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Part 3: RESTful API to expose the Chaincode

The RESTful API is a Node.js application that uses the Fabric SDK to interact with the Fabric chaincode and exposes the chaincode functions as REST APIs. This allows loose coupling between the UI application and the underlying Fabric network.

Pre-requisites

For the Fabric workshop, the REST API server will run on the Fabric client node.

From Cloud9, SSH into the Fabric client node. The key (i.e. the .PEM file) should be in your home directory. The DNS of the Fabric client node EC2 instance can be found in the output of the AWS CloudFormation stack you created in Part 1

ssh ec2-user@<dns of EC2 instance> -i ~/<Fabric network name>-keypair.pem

You should have already cloned this repo in Part 1

cd ~
git clone https://github.com/aws-samples/non-profit-blockchain.git

You will need to set the context before carrying out any Fabric CLI commands. We do this using the export files that were generated for us in Part 1

Source the file, so the exports are applied to your current session. If you exit the SSH session and re-connect, you'll need to source the file again. The source command below will print out the values of the key ENV variables. Make sure they are all populated. If they are not, follow Step 4 in Part 1 to repopulate them:

cd ~/non-profit-blockchain/ngo-fabric
source fabric-exports.sh

Step 1 - Install Node

On the Fabric client node.

Install Node.js. We will use v8.x.

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.0/install.sh | bash

. ~/.nvm/nvm.sh
nvm install lts/carbon
nvm use lts/carbon

Amazon Linux seems to be missing g++, so:

sudo yum install gcc-c++ -y

Step 2 - Install dependencies

On the Fabric client node.

cd ~/non-profit-blockchain/ngo-rest-api
npm install

Step 3 - Generate a connection profile

On the Fabric client node.

The REST API needs a connection profile to connect to the Fabric network. Connection profiles describe the Fabric network and provide information needed by the Node.js application in order to connect to the Fabric network. The instructions below will auto-generate a connection profile.

Generate the connection profile using the script below and check that the connection profile contains URL endpoints for the peer, ordering service and CA, an 'mspid', a 'caName', and that the admin username and password match those you entered when creating the Fabric network. If they do not match, edit the connection profile and update them. The connection profile can be found here: ~/non-profit-blockchain/tmp/connection-profile/ngo-connection-profile.yaml

cd ~/non-profit-blockchain/ngo-rest-api/connection-profile
./gen-connection-profile.sh
cd ~/non-profit-blockchain/tmp/connection-profile/
cat ngo-connection-profile.yaml

Step 4 - Run the REST API Node.js application

On the Fabric client node.

Run the app:

cd ~/non-profit-blockchain/ngo-rest-api
nvm use lts/carbon
node app.js

Step 5 - Test the REST API

Open a new terminal pane within Cloud 9. Click on Window -> New Terminal.

From the new terminal, SSH into the Fabric cilent node.

export REGION=us-east-1
export STACKNAME=$(aws cloudformation describe-stacks --region $REGION --query 'Stacks[?Description==`Amazon Managed Blockchain. Creates network with a single member and peer node`] | [0].StackName' --output text)
export NETWORKNAME=$(aws cloudformation describe-stacks --stack-name $STACKNAME --region $REGION --query 'Stacks[0].Outputs[?OutputKey==`NetworkName`].OutputValue' --output text)
export EC2URL=$(aws cloudformation describe-stacks --stack-name ngo-fabric-client-node --query "Stacks[0].Outputs[?OutputKey=='EC2URL'].OutputValue" --output text --region $REGION)
ssh ec2-user@$EC2URL -i ~/$NETWORKNAME-keypair.pem

On the Fabric client node.

Once the app is running you can register an identity, and then start to execute chaincode. The command below registers a user identity with the Fabric CA. This user identity is then used to run chaincode queries and invoke transactions.

Register/enroll a user:

request:

curl -s -X POST http://localhost:3000/users -H "content-type: application/x-www-form-urlencoded" -d 'username=michael&orgName=Org1'

response:

{"success":true,"secret":"","message":"michael enrolled Successfully"}

If you encounter an error such as {"code":20,"message":"Authorization failure"}, it is likely because the admin credentials in config.json above are incorrect. Update those and restart the REST API server that is running in the other terminal.

POST a Donor

request:

curl -s -X POST "http://localhost:3000/donors" -H "content-type: application/json" -d '{ 
   "donorUserName": "edge2", 
   "email": "edge2@def.com", 
   "registeredDate": "2018-10-22T11:52:20.182Z" 
}'

response: A transaction ID, which can be ignored:

{"transactionId":"2f3f3a85340bde09b505b0d37235d1d32a674e43a66229f9a205e7d8d5328ed1"}

Get all donors

request:

curl -s -X GET   "http://localhost:3000/donors" -H "content-type: application/json"

response:

[
    {"docType":"donor","donorUserName":"edge","email":"edge@def.com","registeredDate":"2018-10-22T11:52:20.182Z"}
]

Step 6 - Load the workshop test data

On the Fabric client node.

Loading the test data uses cURL commands similar to those you used above to test the API. This step outputs a lot of text as it is creating the test data, so if you prefer to run this from a new terminal, you can open a new Cloud 9 terminal and SSH into the Fabric client node to create a new terminal session. If you do this, remember to rerun the statements under Pre-requisites above.

To run the script:

cd ~/non-profit-blockchain/ngo-rest-api
./ngo-load-workshop.sh

Testing

The workshop runs the REST API server on the Fabric client node. If you exit the SSH session on the Fabric client node, the running REST API server will automatically exit. You would need to restart it after SSH'ing back into the Fabric client node.

For purposes of the workshop we can just leave the SSH session open. However, if we need to keep the REST API application running after we exit the SSH session, we can use various methods to do this. I use PM2, using a command such as pm2 start app.js, which will keep the app running. The logs can be found in ~/.pm2/logs.

Move on to Part 4

The workshop instructions can be found in the README files in parts 1-4:

  • Part 1: Start the workshop by building the Hyperledger Fabric blockchain network using Amazon Managed Blockchain.
  • Part 2: Deploy the non-profit chaincode.
  • Part 3: Run the RESTful API server.
  • Part 4: Run the application.
  • Part 5: Add a new member to the network.
  • Part 6: Read and write to the blockchain with Amazon API Gateway and AWS Lambda.