Hedera Stable Coin

Prerequisites

• Java 14+

• PostgreSQL 12+

• TimescaleDB

see install prerequisites at the end of this document for assistance if needed

Build

# Create the development database. Assumes that TimescaleDB is running on `localhost:5432`
sudo su -l postgres
createdb -h localhost -U postgres stable_coin
# CTRL+D to exit postgres user shell

# Install git
sudo apt install git

# Clone the repository (note, if you're setting up the full demo, you can skip this)
git clone https://github.com/hashgraph/hedera-stable-coin.git

#if you're setting up the full demo
cd stable-coin-java-hcs
#else
cd hedera-stable-coin

# Assemble JAR.
./gradlew build

Prepare environment variables

cp .env.sample .env
nano .env

set the following environment variables

Required variables

These variables must be set to your environment before starting the token node

Database information for transaction and event logging

• HSC_DATABASE_URL=postgresql://localhost:5432/
• HSC_POSTGRES_DB=stable_coin
• HSC_DATABASE_USERNAME=postgres
• HSC_DATABASE_PASSWORD=password

Hedera Network to use (mainnet, testnet, previewnet)

• HSC_NETWORK=testnet

Operator on Hedera to use to execute any transactions (This is the account that will get charged).

Note that an operator is not required to run a token node on an existing topic.

• HSC_OPERATOR_ID={0.0.___}
• HSC_OPERATOR_KEY={Private key 302e___}

First Run

java -jar build/libs/stable-coin-0.2.0.jar

Note the topic id output to the console on first run and update .env file accordingly for subsequent runs. You can CTRL+C as soon as the new topic id is shown.

After first run

After the first token node is run, it will output a topic id for subsequent uses, copy this topic id and update below.

HSC_TOPIC_ID={0.0.____}

Subsequent runs

java -jar build/libs/stable-coin-0.2.0.jar

Optional .env variables

These variables are defaulted and may be ignored for initial testing

Required when creating a new stable coin contract instance.

• HSC_TOKEN_NAME=Fire
• HSC_TOKEN_SYMBOL=XFR
• HSC_TOKEN_DECIMAL=2
• HSC_TOTAL_SUPPLY=10000

Optional when creating a new stable coin contract instance.

Defaults to the operator key.

Note: Running java -jar build/libs/stable-coin-0.2.0.jar --newkeys will generate and output a set of keys you may use here in the environment file.

Remember to uncomment these variables.

• HSC_OWNER_KEY={Private Key 302___}
• HSC_SUPPLY_MANAGER_KEY_PUB={Public Key 302___}
• HSC_COMPLIANCE_MANAGER_KEY_PUB={Public Key 302___}
• HSC_ENFORCEMENT_MANAGER_KEY_PUB={Public Key 302___}

Port the HTTP service will be served on

• HSC_STATE_PORT=9000

How often (in seconds) to commit to a persistent store for logging and state.

• HSC_COMMIT_INTERVAL=5

Directory to store state snapshots.

The token node will read the latest snapshot on launch to skip reading from the entire topic.

• HSC_STATE_DIR=_state

Maximum number of state snaphots to keep in the state directory

• HSC_STATE_HISTORY_SIZE=3

Optional when running generate

• GENERATE_OWNER_KEY={private keys 302___}
• HSC_SUPPLY_MANAGER_KEY_PUB={private keys 302___}
• GENERATE_COMPLIANCE_MANAGER_KEY={private keys 302___}
• GENERATE_ENFORCEMENT_MANAGER_KEY={private keys 302___}

API

The current state of the contract is available via the State API. By default, this is exposed at port 9000 and can be changed via the HSC_STATE_PORT variable.

Get Token Information

http GET :9000/

{
    "complianceManager": "cf750f7c2adc1baf87b3de9df1c317a5f845c994d0b28a6ec4655e7fc59b75dc",
    "decimals": "2",
    "name": "Fire",
    "owner": "cf750f7c2adc1baf87b3de9df1c317a5f845c994d0b28a6ec4655e7fc59b75dc",
    "proposedOwner": "0000000000000000000000000000000000000000000000000000000000000000",
    "supplyManager": "cf750f7c2adc1baf87b3de9df1c317a5f845c994d0b28a6ec4655e7fc59b75dc",
    "symbol": "XFR",
    "totalSupply": "10000"
}

Get Address

http GET :9000/:address
http GET :9000/cf750f7c2adc1baf87b3de9df1c317a5f845c994d0b28a6ec4655e7fc59b75dc

{
    "balance": "10000",
    "isFrozen": false,
    "isKycPassed": true
}

Get Allowance for Address

http GET :9000/:address/allowance/:other
http GET :9000/cf750f7c2adc1baf87b3de9df1c317a5f845c994d0b28a6ec4655e7fc59b75dc/allowance/cf750f7c2adc1baf87b3de9df1c317a5f845c994d0b28a6ec4655e7fc59b75dd

{
    "allowance": "0"
}

Install prerequisites

Note: These installation instructions are applicable to Debian 4.19, other operating systems may differ.

Java 14+

# update and upgrade apt
sudo apt upgrade
sudo apt update

# install curl and wget
sudo apt -y install wget curl

# download JDK14
curl -O https://download.java.net/java/GA/jdk14/076bab302c7b4508975440c56f6cc26a/36/GPL/openjdk-14_linux-x64_bin.tar.gz

# Extract
tar xvf openjdk-14_linux-x64_bin.tar.gz

# Move to /opt
sudo mv jdk-14 /opt/

# Setup environment
sudo nano /etc/profile.d/jdk14.sh
export JAVA_HOME=/opt/jdk-14
export PATH=$PATH:$JAVA_HOME/bin
# save file

# Source profile
source /etc/profile.d/jdk14.sh

# Confirm java version
echo $JAVA_HOME
/opt/jdk-14

java -version
openjdk version "14" 2020-03-17
OpenJDK Runtime Environment (build 14+36-1461)
OpenJDK 64-Bit Server VM (build 14+36-1461, mixed mode, sharing)

TimescaleDB

(instructions from https://docs.timescale.com/latest/getting-started/installation/debian/installation-apt-debian)

Note: Assumes wget is installed

# `lsb_release -c -s` should return the correct codename of your OS
echo "deb http://apt.postgresql.org/pub/repos/apt/ $(lsb_release -c -s)-pgdg main" | sudo tee /etc/apt/sources.list.d/pgdg.list
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update

# Add timescale repository
sudo sh -c "echo 'deb https://packagecloud.io/timescale/timescaledb/debian/ `lsb_release -c -s` main' > /etc/apt/sources.list.d/timescaledb.list"
wget --quiet -O - https://packagecloud.io/timescale/timescaledb/gpgkey | sudo apt-key add -
sudo apt-get update

# Now install appropriate package for PG version
sudo apt-get install timescaledb-postgresql-12

# Configure the database, respond "y" to prompts
sudo timescaledb-tune

# Restart PostgreSQL instance
sudo service postgresql restart

# Set password for postgres user
sudo passwd postgres

# Connect to the database
sudo su -l postgres
psql

# psql (12.4 (Debian 12.4-1.pgdg100+1))
# Type "help" for help.

# Set postgres user password to 'password'
alter user postgres with password 'password';

CTRL+D to exit psql

CTRL+D again to return to your user shell

Developing further

If you make changes to the database schema, you'll need to rebuild the automatically generated code.

# Set environment variables
export HSC_DATABASE_URL="postgresql://localhost:5432/"
export HSC_POSTGRES_DB="stable_coin"
export HSC_DATABASE_USERNAME="postgres"
export HSC_DATABASE_PASSWORD="password"

# Create / update entities in the database
./gradlew flywayMigrate

# Build java artifacts
./gradlew jooqGenerate

License

Licensed under Apache License, Version 2.0 – see LICENSE in this repo or apache.org/licenses/LICENSE-2.0.