22 posts tagged with "gcp"

At the time of this writing, GCP does not have a generally available non-public facing Layer 7 load balancer. While this is sure to change in the future, this article outlines a design pattern which has been proven to provide scalable and extensible application load balancing services for multiple applications running in Kubernetes pods on GKE.

When you create a service of type LoadBalancer in GKE, Kubernetes hooks into the provider (GCP in this case) on your behalf to create a Google Load Balancer, while this may be specified as INTERNAL, there are two issues:

Issue #1:​

The GCP load balancer created for you is a Layer 4 TCP load balancer.

Issue #2:​

The normal behaviour is for Google to enumerate all of the node pools in your GKE cluster and “automagically” create mapping GCE instance groups for each node pool for each zone the instances are deployed in. This means the entire surface area of your cluster is exposed to the external network – which may not be optimal for internal applications on a multi tenanted cluster.

The Solution:​

Using Istio deployed on GKE along with the Istio Ingress Gateway along with an externally created load balancer, it is possible to get scalable HTTP load balancing along with all the normal ALB goodness (stickiness, path-based routing, host-based routing, health checks, TLS offload, etc.).

An abstract depiction of this architecture is shown here:

This can be deployed with a combination of Terraform and kubectl. The steps to deploy at a high level are:

1. Create a GKE cluster with at least two node pools: ingress-nodepool and service-nodepool. Ideally create these node pools as multi-zonal for availability. You could create additional node pools for your Egress Gateway or an operations-nodepool to host Istio, etc as well.
2. Deploy Istio.
3. Deploy the Istio Ingress Gateway service on the ingress-nodepool using Service type NodePort.
4. Create an associated Certificate Gateway using server certificates and private keys for TLS offload.
5. Create a service in the service-nodepool.
6. Reserve an unallocated static IP address from the node network range.
7. Create an internal TCP load balancer:
   1. Specify the frontend as the IP address reserved in step 6.
   2. Specify the backend as the managed instance groups created during the node pool creation for the ingress-nodepool (ingress-nodepool-ig-a, ingress-nodepool-ig-b, ingress-nodepool-ig-c).
   3. Specify ports 80 and 443.
8. Create a GCP Firewall Rule to allow traffic from authorized sources (network tags or CIDR ranges) to a target of the ingress-nodepool network tag.
9. Create a Cloud DNS A Record for your managed zone as *.namespace.zone pointing to the IP Address assigned to the load balancer frontend in step 7.1.
10. Enable Health Checks through the GCP firewall to reach the ingress-nodepool network tag at a minimum – however there is no harm in allowing these to all node pools.

The service should then be resolvable and routable from authorized internal networks (peered private VPCs or internal networks connected via VPN or Dedicated Interconnect) as:

https://_service.namespace.zone/endpoint__

The advantages of this design pattern are...​

1. The Ingress Gateway provides fully functional application load balancing services.
2. Istio provides service discovery and routing using names and namespaces.
3. The Ingress Gateway service and ingress gateway node pool can be scaled as required to meet demand.
4. The Ingress Gateway is multi zonal for greater availability

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GCP and AWS share many similarities, they both provide similar services and both leverage containerization, virtualization and software defined networking.

There are some significant differences when it comes to their respective implementations, networking is a key example of this.

Before we compare and contrast the two different approaches to networking, it is worthwhile noting the genesis of the two major cloud providers.

Google was born to be global, Amazon became global​

By no means am I suggesting that Amazon didn't have designs on going global from it's beginnings, but AWS was driven (entirely at the beginning) by the needs of the Amazon eCommerce business. Amazon started in the US before expanding into other regions (such as Europe and Australia). In some cases the expansion took decades (Amazon only entered Australia as a retailer in 2018).

Google, by contrast, was providing application, search and marketing services worldwide from its very beginning. GCP which was used as the vector to deliver these services and applications was architected around this global model, even though their actual data centre expansion may not have been as rapid as AWS’s (for example GCP opened its Australia region 5 years after AWS).

Their respective networking implementations reflect how their respective companies evolved.

AWS is a leader in IaaS, GCP is a leader in PaaS​

This is only an opinion and may be argued, however if you look at the chronology of the two platforms, consider this:

• The first services released by AWS (simultaneously for all intents and purposes) were S3, SQS and EC2
• The first service released by Google was AppEngine (a pure PaaS offering)

Google has launched and matured their IaaS offerings since as AWS has done similarly with their PaaS offerings, but they started from much different places.

With all of that said, here are the key differences when it comes to networking between the two major cloud providers:

GCP VPCs are Global by default, AWS VPCs are Regional only​

This is the first fundamental difference between the two providers. Each GCP project is allocated one VPC network with Subnets in each of the 18 GCP Regions. Whereas each AWS Account is allocated one Default VPC in each AWS Region with a Subnet in each AWS Availability Zone for that Region, that is each account has 17 VPCs in each of the 17 Regions (excluding GovCloud regions).

It is entirely possible to create VPCs in GCP which are Regional, but they are Global by default.

This global tenancy can be advantageous in many cases, but can be limiting in others, for instance there is a limit of 25 peering connections to any one VPC, the limit in AWS is 125.

GCP Subnets are Regional, AWS Subnets are Zonal​

Subnets in GCP automatically span all Zones in a Region, whereas AWS VPC Subnets are assigned to Availability Zones in a Region. This means you are abstracted from some of the networking and zonal complexity, but you have less control over specific network placement of instances and endpoints. You can infer from this design that Zones are replicated or synchronised within a Region, making them less of a direct consideration for High Availability (or at least as much or your concern as they otherwise would be).

All GCP Firewall Rules are Stateful​

AWS Security Groups are stateful firewall rules – meaning they maintain connection state for inbound connections, AWS also has Network ACLs (NACLs) which are stateless firewall rules. GCP has no direct equivalent of NACLs, however GCP Firewall Rules are more configurable than their AWS counterparts. For instance, GCP Firewall Rules can include Deny actions which is not an option with AWS Security Group Rules.

Load Balancers in GCP are layer 4 (TCP/UDP) unless they are public facing​

AWS Application Load Balancers can be deployed in private VPCs with no external IPs attached to them. GCP has Application Load Balancers (Layer 7 load balancers) but only for public facing applications, internal facing load balancers in GCP are Network Load Balancers. This presents some challenges with application level load balancing functionality such as stickiness. There are potential workarounds however such as NGINX in GKE behind

Firewall rules are at the Network Level not at the Instance or Service Level​

There are simple firewall settings available at the instance level, these are limited to allowing HTTP and HTTPS traffic to the instance only and don’t allow you to specify sources. Detailed Firewall Rules are set at the GCP VPC Network level and are not attached or associated with instances as they are in AWS.

Hopefully this is helpful for AWS engineers and architects being exposed to GCP for the first time!

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