mempool/backend

Mempool Backend

These instructions are mostly intended for developers.

If you choose to use these instructions for a production setup, be aware that you will still probably need to do additional configuration for your specific OS, environment, use-case, etc. We do our best here to provide a good starting point, but only proceed if you know what you're doing. Mempool does not provide support for custom setups.

See other ways to set up Mempool on the main README.

Jump to a section in this doc:

• Set Up the Backend
• Development Tips

Setup

1. Clone Mempool Repository

Get the latest Mempool code:

git clone https://github.com/mempool/mempool
cd mempool

Check out the latest release:

latestrelease=$(curl -s https://api.github.com/repos/mempool/mempool/releases/latest|grep tag_name|head -1|cut -d '"' -f4)
git checkout $latestrelease

2. Configure Bitcoin Core

Turn on txindex, enable RPC, and set RPC credentials in bitcoin.conf:

txindex=1
server=1
rpcuser=mempool
rpcpassword=mempool

3. Configure Electrum Server

Pick an Electrum Server implementation, configure it, and make sure it's synced.

This step is optional. You can run Mempool without configuring an Electrum Server for it, but address lookups will be disabled.

4. Configure MariaDB

Mempool needs MariaDB v10.5 or later. If you already have MySQL installed, make sure to migrate any existing databases before installing MariaDB.

Get MariaDB from your operating system's package manager:

# Debian, Ubuntu, etc.
apt-get install mariadb-server mariadb-client

# macOS
brew install mariadb
mysql.server start

Create a database and grant privileges:

MariaDB [(none)]> drop database mempool;
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> create database mempool;
Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> grant all privileges on mempool.* to 'mempool'@'%' identified by 'mempool';
Query OK, 0 rows affected (0.00 sec)

5. Prepare Mempool Backend

Build

Make sure to use Node.js 16.10 and npm 7.

Install dependencies with npm and build the backend:

cd backend
npm install
npm run build

Configure

In the backend folder, make a copy of the sample config file:

cp mempool-config.sample.json mempool-config.json

Edit mempool-config.json as needed.

In particular, make sure:

• the correct Bitcoin Core RPC credentials are specified in CORE_RPC
• the correct BACKEND is specified in MEMPOOL:
  • "electrum" if you're using romanz/electrs or cculianu/Fulcrum
  • "esplora" if you're using Blockstream/electrs
  • "none" if you're not using any Electrum Server

6. Run Mempool Backend

Run the Mempool backend:

npm run start

You can also set env var MEMPOOL_CONFIG_FILE to specify a custom config file location:

MEMPOOL_CONFIG_FILE=/path/to/mempool-config.json npm run start

When it's running, you should see output like this:

Mempool updated in 0.189 seconds
Updating mempool
Mempool updated in 0.096 seconds
Updating mempool
Mempool updated in 0.099 seconds
Updating mempool
Calculated fee for transaction 1 / 10
Calculated fee for transaction 2 / 10
Calculated fee for transaction 3 / 10
Calculated fee for transaction 4 / 10
Calculated fee for transaction 5 / 10
Calculated fee for transaction 6 / 10
Calculated fee for transaction 7 / 10
Calculated fee for transaction 8 / 10
Calculated fee for transaction 9 / 10
Calculated fee for transaction 10 / 10
Mempool updated in 0.243 seconds
Updating mempool

7. Set Up Mempool Frontend

With the backend configured and running, proceed to set up the Mempool frontend.

Development Tips

Set Up Backend Watchers

The Mempool backend is static. TypeScript scripts are compiled into the dist folder and served through a Node.js web server.

As a result, for development purposes, you may find it helpful to set up backend watchers to avoid the manual shutdown/recompile/restart command-line cycle.

First, install nodemon and ts-node:

npm install -g ts-node nodemon

Then, run the watcher:

nodemon src/index.ts --ignore cache/ --ignore pools.json

nodemon should be in npm's global binary folder. If needed, you can determine where that is with npm -g bin.

Useful Regtest Commands

Helpful link: https://gist.github.com/System-Glitch/cb4e87bf1ae3fec9925725bb3ebe223a

Run bitcoind on regtest:

bitcoind -regtest -rpcport=8332

Create a new wallet, if needed:

bitcoin-cli -regtest -rpcport=8332 createwallet test

Load wallet (this command may take a while if you have lot of UTXOs):

bitcoin-cli -regtest -rpcport=8332 loadwallet test

Get a new address:

address=$(./src/bitcoin-cli -regtest -rpcport=8332 getnewaddress)

Mine blocks to the previously generated address. You need at least 101 blocks before you can spend. This will take some time to execute (~1 min):

bitcoin-cli -regtest -rpcport=8332 generatetoaddress 101 $address

Send 0.1 BTC at 5 sat/vB to another address:

./src/bitcoin-cli -named -regtest -rpcport=8332 sendtoaddress address=$(./src/bitcoin-cli -regtest -rpcport=8332 getnewaddress) amount=0.1 fee_rate=5

See more example of sendtoaddress:

./src/bitcoin-cli sendtoaddress # will print the help

Mini script to generate transactions with random TX fee-rate (between 1 to 100 sat/vB). It's slow so don't expect to use this to test mempool spam, except if you let it run for a long time, or maybe with multiple regtest nodes connected to each other.

#!/bin/bash
address=$(./src/bitcoin-cli -regtest -rpcport=8332 getnewaddress)
for i in {1..1000000}
do
  ./src/bitcoin-cli -regtest -rpcport=8332 -named sendtoaddress address=$address amount=0.01 fee_rate=$(jot -r 1  1 100)
done

Generate block at regular interval (every 10 seconds in this example):

watch -n 10 "./src/bitcoin-cli -regtest -rpcport=8332 generatetoaddress 1 $address"