Chainlink External Adapter for writing to Ethereum-based Blockchains

This external adapter allows you to configure an endpoint and private key to sign and send transactions to external Ethereum-based blockchains.

A typical workflow of a Chainlink job for this external adapter could look like:

• Retrieve a piece of data from some data source
• Parse the desired field from that data source's response
• Utilize this adapter to write the value to ChainB
• Parse the transaction object from ChainB for the transaction hash
• Write the transaction hash from ChainB to ChainA

Install

npm install

Deploy & Test

• Run ganache-cli or some local blockchain with RPC enabled
• Set local environment variable URL to the RPC endpoint for that client. For example http://localhost:8545
• Set the local environment variable PRIVATE_KEY to the private key of a funded wallet. For example 0xde1673a55d14576f10f5223efbe6b1df771409eb3d51d24d3fb0e04bd615a619 (Ganache's default)
• Run:

node deploy_contract.js

The output should include a deployed contract address

• Set the local environment variable CONTRACT_ADDRESS to that address
• Run:

npm test

Verify the contract was written

• Run:

node read_contract.js

Create the zip

zip -r cl-ethtx.zip .

Install to AWS Lambda

• In Lambda Functions, create function
• On the Create function page:
  • Give the function a name
  • Use Node.js 8.10 for the runtime
  • Choose an existing role or create a new one
  • Click Create Function
• Under Function code, select "Upload a .zip file" from the Code entry type drop-down
• Click Upload and select the cl-ethtx.zip file
• Handler should remain index.handler
• Add the environment variable:
  • Key: URL
  • Value: RPC_Endpoint_To_Connect
  • Key: PRIVATE_KEY
  • Value: Your_Private_key
• Save

Install to GCP

• In Functions, create a new function, choose to ZIP upload
• Click Browse and select the cl-ethtx.zip file
• Select a Storage Bucket to keep the zip in
• Function to execute: gcpservice
• Click More, Add variable
  • NAME: URL
  • VALUE: RPC_Endpoint_To_Connect
  • NAME: PRIVATE_KEY
  • VALUE: Your_Private_key