APPUiO Managed OpenShift 4 on VMWare vSphere

Architecture overview

The APPUiO Managed OpenShift 4 architecture on VMWare vSphere is based on the generic APPUiO Managed OpenShift 4 architecture. We expect that readers of this document are familiar with the generic APPUiO Managed OpenShift 4 architecture and the overall Kubernetes and OpenShift 4 architecture.

This architecture document extends upon the generic architecture by defining how the APPUiO Managed OpenShift 4 cluster is embedded into the VMWare vSphere environment. The diagram below shows a detailed view of how an APPUiO Managed OpenShift 4 cluster is embedded into the VMWare vSphere environment.

OCP4 VMWare vSphere architecture
Figure 1. APPUiO Managed OpenShift4 on VMWare vSphere architecture

The following sections of this document provide detailed descriptions for the elements shown in the architecture diagram.

VMWare vSphere requirements

Red Hat OpenShift 4 imposes version requirements on the VMWare virtual hardware version, VMWare vSphere ESXi and vCenter. See the upstream documentation for the specific version requirements as well as further details on required VMWare vSphere requirements.

APPUiO Managed OpenShift 4 needs credentials to access the VMWare vSphere API for three main reasons:

  1. The OpenShift 4 installer needs access to VMWare vSphere to setup the OpenShift 4 cluster

    The installer also needs to be able to access at least one ESXi host to upload the VM template from which all the cluster VMs will be created.

  2. OpenShift 4 manages the VMs making up the cluster from within the cluster.

  3. The VMWare vSphere CSI driver manages additional block devices that can be used by applications

The upstream OpenShift 4 documentation has detailed informations about the required permissions on VMWare vSphere.

Entries for "VMWare vSphere CSI Driver Operator" are required.

Networking

Bastion host

To deploy an APPUiO Managed OpenShift 4 cluster on VMWare vSphere, a bastion host inside the customer’s premise is required. The bastion host:

  • must be accessible via SSH from a management system operated by VSHN

  • must have access to the vCenter API

  • must have access to at least one ESXi host to import the RHCOS VM template

  • must have unrestricted network access to the cluster’s machine network

  • must run a recent Ubuntu version

The bastion host is used to run the installer from, and for troubleshooting access to both the cluster and the vCenter. The bastion host must be provided by the VMWare vSphere infrastructure operator, but VSHN can handle management and maintenance.

Machine network

Each APPUiO Managed OpenShift 4 cluster is deployed into a /24 "cluster machine network" (sometimes also "cluster network" or "machine network") This network must be provided by the VMWare vSphere infrastructure operator. DHCP is mandatory for this network, but a number of IPs must be reserved to be used as Virtual IPs for the cluster.

Traffic inside this network shouldn’t be restricted.

VMs in this network must be able to reach various services on the internet. See below for a detailed list of external systems that must be reachable.

Virtual IPs

To expose applications and the Kubernetes API outside the cluster, APPUiO Managed OpenShift 4 manages two floating IPs:

  1. The "API VIP" for the Kubernetes and OpenShift API. APPUiO Managed OpenShift 4 uses .10 in the machine network as the API VIP.

  2. The "Ingress VIP" for the OpenShift Ingress Router APPUiO Managed OpenShift 4 uses .11 in the machine network as the Ingress VIP.

APPUiO Managed OpenShift 4 runs two keepalived instances to manage the API and ingress VIPs through VRRP.

If applications should be exposed for non-HTTP(S) traffic (via LoadBalancer services), additional IPs in the machine network must be reserved to be used as VIPs. These additional VIPs will be managed by keepalived instances on the cluster.

Pod and service networks

APPUiO Managed Openshift 4 uses Cilium to provide in-cluster networking. Cilium allocates two cluster-internal networks:

  1. The pod network: every pod on the cluster will get an IP address from this network. This network enables basic in-cluster connectivity. APPUiO Managed OpenShift 4 uses 10.128.0.0/14 as the pod network. Each node in the cluster is assigned a /23 from this range. Pods on a node are always assigned an IP from the range allocated to that node.

  2. Service network: used for service discovery. Traffic to IPs in this network is forwarded to the appropriate pods by Cilium. APPUiO Managed OpenShift 4 uses 172.30.0.0/16 as the service network.

Both of these networks are interanl to the OpenShift 4 cluster. Therefore, the IP CIDRs for these networks must not be routable from the outside. Additionally, the same IP CIDRs can be reused for multiple OpenShift 4 clusters.

However, the chosen CIDRs shouldn’t overlap with existing networks allocated by the customer. If there are overlaps, external systems in the overlapping ranges won’t be accessible from within the OpenShift 4 cluster. The pod and service network CIDRs can be customized if and only if there are conflicts.

Exposing the cluster

The VMWare vSphere infrastructure operator must provide some form of ingress and egress gateway for the cluster. The ingress gateway must expose two public IPs:

  1. A public IP for the API. Traffic to port 6443/tcp on this IP must be forwarded to the "API VIP" in the machine network. The forwarding of this traffic must happen transparently. In particular, no TLS interception can be performed as the Kubernetes API depends on mutual TLS authentication. VSHN will manage a DNS record pointing to this IP.

  2. A public IP for HTTP(s) ingress. Traffic to ports 80/tcp and 443/tcp on this IP must be forwarded to the "Ingress VIP" in the machine network. The PROXY protocol should be enabled to preserve source IPs. Forwarding should happen transparently in TCP mode. VSHN will manage a wildcard DNS record pointing to this IP. Additional DNS records can be pointed to this IP by the customer.

External services

APPUiO Managed OpenShift 4 requires various external services.

VSHN services

APPUiO Managed OpenShift 4 requires access to VSHN’s Project Syn infrastructure. The Project Syn infrastructure components that must be reachable are

  • the Project Syn API at https://api.syn.vshn.net

  • the Project Syn Vault at https://vault-prod.syn.vshn.net

  • VSHN’s GitLab instance at ssh://git@git.vshn.net

  • VSHN’s acme-dns instance at https://acme-dns-api.vshn.net

Additionally, APPUiO Managed OpenShift 4 requires access to VSHN’s identity management:

  • VSHN SSO at https://id.vshn.net

Finally, APPUiO Managed OpenShift 4 requires access to VSHN’s central metrics storage at https://metrics-receive.appuio.net

Red Hat services

See the upstream documentation for the full list of services.

The most important services for APPUiO Managed OpenShift 4 are

  • the Red Hat container registries at registry.redhat.io and registry.access.redhat.com.

  • the OpenShift Update Service (OSUS) at https://api.openshift.com.

3rd party services

Finally, APPUiO Managed OpenShift 4 requires access to a number of third party services:

  • OpsGenie at https://api.opsgenie.com

  • Passbolt at https://cloud.passbolt.com/vshn

  • Let’s Encrypt at https://acme-v02.api.letsencrypt.com and https://acme-staging-v02.api.letsencrypt.com

  • Various container registries

    • GitHub at ghcr.io

    • Quay at quay.io

    • DockerHub at docker.io

    • Google container registry at gcr.io

    • Kubernetes container registry at registry.k8s.io

Storage

APPUiO managed OpenShift 4 requires 3 different types of storage:

  1. Root disks

  2. Persistent volumes

  3. S3 compatible object storage

Root disks

Root disks are virtual block devices (100 GiB) which are attached to the VMs which make up the APPUiO Managed OpenShift 4 cluster. The root disks are allocated and attached to the VM when the VM is created. They hold the operating system and temporary data. They’re ephemeral (no application data is stored on them), and don’t need to be backed up. Finally, root disks are deleted when the VM to which they’re attached is deleted.

Persistent volumes

Persistent volumes are virtual block devices with arbitrary sizes. They’re allocated dynamically based on requests from workloads (applications or infrastructure components) within the cluster. These block devices are automatically attached to the VM hosting the application container. They’re deleted when the corresponding Kubernetes PersistentVolume resource is deleted.

The VMWare vSphere CSI driver is the in-cluster component which is responsible for allocating, attaching and deleting the persistent volume block devices.

These devices hold application data, but backups are usually done from within the cluster.

S3 compatible object storage

Various OpenShift components, such as the integrated image registry, the logging stack and backups, require S3 compatible object storage. The customer or VMWare vSphere infrastructure operator must provide S3 compatible object storage. Most modern storage solutions offer some object storage functionality.

If VSHN’s Application Catalog (AppCat) offering is required on the cluster, the object storage must support automatic bucket creation via an AppCat-supported provisioner.

If no object storage is available, we can use external object storage as a fallback.

Glossary

Components vSphere

Name Description provided by

Bastion host

A simple Ubuntu VM which is used by VSHN to bootstrap the cluster(s) and for emergency administrative access. Requirements

  • CPU: 2

  • Memory: 4GiB

  • Disk space: 20 GiB

  • Connectivity:

    • accessible for VSHNeers via SSH

    • outgoing access to the internet

    • access to the cluster machine network

    • access to the vSphere API

    • access to at least one ESXi host to allow the initial VM template upload

VMWare vSphere infrastructure operator

VMWare vSphere & vCenter

VMWare virtualization platform.

See the upstream documentation for supported versions, network connectivity and required permissions.

Entries for "VMWare vSphere CSI Driver Operator" are required.

VMWare vSphere infrastructure operator

Cluster machine network (sometimes "cluster network" or "machine network")

An internal subnet, usually a /24, in which the OpenShift 4 cluster will be placed.

The terms "cluster machine network," "cluster network" and "machine network" are used interchangeably. Only one network is required.

VMs in this network must be assigned an IP address via DHCP. DHCP replies must include a DNS server which is reachable from the network.

Some IPs must be reserved and will be used as Virtual / Floating IPs. OpenShift manages the floating IPs with VRRP.

At minimum two IPs must be allocated as floating IPs. These two IPs are used for the Kubernetes API and the ingress router.

VMWare vSphere infrastructure operator

S3 compatible storage

Various OpenShift components require S3 compatible storage. This storage must be provided by the customer.

The main APPUiO Managed OpenShift 4 components that use object storage are

  • OpenShift integrated image registry

  • OpenShift logging stack

  • APPUiO Managed cluster backups

Customer / VMWare vSphere infrastructure provider

Access gateway

To access the OpenShift API and applications deployed on the cluster, two public IPs are required. The following forwarding is required:

* For the ingress public IP, ports 80/tcp and 443/tcp must be forwarded to the "Ingress VIP" in the machine network. * For the API public IP, port 6443/tcp must be forwarded to the "API VIP" in the machine network.

Customer / VMWare vSphere infrastructure provider

Components General

Name Description provided by

Installer

A CLI tool that bootstraps an OpenShift 4 cluster based on a configuration file.

VSHN / Red Hat

Bootstrap Node

A temporary VM in the cluster machine network which is provisioned by the installer to facilitate the initial setup of the cluster. This VM is decommissioned by the installer once the cluster installation is completed.

VSHN / Installer

Pod network

A subnet that’s internal to the Openshift 4 cluster. This subnet shouldn’t be routable from outside the cluster.

This subnet is managed by Cilium and is implemented with VXLAN traffic between the cluster VMs

APPUiO Managed OpenShift 4 uses 10.128.0.0/14 as the pod network. If the pod network IP range conflicts with existing subnets, the pod network IP range can be adjusted.

VSHN / Cilium

Service network

A subnet that’s internal to the OpenShift 4 cluster. This subnet shouldn’t be routable from outside the cluster.

This subnet is managed by Cilium and is implemented with eBPF rules on the cluster VMs.

APPUiO Managed OpenShift 4 uses 172.30.0.0/16 as the service network. If the service network IP range conflicts with existing subnets, the service network IP range can be adjusted.

VSHN / Cilium

DNS

The APPUiO Managed OpenShift 4 cluster’s base DNS records are defined and managed by VSHN. All records must be publicly resolvable. To expose applications under a customer domain, a CNAME target is provided.

VSHN

Other terms

Name Description

Node

A virtual machine that’s part of an OpenShift 4 cluster

Control plane

A collection of components that

  • facilitate the management of the container platform

  • manage the virtual hardware making up the cluster

  • manage the applications running on the cluster