Configure Private Service Connect for a destination cluster

This page describes how to set up Database Migration Service to migrate your Oracle to AlloyDB for PostgreSQL workloads using the private IP address of the destination AlloyDB for PostgreSQL cluster. Private connections allow Database Migration Service to access services without going through the internet or using external IP addresses.

Database Migration Service uses Private Service Connect to connect to your 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.

Private Service Connect for PSC-enabled AlloyDB for PostgreSQL clusters

Note: PSC-enabled AlloyDB for PostgreSQL clusters come with certain functionality limitations. Make sure such configurations meet your requirements before you migrate to PSC-enabled AlloyDB for PostgreSQL clusters. See Private Service Connect limitations in AlloyDB for PostgreSQL documentation.

If you create your AlloyDB for PostgreSQL destination instance with Private Service Connect enabled, you can use Private IP connectivity without any additional network setup. You only need to ensure the following when you create the destination database connection profile:

• Use your AlloyDB for PostgreSQL cluster's DNS record instead of the destination's hostname.

• For programmatic access via Google Cloud CLI or API only: Explicitly specify your destination's service attachment in the request (this is done automatically by Database Migration Service when you create connection profiles in the Google Cloud console).

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

To expose a service using Private Service Connect for AlloyDB for PostgreSQL clusters, create a service attachment in your project. You can use example gcloud and Terraform scripts in the Create the Private Service Connect producer setup section to create the required resources.

The following diagram shows the various compute and networking resources that Database Migration Service uses to set up private connectivity to your AlloyDB for PostgreSQL cluster.

The Database Migration Service worker is an internal processing unit in charge of your Database Migration Service migration. It uses an outgoing Private Service Connect forwarding rule to send the traffic from the worker to the VPC network in which the bastion virtual machine (VM) resides.

The key resources that the scripts help you create are:

• A service attachment: A resource that exposes a service by forwarding traffic to its target service. In the diagram, the target service is an incoming forwarding rule.
• An incoming forwarding rule: A traffic forwarder that routes the incoming traffic from the service attachment to a dedicated target (for example, a VM or an instance group). In the diagram, the rule forwards the traffic to a bastion VM.
• A bastion VM: A VM with two network interface controllers (NICs), one of which is attached to the dedicated Private Service Connect network, and the other to the network to which the AlloyDB for PostgreSQL cluster is peered. The bastion is running a Dante SOCKS server, which is used to forward the connections securely. The example scripts create a dedicated network and subnets in the Private Service Connect network for you.

The Google Cloud project you use to publish your service using the service attachment is the service producer. The service consumer is Database Migration Service. For more information about Private Service Connect, its setup and architecture, see the Private Service Connect documentation.

Create the Private Service Connect producer setup

You can use the following scripts to create the Private Service Connect setup and connect to your destination AlloyDB for PostgreSQL cluster. If you experience issues during connectivity setup, consult connectivity troubleshooting pages.

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

Replace the following:

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

Terraform

The following files can be used in a Terraform module to create the Private Service Connect producer setup for the destination database. 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-cloud-sql-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
}

You can create the compute and networking resources required to expose your AlloyDB for PostgreSQL database without using the scripts. However, you need to ensure that you have a service attachment that exposes the database, and that you can use it from a different Google Cloud project. For more information, see the Private Service Connect documentation.