Introduction to Babelfish
Migrating an SQL Server database to Amazon Web Services, while possible, can be expensive. Microsoft's SQL Server licensing model is expensive when compared to an open source alternative like PostgreSQL. Thanks to an open-source project called Babelfish for PostgreSQL you can move your SQL Server workloads to the cloud and benefit from the cost efficiencies that PostgreSQL offer.
Babelfish for PostgreSQL adds a Microsoft SQL Server-compatible end-point to PostgreSQL. Babelfish allows PostgreSQL to understand T-SQL, SQL Server's proprietary SQL dialect, and supports the TDS communication protocol, so applications originally written for SQL Server may work with PostgreSQL with fewer code changes and without changing database drivers.
Software suppliers will need to test their software using a Babelfish endpoint, but most applications will work with minor changes.
Provisioning an Aurora PostgreSQL Cluster with Babelfish Enabled Using Terraform
Below is a sample Terraform script to provision an RDS Aurora Cluster with a Babelfish endpoint enabled.
I hope you find this useful.
The code is commented, and you can change elements to suit your requirements.
resource "aws_rds_cluster" "rds_cluster_maywoods_audit_tool" { cluster_identifier = "maywoods-audit-tool" availability_zones = ["eu-west-2a", "eu-west-2b", "eu-west-2c"] // database engine type, mode and version engine = "aurora-postgresql" engine_mode = "provisioned" engine_version = "13.7" // database_nam must begin with a letter and // contain only alphanumeric characters. // ensure a strong long password is used. database_name = "MaywoodsAuditToolsQA" master_password = "**********************************" master_username = "MaywoodsAuditAdmin" backup_retention_period = "60" copy_tags_to_snapshot = true db_cluster_parameter_group_name = aws_rds_cluster_parameter_group.rds_cluster_maywoods_audit_tool_pg.name db_subnet_group_name = aws_db_subnet_group.rds_cluster_maywoods_audit_tool_sng.name deletion_protection = true enabled_cloudwatch_logs_exports = ["postgresql"] skip_final_snapshot = flase final_snapshot_identifier = "maywoods-audit-tool-cluster-final-snapshot" iam_database_authentication_enabled = false iam_roles = [] preferred_backup_window = "23:00-00:00" preferred_maintenance_window = "sun:01:00-sun:02:00" storage_encrypted = true kms_key_id = "aws/rds" vpc_security_group_ids = var.sg_id_list tags = { // override any tags already set within the // default_tags block with the providers.tf Application = "CORE SERVICE - AUDIT TOOL DATABASE", Provider = "MAYWOODS" } } resource "aws_rds_cluster_instance" "rds_cluster_maywoods_audit_tool_instance" { cluster_identifier = aws_rds_cluster.rds_cluster_maywoods_audit_tool.id // change instance type/size and count // based on the workloads requirements instance_class = "db.r5.large" count = 1 identifier = "maywoods-audit-tool-inst-0" // use the same engine/version as define in the cluster engine = aws_rds_cluster.rds_cluster_maywoods_audit_tool.engine engine_version = aws_rds_cluster.rds_cluster_maywoods_audit_tool.engine_version auto_minor_version_upgrade = true copy_tags_to_snapshot = true db_parameter_group_name = "maywoods-audit-tool-pg" db_subnet_group_name = aws_db_subnet_group.rds_cluster_maywoods_audit_tool_sng.name monitoring_interval = "0" monitoring_role_arn = "" performance_insights_enabled = true preferred_maintenance_window = "sun:01:00-sun:02:00" publicly_accessible = false tags = { // override any tags already set within the // default_tags block with the providers.tf Application = "CORE SERVICE - AUDIT TOOL DATABASE", Provider = "MAYWOODS" } } resource "aws_rds_cluster_parameter_group" "rds_cluster_maywoods_audit_tool_pg" { name = "maywoods-audit-tool-pg" family = "aurora-postgresql13" # enable babelfish to be active parameter { name = "rds.babelfish_status" value = "on" apply_method = "pending-reboot" } tags = { // override any tags already set within the // default_tags block with the providers.tf Application = "CORE SERVICE - AUDIT TOOL DATABASE", Provider = "MAYWOODS" } } resource "aws_db_subnet_group" "rds_cluster_maywoods_audit_tool_sng" { name = "${var.name_prefix}maywoods-db-subnet" subnet_ids = [var.private_subnet_zero, var.private_subnet_one] tags = { Application = "ScR CORE SERVICE - AUDIT TOOL DB", Provider = "MAYWOODS" } } resource "aws_cloudwatch_log_group" "rds_cluster_maywoods_audit_tool_lg" { name = "/aws/rds/cluster/${aws_rds_cluster.rds_cluster_maywoods_audit_tool.cluster_identifier}/postgresql" retention_in_days = 60 } Security Groups
To allow servers to connect to the RDS Aurora PostgreSQL Cluster you'll also need to define a security group.
The security group will need to open ports 5432 for native PostgreSQL traffic, and port 1433 for Babelfish traffic.
resource "aws_security_group" "rds_maywoods_audit_tool_sg" { name = "${var.name_prefix}rds_maywoods_audit_tool_sg" description = "Maywoods Audit Tool Database Access" vpc_id = var.vpc_id tags = { Name = "${var.name_prefix}rds_maywoods_audit_tool_sg", } } resource "aws_security_group_rule" "rds_maywoods_audit_tool_psql_inbound" { security_group_id = aws_security_group.rds_maywoods_audit_tool_sg.id description = "Ingress PostgreSQL traffic from hospital servers" type = "ingress" from_port = 5432 to_port = 5432 protocol = "tcp" cidr_blocks = ["10.164.33.38/32", "10.164.33.37/32"] } resource "aws_security_group_rule" "rds_maywoods_audit_tool_psql_outbound" { security_group_id = aws_security_group.rds_maywoods_audit_tool_sg.id description = "Egress PostgreSQL traffic from hospital servers" type = "egress" from_port = 5432 to_port = 5432 protocol = "tcp" cidr_blocks = ["10.164.33.38/32", "10.164.33.37/32"] } resource "aws_security_group_rule" "rds_maywoods_audit_tool_babelfish_inbound" { security_group_id = aws_security_group.rds_maywoods_audit_tool_sg.id description = "Ingress Babelfish traffic from hospital servers" type = "ingress" from_port = 1433 to_port = 1433 protocol = "tcp" cidr_blocks = ["10.164.33.38/32", "10.164.33.37/32"] } resource "aws_security_group_rule" "rds_maywoods_audit_tool_babelfish_outbound" { security_group_id = aws_security_group.rds_maywoods_audit_tool_sg.id description = "Egress Babelfish traffic from hospital servers" type = "egress" from_port = 1433 to_port = 1433 protocol = "tcp" cidr_blocks = ["10.164.33.38/32", "10.164.33.37/32"] } 
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