Configure private IP connectivity for AlloyDB for PostgreSQL destinations

Database Migration Service uses Private Service Connect to connect to your destination AlloyDB for PostgreSQL cluster using a private IP address. With Private Service Connect, you can expose your destination database to incoming secure connections, and control who can access the database.

Network architecture setup for Private Service Connect differs depending on whether you use a PSC-enabled or a non-PSC-enabled destination AlloyDB for PostgreSQL cluster.

For more information about destination connectivity methods, see Destination database connectivity methods overview.

Private Service Connect for PSC-enabled AlloyDB for PostgreSQL clusters

To use private connectivity with PSC-enabled AlloyDB for PostgreSQL destinations, follow these steps:

  1. When you create and configure the destination cluster, make sure you create it as a PSC-enabled cluster with a private IP. You can't modify an existing AlloyDB for PostgreSQL cluster so that it becomes enabled for Private Service Connect.
  2. At a later stage, when you create the destination connection profile, do the following:
    1. Use the Hostname or IP address field to select the DNS record of your Private Service Connect endpoint for the destination cluster.
    2. In the Define connectivity method section, select Private IP.

Private Service Connect for non-PSC-enabled AlloyDB for PostgreSQL clusters

To use private IP connectivity for AlloyDB for PostgreSQL destinations that aren't created with Private Service Connect enabled, you need to create additional network components for routing traffic between Database Migration Service and your destination. For more information, see Private IP destination connectivity for non-PSC AlloyDB for PostgreSQL clusters.

If one bastion virtual machine (VM) is not sufficient for your networking needs, configure an instance group for your network producer setup. For more information, see Network connectivity in managed services.

To create the required Private Service Connect producer setup, we recommend that you use Google Cloud CLI or Terraform automation scripts. Before using any of the command data below, make the following replacements:

  • PROJECT_ID with the project in which you create the Private Service Connect producer setup.
  • REGION with the region in which you create the Private Service Connect producer setup.
  • ZONE with the zone within REGION in which you create all of the zonal resources (for example, the bastion VM).
  • BASTION with the bastion VM to create.
  • DB_SUBNETWORK with the subnetwork to which the traffic will be forwarded. The subnetwork needs to have access to the AlloyDB for PostgreSQL cluster.
  • DB_SUBNETWORK_GATEWAY with the IPv4 gateway of the subnetwork.
  • PORT with the port that the bastion will use to expose the underlying database.
  • ALLOYDB_INSTANCE_PRIVATE_IP with the private IP address of the destination AlloyDB for PostgreSQL cluster.

gcloud

The following bash script uses Google Cloud CLI to create the Private Service Connect producer setup for the destination database. Note that some defaults might need to be adjusted; for example, the Private Service Connect subnet CIDR ranges.

#!/bin/bash

# Create the VPC network for the Database Migration Service Private Service Connect.
gcloud compute networks create dms-psc-vpc \
--project=PROJECT_ID \
--subnet-mode=custom

# Create a subnet for the Database Migration Service Private Service Connect.
gcloud compute networks subnets create dms-psc-REGION \
--project=PROJECT_ID \
--range=10.0.0.0/16 --network=dms-psc-vpc \
--region=REGION

# Create a router required for the bastion to be able to install external
# packages (for example, Dante SOCKS server):
gcloud compute routers create ex-router-REGION \
--network dms-psc-vpc \
--project=PROJECT_ID \
--region=REGION

gcloud compute routers nats create ex-nat-REGION \
--router=ex-router-REGION \
--auto-allocate-nat-external-ips \
--nat-all-subnet-ip-ranges \
--enable-logging \
--project=PROJECT_ID \
--region=REGION

# Create the bastion VM.
gcloud compute instances create BASTION \
    --project=PROJECT_ID \
    --zone=ZONE \
    --image-family=debian-11 \
    --image-project=debian-cloud \
    --network-interface subnet=dms-psc-REGION,no-address \
    --network-interface subnet=DB_SUBNETWORK,no-address \
    --metadata=startup-script='#!/bin/bash

# Route the private IP address using the gateway of the database subnetwork.
# To find the gateway for the relevant subnetwork go to the VPC network page
# in the Google Cloud console. Click VPC networks and select the database VPC
# to see the details.
ip route add ALLOYDB_INSTANCE_PRIVATE_IP via DB_SUBNETWORK_GATEWAY

# Install Dante SOCKS server.
apt-get install -y dante-server

# Create the Dante configuration file.
touch /etc/danted.conf

# Create a proxy.log file.
touch proxy.log

# Add the following configuration for Dante:
cat > /etc/danted.conf << EOF
logoutput: /proxy.log
user.privileged: proxy
user.unprivileged: nobody

internal: 0.0.0.0 port = PORT
external: ens5

clientmethod: none
socksmethod: none

client pass {
        from: 0.0.0.0/0
        to: 0.0.0.0/0
        log: connect error disconnect
}
client block {
        from: 0.0.0.0/0
        to: 0.0.0.0/0
        log: connect error
}
socks pass {
        from: 0.0.0.0/0
        to: ALLOYDB_INSTANCE_PRIVATE_IP/32
        protocol: tcp
        log: connect error disconnect
}
socks block {
        from: 0.0.0.0/0
        to: 0.0.0.0/0
        log: connect error
}
EOF

# Start the Dante server.
systemctl restart danted

tail -f proxy.log'

# Create the target instance from the created bastion VM.
gcloud compute target-instances create bastion-ti-REGION \
--instance=BASTION \
--project=PROJECT_ID \
--instance-zone=ZONE \
--network=dms-psc-vpc

# Create a forwarding rule for the backend service.
gcloud compute forwarding-rules create dms-psc-forwarder-REGION \
--project=PROJECT_ID \
--region=REGION \
--load-balancing-scheme=internal \
--network=dms-psc-vpc \
--subnet=dms-psc-REGION \
--ip-protocol=TCP \
--ports=all \
--target-instance=bastion-ti-REGION \
--target-instance-zone=ZONE

# Create a TCP NAT subnet.
gcloud compute networks subnets create dms-psc-nat-REGION-tcp \
--network=dms-psc-vpc \
--project=PROJECT_ID \
--region=REGION \
--range=10.1.0.0/16 \
--purpose=private-service-connect

# Create a service attachment.
gcloud compute service-attachments create dms-psc-svc-att-REGION \
--project=PROJECT_ID \
--region=REGION \
--producer-forwarding-rule=dms-psc-forwarder-REGION \
--connection-preference=ACCEPT_MANUAL \
--nat-subnets=dms-psc-nat-REGION-tcp

# Create a firewall rule allowing the Private Service Connect NAT subnet.
# access the Private Service Connect subnet
gcloud compute \
--project=PROJECT_ID firewall-rules create dms-allow-psc-tcp \
--direction=INGRESS \
--priority=1000 \
--network=dms-psc-vpc \
--action=ALLOW \
--rules=all \
--source-ranges=10.1.0.0/16 \
--enable-logging

# Print out the created service attachment.
gcloud compute service-attachments describe dms-psc-svc-att-REGION \
--project=PROJECT_ID \
--region=REGION

Terraform

The following files can be used in a Terraform module to create the Private Service Connect producer setup for the destination database. Note that some defaults might need to be adjusted; for example, the Private Service Connect subnet CIDR ranges.

variables.tf:

variable "project_id" {
  type        = string
  description = <<DESC
The Google Cloud project in which the setup is created. This should be the same project as
the one that the AlloyDB for PostgreSQL cluster belongs to.
DESC
}

variable "region" {
  type        = string
  description = "The Google Cloud region in which you create the Private Service Connect
regional resources."
}

variable "zone" {
  type        = string
  description = <<DESC
The Google Cloud zone in which you create the Private Service Connect zonal resources
(should be in the same region as the one specified in the "region" variable).
DESC
}

variable "primary_instance_private_ip" {
  type = string
  description = "The cluster's primary instance private IP"
}

variable "port" {
  type        = string
  description = "The port that the bastion will use to expose the underlying database."
  default     = "5432"
}

variable "alloydb_cluster_network" {
  type        = string
  description = <<DESC
The VPC to which the AlloyDB for PostgreSQL cluster is peered. This is where the bastion will
forward connections to (the destination database needs to be accessible in this VPC).
DESC
}

main.tf:

/* To execute the call:
terraform apply
-var="project_id=PROJECT_ID"
-var="region=REGION"
-var="zone=ZONE"
-var="primary_instance_private_ip=PRIMARY_INSTANCE_PRIVATE_IP"
-var="port=PORT"
-var="alloydb_cluster_network=ALLOYDB_CLUSTER_NETWORK" */

# Needed for getting the IPv4 gateway of the subnetwork for the database.
data "google_compute_subnetwork" "db_network_subnet" {
  name    = var.alloydb_cluster_network
  project = var.project_id
  region  = var.region
}

resource "google_compute_network" "psc_sp_network" {
  name                    = "dms-psc-network"
  project                 = var.project_id
  auto_create_subnetworks = false
}

resource "google_compute_subnetwork" "psc_sp_subnetwork" {
  name    = "dms-psc-subnet"
  region  = var.region
  project = var.project_id
  network = google_compute_network.psc_sp_network.id

  # CIDR range can be lower.
  ip_cidr_range = "10.0.0.0/16"
}

resource "google_compute_subnetwork" "psc_sp_nat" {
  provider = google-beta
  name     = "dms-psc-nat"
  region   = var.region
  project  = var.project_id
  network = google_compute_network.psc_sp_network.id
  purpose = "PRIVATE_SERVICE_CONNECT"
  # CIDR range can be lower.
  ip_cidr_range = "10.1.0.0/16"
}

resource "google_compute_service_attachment" "psc_sp_service_attachment" {
  provider = google-beta
  name     = "dms-psc-svc-att"
  region   = var.region
  project  = var.project_id

  enable_proxy_protocol = false
  connection_preference = "ACCEPT_MANUAL"
  nat_subnets           = [google_compute_subnetwork.psc_sp_nat.id]
  target_service        = google_compute_forwarding_rule.psc_sp_target_direct_rule.id
}

resource "google_compute_forwarding_rule" "psc_sp_target_direct_rule" {
  name       = "dms-psc-fr"
  region     = var.region
  project    = var.project_id
  network    = google_compute_network.psc_sp_network.id
  subnetwork = google_compute_subnetwork.psc_sp_subnetwork.id

  load_balancing_scheme = "INTERNAL"
  ip_protocol           = "TCP"
  all_ports             = true

  target = google_compute_target_instance.psc_sp_target.id

}

resource "google_compute_target_instance" "psc_sp_target" {
  provider = google-beta
  name     = "dms-psc-fr-target"
  zone     = var.zone
  instance = google_compute_instance.psc_sp_bastion.id
  network  = google_compute_network.psc_sp_network.id
}

resource "google_compute_instance" "psc_sp_bastion" {
  name           = "dms-psc-alloydb-bastion"
  project        = var.project_id
  machine_type   = "e2-medium"
  zone           = var.zone
  can_ip_forward = true

  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-11"
    }
  }

  # The incoming NIC defines the default gateway which must be the Private Service Connect subnet.

  network_interface {
    network    = google_compute_network.psc_sp_network.id
    subnetwork = google_compute_subnetwork.psc_sp_subnetwork.id
  }

  # The outgoing NIC which is on the same network as the AlloyDB for PostgreSQL cluster.

  network_interface {
    network = data.google_compute_subnetwork.db_network_subnet.network
  }

  metadata_startup_script = <<SCRIPT

#!/bin/bash
# Route the private IP address of the database using the gateway of the database subnetwork.
# To find the gateway for the relevant subnetwork, go to the VPC network page
# in the Google Cloud console. Click VPC networks, and select the database VPC
# to see the details.
ip route add ${var.primary_instance_private_ip} \
via ${data.google_compute_subnetwork.db_network_subnet.gateway_address}

# Install Dante SOCKS server.
apt-get install -y dante-server

# Create the Dante configuration file.
touch /etc/danted.conf

# Create a proxy.log file.
touch proxy.log

# Add the following configuration for Dante:
cat > /etc/danted.conf << EOF
logoutput: /proxy.log
user.privileged: proxy
user.unprivileged: nobody

internal: 0.0.0.0 port = ${var.port}
external: ens5

clientmethod: none
socksmethod: none

client pass {
        from: 0.0.0.0/0
        to: 0.0.0.0/0
        log: connect error disconnect
}
client block {
        from: 0.0.0.0/0
        to: 0.0.0.0/0
        log: connect error
}
socks pass {
        from: 0.0.0.0/0
        to: ${var.primary_instance_private_ip}/32
        protocol: tcp
        log: connect error disconnect
}
socks block {
        from: 0.0.0.0/0
        to: 0.0.0.0/0
        log: connect error
}
EOF

# Start the Dante server.

systemctl restart danted

tail -f proxy.log

SCRIPT
}

# Required firewall rules:
/* Firewall rule allowing the Private Service Connect NAT subnet to access
the Private Service Connect subnet. */
resource "google_compute_firewall" "psc_sp_in_fw" {
  name    = "dms-psc-ingress-nat-fw"
  project = var.project_id
  network = google_compute_network.psc_sp_network.id

  log_config {
    metadata = "INCLUDE_ALL_METADATA"
  }

  allow {
    protocol = "all"
  }

  priority  = 1000
  direction = "INGRESS"
  source_ranges = [google_compute_subnetwork.psc_sp_nat.ip_cidr_range]
}

/* The router that the bastion VM uses to install external packages
(for example, Dante SOCKS server). */

resource "google_compute_router" "psc_sp_ex_router" {
  name    = "dms-psc-external-router"
  project = var.project_id
  region  = var.region
  network = google_compute_network.psc_sp_network.id
}

resource "google_compute_router_nat" "psc_sp_ex_router_nat" {
  name    = "dms-psc-external-router-nat"
  project = var.project_id
  region  = var.region
  router  = google_compute_router.psc_sp_ex_router.name

  nat_ip_allocate_option             = "AUTO_ONLY"
  source_subnetwork_ip_ranges_to_nat = "ALL_SUBNETWORKS_ALL_IP_RANGES"

  log_config {
    enable = true
    filter = "ERRORS_ONLY"
  }
}

outputs.tf:

# The Private Service Connect service attachment.
output "service_attachment" {
  value = google_compute_service_attachment.psc_sp_service_attachment.id
}

At a later stage, when you create the destination connection profile, do the following:

  1. In the Define connectivity method section, select Private IP.
  2. From the Service attachment name drop-down menu, select dms-psc-svc-att-REGION.