Blockchain / Let's Create Your First Blockchain with BDK!
===================================================

Hey everyone! I wonder if you've noticed this news - Bitcoin recently hit a historic high, and Ethereum, which was previously showing weak trends, has strongly surged nearly thirty points in just one week (as of July 17, 2025). Blockchain really is a fascinating thing, isn't it!? However, today I'm not here to discuss financial markets or cryptocurrencies with you, but to introduce a very interesting tool I recently discovered: "Blockchain Development Kits (BDK)". It's an open-source blockchain deployment tool released on GitHub by Cathay Financial Holdings' blockchain team, aimed at helping industry partners and cross-industry partners quickly deploy through convenient commands, further accelerating the promotion of consortium chains!

Below, we'll use Golang and Docker-Compose to build a Hyperledger Fabric network on Ubuntu and write a smart contract to enable the entire network to support reading and writing data.

Chapter 1: Network Architecture Overview
----------------------------------------

  graph TD
      subgraph "Orderer Organization"
          O1[orderer0:7050]
          O2[orderer1:7150]
          O1 <--> O2
      end

      subgraph "Org0"
          P01[peer0:7051_Anchor]
          P02[peer1]
      end

      subgraph "Org1"
          P11[peer0]
          P12[peer1:7151_Anchor]
      end

      subgraph "Channel: test"
          CC[fabcar chaincode v1]
      end

      %% Orderers serve the channel
      O1 -.-> CC
      O2 -.-> CC

      %% Peers join channel and run chaincode
      P01 --> CC
      P02 --> CC
      P11 --> CC
      P12 --> CC

      %% Peer gossip within orgs
      P01 <--> P02
      P11 <--> P12

      classDef orderer fill:#e1f5fe,stroke:#0277bd,stroke-width:2px
      classDef peer fill:#f3e5f5,stroke:#7b1fa2,stroke-width:2px
      classDef chaincode fill:#e8f5e8,stroke:#388e3c,stroke-width:2px
      classDef external fill:#fff3e0,stroke:#f57900,stroke-width:2px

      class O1,O2 orderer
      class P01,P02,P11,P12 peer
      class CC chaincode
      class P01,P12 external

Chapter 2: Fabric Network
-------------------------

:::danger
Before starting, please ensure that Golang, node.js, docker, and docker-compose are installed on your system!
:::

### 2.1 Compose Up Orderer & Peer

#### 2.1.1 Create `create.json` at `~/.bdk`

My configuration here is slightly different from the official documentation because during implementation, I found that the ports for `org0.peer0` and `org1.peer0` would conflict. Additionally, since we plan to use `org0.peer0` and `org1.peer1` as Anchor Peers later, I made the following modifications.

{
    "ordererOrgs": [
        {
            "name": "Org0Orderer",
            "domain": "orderer.org0.example.com",
            "enableNodeOUs": true,
            "hostname": [
                "orderer0",
                "orderer1"
            ],
            "ports": [
                {
                    "port": 7050,
                    "isPublishPort": true,
                    "operationPort": 8443,
                    "isPublishOperationPort": true
                },
                {
                    "port": 7150,
                    "isPublishPort": true,
                    "operationPort": 8543,
                    "isPublishOperationPort": true
                }
            ]
        }
    ],
    "peerOrgs": [
        {
            "name": "Org0",
            "domain": "org0.example.com",
            "enableNodeOUs": true,
            "peerCount": 2,
            "userCount": 1,
            "ports": [
                {
                    "port": 7051,
                    "isPublishPort": true,
                    "operationPort": 9443,
                    "isPublishOperationPort": true
                },
                {
                    "port": 7051,
                    "isPublishPort": false,
                    "operationPort": 9443,
                    "isPublishOperationPort": false
                }
            ]
        },
        {
            "name": "Org1",
            "domain": "org1.example.com",
            "enableNodeOUs": true,
            "peerCount": 2,
            "userCount": 1,
            "ports": [
                {
                    "port": 7051,
                    "isPublishPort": false,
                    "operationPort": 9443,
                    "isPublishOperationPort": false
                },
                {
                    "port": 7151,
                    "isPublishPort": true,
                    "operationPort": 9543,
                    "isPublishOperationPort": true
                }
            ]
        }
    ]
}

#### 2.1.2 Create Network Command

The logic of `bdk` command syntax design is:

BDK, please execute [what action] on [what thing] on [what platform]

$ bdk fabric network create -f create.json --create-full
# @~/.bdk/fabric

#### 2.1.3 Build Nodes with Interactive Mode

$ bdk fabric orderer up -i
$ bdk fabric peer up -i

### 2.2 Build & Join a Channel

# Org0's peer0 creates a new channel
export BDK_ORG_NAME='Org0'
export BDK_ORG_DOMAIN='org0.example.com'
export BDK_HOSTNAME='peer0'

bdk fabric channel create -i

# Org0's peer0 joins the channel
bdk fabric channel join -i

# Org0's peer1 joins the channel
export BDK_HOSTNAME='peer1'

bdk fabric channel join -i

# Org1's peer0 joins the channel
export BDK_ORG_NAME='Org1'
export BDK_ORG_DOMAIN='org1.example.com'
export BDK_HOSTNAME='peer0'

bdk fabric channel join -i

# Org1's peer1 joins the channel
export BDK_HOSTNAME='peer1'

bdk fabric channel join -i

For the interactive mode options, consistently choose:

✔ What is your channel name? › test
✔ Ordering service endpoint › orderer0.orderer.org0.example.com:7050

### 2.3 Set Up Anchor Peers

# Update Org0's anchor peer
export BDK_ORG_NAME='Org0'
export BDK_ORG_DOMAIN='org0.example.com'
export BDK_HOSTNAME='peer0'

bdk fabric channel update-anchorpeer -i

# Update Org1's anchor peer
export BDK_ORG_NAME='Org1'
export BDK_ORG_DOMAIN='org1.example.com'
export BDK_HOSTNAME='peer1'

bdk fabric channel update-anchorpeer -i

Chapter 3: Smart Contract
-------------------------

For detailed code, please refer to GitHub Repo: https://github.com/marvelcn015/bdk-fabcar

### 3.1 File Structure

chaincode/fabric/go/
├── go.mod              # Go module dependencies
├── main.go             # Chaincode entry point
├── fabcar.go           # Main chaincode structure and interface
├── business_logic.go   # Core business operations (CRUD)
├── queries.go          # Advanced query operations
├── utils.go            # Validation and utility functions
├── fabcar_test.go      # Comprehensive test suite
└── README.md           # This documentation

### 3.2 API Methods

#### 3.2.1 Initialize Chaincode

Function: Init
Description: Initializes the chaincode with sample car data

#### 3.2.2 Query Single Car

Function: queryCar
Arguments: [carKey]
Example: queryCar "CAR0"

#### 3.2.3 Query All Cars

Function: queryAllCars
Arguments: []
Example: queryAllCars

#### 3.2.4 Create New Car

Function: createCar
Arguments: [carKey, make, model, color, owner, year, price]
Example: createCar "CAR100" "BMW" "X5" "black" "John Doe" "2022" "75000"

#### 3.2.5 Update Car

Function: updateCar
Arguments: [carKey, make, model, color, owner, year, price]
Example: updateCar "CAR0" "Toyota" "Prius" "green" "Tomoko" "2018" "26000"

#### 3.2.6 Change Car Owner

Function: changeCarOwner
Arguments: [carKey, newOwner]
Example: changeCarOwner "CAR0" "Alice Smith"

#### 3.2.7 Delete Car

Function: deleteCar
Arguments: [carKey]
Example: deleteCar "CAR0"

#### 3.2.8 Query Cars by Owner

Function: queryCarsByOwner
Arguments: [ownerName]
Example: queryCarsByOwner "John Doe"

#### 3.2.9 Query Cars by Range

Function: queryCarsByRange
Arguments: [startKey, endKey]
Example: queryCarsByRange "CAR0" "CAR9"

#### 3.2.10 Get Car History

Function: getCarHistory
Arguments: [carKey]
Example: getCarHistory "CAR0"

#### 3.2.11 Get Car Count

Function: getCarCount
Arguments: []
Example: getCarCount

Chapter 4: Chaincode Deployment
-------------------------------

### 4.1 Five Stages of Deployment & Commands

flowchart TB
    A[Package<br/>Package] --> B[Install<br/>Install]
    B --> C[Approve<br/>Approve]
    C --> D[Commit<br/>Commit]
    D --> E[Invoke<br/>Invoke]
    
    A --> A1[Compile Code]
    B --> B1[Copy to Each Node]
    C --> C1[Organization Consensus]
    D --> D1[Network-wide Deployment]
    E --> E1[Actual Transaction Execution]
    
    style A fill:#e1f5fe
    style B fill:#e8f5e8
    style C fill:#fff3e0
    style D fill:#fce4ec
    style E fill:#f3e5f5

### 4.2 Participants in Each Stage

| Stage | Executor | Scope | Consensus Required |
| --- | --- | --- | --- |
| Package | Any Developer | Local | ❌ |
| Install | Each Peer Node | Node Level | ❌ |
| Approve | Each Organization | Organization Level | ❌ |
| Commit | Any Organization | Network-wide | ✅ |
| Invoke | Any Authorized User | Network-wide | ✅ |

### 4.3 Install & Approve

# Org0's peer0 installs and approves chaincode
export BDK_ORG_NAME='Org0'
export BDK_ORG_DOMAIN='org0.example.com'
export BDK_HOSTNAME='peer0'

bdk fabric chaincode install -i
bdk fabric chaincode approve -i

# Org1's Anchor Peer does the same
export BDK_ORG_NAME='Org1'
export BDK_ORG_DOMAIN='org1.example.com'
export BDK_HOSTNAME='peer1'

bdk fabric chaincode install -i
bdk fabric chaincode approve -i

# Org0's peer1 installs chaincode
export BDK_ORG_NAME='Org0'
export BDK_ORG_DOMAIN='org0.example.com'
export BDK_HOSTNAME='peer1'

bdk fabric chaincode install -i

# Org1's peer0 does the same
export BDK_ORG_NAME='Org1'
export BDK_ORG_DOMAIN='org1.example.com'
export BDK_HOSTNAME='peer0'

bdk fabric chaincode install -i

### 4.4 Commit & Init Invoke

export BDK_ORG_NAME='Org0'
export BDK_ORG_DOMAIN='org0.example.com'
export BDK_HOSTNAME='peer0'

bdk fabric chaincode commit -i
bdk fabric chaincode invoke -i

---

Now you can execute functions in the contract with various custom arguments!

> BDK Official Document: https://github.com/cathayddt/bdk/tree/master
>
> GitHub Repo: https://github.com/marvelcn015/bdk-fabcar
>
> July 17, 2025, by Aaron Yeh