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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
more ~/non-profit-blockchain/tmp/connection-profile/ngo-connection-profile.yaml

Check the config file used by app.js. Make sure the peer name in config.json (under 'peers:') is the same as the peer name in the connection profile. Also check that the admin username and password are correct and match the values you updated in the connection profile.

cd ~/non-profit-blockchain/ngo-rest-api
vi config.json

config.json should look something like this:

{
    "host":"localhost",
    "port":"3000",
    "channelName":"mychannel",
    "chaincodeName":"ngo",
    "eventWaitTime":"30000",
    "peers":[
        "peer1"
    ],
    "admins":[
       {
          "username":"admin",
          "secret":"Adminpwd1!"
       }
    ]
 }

Step 4 - Run the REST API Node.js application

On the Fabric client node.

Run the app (in the background if you prefer):

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

Step 5 - Test the REST API

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"}

POST a Donor

request:

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

Step 6 - Load the workshop test data

In your Cloud9 terminal.

You can do this step from anywhere as it accesses the ELB DNS endpoint. Executing this from the SSH session is challenging as the SSH session will be outputting a range of INFO logs, which makes it challenging to edit files. So you can open another terminal window in Cloud9 and load the test data from Cloud9.

Loading the test data uses cURL commands similar to those you used above to test the API. If you load the test data from Cloud9 you'll need to point to the AWS Elastic Load Balancer (ELB) that is used to expose your REST API (if you load the test data from your Fabric client node you could use 'localhost' as the endpoint since the REST API server is running on the Fabric client node). To find the DNS endpoint for the ELB, go to the CloudFormation stack created in Part 1 and look for ELBDNS in the Outputs. If you receive an error using the ELB it might be because the underlying EC2 instance has not moved to an 'InService' state. This will happen once the REST API server is running and the ELB is able to execute the desired number of health checks against it. You can check the status in the EC2 console, under Load Balancers.

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

The line to be changed is this one. It should point to your ELB DNS. (it could point to localhost if you run this on the Fabric client node. If you use localhost you also need to change the port to 3000):

export ENDPOINT=ngo10-elb-2090058053.us-east-1.elb.amazonaws.com
export PORT=80

After saving the changes, 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.