MySQL Instance Migration Script – with --dry-run support

mysql_migrate.sh

#!/bin/bash
# =============================================================================
# MySQL Instance Migration – fully compatible with MySQL Shell 8.0.34+ / 8.4+
# No more "Invalid options: maxRate"
# =============================================================================

set -euo pipefail

DRY_RUN=false
[[ "${1:-}" == "--dry-run" || "${1:-}" == "-n" ]] && DRY_RUN=true && shift

# ----------------------------- Config ---------------------------------
SOURCE_LOGIN_PATH="source_migration_user"
TARGET_LOGIN_PATH="target_migration_user"
SOURCE_URI=""
TARGET_URI=""

DUMP_BASE_DIR="${DUMP_BASE_DIR:-/tmp}"
THREADS=$(nproc)
TIMESTAMP=$(date +%Y%m%d_%H%M%S)

SOURCE_DUMP_DIR="$DUMP_BASE_DIR/source_dump_$TIMESTAMP"
TARGET_BACKUP_DIR="$DUMP_BASE_DIR/target_backup_$TIMESTAMP"
LOG_FILE="$DUMP_BASE_DIR/mysql_migration_${TIMESTAMP}${DRY_RUN:+_DRYRUN}.log"

# ----------------------------- Safe logging --------------------------
mkdir -p "$(dirname "$LOG_FILE")"
touch "$LOG_FILE"

log() {
    local msg="$*"
    [[ "$DRY_RUN" == true ]] && msg="[DRY-RUN] $msg"
    printf '%s %s\n' "$(date -u +"%Y-%m-%dT%H:%M:%SZ")" "$msg" >> "$LOG_FILE"
    printf '%s %s\n' "$(date -u +"%Y-%m-%dT%H:%M:%SZ")" "$msg"
}

# ----------------------------- Cleanup -------------------------------
cleanup() {
    [[ "$DRY_RUN" == true ]] && {
        log "Dry-run cleanup: removing temporary directories"
        rm -rf "$SOURCE_DUMP_DIR" "$TARGET_BACKUP_DIR" 2>/dev/null || true
        return
    }
    log "Live run cleanup: removing source dump only"
    rm -rf "$SOURCE_DUMP_DIR" 2>/dev/null || true
}
trap cleanup EXIT

# ----------------------------- Connection ----------------------------
build_conn_opts() {
    local lp="$1" uri="$2"
    [[ -n "$lp" ]] && echo "--login-path=$lp"
    [[ -n "$uri" ]] && echo "--uri=$uri"
    [[ -z "$lp" && -z "$uri" ]] && { log "ERROR: No credentials"; exit 1; }
}

SOURCE_CONN=$(build_conn_opts "$SOURCE_LOGIN_PATH" "$SOURCE_URI")
TARGET_CONN=$(build_conn_opts "$TARGET_LOGIN_PATH" "$TARGET_URI")

# ----------------------------- Start ---------------------------------
log "=== MySQL Migration $( [[ $DRY_RUN == true ]] && echo "DRY-RUN" || echo "LIVE" ) Started ==="
log "Log file : $LOG_FILE"

mkdir -p "$SOURCE_DUMP_DIR" "$TARGET_BACKUP_DIR"

# Step 1 – Source dump (no users)
if [[ "$DRY_RUN" == false ]]; then
    log "Step 1/3: Dumping source instance (users excluded)..."
    mysqlsh $SOURCE_CONN --js -e "
        util.dumpInstance('$SOURCE_DUMP_DIR', {
            users: false,
            checksum: true,
            threads: $THREADS,
            compression: 'zstd',
            chunking: true,
            bytesPerChunk: '64M',
            showProgress: true
        })
    " >> "$LOG_FILE" 2>&1
    log "Source dump completed"
else
    log "Step 1/3: [WOULD] Dump source → $SOURCE_DUMP_DIR"
fi

# Step 2 – Target backup (full)
if [[ "$DRY_RUN" == false ]]; then
    log "Step 2/3: Creating full backup of target..."
    mysqlsh $TARGET_CONN --js -e "
        util.dumpInstance('$TARGET_BACKUP_DIR', {
            users: true,
            checksum: true,
            threads: $THREADS,
            compression: 'zstd',
            chunking: true,
            bytesPerChunk: '64M',
            showProgress: true
        })
    " >> "$LOG_FILE" 2>&1
    log "Target backup completed"
else
    log "Step 2/3: [WOULD] Backup target → $TARGET_BACKUP_DIR"
fi

# Step 3 – Load into target
if [[ "$DRY_RUN" == false ]]; then
    log "Step 3/3: Importing source dump into target..."
    mysqlsh $TARGET_CONN --js -e "
        util.loadDump('$SOURCE_DUMP_DIR', {
            checksum: true,
            threads: $THREADS,
            showProgress: true
        })
    " >> "$LOG_FILE" 2>&1
    log "=== MIGRATION SUCCESSFUL ==="
else
    log "Step 3/3: [WOULD] Load dump into target"
    log "Running compatibility check..."
    mysqlsh $TARGET_CONN --js -e "util.checkInstanceCompatibility('$SOURCE_DUMP_DIR')" >> "$LOG_FILE" 2>&1 || true
    log "=== DRY-RUN COMPLETE – NO CHANGES MADE ==="
fi

log "Target backup $( [[ $DRY_RUN == false ]] && echo "available at" || echo "would be at" ): $TARGET_BACKUP_DIR"
log "Log file kept at: $LOG_FILE"
log "=== Script finished ==="

exit 0