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 only provides support for custom setups to project sponsors through Mempool Enterprise®.

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.

The build process requires Rust to be installed.

Install dependencies with npm and build the backend:

cd backend
npm install --no-install-links # npm@9.4.2 and later can omit the --no-install-links
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/

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

Create a new wallet, if needed:

bitcoin-cli -regtest createwallet test

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

bitcoin-cli -regtest loadwallet test

Get a new address:

address=$(bitcoin-cli -regtest 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 generatetoaddress 101 $address

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

bitcoin-cli -named -regtest sendtoaddress address=$(bitcoin-cli -regtest getnewaddress) amount=0.1 fee_rate=5

See more example of sendtoaddress:

bitcoin-cli sendtoaddress # will print the help

Mini script to generate random network activity (random TX count with random tx fee-rate). 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=$(bitcoin-cli -regtest getnewaddress)
bitcoin-cli -regtest generatetoaddress 101 $address
for i in {1..1000000}
do
   for y in $(seq 1 "$(jot -r 1 1 1000)")
   do
      bitcoin-cli -regtest -named sendtoaddress address=$address amount=0.01 fee_rate=$(jot -r 1 1 100)
   done
   bitcoin-cli -regtest generatetoaddress 1 $address
   sleep 5
done

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

watch -n 10 "bitcoin-cli -regtest generatetoaddress 1 $address"

Mining pools update

By default, mining pools will be not automatically updated regularly (config.MEMPOOL.AUTOMATIC_BLOCK_REINDEXING is set to false).

To manually update your mining pools, you can use the --update-pools command line flag when you run the nodejs backend. For example npm run start --update-pools. This will trigger the mining pools update and automatically re-index appropriate blocks.

You can enabled the automatic mining pools update by settings config.MEMPOOL.AUTOMATIC_BLOCK_REINDEXING to true in your mempool-config.json.

When a coinbase tag or coinbase address change is detected, all blocks tagged to the unknown mining pools (starting from height 130635) will be deleted from the blocks table. Additionaly, all blocks which were tagged to the pool which has been updated will also be deleted from the blocks table. Of course, those blocks will be automatically reindexed.

Re-index tables

You can manually force the nodejs backend to drop all data from a specified set of tables for future re-index. This is mostly useful for the mining dashboard and the lightning explorer.

Use the --reindex command to specify a list of comma separated table which will be truncated at start. Note that a 5 seconds delay will be observed before truncating tables in order to give you a chance to cancel (CTRL+C) in case of misuse of the command.

Usage:

npm run start --reindex=blocks,hashrates

Example output:

Feb 13 14:55:27 [63246] WARN: <lightning> Indexed data for "hashrates" tables will be erased in 5 seconds (using '--reindex')
Feb 13 14:55:32 [63246] NOTICE: <lightning> Table hashrates has been truncated

Reference: mempool#1269