I'm trying to create GCP postgreSQL instance and make it accessible from multiple VPC networks with in one project.
We have VMs in 4 GCP regions. Each region has it's own VPC network and all are peered. But when I create SQL instance I can map its private IP only to one VPC, other don't have access to it.
Is it any steps to follow which will allow to access from multiple VPCs to one SQL instance?
When you configure a Cloud SQL instance to use private IP, you use private services access. Private services access is implemented as a VPC peering connection between your VPC network and the Google services VPC network where your Cloud SQL instance resides.
That said, currently your approach is not possible. VPC network peering has some restrictions, one of which is that only directly peered networks can communicate with each other- transitive peering is not supported.
As Cloud SQL resources are themselves accessed from ‘VPC A’ via a VPC network peering, other VPC networks attached to ‘VPC A’ via VPC network peering cannot access these Cloud SQL resources as this would run afoul of the aforementioned restriction.
On this note, there’s already a feature request for multiple VPC peerings with Cloud SQL VPC.
As a workaround, you could create a proxy VM instance using Cloud SQL proxy. See 1 and 2. For example, the proxy VM instance could be placed in the VPC to which your Cloud SQL instances are attached (VPC A, for example) and it would act as the Cloud SQL Proxy. VM instances in other VPCs connected to VPC A via VPC network peering could forward their SQL requests to the Cloud SQL Proxy VM instance in VPC A, which would then forward the requests to the SQL instance(s) and vice versa.
