Initialize PosgreSQL replica overriding PGDATA

init-replica.sh

#!/bin/bash

set -o errexit
set -o pipefail
set -o nounset

DATA_DIR="/var/lib/postgresql/data"

# Check if the data directory is empty
if [ "$(ls -A "$DATA_DIR")" ]; then
    echo "Data directory is not empty.  Assuming replica is already initialized."
else
    echo "Data directory is empty.  Initializing replica with pg_basebackup..."

    # Create a temporary directory (good practice)
    TEMP_DATA_DIR="/var/lib/postgresql/data_temp"
    mkdir -p "$TEMP_DATA_DIR" || { echo "Failed to create temp dir"; exit 1; }

    # Run pg_basebackup (using environment variables)
    pg_basebackup \
      -h "${POSTGRES_PRIMARY_HOST}" \
      -D "$TEMP_DATA_DIR" \
      -U "${POSTGRES_USER}" \
      -v \
      -P \
      -w \
      -X stream \
      -R || { echo "pg_basebackup failed"; exit 1; }


    # Stop PostgreSQL (if it's somehow running)
    if pg_isready -q -d "user=${POSTGRES_USER} host=/var/run/postgresql"; then
        pg_ctl stop -D /var/lib/postgresql/data -m fast || { echo "Failed to stop PostgreSQL"; exit 1; }
    fi


    # Remove any existing files in the data directory (should be empty, but be safe)
    rm -rf "$DATA_DIR"/* || { echo "Failed to remove old data"; exit 1; }
    rm -rf "$DATA_DIR"/.[!.]* 2>/dev/null || true

    # Move the data from the temporary directory to the correct location
    mv "$TEMP_DATA_DIR"/* "$DATA_DIR"/ || { echo "Failed to move data (1)"; exit 1; }
    mv "$TEMP_DATA_DIR"/.[!.]* "$DATA_DIR"/ 2>/dev/null || true

    # Clean up the temporary directory
    rm -rf "$TEMP_DATA_DIR" || { echo "Failed to remove temp dir"; exit 1; }
fi

# Start PostgreSQL (in standby mode, configured by pg_basebackup -R)
exec docker-entrypoint.sh postgres