Setup ElectrumX Server

An SPV Electrum Server is a server that provides "lite mode" type functionality. These servers run a full node, which maintains a copy of a blockchain's history (a.k.a.) "native mode". The electrum software allows developers and apps like Komodo DeFi Framework to communicate with the blockchain to query balances, transaction history or broadcast signed transactions without needing to download and sync the full chain locally.

A list of known electrum servers is maintained at https://github.com/KomodoPlatform/coins/tree/master/electrums

It's recommended to run at least 2 - 3 electrum servers to ensure stable operation.

Check out the ElectrumX Docs for more info.

Installation

sudo apt-get install python3-setuptools python3-multidict python3.8 libleveldb-dev
cd ~
git clone https://github.com/KomodoPlatform/electrumx-1
cd ~/electrumx-1
pip3 install .
pip3 install .[uvloop,ujson]

Coin Configuration

If you are launching the electrum server for a new smartchain, you will have to add it to the ~/electrumx-1/electrumx/lib/coins.py file. You can skip this step if seeting up an electrum server for KMD or another coin which already exists in this file.

For example, using the RICK Smart Chain:

class Rick(KomodoMixin, EquihashMixin, Coin):
    NAME = "Rick"
    SHORTNAME = "RICK"
    NET = "mainnet"
    TX_COUNT = 55000
    TX_COUNT_HEIGHT = 42000
    TX_PER_BLOCK = 2
    RPC_PORT = 28762
    REORG_LIMIT = 800
    PEERS = []

NAME, SHORTNAME and RPC_PORT are to be changed accordingly.

Electrum Configuration

Run:

cd ~/electrumx-1
sudo mkdir -p /electrumdb/RICK
sudo chown <USERNAME> /electrumdb/RICK
sudo nano /etc/electrumx_RICK.conf

Get your RPC_USER, RPC_PASS and RPC_PORT from your conf file, e.g. ~/.komodo/RICK/RICK.conf, then add them as below:

COIN = Rick
DB_DIRECTORY = /electrumdb/RICK
DAEMON_URL = http://<RPC_USER>:<RPC_PASS>@127.0.0.1:<RPC_PORT>/
SERVICES = tcp://:<ELECTRUM_TCP_PORT>,rpc://:<ELECTRUM_RPC_PORT>,wss://:<ELECTRUM_WSS_PORT>,ssl://:<ELECTRUM_SSL_PORT>
EVENT_LOOP_POLICY = uvloop
PEER_DISCOVERY = self
MAX_SESSIONS = 1000
MAX_SEND = 2000000
INITIAL_CONCURRENT = 50
COST_SOFT_LIMIT = 0
COST_HARD_LIMIT = 0
MAX_SEND = 2000000
BANDWIDTH_UNIT_COST = 10000

# Required for WSS or SSL services
SSL_CERTFILE=/etc/letsencrypt/live/<YOUR_DOMAIN_NAME>/fullchain.pem
SSL_KEYFILE=/etc/letsencrypt/live/<YOUR_DOMAIN_NAME>/privkey.pem

You can read more about the available environment variables in the ElectrumX Docs

Change the SERVICES as required, and allow the SERVICES ports through your firewall. E.g. sudo ufw allow <ELECTRUM_WSS_PORT>

For listing on Komodo DeFi Framework, wss (websocket) and ssl (secure socket) will be required. Please refer to the EFF Certbot instructions for details on setting up SSL certificates (this varies depending on OS and installed web server).

For example, using Ubuntu 20.04 and NGINX:

sudo snap install core; sudo snap refresh core
sudo apt-get remove certbot
sudo snap install --classic certbot
sudo ln -s /snap/bin/certbot /usr/bin/certbot
sudo certbot --nginx

Will create a cert file and key file, and update your nginx sites-enabled config. Add the path to these files in /etc/electrumx_RICK.conf.

Configure as a service

Run:

sudo cp ~/electrumx-1/contrib/systemd/electrumx.service /etc/systemd/system/electrumx_RICK.service
sudo nano /etc/systemd/system/electrumx_RICK.service

Update the following fields in the file (leave the rest as it is):

Description=Electrumx_RICK
EnvironmentFile=/etc/electrumx_RICK.conf
ExecStart=/home/<username>/electrumx-1/electrumx_server
User=<username>

sudo systemctl start electrumx_RICK

To check its status:

sudo systemctl status electrumx_RICK

To review it's logs:

sudo journalctl -f -u electrumx_RICK.service --since today

Confirm the server is running

To issue commands to the electrum server from a local terminal use (change the transaction ID below to one valid for the chain)

echo '{"method":"blockchain.transaction.get","params":["8e3293602465cf6d234fda4a2bb13affb4b5a3fb5bd46eb11a14ed72ac1836e0", true],"id":"test"}' | nc <ELECTRUM_SERVER_IP> <ELECTRUM_TCP_PORT> -i 1 | jq .

To confirm websockets are running:

import websocket

ws = websocket.WebSocket()
ws.connect("wss://<YOUR_DOMAIN_NAME>:<ELECTRUM_WSS_PORT>")
ws.send('{"method":"blockchain.transaction.get","params":["8e3293602465cf6d234fda4a2bb13affb4b5a3fb5bd46eb11a14ed72ac1836e0", true],"id":"test"}')
print(ws.recv())
ws.close()

Maintainence

To keep your electrum server running smoothly, it is recommended to compact the database once a week. We can do this with a crontab entry as below:

33 3 * * 3 sudo systemctl stop electrumx_RICK && COIN=Rick; DB_DIRECTORY=/electrumdb/RICK; /home/<USERNAME>/electrumx-1/electrumx_compact_history && sudo systemctl start electrumx_RICK

This means that every Wednesday at 3:33am, we'll stop the electrum service, compact the database, then restart the service. You should change the day of week for each of your electrum servers so that they dont all go down for maintainence at the same time.

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