Power Automate: Deploy and Execute an Ethereum Smart Contract

Power Automate (aka. Microsoft Flow) is a great cloud-based tool to automate all possible tasks. There is a Ethereum connector (Beta) that can be used to deploy a Smart Contract to an Ethereum Blockchain network and execute functions.

Ethereum Network

You need to connect to an Ethereum network. There is a fully managed Blockchain Service in Azure. I’m running my private network with Proof-of-Authority. At the Azure management portal, go to the transaction node to get the required information to connect.

Smart Contract

I’m using Visual Studio Code with the Ethereum Blockchain Development SDK to implement a Smart Contract in Solidity. You can find the link to the SDK at the Azure Blockchain Service portal.

The SDK requires a lot of other software products to download and install. I found that the solidity compiler installed was newer than expected. As result the demo smart contract you get from the SDK did not compile. The simplest solution was to change the pragma of the contract

pragma solidity >= 0.5.16 <= 0.7.0;

ABI and Bytecode

In order to automate the deployment of a Smart Contract via Power Automate you need to provide the ABI and Bytecode. Both can be found in VS Code, at the build directory in the context menu.

Power Automate

You can directly provide the ABI and Bytecode in the Deploy Smart Contract action. However, I decided to place both in an Azure Table Storage and fetch it from there. To do so, I create a table with a column for the Bytecode, a column for the ABI and a name.

The first step in my flow is to connect to the Azure Storage account and get the smart contract I need. The result from the storage is a JSON string which is parsed so the ABI and Bytecode is available for the next steps

Next the Deploy Smart Contract action is used to deploy the contract. There you need to provide the connection to your Ethereum network. In my example there are two parameters for the constructor and for testing purpose these values are hardcoded. In real life you would provide values from the calling sources. The third parameter for the connector action requires the Bytecode which is taken from the storage account. The result from the deployment is the smart contracts address which is stored in a flow variable.

Interacting with the smart contract

After the Smart Contract has been deployed to the Ethereum Blockchain Network, use the Execute Smart Contract Function action in the flow. For each step you have to provide the address, the ABI, the name of function and the parameter as JSON string. A function without parameters has to be called with {} because the parameter property is mandatory.

Here is an example for a function with some parameters. These parameters have to be provided as JSON string in Flow.

function SetupMachine(int sawLength, 
                      int waterTemp, 
                      int rpm,
                      int speed) public
    {
        if (State != StateType.Assigned)
        {
            revert('Assign to a machine first');
        }

        SawLengthMM = sawLength;
        WaterTempDgrC = waterTemp;
        ExtruderRPM = rpm;
        ExtruderSpeed = speed;

        State = StateType.Setup;
        Worker = msg.sender;
    }