Getting started with DApp development

HotPocket developer kit (hpdevkit)

Evernode uses HotPocket as its smart contract engine. HotPocket smart contracts can be developed using any POSIX-compliant language/framework. Using the HotPocket developer kit, you can easily develop and test HotPocket smart contracts on your local PC for free.

Throughout our documentation we may use the terms “DApp”, “smart contract” or “contract” due to historical reasons. They all mean the same thing.

Installation

Prerequisites

The HotPocket developer kit requires you to install Docker Engine and NodeJs on your development machine.

Cross-platform support

The HotPocket developer kit is a global npm package that supports both Linux and Windows operating systems.

Install prerequisites.
Run the following command to install hpdevkit on your machine:
```
npm i hpdevkit -g
```

NOTE: In Linux platforms, installation requires root privileges. Hence, add sudo to the above command. Final contract bundles are deployed and run in Linux environment. Binary outputs built-in Windows environments might cause errors. Hence the recommended development platform is Linux

Creating a HotPocket smart contract

You can use the HotPocket developer kit to generate smart contract projects such that everything is pre-configured. Here, we are creating a NodeJs smart contract (This assumes you have prior experience with developing NodeJs applications):

hpdevkit gen nodejs starter-contract myproj
cd myproj
npm install
npm start

The ‘npm start’ command will build and deploy the NodeJs smart contract into a HotPocket cluster running on your machine. It will also start printing the console output from the HotPocket instance. You can press Ctrl+C at any time to exit from monitoring the HotPocket console output. However, the HotPocket instance will continue to run even after you exit the monitoring console.

Viewing logs

You can re-enter the monitoring console with the command hpdevkit logs 1, where 1 is the HotPocket instance number you wish to monitor.

Changing the cluster size

In order to resize the HotPocket cluster, you need to delete and re-create it:

NOTE: This will delete the running app cluster. you will lose the app data.

Delete the existing cluster using the hpdevkit clean command.

Set the HP_CLUSTER_SIZE environment variable to the size you want.

# Windows (command prompt)
set HP_CLUSTER_SIZE=5

# Windows (powershell)
$env:HP_CLUSTER_SIZE=5

# Linux (bash)
export HP_CLUSTER_SIZE=5

Deploy your contract again with npm start.

Creating HotPocket client application

You can use the HotPocket developer kit to generate a HotPocket client application such that everything is pre-configured. Here, we are creating a NodeJs client (This assumes you have prior experience with developing NodeJs applications):

hpdevkit gen nodejs blank-client myclient
cd myclient
npm install
node myclient.js

This will start the client application and connect a HotPocket node listening to port 8081. Also, note that you need to have HotPocket nodes running on your machine for the client to connect.

Listing available code templates

You can use the hpdevkit list command to list all available comtract and client code templates.

hpdevkit list <platform>

<platform> is an optional parameter that can be used to filter code templates based on the platform they are designed for.

Deploying contract files directory to the cluster

You can use the hpdevkit deploy command to deploy a specified contract file directory to a HotPocket cluster.

hpdevkit deploy <contract-files-directory>

<contract-files-directory> should contain the path of the contract directory to be deployed.

The following options can be specified with this command:

Name	Description
`-m, --multi-sig [multi-sig]`	Multi-signing enabled.
`-a, --master-addr [master-addr]`	Master address for multi-signing.
`-s, --master-sec [master-sec]`	Master secret for multi-signing.

Advanced usage

# Stop and clean-up everything (required for changing cluster size)
hpdevkit clean

# View a specific node's logs
hpdevkit logs <node number>

# Start/stop all nodes
hpdevkit start
hpdevkit stop

# Start/stop a specific node
hpdevkit start <node number>
hpdevkit stop <node number>

# Add a new node to the cluster
# (The new node will use the existing UNL and become an observer node)
hpdevkit spawn

If the contract files directory also contains a file named hp.cfg.override, it will be used to override the hp.cfg of all nodes. This can be used to set contract-specific parameters like ‘bin_path’ and ‘bin_args’

An example hp.cfg.override file for a NodeJs application (the HotPocket developer kit NodeJs starter contract automatically includes this file for you):

{
    "contract": {
        "bin_path": "/usr/bin/node",
        "bin_args": "app.js"
    }
}

Inspect contract files of all nodes

You can inspect the files of all the nodes of the cluster using Docker Desktop. hpdevkit volume

Environment variables

hpdevkit CLI supports the following environment variables, all of which are optional:

Name	Description	Default value
HP_CLUSTER_SIZE	The number of nodes in the cluster. This only takes effect with a fresh cluster.	`3`
HP_DEFAULT_NODE	The node which the ‘deploy’ command uses to display logs.	`1`
HP_DEVKIT_IMAGE	The Docker image to be used for devkit cluster management.	`evernode/hpdevkit`
HP_INSTANCE_IMAGE	The Docker image to be used for HotPocket instances.	`evernode/hotpocket:latest-ubt.20.04-njs.20`
HP_USER_PORT_BEGIN	The starting user port number for the cluster.	`8081`
HP_PEER_PORT_BEGIN	The starting peer port number for the cluster.	`22861`
HP_EV_NETWORK	Evernode network to be used. This is only for Xahau transaction contracts.	`mainnet`
HP_MULTI_SIGNER_WEIGHT	Multi signer weight for each cluster node’s signer account. This is only for Xahau transaction contracts.	`1`
HP_MULTI_SIGNER_QUORUM	Multi signer quorum ([0-1] - Percentage of total weights) for each cluster node’s signer account. This is only for Xahau transaction contracts.	`0.8`

Updates

Run one of the following commands to update hpdevkit to the latest version, and update the supporting docker images:

Using hpdevkit CLI
```
hpdevkit update
```
Using npm
```
npm update hpdevkit -g
```

NOTE: You need to re-deploy your contracts for the new changes to take effect.

Uninstall

Run the following command to uninstall hpdevkit and the supporting docker images and containers:

Using hpdevkit CLI
```
hpdevkit uninstall
```

NOTE: Uninstalling from hpdevkit CLI is recommended. If you uninstall using npm, you will have to clean the hpdevkit supporting docker images and containers manually.

NOTE: In Linux platforms, you will need root privileges to execute updates and uninstallations. Hence, add sudo to the above commands.

Reporting issues

Report issues here.

Continue reading

HotPocket Concepts.

HotPocket SDK Basics.

Deploy your locally developed DApp in evernode using evdevkit.