chainlink Functions Starter Kit repository.

2. cd functions-hardhat-starter-kit/
   

3. Switch to correct branch:

   git checkout feature/Outerbridge-Webhook
   

4. npm install
   

5. Configure .env file:

   touch .env && open .env
   

   We are going to use Mumbai testnet:

   MUMBAI_RPC_URL="https://rpc.ankr.com/polygon_mumbai"
   PRIVATE_KEY="<YOUR_PRIVATE_KEY>"
   

6. Compile the contracts in the repository:

   npx hardhat compile
   

7. In Functions-request-config.js file, search for messageToSend and replace with whatever message that you like to post on Discord.

8. In Functions-request-source.js file line 10, replace url: https://app.outerbridge.io/api/v1/webhook/7ylldwflap7630p with your webhook URL. You can grab the webhook URL from Outerbridge:

   • Use the Tunnel URL when running Outerbridge locally:

   • Use the Webhook URL when using Cloud-hosted Outerbridge

9. Simulate the request:

   npx hardhat functions-simulate
   

   You should be able to see the message successfully posted on Discord channel.

10. Follow guides to configure on chain resources.

11. Finally, run the request. Specify your subscription ID with the --subid flag and specify your consumer contract address with the --contract flag:

    npx hardhat functions-request --subid YOUR_SUBSCRIPTION_ID --contract YOUR_CONSUMER_CONTRACT_ADDRESS --network mumbai
    

    If success, you should be able to see the following output:

    If all 100000 callback gas is used, this request is estimated to cost 0.200173241062964508 LINK
    Continue? (y) Yes / (n) No
    y
    
    Requesting new data for FunctionsConsumer contract 0x5F5063DaE69d1b3eaE4D2409e09246D5892c714D on network mumbai
    Waiting 2 blocks for transaction 0xd10ea65017e2b688aabd18265172ff4770297eca87dcdd2cb7a0181a90796ca8 to be confirmed...
    
    Request 0xd8cfb094958b5417e07e768f849d1e220faf55459f64c7a2a6dde660454ac454 initiated
    Waiting for fulfillment...
    
    Request 0xd8cfb094958b5417e07e768f849d1e220faf55459f64c7a2a6dde660454ac454 fulfilled!
    Response returned to client contract represented as a hex string: 0x5b7b2264617461223a2248657920446973636f726421227d5d
    Decoded as a string: [{"data":"Hey Discord!"}]
    
    Transmission cost: 0.001431547524481958 LINK
    Base fee: 0.0 LINK
    Total cost: 0.201431547524481958 LINK
    

🎉 That's it! You have successfully:

• ✅ Built a workflow that send message to Discord, and return the message as final result back to your smart contract
• ✅ Made a HTTP POST to webhook URL from Chainlink Function
• ✅ Triggered the workflow