Neha Chaudhary

June 7, 2024

Guide to Build Dapps on Polkadot

Unlocking the Power of Decentralized Applications on the Polkadot Network

The world of decentralized applications (dApps) is booming, and Polkadot is at the forefront of this exciting frontier. But building a successful dApp on Polkadot requires more than just a great idea – it demands a strong understanding of both front-end and back-end development. This comprehensive guide will walk you through the entire process, from choosing the right front-end framework and writing smart contracts to setting up a serverless backend and optimizing performance. We'll delve into security best practices, testing strategies, and even cover the intricacies of deploying and maintaining your dApp on the Polkadot network. Whether you're a seasoned blockchain developer or just starting, this guide will equip you with the knowledge and tools to bring your Polkadot dApp vision to life.

Front-end development

Choosing a front-end framework (React, Vue, etc.)

When creating decentralized applications (dApps) on Polkadot, selecting the right front-end framework is important to ensure a smooth user experience. Among the most popular frameworks for front-end development are React and Vue.js.

React

React is a JavaScript library used for building user interfaces and is maintained by Facebook. It is known for its flexibility, performance, and a large ecosystem of tools and libraries.

‍

Advantages of React and Why Should You Choose It?

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Component-Based Architecture: It is worth noting that this encourages reusable components which in turn makes the codebase more modular and hence easy to maintain.
Rich Ecosystem: React has various libraries such as React Router for routing and Redux for state management which work hand in hand with the tools provided thus solving different problems when building an application.
Performance: Virtual DOM ensures that updates are made and rendered efficiently. The reason behind this is that when any object changes within the real DOM tree, Full DOM will restructure and repaint all its nodes which is slow.

Vue.js

Vue.js is a progressive JavaScript framework for building user interfaces. It is known for its simplicity and ease of integration with other projects and libraries.

Advantages of Vue and Why Should You Choose It?

Ease of Learning: Simpler and more approachable syntax, making it easier for beginners to get started.
Versatility: Vue be used for both small and large-scale applications.
Performance: Efficient reactivity system and a lightweight core.

Integrating with Polkadot using Polkadot.js API

Polkadot.js is a collection of tools and libraries that enable interaction with the Polkadot network from a web application. It provides APIs for connecting to the blockchain, querying data, and submitting transactions.

Steps to Integrate Polkadot.js API

Install Polkadot.js API: First, you need to install the Polkadot.js API library in your project.

npm install @polkadot/api

‍

Connecting to the Polkadot Network: Initialize the API and connect to a Polkadot node.

import { ApiPromise, WsProvider } from '@polkadot/api';

// Create a WebSocket provider to connect to a local node
const wsProvider = new WsProvider('wss://rpc.polkadot.io');

// Create the API and wait until ready
const api = await ApiPromise.create({ provider: wsProvider });

// You can now use the API to interact with the blockchain

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Querying Blockchain Data: Use the API to query data from the blockchain, such as account balances or block information.

// Query the balance of an account
const { data: balance } = await api.query.system.account('5D4U...abc');
console.log(`Free balance: ${balance.free}`);

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Submitting Transactions: Use the API to submit transactions, such as transferring tokens or interacting with smart contracts.

import { Keyring } from '@polkadot/api';

// Create a new keyring instance
const keyring = new Keyring({ type: 'sr25519' });

// Add an account to the keyring
const alice = keyring.addFromUri('//Alice');

// Create a transfer transaction
const transfer = api.tx.balances.transfer('5F3...xyz', 1000000000000);

// Sign and send the transaction
const hash = await transfer.signAndSend(alice);
console.log(`Transaction sent with hash: ${hash}`);

‍

In the above code,

Import Keyring: Imports Keyring from @polkadot/api.
Create Keyring: Initializes a new keyring instance with type: 'sr25519'.
Add Account: Adds an account (Alice) to the keyring using keyring.addFromUri('//Alice').
Create Transaction: Creates a transfer transaction with api.tx.balances.transfer to send tokens.
Sign and Send: Signs and sends the transaction with alice, logging the transaction hash.

‍

To create powerful and interactive dApps that make the most of the Polkadot network, it is important to select the right front-end framework and link it up with the Polkadot.js API.

Back-end development

Writing and deploying smart contracts

Smart contracts are contracts that can be self-executing with the terms of the agreement being directly written into the code. In Polkadot, smart contracts can be written using Ink! language that is made specifically for the Substrate framework. Here are some steps on how to write and deploy smart contracts on Polkadot:

Writing Smart Contracts with Ink!

Set Up the Environment: Install Rust and the required Substrate prerequisites.

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
rustup update nightly
rustup target add wasm32-unknown-unknown --toolchain nightly
cargo install --force --locked cargo-contract

‍

Create a New Ink! Project: Use the cargo-contract tool to create a new Ink! project

cargo contract new my_contract
cd my_contract

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Write the Smart Contract: Define your smart contract logic in the lib.rs file within the src directory.

#[ink::contract]
mod my_contract {
    #[ink(storage)]
    pub struct MyContract {
        value: i32,
    }

    impl MyContract {
        #[ink(constructor)]
        pub fn new(init_value: i32) -> Self {
            Self { value: init_value }
        }

        #[ink(message)]
        pub fn get_value(&self) -> i32 {
            self.value
        }

        #[ink(message)]
        pub fn set_value(&mut self, new_value: i32) {
            self.value = new_value;
        }
    }
}

‍

In the above code,

Contract Declaration: Declares an ink! smart contract module named my_contract.
Storage Structure: Defines MyContract struct with a single storage field value of type i32.
Constructor: Implements a new constructor to initialize the contract with a given init_value.
Getter Method: Implements get_value message to return the current value of the storage field.
Setter Method: Implements set_value message to update the storage field with a new value.

‍

Compile the Smart Contract: Compile your contract to WebAssembly (Wasm)

cargo +nightly contract build

Deploying Smart Contracts

Deploy Using Polkadot.js Apps:
- Open the Polkadot.js Apps portal.
- Navigate to the "Contracts" tab and upload your contract's Wasm and metadata files.
- Deploy the contract by specifying the constructor parameters and funding the deployment.
Interacting with the Deployed Contract:
- Use the Polkadot.js interface to interact with your deployed contract by calling its methods and querying its state.

Setting up a serverless backend

A serverless backend allows you to run backend services without managing the underlying infrastructure. Popular serverless platforms include AWS Lambda, Google Cloud Functions, and Azure Functions. Here’s how to set up a serverless backend for your Polkadot dApp:
‍

Choose a Serverless Platform: Select a serverless platform such as AWS Lambda, Google Cloud Functions, or Azure Functions.
Create a Serverless Function
AWS Lambda

aws lambda create-function --function-name my-function \
  --runtime nodejs14.x \
  --role arn:aws:iam::account-id:role/service-role/role-name \
  --handler index.handler \
  --zip-file fileb://function.zip

‍

In the above code,

AWS Lambda Command: Uses the AWS CLI to create a new Lambda function.
Function Name: --function-name my-function specifies the name of the Lambda function.
Runtime: --runtime nodejs14.x sets the runtime environment to Node.js 14.x.
Role: --role arn:aws:iam::account-id:role/service-role/role-name specifies the IAM role ARN that the function assumes during execution.
Handler: --handler index.handler defines the handler method for the function, typically the file name and the exported handler function.
Code Package: --zip-file fileb://function.zip specifies the zip file containing the function code to be uploaded.

Google Cloud Functions

gcloud functions deploy myFunction --runtime nodejs14 --trigger-http --allow-unauthenticated

‍

Write the logic of the function. One example for handling the request is stated below.

exports.handler = async (event) => {
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
    };
    return response;
};

‍

In the above code,

Export Handler: exports.handler = async (event) => { ... } defines an asynchronous handler function for the AWS Lambda.
Response Object: Creates a response object with:
statusCode: 200: Indicates a successful HTTP response.
body: JSON.stringify('Hello from Lambda!'): The response body contains a JSON-encoded string message.
Return Response: Returns the response object.
Deploy the Function: Deploy the function to your chosen platform and ensure it’s accessible via an HTTP endpoint.

Integrating with Polkadot

Set Up API Access: Use the Polkadot.js API within your serverless function to interact with the Polkadot network.

const { ApiPromise, WsProvider } = require('@polkadot/api');

async function connect() {
    const provider = new WsProvider('wss://rpc.polkadot.io');
    const api = await ApiPromise.create({ provider });

    const blockNumber = await api.query.system.number();
    return blockNumber.toString();
}

exports.handler = async (event) => {
    const blockNumber = await connect();
    const response = {
        statusCode: 200,
        body: `Current block number is ${blockNumber}`,
    };
    return response;
};

‍

In the above code,

Import Modules: Imports ApiPromise and WsProvider from @polkadot/api.
Connect Function: connect function establishes a connection to the Polkadot blockchain.
Create API Instance: Uses ApiPromise.create({ provider }) to create an API instance with the WebSocket provider.
Fetch Block Number: Retrieves the current block number using api.query.system.number().
Handler Function: Exports an asynchronous handler function that returns the current block number in an HTTP response.

‍

Handle Requests: Configure your function to handle incoming HTTP requests, process them, and respond with data from the Polkadot network.

If you want to make a strong, flexible Polkadot dApp that takes advantage of decentralized and serverless technologies, you should use Ink! to write and deploy smart contracts and also set up a serverless backend.

Connecting the front-end and back-end

Handling transactions and wallet integration

Integrating Polkadot.js API with the Front-end

To handle transactions and wallet integration, you need to integrate the Polkadot.js API with your front-end application. This allows your dApp to interact with the Polkadot blockchain, including sending transactions and querying data.

‍

Steps to Integrate Polkadot.js API

Install Polkadot.js API

npm install @polkadot/api @polkadot/extension-dapp

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Connecting to the Polkadot Network

import { ApiPromise, WsProvider } from '@polkadot/api';

const wsProvider = new WsProvider('wss://rpc.polkadot.io');
const api = await ApiPromise.create({ provider: wsProvider });

// Now api can be used to interact with the blockchain

‍

In the above code,

Import Modules: Imports ApiPromise and WsProvider from @polkadot/api.
Create WebSocket Provider: const wsProvider = new WsProvider('wss://rpc.polkadot.io'); initializes a WebSocket provider to connect to the Polkadot node.
Create API Instance: `const api = await Api

‍

Polkadot.js extension can be used for the management of the accounts and sign transactions.

import { web3Accounts, web3Enable } from '@polkadot/extension-dapp';

const enableExtension = async () => {
  await web3Enable('my-dapp');
  const allAccounts = await web3Accounts();
  // Display accounts and let user select
};

‍

In the above code,

Import Functions: Imports web3Accounts and web3Enable from @polkadot/extension-dapp.
Enable Extension: await web3Enable('my-dapp'); enables the Polkadot extension for the dApp.
Fetch Accounts: const allAccounts = await web3Accounts(); retrieves all accounts from the extension.
Display Accounts: Placeholder comment indicating that the accounts should be displayed for user selection.

‍

The transactions can be sent through the following code:

const transfer = api.tx.balances.transfer('5F3...xyz', 1000000000000);

const signAndSend = async (account) => {
  await transfer.signAndSend(account, ({ status }) => {
    if (status.isInBlock) {
      console.log('Transaction included in block');
    }
  });
};

‍

In the above code,

Create Transfer Transaction:some text
- const transfer = api.tx.balances.transfer('5F3...xyz', 1000000000000): Creates a transfer transaction to send tokens to a specified address.
Sign and Send Function:some text
- const signAndSend = async (account) => { ... }: Defines an asynchronous function to sign and send the transaction.
Sign and Send Transaction:some text
- await transfer.signAndSend(account, ({ status }) => { ... }): Signs the transaction with the specified account and sends it.
- Status Callback: Checks the transaction status:some text
- - Logs "Transaction included in block" if status.isInBlock.

Handling Transactions

Transactions in a Polkadot dApp typically involve interacting with smart contracts or transferring tokens. You need to handle these securely and efficiently. An example of the transaction handling is described below.

Prepare Transaction

const prepareTransaction = async (recipient, amount) => {
  const transfer = api.tx.balances.transfer(recipient, amount);
  return transfer;
};

‍

In the above code,

Prepare Transaction Function:some text
- const prepareTransaction = async (recipient, amount) => { ... }: Defines an asynchronous function to prepare a transfer transaction.
Create Transfer Transaction:some text
- const transfer = api.tx.balances.transfer(recipient, amount): Creates a transfer transaction with the specified recipient and amount.
Return Transfer:some text
- return transfer: Returns the prepared transfer transaction.

‍

Sign and Send Transaction

const sendTransaction = async (transfer, account) => {
  const unsub = await transfer.signAndSend(account, ({ status, events }) => {
    if (status.isInBlock) {
      console.log('Transaction included at blockHash', status.asInBlock);
    }
  });
  return unsub;
};

‍

In the above code,

Function Declaration: sendTransaction is an asynchronous function that takes transfer and account as parameters.
Sign and Send: Uses transfer.signAndSend(account, callback) to sign and send the transaction.
Callback Function: Callback checks if the transaction is included in a block with status.isInBlock.
Log BlockHash: Logs the block hash with console.log when the transaction is included in a block.
Return Unsubscribe: Returns the unsub function to allow unsubscribing from further updates.

Implementing user authentication and session management

User Authentication

User authentication in a decentralized application typically involves managing user identities via blockchain accounts. You can leverage Polkadot's identity system and external authentication services to manage user sessions.
‍

Steps for Authentication

Connect and Authenticate

import { web3Enable, web3Accounts, web3FromAddress } from '@polkadot/extension-dapp';

const authenticateUser = async () => {
  await web3Enable('my-dapp');
  const accounts = await web3Accounts();
  const account = accounts[0];
  const injector = await web3FromAddress(account.address);

  // Store account and injector for session management
  sessionStorage.setItem('account', JSON.stringify(account));
  sessionStorage.setItem('injector', JSON.stringify(injector));
};

‍

In the above code,

‍

Import Functions: Imports web3Enable, web3Accounts, and web3FromAddress from @polkadot/extension-dapp.
Enable Extension: Uses web3Enable('my-dapp') to enable the Polkadot extension.
Fetch Accounts: Retrieves accounts with web3Accounts() and selects the first account.
Get Injector: Obtains the injector for the account using web3FromAddress(account.address).
Store Data: Saves account and injector in session storage using sessionStorage.setItem().

‍

Session Managementsome text
- Storing Session Data: Store user session data (e.g., account information) in a secure manner, such as in session storage or a secure cookie.
- Retrieving Session Data: Retrieve and use the session data when needed to maintain the user session.
- Handling Logout: Clear session data upon user logout to end the session

Example Flow

Full Integration Flow

User Logs In:some text
- Connect wallet
- Authenticate and store session data
Perform Actions:some text
- Use session data to sign and send transactions
User Logs Out:some text
- Clear session data

To ensure a smooth and safe user experience in your decentralized application, you can do the front-end and back-end linkage of your Polkadot dApp, transaction processing, wallet functionality integration, user certification and session management by following these steps.

Testing and Debugging

Unit Testing Substrate Modules

Writing Test Cases

Importance

Unit testing is very essential because it makes certain that your Substrate modules are working perfectly and reliably. Early detection of bugs is made possible by unit tests during development which also prevents new issues from being introduced by code changes.
‍

Steps to Write Test Cases

‍

Set Up Test Environment: Create a test environment using the `sp_io::TestExternalities` struct to simulate blockchain state.

‍

 #[cfg(test)]
    mod tests {
        use super::*;
        use frame_support::{assert_ok, assert_err};
        use sp_io::TestExternalities;

        fn new_test_ext() -> TestExternalities {
            frame_system::GenesisConfig::default().build_storage::<Runtime>().unwrap().into()
        }
    }

‍

In the above code,

Test Module Declaration: #[cfg(test)] mod tests defines a module for tests, only compiled in test mode.
Imports: Imports items from the parent module and frame_support for testing utilities.
TestExternalities Setup: new_test_ext() function creates a new test environment:some text
- Uses frame_system::GenesisConfig::default() to set up default genesis configuration.
- build_storage::<Runtime>().unwrap().into() builds the storage for the runtime and converts it into TestExternalities.

‍

Write Test Functions: Implement test functions to verify the behavior of your pallet's functions.

 ```rust
    #[test]
    fn it_works_for_default_value() {
        new_test_ext().execute_with(|| {
            // Dispatch a signed extrinsic.
            assert_ok!(TemplateModule::do_something(Origin::signed(1), 42));
            // Read pallet storage and assert an expected result.
            assert_eq!(TemplateModule::something(), Some(42));
        });
    }

    #[test]
    fn correct_error_for_none_value() {
        new_test_ext().execute_with(|| {
            // Ensure the expected error is thrown when no value is set.
            assert_err!(TemplateModule::cause_error(Origin::signed(1)), Error::<Runtime>::NoneValue);
        });
    }
    ```

‍

In the above code,

Test for Default Valuesome text
- #[test] fn it_works_for_default_value(): Defines a test function.
- Sets up the test environment with new_test_ext().execute_with.
- Dispatches do_something extrinsic and asserts it succeeds with assert_ok!.
- Asserts the storage value is set correctly with assert_eq!.
Test for Error Handlingsome text
- #[test] fn correct_error_for_none_value(): Defines another test function.
- Sets up the test environment with new_test_ext().execute_with.
- Dispatches cause_error extrinsic and asserts it fails with assert_err!.
- Checks the specific error Error::<Runtime>::NoneValue is returned

Using Substrate's Test Framework

Setting Up

Substrate provides a testing framework to facilitate the development and execution of tests for your modules. It includes tools for simulating blockchain state and dispatching transactions.

‍

Import Test Framework: Ensure you have the necessary dependencies in your `Cargo.toml` file.

‍

  ```toml
    [dev-dependencies]
    sp-core = { version = "4.0.0", default-features = false }
    sp-runtime = { version = "4.0.0", default-features = false }
    frame-support = { version = "4.0.0" }
    frame-system = { version = "4.0.0" }
    ```

‍

Build and Run Tests: Use Cargo to build and run your tests.

‍

 ```sh
    cargo test
    ```

Debugging Tools and Techniques

Common Debugging Strategies

Approaches

‍

Print Statements: Use print statements (`debug::info!`) to log variable values and execution flow.

‍

  ```rust
    debug::info!("Current value: {:?}", value);
    ```

‍

Error Handling: Check error messages and use proper error handling to identify issues.

 ```rust
    let result = some_function();
    if let Err(e) = result {
        debug::error!("Error: {:?}", e);
    }
    ```

‍

Step-by-Step Execution: Break down complex functions and test each part individually.

Using Polkadot Explorer and Other Debugging Tools

Tools

Polkadot.js: Use the Polkadot.js UI to interact with your local node, inspect storage values, and submit extrinsics.
Substrate Debug Kit: Utilize tools like the Substrate Debug Kit for detailed insights into runtime execution.

‍

 ```sh
    cargo install substrate-debug-kit
    ```

‍

IDE Debuggers: Use IDE debuggers (e.g., Visual Studio Code with Rust extensions) to set breakpoints and inspect runtime behavior.

Continuous Integration and Deployment

Setting Up CI/CD Pipelines

Importance

‍

CI/CD pipelines automate the process of testing, building, and deploying code changes, ensuring that your Substrate project remains stable and up-to-date.

Steps to Set Up

Choose a CI/CD Service: Select a CI/CD service (e.g., GitHub Actions, GitLab CI, Jenkins).
Create Configuration File: Write a configuration file to define your CI/CD pipeline.

```yaml
    name: CI

    on: [push, pull_request]

    jobs:
      build:
        runs-on: ubuntu-latest
        steps:
        - uses: actions/checkout@v2
        - name: Install Rust
          run: |
            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
            source $HOME/.cargo/env
            rustup default stable
        - name: Build
          run: cargo build --release
        - name: Test
          run: cargo test
    ```

‍

In the above code,

CI Configuration: Defines a continuous integration (CI) workflow for GitHub Actions.
Trigger Events: Runs on push and pull_request events.
Jobs Section: Specifies the job named build.
Runs on Ubuntu: Job executes on ubuntu-latest environment.
Steps:some text
- Checkout Code: Uses actions/checkout@v2 to checkout the repository code.
- Install Rust: Installs Rust using a script from rustup.rs.
- Build Project: Runs cargo build --release to build the project in release mode.
- Run Tests: Executes cargo test to run the project's tests.

‍

Automate Deployments: Add steps to automate deployments to your testnet or mainnet.

```yaml
    deploy:
      needs: build
      runs-on: ubuntu-latest
      steps:
      - name: Deploy to Testnet
        run: |
          ./scripts/deploy.sh
    ```

‍

In the above code,

Deploy Job: Defines a deployment job named deploy.
Dependency: Indicates deploy depends on the completion of the build job.
Runs on Ubuntu: Job executes on ubuntu-latest environment.
Deployment Step:some text
- Deploy to Testnet: Runs a deployment script ./scripts/deploy.sh to deploy the application to a testnet.

Automated Testing and Deployment

Implementation

Automated Testing: Integrate automated testing into your CI/CD pipeline to ensure code quality.

 ```yaml
    test:
      runs-on: ubuntu-latest
      steps:
      - name: Run Tests
        run: cargo test --release
    ```

‍

Continuous Deployment: Configure your pipeline to automatically deploy successful builds to a testnet or mainnet.

‍

```yaml
    deploy:
      needs: test
      runs-on: ubuntu-latest
      steps:
      - name: Deploy to Network
        run: |
          ssh user@server 'bash -s' < ./scripts/deploy.sh
    ```

‍

To guarantee the resilience, privacy, and reliability of your Polkadot-centric software, employ these sophisticated testing and debugging methods. To uphold a high level of code quality as well as simplify the development process, adhere to the continuous integration and deployment principles.

Deploying Your Polkadot dApp

Preparing for Deployment

Final Testing and Optimization

Comprehensive Testing

‍

Unit Tests: Ensure all unit tests are comprehensive and pass successfully. Unit tests should cover all critical functionalities of your dApp.

 ```sh
    cargo test
    ```

‍

Integration Tests: Conduct integration tests to verify that different components of your dApp interact correctly.

 #[cfg(test)]
    mod integration_tests {
        use super::*;

        #[test]
        fn test_end_to_end_scenario() {
            // Setup test environment and execute full dApp functionality
        }
    }

Load Testing: Perform load testing to assess how your dApp handles high traffic and stress conditions. Tools like Apache JMeter or Locust can be useful.

Optimization

‍

Code Optimization: Review and optimize your code for efficiency and performance. Ensure there are no redundant computations or memory leaks.
Gas Optimization: Optimize transactions to minimize gas usage. Avoid expensive operations and optimize data structures.

Setting Up Mainnet Deployment

Preparing for Mainnet

‍

Mainnet Configuration: Configure your dApp for the mainnet environment, including network-specific parameters and endpoints.

    ```rust
    #[cfg(feature = "mainnet")]
    const ENDPOINT: &str = "wss://mainnet.polkadot.io";
    ```

‍

Security Audit: Conduct a thorough security audit to identify and fix vulnerabilities. Consider third-party audits for an additional layer of security.
Funding Accounts: Ensure that your deployment accounts are adequately funded for transaction fees and other costs associated with deployment.

Deployment Process

Deploying Parachains and Parathreads

‍

Parachains

‍

Registering a Parachain: Follow the procedure for registering your parachain with the Polkadot relay chain.

 ```sh
    polkadot-js-cli --seed "//Alice" --ws wss://rpc.polkadot.io \
        tx.parachains.register {your_parachain_spec}
    ```

‍

Bonding: Bond the necessary tokens for your parachain slot.

  ```sh
    polkadot-js-cli --seed "//Alice" --ws wss://rpc.polkadot.io \
        tx.staking.bondExtra {amount}
    ```

‍

Genesis Block: Ensure your parachain's genesis block is correctly configured and deployed.

‍

Parathreads

‍

Parathread Registration: Register your parathread similarly to a parachain, but on a pay-as-you-go model.

   ```sh
    polkadot-js-cli --seed "//Alice" --ws wss://rpc.polkadot.io \
        tx.parachains.registerParathread {your_parathread_spec}
    ```

‍

Auction Participation: Participate in the auction process for parathread slots if necessary.

Updating and Maintaining Deployed Applications

On-Chain Governance

‍

Proposing Updates: Use the on-chain governance mechanism to propose and vote on updates to your dApp.

    ```sh
    polkadot-js-cli --seed "//Alice" --ws wss://rpc.polkadot.io \
        tx.democracy.propose {update_proposal}
    ```

‍

Runtime Upgrades: Implement forkless runtime upgrades to enhance or fix issues in your dApp without causing disruptions.

  ```rust
    let wasm_binary = include_bytes!("../runtime/wasm/target/wasm32-unknown-unknown/release/runtime.wasm").to_vec();
    let code = wasm_binary.to_vec();
    System::set_code(frame_system::RawOrigin::Root.into(), code);
    ```

‍

In the above code,

Include WASM Binary: include_bytes! macro loads the WASM binary from a specified file path into a byte array.
Convert to Vec: Converts the byte array to a vector using .to_vec().
Set Runtime Code: Uses System::set_code to update the blockchain's runtime code, with RawOrigin::Root providing root-level permissions for the operation.

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Post-Deployment Considerations

Monitoring and Analytics

Monitoring Tools

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Telemetry: Use Polkadot Telemetry to monitor the health and performance of your parachain or parathread.

```sh
    telemetry-polkadot --chain mainnet
    ```

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Logs and Alerts: Set up logging and alerting mechanisms to track events and respond to issues promptly.

  ```sh
    journalctl -fu polkadot
    ```

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Analytics: Implement analytics tools to track user behavior, transaction patterns, and other key metrics.

Handling User Feedback and Updates

Feedback Mechanisms

User Feedback: Establish channels for users to provide feedback, such as a dedicated support email, social media channels, or community forums.
Bug Reporting: Set up a bug reporting system to collect and address issues reported by users.

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Regular Updates

Release Schedule: Plan and communicate a regular release schedule to keep users informed about upcoming updates and new features.
User Notifications: Notify users about significant updates, especially those that might require user action or affect their experience.

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Best Practices and Tips for Polkadot Development

Code organization and modularity

Structuring your codebase

It is important to structure the code effectively to maintain its scalability. It is expected from a professional programmer to have clean code that is well organized and can be easily maintained. This enables the developers to navigate through the project in a convenient manner and they can easily make the changes in the code if it is well structured.

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Some of the best practices are

Having a consistent and logical structure for your project. You can avoid any confusion by simply organizing the code into modules and directories. Here is what an organized Polkadot project structure should look like.

substrate-node-template/

├── node/
├── pallets/
│   ├── pallet-example/
│   └── pallet-template/
├── runtime/
├── scripts/
├── tests/
└── README.md

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Directory Structure: Organize your code into directories based on functionality.some text
- Root Directory: Contains project-wide files like Cargo.toml, README, and configuration files.
- /pallets: Contains custom pallets, each in its own subdirectory.
- /runtime: Contains the runtime logic that integrates various pallets.
- /node: Contains node-specific code, including configuration and bootstrapping logic.
Having a modular design can help understand the functionality and break it down into reusable modules known as pallets. Each pallet defines a specific behavior and provides more information about a feature. The modular design looks something like this.

pub mod pallet_example {
    // Pallet code here
}

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A well-written documentation helps fellow developers to comprehend the code in a convenient manner. Make sure you properly document your code so that the other developers may understand the purpose and usage of each module. Here is an example of how you may document your code.

/// This pallet handles example functionality.
pub mod pallet_example {
    // Detailed documentation here
}

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Using libraries and modules

Using the libraries and modules can reduce redundancy and improve code quality.

The libraries may be used to improve the reusability of the existing libraries and modules can be used to cut down the development time by making sure that you are using a well-tested code.

[dependencies]
frame-support = { version = "4.0.0" }
frame-system = { version = "4.0.0" }

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External Libraries: Use well-maintained external libraries for common tasks (e.g., cryptographic functions, serialization).
Internal Modules: Create internal modules to encapsulate reusable code.some text
- Utilities Module: Include utility functions and helpers.
- Constants Module: Define and manage project-wide constants.

Here is an example showing how you may use an internal module.

// In src/utils.rs
pub fn calculate_hash(data: &[u8]) -> H256 {
    sp_io::hashing::blake2_256(data)
}

// In main module
mod utils;
use utils::calculate_hash;

Security best practices

Having a well-secured blockchain is a priority for every blockchain developer. This section will shed some light on some of the best security practices

Secure coding guidelines

Some of the best security guidelines that may protect your dApp from vulnerabilities are stated below.

Least Privilege: Ensure each component or module operates within the minimum privileges required to perform the function.
Input Validation: Make sure that you always validate and sanitize inputs to prevent injection attacks and other vulnerabilities. This will make your code more secure.

ensure!(input.is_valid(), Error::<T>::InvalidInput);

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Access Control: Implementing strict access controls and ensuring that only authorized entities can be helpful in the rightful execution of the code and help to improve the security of the system.

ensure_signed(origin)?;

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Error Handling: An experienced developer should handle the error in a graceful manner and try to avoid exposing any sensitive information by throwing error messages at the rightful occasion.

if let Err(e) = some_function() {
    log::error!("Error occurred: {:?}", e);
}

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A more detailed explanation of the input validation is stated below.

fn set_value(origin: OriginFor<T>, value: u32) -> DispatchResult {
    ensure!(value <= MAX_VALUE, "Value exceeds maximum allowed");
    SomeValue::put(value);
    Ok(())
}

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In the above code,

Function Definition: `set_value` takes `origin` (caller information) and `value` (an unsigned 32-bit integer) as parameters, returning a `DispatchResult` to indicate success or error.
Value Check: Uses `ensure!` macro to verify `value` does not exceed `MAX_VALUE`, returning an error message if it does.
State Update: Stores `value` in on-chain storage using `SomeValue::put(value)` if the check passes.
Success Response: Returns `Ok(())` to indicate successful execution if the value is valid and stored.

Regular audits and reviews

Regular code audits and reviews are essential to maintaining the security of the blockchain.

Code Reviews: Conducting regular code reviews can be helpful in the identification of potential vulnerabilities and bugs. Identifying these bugs at the time can help them get them fixed time fully.
Automated Tools: Ceraun automated security analysis tools can help to scan the codebase to find the common vulnerabilities. The following command is an example of an automated tool that can perform the audit of the code.

cargo audit

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Third-Party Audits: Another benefit to performing a security audit of your code is by using third-party audits. Peer reviews can also be beneficial in making sure that your code has greater security that can prevent it from any attacks or vulnerabilities.

Performance tuning

Optimizing for speed and efficiency

To have an efficient code, it is important to optimize it. This is crucial for the proper functioning of the dApp.

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Using efficient data structures and algorithms can effectively minimize the computational overhead.

for i in 0..n {
    // Optimized loop
}

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Profiling tools are marble to modify the code by adding the parts of code into the source or an executable code. Profiling tools can be used to identify the bottlenecks in the code. The following command is used to identify the bottlenecks in the code.

cargo flamegraph

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The redundant computational overhead can be further reduced by the rightful implementation of the caching strategies.

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Benchmarking is a process why which you can compare your code to various parameters to improve its efficiency. This can help identify and address any performance bottlenecks provided in the code.

Leveraging Polkadot’s unique features

Polkadot offers unique features that can enhance your tool’s performance and capabilities.

Parallel Processing: Use Polkadot’s parallel processing capabilities to split work among many chains.
Shared Security: Use Polkadot’s shared security model to avoid building custom security from scratch.
On-Chain Governance: Use on-chain governance for efficient update management.

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An example of the code snippet for leveraging the parallel processing is given below.

// Implement functionality that can be executed in parallel across parachains
fn parallel_task(data: Vec<u8>) -> Vec<u8> {
data.par_iter().map(|&x| x * 2).collect()
}

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