nomadcoin-rs

About the project

This project is a rust version of nomadcoin. There's a online class called 'Nomadcoin', where you can learn how to create your simple blockchain with golang. Although the main language of the lecture is golang, I studied Rust recently, and wanted to use it in my project to get used to the language. That's why I started this project with Rust.

So, I have two objectives for this project.

1. Understand blockchain technically and how to create it on my own.
2. Get used to Rust so that I can confidently say I am a rustcean even if I'm not that good at it.

Project History

1. Created simple blockchain (Lecture #4)

   • I created Block and Blockchain struct and some functions.
   • Blockchain hashes data when adding block to its chain.

2. Created explorer html webpage with rocket (Lecture #5)

   • I used rocket crate to do this and create rest api in the next section.

3. Created rest api with rocket (Lecture #6)

   • At this point, I used workspace to support both explorer and rest api. But I decided to remove explorer in the next section and only supports restapi as main entrypoint.
   • In the lecture, nico uses reference of block, but it was somewhat hard to use reference of block in Rust because of lifetime issue. So, I asked a question about it to Korean Rust Discord, and I got an answer from someone that it's okay to use clone() and it's not that costly most of the time, and optimization should be done later.

4. Used database for persisting blockchain snapshot and blocks (Lecture #8)

   • I used nut which is a rust version of Bolt DB. I changed it to PickleDB because it felt like the library has some bug at that time.
   • From this section, blockchain persisted even after server restarted.

5. Applied 'proof of work' concept to mine block and changed database to PickleDB (Lecture #9)

6. Created testutils to drop databse after each test

   • I wanted to drop database resource after each test. I created DBResource struct and used Drop trait to do that. But I don't think that its interface is good and I want to know a better way to do this in Rust. (Actually I removed this later because I thought saving to /tmp is okay, but I still want to know a cool way)

7. Implemented transaction feature in blockchain network (Lecture #10)

   • This was kind of difficult part to make it work correctly, but I managed to do it.
   • In the lecture, golang suffered some race condition situations. but Rust felt safe in those conditions, because in concurreny situation, Rust forces us to use mutex lock on the compilation level.

8. Implemented wallet(auth) feature to verify transaction (Lecture #11)

   • I used p256 crate to use p256 Elliptic Curves algorithm for cryptography and hex crate to create hax string.

9. Implemented p2p feature for all peers in the block chain to have same blockchain and share their own events (Lecture #12)

   • I used SSE (Server Sent Event) to implement this feature instead of websocket, because Rocket didn't support websocket at the time. I implemented this feature, but did somewhat little dirty things (like sleep 1 sec to give time to ensure inter-connection)
   • I used tokio crate to support async concurrency.
   • I learned Arc to control lifetime in concurreny situation.

10. Refactored some codes about p2p feature

    • Used the same parameters for event handling to enhance its adaptibility in the future.

11. Refactored entire code and test

    • Created repository layer and used test double(stub) for testing blockchain.
    • I learned that I should use Box smart pointer to abstract a trait like repository patteren.
    • I learned that I should use Mutex (Or RefCell) to borrow immutables as mutables. I used this in TestRepository and PickleDBRepository, which are required to borrow as mutables to write to db, whereas some database library don't have to do that.

12. Create dockerfile and docker-compose and refactored http file

    • I refered to this blog post

Future Plan

This is just my toy project, so I have no plan to add new features, or maintain it. But I want to get feedback about my code like what I'm doing wrong in Rust, and how to improve my rust code. I want to be a good rustcean.

Final Comment

It was very meaningful to do this project. I can confidently say that I kind of achieved both objectives. (Not that good though). I understood the basics of blockchain and got used to program with Rust.