electrum – How can I simulate a reorg for testing?

I was able to successfully get electrs to change a transaction from confirmed to unconfirmed by using a second mining node, as suggested by Murch on twitter. My test setup looks like this:

electrum -> electrs -> bitcoind(1) -> bitcoind(2) (generates/invalidates blocks)

The trick was that I had to invalidate two blocks on my mining node (2) which also removed my test transaction from the mining nodes mempool. Then I had to generate 3 more to make a new longest chain that didn’t contain my test transaction. After all that then my electrs node change the transaction from confirmed to unconfirmed.

I don’t know why electrs doesn’t mark the transaction to unconfirmed when I invalidate the block on the one node it’s connected to. I tried the same test with electrumx and it behaved the same way as electrs. For anyone else trying to repro this test all the gory details are below:

Install electrs

sudo apt-get update
sudo apt-get install librocksdb-dev wget
sudo apt-get install -qqy cargo clang cmake build-essential

From electrs git repo being tested:

ROCKSDB_INCLUDE_DIR=/usr/include
ROCKSDB_LIB_DIR=/usr/lib
cargo install --locked --path .
electrs --version

Install bitcoind

BITCOIND_VERSION=22.0

wget -q https://bitcoincore.org/bin/bitcoin-core-$BITCOIND_VERSION/bitcoin-$BITCOIND_VERSION-x86_64-linux-gnu.tar.gz
tar xvf bitcoin-$BITCOIND_VERSION-x86_64-linux-gnu.tar.gz
mv -v bitcoin-$BITCOIND_VERSION/bin/bitcoind .
mv -v bitcoin-$BITCOIND_VERSION/bin/bitcoin-cli .

Install electrum client

sudo apt-get install -qqy git libsecp256k1-0 python3-cryptography python3-setuptools python3-pip jq curl

git clone --recurse-submodules https://github.com/spesmilo/electrum/

python3 -m pip install -e electrum/

electrum version --offline

Remove old data

rm -rf data/
mkdir -p data/{bitcoin1,bitcoin2,electrum,electrs}

Start bitcoind node 1 and fund wallet

./bitcoind -version
./bitcoind -regtest -regtest -txindex=1 -datadir=data/bitcoin1 -printtoconsole=0 -fallbackfee=0.0001 &
BITCOIND1_PID=$!

Start and fund mining bitcoind node 2 and add to node 1

./bitcoind -regtest -txindex=1 -datadir=data/bitcoin2 -port=28444 -rpcport=28443 -printtoconsole=0 -fallbackfee=0.0001 &
BITCOIND2_PID=$!

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 createwallet "test"
NODE_ADDR=`./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getnewaddress`
echo $NODE_ADDR

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 generatetoaddress 101 $NODE_ADDR 
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getwalletinfo

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 addnode "127.0.0.1:18444" "add"

./bitcoin-cli -regtest -datadir=data/bitcoin1 getpeerinfo
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getpeerinfo

Status of bitcoind nodes

Start electrs and electrum

export RUST_LOG=electrs=debug
electrs \
  --db-dir=data/electrs \
  --daemon-dir=data/bitcoin1 \
  --network=regtest \
  2> data/electrs/regtest-debug.log &
ELECTRS_PID=$!

electrum --regtest daemon --server localhost:60401:t -1 -vDEBUG 2> data/electrum/regtest-debug.log &
ELECTRUM_PID=$!

Fund electrum wallet

electrum --regtest --wallet=data/electrum/wallet getinfo
electrum --regtest --wallet=data/electrum/wallet create --seed_type=segwit
electrum --regtest --wallet=data/electrum/wallet load_wallet
electrum --regtest --wallet=data/electrum/wallet getbalance
WALLET_ADDR1=`electrum --regtest --wallet=data/electrum/wallet getunusedaddress`
echo $WALLET_ADDR1

TX1=`./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 sendtoaddress $WALLET_ADDR1 1.11 "test1"`

./bitcoin-cli -regtest -datadir=data/bitcoin1 getrawtransaction $TX1 true

electrum --regtest --wallet=data/electrum/wallet getaddresshistory $WALLET_ADDR1
electrum --regtest --wallet=data/electrum/wallet getbalance

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 generatetoaddress 1 $NODE_ADDR

./bitcoin-cli -regtest -datadir=data/bitcoin1 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getrawtransaction $TX1 true

electrum --regtest --wallet=data/electrum/wallet getaddresshistory $WALLET_ADDR1
electrum --regtest --wallet=data/electrum/wallet getbalance

Status of bitcoind nodes

Status of electrum wallet

confirmed: 1.11

Invalidate 1st block on node 2

TIP=`./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443  getbestblockhash`
echo $TIP

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 invalidateblock $TIP

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getmempoolinfo 

./bitcoin-cli -regtest -datadir=data/bitcoin1 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin1 getmempoolinfo 

electrum --regtest --wallet=data/electrum/wallet getbalance

Status of bitcoind nodes

Status of electrum wallet

confirmed: 1.11

Invalidate 2nd block on node 2

TIP=`./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getbestblockhash`
echo $TIP

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 invalidateblock $TIP

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getblockchaininfo
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getmempoolinfo 

./bitcoin-cli -regtest -datadir=data/bitcoin1 getblockchaininfo
./bitcoin-cli -regtest -datadir=data/bitcoin1 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin1 getmempoolinfo

electrum --regtest --wallet=data/electrum/wallet getbalance
electrum --regtest --wallet=data/electrum/wallet listunspent

Status of bitcoind nodes

Status of electrum wallet

confirmed: 1.11

Generate 3 new blocks on node 2

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 generatetoaddress 3 $NODE_ADDR

./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getblockchaininfo
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin2 -rpcport=28443 getmempoolinfo

./bitcoin-cli -regtest -datadir=data/bitcoin1 getblockchaininfo
./bitcoin-cli -regtest -datadir=data/bitcoin1 getrawtransaction $TX1 true
./bitcoin-cli -regtest -datadir=data/bitcoin1 getmempoolinfo

electrum --regtest --wallet=data/electrum/wallet getbalance

Status of bitcoind nodes

Status of electrum wallet

confirmed: 0
unconfirmed: 1.11

Stop daemons

electrum --regtest --wallet=data/electrum/wallet stop
wait $ELECTRUM_PID

kill -INT $ELECTRS_PID
wait $ELECTRS_PID

./bitcoin-cli -regtest -datadir=data/bitcoin1 stop
wait $BITCOIND1_PID

./bitcoin-cli -regtest -datadir=data/bitcoin2 --rpcport=28443 stop
wait $BITCOIND2_PID