Fruzhin is a Java Implementation of the Polkadot Host. The ultimate goal for Fruzhin is to be able to function as an authoring and relaying node, increasing security of the Polkadot Protocol. It's been funded by Polkadot Pioneers Prize.

Warning Fruzhin is in pre-production state

Status

• Light Client
• Full Node
• Authoring Node
• Relaying Node

Getting started

Clone

git clone https://github.com/LimeChain/Fruzhin.git
cd Fruzhin

Setup & Build steps

Java Version

Fruzhin only works with Java 21 Coretto. Using any other version may cause "cannot calculate secret" errors when running the node:

org.bouncycastle.tls.crypto.TlsCryptoException: cannot calculate secret

If you have multiple java version installed please make sure you're using 21:

export JAVA_HOME=`/usr/libexec/java_home -v 21`

Wasmer-Java dylib setup

Note: This step will be automated in the future

Apple silicon users can skip this step. For now, you will have to manually grab the compiled wasmer-java dynamic library file from the subfolder under ./wasmer-setup corresponding to your architecture type. Copy the file to the Java Extensions folder:

/Library/Java/Extensions

Build

./gradlew build

Running Fruzhin

Sync with official chain

java -jar build/libs/Fruzhin-0.1.0.jar -n polkadot --node-mode full --sync-mode full

• -n(network) could be westend, polkadot or kusama
• --node-mode could be full or light
• --sync-mode could be full or warp

Local development

In order to use the Fruzhin node for local development you will first need to start another node that would serve as a peer.

For the sake of this example we will use Paritytech's implementation. If you are not familiar with how to run a node see this.

Once you have successfully built the Polkadot project run the node via polkadot --dev. (The node starts on port 9944 by default)

Now you have 2 options:

• Use the automated local_dev.sh script
• Manual setup.

Automated script

1. Install JQ.

   sudo apt-get install jq Ubuntu

   brew install jq MacOS

2. Head to the main directory of Fruzhin execute the script ./local_dev.sh.

Manual setup

1. Fetch the chain spec

   curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "sync_state_genSyncSpec", "params": [true]}' http://localhost:9944

   The lightSyncState field is important for the light client to work. Without it, the light client won't have a checkpoint to start from and could be long-range attacked

2. Create a new westend-local.json inside of the genesis project directory.

3. Copy the contents of the result field from the fetched chain spec into the newly created westend-local.json.

4. In order to comply with the project requirements change the json structured as follows:

Fetched chain spec

{
  "genesis": {
    "raw": {
      "top": {},
      "childrenDefault": {}
    }
  }
}

Desired chain spec

{
  "genesis": {
     "top": {},
     "childrenDefault": {}
  }
}

5. Fetch the local boot nodes.

   curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "system_localListenAddresses"}' http://localhost:9944

   Paste the response into the bootNodes field of the westend-local.json chain spec.

Build & Run

1. Build project

   ./gradlew build
   

2. Run Fruzhin

   java -jar build/libs/Fruzhin-0.1.0.jar -n 'local' --node-mode 'full'/'light' --sync-mode 'full'/'warp' --db-recreate true/false