TOY BLOCKCHAIN NETWORK WITH CLOJURE + DOCKER

Content

• Introduction
• Get up and running
• Note
• Future Improvments
• Contributions and issues
• License

Introduction

This is a toy Blockchain made with Clojure and Docker for network simulation. Our toy Blockchain is a typical simple Proof-of-Work blockchain. By running this app, we will have a pretty-decentralized network of multiple blockchain-nodes that can communicate with each others. To mine a block on any specific node, we can use a http client to send predefined request to such node. New block will be broadcasted to other nodes in the network so they will validate the new block and update their current blockchain.

This is to support the story I wrote in Medium:

https://medium.com/@vutr/build-blockchain-with-docker-network-part-1-d041b7275b77

https://medium.com/@vutr/build-blockchain-with-docker-network-part-2-b04206289724

Get up and running

To run the app, first you need to have Docker installed and running. Then clone this repo and cd into its folder:

$ git clone https://github.com/vutran1710/pow-blockchain-http
$ cd pow-blockchain-http

Now, we are ready to build the image and fire up Docker. But before that, let’s examine the blockchain network setting that is set up in the file docker-compose.yaml. Have a look at the node ports setting:

node:
...
  ports:
    - "3001-3003:80"

Such port setting indicates that we can have up to 3 child nodes and 1 boot node in the network. To scale for more node running at the same time, you can change it to a broader range, eg: 3001:3010

If you are already happy for such setting, let’s get our network up!

$ docker-compose up --scale node=3

Now go a have a cup of coffee while Docker is building the image and fetching neccessary libaries for Clojure. After 2 sips, you will probably see something like this

Great! Now let’s examine the our blockchain network. Open a new tab of the current terminal, type in the following code. You would see a list of online network by Docker

$ docker network ls

NETWORK ID          NAME                        DRIVER              SCOPE
f67383a86a96        bridge                      bridge              local
7e3161956e4e        host                        host                local
e32dda69c01e        none                        null                local
34888cf7754f        pos-blockchain_blockchain   bridge              local

There it is, our blockchain! Let’s inspect it! There will a very long text, but we care about the containers part only

$ docker inspect 34888cf7754f

"Containers": {
        "1f511d473a11112cac427b0fd672b31be76b22825d035dba07d6a019c9133636": {
        "Name": "pos-blockchain_node_2",
        "EndpointID": "af94efbeb0c93737bc5574307f9ed8df34303ec22b55c01f468852a87b36e79e",
        "MacAddress": "02:42:ac:10:ee:02",
        "IPv4Address": "172.16.238.2/24",
        "IPv6Address": ""
    },
    "20c1c8dacc525807933f1211c454b45292b06e175a30cc14e5bf749592710ed2": {
        "Name": "pos-blockchain_node_1",
        "EndpointID": "a6dc7a0f39415537776e256c21175437f96c19eaecbf59e7079c749dbf5db565",
        "MacAddress": "02:42:ac:10:ee:03",
        "IPv4Address": "172.16.238.3/24",
        "IPv6Address": ""
    },
    "581da2de7dce9771ac0ed215229b72cb3aa2379f5e8b87820225a5734d184f9c": {
        "Name": "pos-blockchain_boot_1",
        "EndpointID": "46586524a421c83a2fede99eaf2f5bd4647785ccf298395b5e2cba5ebe99de1a",
        "MacAddress": "02:42:ac:10:ee:0a",
        "IPv4Address": "172.16.238.10/24",
        "IPv6Address": ""
    },
    "708882e36638c4482e31003c4a911dfd93f5a5baaa3e3a2fe265147ab739cd5a": {
        "Name": "pos-blockchain_node_3",
        "EndpointID": "6dbc699c9873385bf090ed7209c5943d04f3b3152ad4c1d7d5bc1c2a1158316c",
        "MacAddress": "02:42:ac:10:ee:04",
        "IPv4Address": "172.16.238.4/24",
        "IPv6Address": ""
    }
},

There are 4 nodes, each with its own IPv4Address. This is how containers would talk with each others within our docker network. Now, how about mine some block for starting? Let’s inspect the ports of these containers! Type in:

$ docker ps

CONTAINER ID     IMAGE          COMMAND                  CREATED          STATUS           PORTS                    NAMES
708882e36638     boot:latest    "/usr/src/app/delay.…"   2 hours ago      Up 13 minutes    0.0.0.0:3003->80/tcp     pos-blockchain_node_3
20c1c8dacc52     boot:latest    "/usr/src/app/delay.…"   2 hours ago      Up 13 minutes    0.0.0.0:3002->80/tcp     pos-blockchain_node_1
1f511d473a11     boot:latest    "/usr/src/app/delay.…"   2 hours ago      Up 13 minutes    0.0.0.0:3001->80/tcp     pos-blockchain_node_2
581da2de7dce     boot:latest    "java -jar app-stand…"   2 hours ago      Up 13 minutes    0.0.0.0:3000->80/tcp     pos-blockchain_boot_1

Cool! We now can use some http-client to send request to these container through localhost with ports from 3000 -> 3003. Below are the api endpoint available of a single node (port varies for each node):

1. GET http://localhost:3000/ :: This will return the current blockchain and node-list
2. POST http://localhost:3000/ :: This is to submit a new blockchain to the node
3. GET http://localhost:3000/mine :: Mine a block. After having mined a block, the node will automatically broadcast its new blockchain to all nodes in the network that it is aware of.
4. GET http://localhost:3000/update :: Manully ask a node to look around and ask its peers for update of the blockchain and node-list

That’s all there is to it! Happy hacking!

Note

You can always have more nodes in the network by 2 ways:

1. Modify port-range for node in docker-compose.yaml and specify the scale argument in command docker-compose up --scale node=n, where n is the number of nodes you want.
2. Fire up another container and attach it the existing blockchain network.

Future Improvments

Dashboard

I want a dashboard so we can easily fire up nodes as well as mining from a friendly user interface. Maybe a small Express server with React will do the job.

Transactions

If a blockchain cannot hold any transaction, it’s useless.

Wallet-logic

A wallet would be cool to huh?

Contributions and issues

…are welcome!

License

MIT 2018 by Vu Tran