init_replication.sh

#!/bin/bash

# Wait for master to be healthy
echo "Waiting for postgres-master to be healthy..."
docker compose ps postgres-master | grep "healthy" > /dev/null
while [ $? -ne 0 ]; do
  sleep 5
  docker compose ps postgres-master | grep "healthy" > /dev/null
done
echo "postgres-master is healthy."

MASTER_HOST=postgres-master
REPLICA_CONTAINER=postgres-replica
POSTGRES_USER=${POSTGRES_USER:-myuser}
POSTGRES_DB=${POSTGRES_DB:-mydb}

# Stop replica if running
docker compose stop $REPLICA_CONTAINER

# Remove existing replica data (CAUTION: This will delete existing replica data)
docker compose rm -s -f -v $REPLICA_CONTAINER
docker volume rm postgres_replica_data || true # Ensure the volume is removed

# Recreate replica service to ensure fresh volume
docker compose create $REPLICA_CONTAINER

# Create replication user on master
echo "Creating replication user on master..."
docker compose exec postgres-master psql -U $POSTGRES_USER -d $POSTGRES_DB -c "CREATE USER repl_user REPLICATION LOGIN CONNECTION LIMIT -1 ENCRYPTED PASSWORD 'repl_password';"

# Take base backup from master to replica's data directory
echo "Taking base backup from master to replica..."
docker compose exec $REPLICA_CONTAINER sh -c "pg_basebackup -h $MASTER_HOST -U repl_user -D /var/lib/postgresql/data/pgdata_replica -F p -X stream -P -R -w"

# Create recovery.signal file in replica's data directory
echo "Creating recovery.signal on replica..."
docker compose exec $REPLICA_CONTAINER touch /var/lib/postgresql/data/pgdata_replica/recovery.signal

# Start replica
echo "Starting postgres-replica..."
docker compose start $REPLICA_CONTAINER

echo "PostgreSQL replication setup complete."