Intro to Solana Onchain Development

Summary #

• Onchain programs (sometimes called 'smart contracts') run directly on Solana, just like programs on your computer.
• These programs consist of instruction handlers - functions that process instructions from transactions.
• Programs interact with the blockchain by reading from and writing to Solana accounts.
• Solana programs are most commonly written in Rust, often using the Anchor framework for simplified development.
• Anchor generates Interface Description Language (IDL) files, which:
  • Describe the program's structure and functionality
  • Enable automatic creation of JavaScript/TypeScript client libraries
• Solana's architecture allows for parallel execution of non-overlapping transactions, contributing to its high speed and efficiency.
• Rent is a concept in Solana where accounts must maintain a minimum balance to stay alive on the blockchain.

Overview #

Solana operates on various clusters, each functioning as a unified, globally synchronized system:

• mainnet-beta: The main production network
• testnet: For testing new features
• devnet: For application development
• localnet: For local testing

The program that run on Solana - the ones that create tokens, swap tokens, art marketplaces, escrows, market makers, DePIN apps, auctions, retail payments platforms, etc - are called Solana apps.

The most popular way to build onchain apps is using Rust language and the Anchor framework. There is also another way of developing Solana programs that is, by using the native onchain program development, however Anchor makes things a lot simpler and safer. Some pros of using Anchor are:

• Security checks are implemented automatically
• Automatic routing of incoming instructions to the correct instruction handler
• Automatic serialization and deserialization of the data inside transactions
• Account validation, including:
  • Type checking
  • Ensuring account uniqueness

Regardless of the language and framework you choose, Solana works the same. Let's refresh how programs work on Solana.

Diagram showing a transaction with two instructions

Programs are deployed at addresses #

In the same way that we can send tokens to users using their public key, we can find programs using the program's public key. When using Anchor, a keypair is created during anchor init, and the private key is saved in the target/deploy directory of your project.

A program's public key is sometimes called a 'program ID' or 'program address'. Which can be seen in the programs/<insert_project_name>/src/lib.rs and Anchor.toml files.

Programs have instruction handlers #

For example, a Solana client making a transaction transferring some USDC with a memo saying 'thanks' would have two instructions:

• one instruction for the Token program's transfer instruction handler
• the other instruction for the Memo program's memo instruction handler.

Both these instructions must be completed successfully for the transaction to execute.

Instruction handlers are how blockchain programs process the instructions from clients. Every exchange, lending protocol, escrow, oracle, etc. provides their functionality by instruction handlers.

Instruction handlers write their state to Solana accounts #

If you have done web development before, think of instruction handlers like HTTP route handlers, and incoming instructions like HTTP requests.

However, unlike HTTP route handlers, Solana instruction handlers don't return data. Instead, they write their data to accounts on Solana.

Programs on Solana can transfer tokens to user wallet addresses (for SOL) or user token accounts (for other tokens).

More importantly, programs can create additional addresses to store data as needed.

This is how Solana programs store their state.

Program Derived Addresses (PDAs): Solana's Key-Value Store #

Data for Solana programs are stored in program-derived addresses (PDAs). Solana's PDAs can be thought of as a key/value store. A PDA can be designed to store any form of data as required by the program.

Key Concepts #

1. Structure

   • Key: The PDA's address
   • Value: Data stored in the account at that address

2. Address Generation

   • Seed: chosen by the programmer
   • Bump: An additional value to ensure unique PDA creation
   • Deterministic: Same combination of seed and bump always produce the same address. This helps the program and the client to accurately determine the address of the data.

3. Data Storage

   • Programmers define the structure of data stored in PDAs
   • Can store any type of program-specific information

4. Some properties:

   • PDAs are off the Ed25519 elliptic curve. While the data type web3.js uses is a PublicKey, PDA addresses are not public keys and do not have a matching private key.
   • A program's PDAs are unique so, they won't conflict with other programs.
   • PDAs can also act as signer in an instruction. We'll learn more about this in further lessons.

Examples of PDA Usage #

Benefits #

1. Uniqueness: PDAs are specific to your program, avoiding conflicts
2. Determinism: Consistent address generation across clients and on-chain programs
3. Flexibility: Can store various types of data structures
4. Efficiency: Quick lookup and access to program-specific data

Solana instructions need to specify all the accounts they will use #

As you may already know, Solana is fast because it can process transactions that don't overlap at the same time i.e., just like in the real world, Alice sending to Bob doesn't stop Chris from sending something to Diana. Your front-end apps need to specify the addresses of all the accounts they will use.

This includes the PDAs you make. Thankfully, you can calculate the address for PDAs in your front-end code before you write data there!

// There's nothing at this address right now, but we're going to use in our transaction
const address = findProgramAddressSync(["seed", "another seed"], PROGRAM_ID);

There are multiple ways to build onchain, but we recommend Anchor #

You currently have two options for onchain program development:

• We recommend new onchain programmers start with Anchor. Anchor's defaults make it easy to create safe programs.
• There's also a separate native onchain program development course.

Whichever way you pick, Solana Foundation maintains examples in both languages, and Solana Stack Exchange is there to help.

For now, let's set up your computer!