Lisk SDK Overview

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Introduction

Please read this carefully. The current version of the SDK is the alpha release stage. The Lisk SDK has been released in its current form in order to improve the development experience through community feedback and contributions.

It is definitely NOT recommended to use the alpha release of the Lisk SDK for any production-based blockchain applications, i.e. a blockchain operating on a live mainnet.

Over the course of the SDK’s alpha phase there will be significant changes in the Lisk protocol and implementation, which will eventually bring the accessibility and reliability to a level which is feasible for production-based blockchain applications.

At this time it is only recommended that the alpha version of the Lisk SDK is used for proof-of-concept blockchain applications, i.e. a blockchain operating on a stand-alone network.

Please note that the dummy delegate accounts are insecure, as their secret passphrases are public. In addition, the convenient creation of a new genesis block is not supported by the alpha release of the Lisk SDK.

The only application built using the Lisk SDK currently feasible for production usage is Lisk Core, the client of the Lisk network itself.

Please be advised that it is not possible to guarantee that blockchains created with the alpha release of the Lisk SDK will remain compatible with the planned (beta/rc) releases.

We wish you an enjoyable experience building your proof-of-concept blockchain applications using the Lisk SDK and look forward to receiving your feedback and contributions during the alpha phase.

What is the Lisk SDK?

The Lisk SDK aims to provide an easy and reliable software development kit for building blockchain applications compatible with the Lisk Protocol.

The architecture of the Lisk SDK has been designed so that it can be extended to meet the requirements of a wide variety of blockchain use cases.

The codebase is written entirely in JavaScript, which means for a majority of developers no significant change of tools is required to get started.

The Lisk SDK makes every effort to allow developers to focus simply and purely on writing the code that matters to their own blockchain application and nothing else.

SDK components

Directory Description

Framework

Lisk Framework is an application framework responsible for establishing and maintaining the interactions between the modules of a Lisk blockchain application.

Elements

Lisk Elements is a collection of libraries, each of them implementing some form of blockchain application functionality such as cryptography, transactions, p2p, etc. Each library is designed to be compatible with the Lisk Protocol.

Commander

Lisk Commander is a command line tool which allows the management of a Lisk node instance and interaction with a Lisk compatible network.

Architecture Overview

The Lisk SDK operates on the NodeJS runtime and consists primarily of an application framework (Lisk Framework). This consists of a collection of libraries providing blockchain application functionalities (Lisk Elements), and a powerful Command Line Interface (Lisk Commander), which allows developers to manage a Lisk node instance and interact with a Lisk compatible network.

The diagram below provides a high-level overview of the architecture:

Diagram

Usage

Dependencies

Before running Lisk SDK, the following dependencies need to be installed in order to run applications created with the Lisk SDK:

Dependencies Version

NodeJS

10.17.0

PostgreSQL

10+

Redis (optional)

5+

Python

2

Further details on installing these dependencies can be found in the pre-installation setup guide.

Please be aware that primarily it is necessary to create a database. The default database name is lisk_dev, so for the development purposes, a command createdb lisk_dev must be used for the set up. The default database user and password are lisk and password, they can be both changed in the configuration of the Lisk SDK.

Installation

Installation of the Lisk Alpha SDK is straightforward and limited to getting a single NPM package, lisk-sdk, to your Node.js project as shown below:

npm install lisk-sdk

Lisk SDK is an all-in-one package that provides the tools to create, run and maintain blockchain applications in JavaScript.

In the case whereby only a specific functionality is required, it is possible to install only the relevant package as shown below:

npm install lisk-commmander (1)
npm install lisk-elements (2)
npm install @liskhq/lisk-transactions (3)
npm install @liskhq/lisk-cryptography (4)
1 Install Lisk Commander.
2 Install Lisk Elements with all packages included.
3 Install Lisk Elements Transactions Package.
4 Install Lisk Elements Cryptography Package.

How to build a blockchain application in 3 steps

3 steps to build a blockchain application

We are constantly working on new proof of concept applications that show the features, capabilities and current limitations of the Lisk SDK.

For proven examples of how to build blockchain applications, please see the Tutorials page. Detailed step-by-step guides can be found here to assist with building the example applications.

Lisk SDK Setup

To create the project structure of your blockchain application, firstly install the Lisk SDK dependencies followed by the Lisk SDK afterwards as shown below:

npm init (1)
npm install lisk-sdk (2)
1 Initialize the project by creating a package.json file.
2 Install the lisk-sdk package as dependency of your project. Ensure the installed dependencies of the Lisk SDK are completed beforehand.

To create a blockchain application, it is necessary to provide an entry point of your application, (for example, index.js) and then set-up your network by using the modules of Lisk SDK.

It is quite simple to have a working blockchain application, mirroring the configuration of the existing Lisk network. This can be achieved by copying the following three lines of code shown below to your index.js:

const { Application, genesisBlockDevnet, configDevnet} = require('lisk-sdk'); (1)

const app = new Application(genesisBlockDevnet, configDevnet); (2)

app.run() (3)
   .then(() => app.logger.info('App started...')) (4)
   .catch(error => { (5)
        console.error('Faced error in application', error);
        process.exit(0);
});
1 Require the lisk-sdk package.
2 Create a new application with default genesis block for a local devnet.
3 Start the application.
4 Code that is executed after the successful start of the application.
5 Code that is executed if the application start fails.

Now, save and close index.js and try to start your newly created blockchain application by running the following command:

node index.js | npx bunyan -o short
node index.js will start the node, and | npx bunyan -o short will pretty-print the logs in the console.

This should start the application with the pre-defined default configurations, which will connect your app to a local devnet. From this point it is possible to start to configure and customize the application further.

For more detailed explanations, please see the example applications, which describe the process of creating blockchain applications step-by-step.

Configure your blockchain parameters

It is also possible to define your blockchain application parameters such as BLOCK_TIME, EPOCH_TIME, MAX_TRANSACTIONS_PER_BLOCK and more, with an optional configurations object.

const app = new Application(genesisBlockDevnet, {
    app: {
        label: 'my-blockchain-application',
        minVersion: '0.0.2',
        version: '2.3.4',
        protocolVersion: '4.1',
        genesisConfig: {
            EPOCH_TIME: new Date(Date.UTC(2016, 4, 24, 17, 0, 0, 0)).toISOString(),
            BLOCK_TIME: 10,
            MAX_TRANSACTIONS_PER_BLOCK: 25,
        },
        ...
});

Register a custom transaction

It is possible to define your own transaction types with Lisk SDK. This is where the custom logic for your blockchain application resides.

Add the custom transaction type to the blockchain application by registering it to the application instance as shown below:

const { Application, genesisBlockDevnet, configDevnet } = require('lisk-sdk');

const MyTransaction = require('./my_transaction'); (1)

const app = new Application(genesisBlockDevnet, configDevnet);

app.registerTransaction(MyTransaction); (2)

app
    .run()
    .then(() => app.logger.info('App started...'))
    .catch(error => {
        console.error('Faced error in application', error);
        process.exit(0);
    });
1 Require the custom transaction.
2 Register the custom transaction with the application.
For information on creating your own custom transaction, please see the customize page or follow the tutorials.

How to interact with the network

While your network is up and running interact with it and also the node through the API, and use Lisk Commander or Lisk Elements to create sendable transaction objects.

To monitor and explore the network, a monitoring solution like https://github.com/LiskHQ/lisk-explorer[Lisk Explorer]. can be set up.

Depending on the level of customization, Lisk Explorer and Lisk Commander may also require customization to prevent other services from failing.

Another simple way to interact with the network is by connecting it to Lisk Desktop. Lisk Desktop provides a simple and user-friendly interface to create and manage accounts on the network, and furthermore to interact with the network by sending different types of transactions.

Once your blockchain is finished and it is possible to send the transactions, (and custom transactions) it is possible to create a front-end to allow users to interact and use your blockchain application. To connect your front-end to your network, it is recommended to make use of the Lisk Elements’ packages such as the lisk-api-client.

Please see the example applications in the tutorials, whereby proven examples of how to make first interactions with a blockchain application can be found.

See more options on the Interact with the network page.

Exploring the API

The available API endpoints for Lisk SDK node applications are currently identical to the endpoints of the Lisk Core API. Please see the complete API reference for Lisk Core here.

The module http_api of the Lisk Framework describes all API endpoints using swagger.

The API definition file is exported by a node under the path: localhost:3000/api/spec (exchange localhost with the IP of the node you wish to explore). An example of the definition file of a public Lisk Core Testnet node can be seen here: https://testnet.lisk.io/api/spec

This API definiton can be pasted into the swagger-ui front-end to render an interactive API specification of that particular node.

It is also possible to send requests and receive live responses from the node using Swagger UI.

By using the Alpha release of the Lisk SDK, you acknowledge and agree that you have an adequate understanding of the risks associated with the use of the Alpha release of the Lisk SDK, and that it is provided on an "as is" and "as available" basis; without any representations or warranties of any kind. To the fullest extent permitted by law, in no event shall the Lisk Foundation or other parties involved in the development of the Alpha release of the Lisk SDK have any liability whatsoever to any person for any direct or indirect loss, liability, cost, claim, expense, or damage of any kind, whether in contract or in tort; including negligence or otherwise, arising out of or related to the use of all or part of the Alpha release of the Lisk SDK.