Your first Kagome chain

In this tutorial you will learn how to execute Kagome-based Polkadot-host chain which can be used as a cryptocurrency, and interact with it by sending extrinsics and executing queries.

Prerequisites

1. Kagome validating node binary built as described here.

2. For your convenience make sure you have this binary included into your path:

   ```bash

   from Kagome's root repo:

   PATH=$PATH:/build/node/ ```

3. Python 3 installed in the system with substrate-interface package installed

   > If you are not sure if you have requests package installed in your python run pip3 install substrate-interface

Tutorial

During this tutorial we will:

1. Launch Kagome network using prepared genesis file
2. Query the balance of Alice account
3. Send extrinsic that transfers some amount of currency from Alice to Bob
4. Query again the balance of Alice to make sure balance was updated

Launch Kagome network

For this tutorial we will spin up a simple network of a single peer with predefined genesis.

To start with let's navigate into the node's folder:

cd examples/first_kagome_chain

first_kagome_chain folder contains necessary configuration files for our tutorial:

• localchain.json – genesis file for our network. It contains necessary key-value pairs that should be inserted before the genesis block
• base_path – Directory, containing kagome base path. It contains several dirs, each one named with the chain id, which data it stores (dev in this case). Data for each chain consists of db/ (will be initialized on node startup) and keystore/ (keys to sign the messages sent by our authority). The latter has to exist prior to the node start. This behaviour will be improved in the future.

localchain.json contains Alice and Bob accounts. Both have 999998900.0 amount of crypto. Their keys can be generated using subkey tool:

subkey inspect //Alice
# Secret Key URI `//Alice` is account:
# Secret seed:      0xe5be9a5092b81bca64be81d212e7f2f9eba183bb7a90954f7b76361f6edb5c0a
# Public key (hex): 0xd43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d
# Account ID:       0xd43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d
# SS58 Address:     5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY

subkey inspect //Bob  
# Secret Key URI `//Bob` is account:
# Secret seed:      0x398f0c28f98885e046333d4a41c19cee4c37368a9832c6502f6cfd182e2aef89
# Public key (hex): 0x8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48
# Account ID:       0x8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48
# SS58 Address:     5FHneW46xGXgs5mUiveU4sbTyGBzmstUspZC92UhjJM694ty

If you are running this tutorial not for the first time, then make sure you cleaned up your storage as follows (assuming storage files are generated in ldb/ folder):

rm -rf ldb

---

For this tutorial you can start a single node network as follows:

kagome \
    --validator \
    --chain localchain.json \
    --base-path base_path \
    --port 30363 \
    --rpc-port 9933 \
    --ws-port 9944

Let's look at this flags in detail:

Flag	Description
--validator	optional, enables validator mode
--chain	mandatory, chainspec file path
--base-path	mandatory, base kagome directory path
--port	port for p2p interactions
--rpc-port	port for RPC over HTTP
--ws-port	port for RPC over Websocket protocol

More flags info available by running kagome --help.

You should see the log messages notifying about produced and finalized the blocks.

Now chain is running on a single node. To query it we can use localhost's ports 9933 for http- and 9944 for websockets-based RPCs.

Kagome blockchain is constantly producing new blocks, even if there were no transactions in the network.

Query the balance

Now open second terminal and go to the transfer folder, available from the projects root directory.

cd examples/transfer

This folder contains two python scripts:

1. balance.py <address> <account_id> – executes query to kagome, which returns balance of provided account
   • <address> address node's http service
   • <account_id> id of account being queried
2. transfer.py <address> <seed> <dest> <amount> – sends provided extrinsic
   • <address> address node's http service
   • <seed> secret seed of source account
   • <dest> destination account
   • <amount> amount of crypto to be transferred

Let's query current balance of Alice's account.

python3 balance.py localhost:9933 5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY
# Current free balance: 10000.0  

Let's do the same for the Bob's account.

python3 balance.py localhost:9933 5FHneW46xGXgs5mUiveU4sbTyGBzmstUspZC92UhjJM694ty
# Current free balance: 10000.0  

Send extrinsic

We can generate extrinsic using the following command:

This command will create extrinsic that transfers 1 from Alice to Bob's account (Alice's account is defined by secret seed and Bob's account by account id).

To send extrinsic use transfer.py script as follows:

python3 transfer.py localhost:9933 0xe5be9a5092b81bca64be81d212e7f2f9eba183bb7a90954f7b76361f6edb5c0a 5FHneW46xGXgs5mUiveU4sbTyGBzmstUspZC92UhjJM694ty 1
Extrinsic '0x315060176633a3e20656bd15c6eceff63b9f8bdc45595dc8ad52a02ae38d1708' sent

Query again the balances

Now let's check that extrinsic was actually applied:

Get the balance of Bob's account:

python3 balance.py localhost:9933 5FHneW46xGXgs5mUiveU4sbTyGBzmstUspZC92UhjJM694ty
# Current free balance: 10001.0  

We can see that Bob's balance was increased by 1 as it was set on the subkey command

Now let's check Alice's account:

python3 balance.py localhost:9933 5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY
Current free balance: 9998.999829217584  

We can see that Alice's account was decreased by more than 1. This is caused by the commission paid for transfer

Conclusion

Now you know how to set up single peer kagome network and execute transactions on it