Networking

Ipv4

All networking in Rahti 2 uses IPv4. All IPs in this document and Rahti 2's system itself are ipv4 only, no ipv6 IP is used.

Namespaces

Rahti 2 is divided in Namespaces. Depending on the context, namespaces can be referred as Projects. Every object in Rahti 2 must belong to and run inside a namespace.

NetworkPolicy

From a networking point of view, namespaces are configured by default to provide an isolated VLAN to everything that runs inside it, notably to Pods and Services. Traffic to any Pod or Service coming from outside the namespace (even from other namespaces in Rahti 2) will be blocked. The only traffic that will be able to pass from outside the namespace will be the one going through the Route. This isolation is obtained via Network Policies. It is possible to change this by editing the two NetworkPolicy objects that are created by default in Rahti 2.

Advanced networking

In the Administrator menu, under Networking > NetworkPolicies it is possible to browse and edit the default network policies, but only in YAML format. Only change the NetworkPolicies if you are really sure of what you are doing.

Pods

Pods are the basic unit in Kubernetes. They accommodate one or more containers that contain the software and the environment needed to run an application. Each Pod has a private IP, which is only reachable from inside the namespace/VLAN. It is not advisable to use these Pod IPs directly in applications, they are meant to be used by Services. This is because not only other Pods in other namespaces may share this private IP, but more importantly, when a Pod is recreated it will get a new IP.

For example, if we deploy the nginx image in a Pod. This Pod will get a random private IP like 10.1.1.200. Any unprivileged port (>=1024) that the image exports, like for example 8081, will be reachable in that IP. A Pod will fail to start if it tries to export a privileged port ([0-1023]). If the Pod is killed, normally due to a change in its configuration, but also possibly due to unexpected reasons like hardware failure, a new Pod with a different IP will be created, like for example 10.1.1.140. These IPs will respond to traffic from within the namespace only. If we set up a Pod that will query the first IP (10.1.1.200), it will obviously stop working at the moment of the recreation of the Pod associated with it. This is why we use services.

Services

Services (also abbreviated svc) provide a stable private IP to one or more Pods. This IP will act as a load balancer, distributing the traffic load between the Pods behind it. For this, the service will make sure to keep an updated list of IPs so requests are only sent to valid ones.

Services are built to export one or more ports, and they also provide an internal DNS name. Any of these names are valid and will resolve to the same service IP:

• <service_name>, e.g., nginx.
• <service_name>.<namespace>, e.g., ngin.fenic
• and <service_name>.<namespace>.svc.cluster.local, e.g., nginx.fenic.svc.cluster.local.

In the same manner as Pods, Rahti 2 Services can only be reached from inside the namespace they run, any request from another namespace will be able to resolve the DNS into an IP, but it will never connect. Another feature of services is that they can forward requests from one port to another target port (ex: 80 to 8080). This is useful in Rahti 2 as Pods cannot listen on privileged ports (<1024).

Services can be used for internal connections. For example, if we have one or more MongoDB database replicas running in the fenic namespace, each in a different pod, and they export port 27017. We can create a service called mongo associated with the pods under the same name. Then we can launch nginx Pods that run a Python application which will use the URL <mongo:27017 to connect to the database. When connections to the service are attempted, one of the mongo pods will be selected to serve the data request.

Routes

Routes are the OpenShift equivalent of Ingress in vanilla Kubernetes, they expose a single port of a single Service object to traffic from outside the namespace and the Internet, via HTTP/HTTPS only. If the route is configured to provide no encrypted HTTP traffic, the pods associated should talk in HTTP non encrypted traffic. If the route is configured to provide TLS/HTTPS secure traffic, several options are available regarding the Route encryption:

• Edge, this is the default and the simplest to configure. The Route provides the certificate, which is stored in the Route object itself. The traffic is decrypted and the Pod is contacted using plain text un-encrypted HTTPD traffic.
• Passthrough is when the encryption is delegated to the pod, which must listen for TLS/HTTPS traffic and provide the certificate the client will receive.
• Re-encrypt, this is a mixture of two previous options, the Route will provide a certificate, but it will connect to the Pod using TLS/HTTPS and expect a valid certificate for the domain name of the service. The client will still get the certificate stored by the Route. This is for example used when the internal network between nodes in the cluster is not considered secure enough and we still want the Route to control the certificates that the client will get. Also in some rare applications is not possible to disable TLS in the Pods.

Re-encrypt

For Re-encrypt to work, it is necessary to provide your own certificate. There are 3 steps: (1) You must have a certificate/key pair in PEM-encoded files, where the certificate is valid for the route host. (2) You may have a separate CA certificate in a PEM-encoded file that completes the certificate chain. (3) You must have a separate destination CA certificate in a PEM-encoded file. If one of these steps is not followed correctly, the route will not work.

A Route can also be configured to (1) provide a HTTP/302 redirection from port 80 to 443. It is also possible to (2) serve the same content in both ports, or to (3) not serve anything at all in the un secure 80 port.

An important limitation for Rahti 2 is that only the HTTP/80 and HTTPS/443 ports are exposed for incoming traffic, and they only can serve HTTPD protocol requests. Internally to a namespace, any port and protocol is supported, this means we can connect an application to a database with no issues, but we will never be able to expose that database to outside traffic. This is due to the fact that the same incoming virtual IP is shared with all the incoming traffic in Rahti 2's HAProxy load balancers. Name-based virtual hosts are used to redirect the traffic to the correct Route. Other protocols that are not HTTPD, do not have this feature and will need a dedicated IP/port pair to work.

Rahti 2 provides a range of pre-created domain names, XXXX.2.rahtiapp.fi where XXXX can be any combination of letters, numbers and dashes. These pre-created domain names also come with a valid TLS certificate.

Every single pre-created domain name is configured to point to the HAProxy load balancers.

Custom domains

Any existing possible domain name could potentially be used in Rahti, but the DNS configuration and the certificates must be managed by the customer:

• For the DNS configuration, you need to configure a CNAME pointing to router-default.apps.2.rahti.csc.fi or in cases that this is not possible, another possibility is to configure an A record containing the IP of router-default.apps.2.rahti.csc.fi has to be configured. The way this needs to be configured depends on the register of the DNS record.

  $ host ?????.??
  ?????.?? is an alias for router-default.apps.2.rahti.csc.fi.
  router-default.apps.2.rahti.csc.fi has address 195.148.21.61
  

• Any certificate provider can be used, like for example use the free certificates provided by the Let's Encrypt controller.

Another aspect of routes is the IP white listing feature, ie: only allowing a range of IPs to access the route. This is controlled by creating an annotation in the Route object with the key haproxy.router.openshift.io/ip_whitelist, and by setting the value to a space separated list of IPs and or IP ranges. Assuming variable route_name holds the name of the route

• This first example will white list a range of IPs (193.166.[0-255].[1-254]):

  oc annotate route $route_name haproxy.router.openshift.io/ip_whitelist='193.166.0.0/16'
  

• This other example will white list only a specific IP:

  oc annotate route $route_name haproxy.router.openshift.io/ip_whitelist='188.184.9.236'
  

• And this example will combine both:

  oc annotate route $route_name haproxy.router.openshift.io/ip_whitelist='193.166.0.0/15 193.167.189.25'
  

Egress IPs

The IP for all outgoing customer traffic is 86.50.229.150. Any pod that runs in Rahti 2 will use by default this IP to reach anything located outside Rahti 2 or a Route. It is possible, for selected namespaces that need it, to configure a dedicated IP. Each request is reviewed individually due to the fact that there is a limited pool of virtual IPs available.

Egress IP may change

The egress IP of Rahti 2 might change in the future. For example, if several versions of Rahti 2 are run in parallel each will have a different IP. Or if a major change in the underlining network infrastructure happens.

Using LoadBalancer Service Type with Dedicated IPs

Unlike routes, the LoadBalancer service type makes it possible to expose services to the internet without being limited to HTTP/HTTPS. This feature allows you to expose services to receive external inbound traffic on a dedicated public IP address, ensuring that external users or services can interact with your applications. To enable and use LoadBalancer services within your Rahti 2 project, you must submit a request to the service desk (servicedesk@csc.fi). The request must include the following details:

• Project Name: Provide the exact name of the Rahti 2 project for which you want to enable LoadBalancer services.

• Use Case: Clearly describe the use case, including:

  • The type of services you plan to expose (e.g., web applications, APIs).
  • Any specific requirements or considerations.

When your request is approved by the admins, you will receive the public IP address that can be used to access your services, and you can then proceed with the creation of the LoadBalancer service.

For example, the following service definition exposes a MySQL service on the assigned public IP at port 33306.

kind: Service
apiVersion: v1
metadata:
  name: mysqllb
  namespace: my-namespace
spec:
  ports:
    - protocol: TCP
      port: 33306
      targetPort: 3306
  allocateLoadBalancerNodePorts: false
  type: LoadBalancer
  selector:
    app: mysql

Ensure that the service type is set to LoadBalancer, and that the allocateLoadBalancerNodePorts field is set to false (the default is true) because NodePorts are not enabled in Rahti 2. If this field is not set correctly, the allocated node port will be unusable, and service creation may fail if the entire default node port range (30000-32767) is already allocated.

Additionally, the port field in the service definition (e.g., 33306 in the previous example) must be within the range of 30000-35000.

Multiple LoadBalancer Services

It is also possible to expose multiple LoadBalancer services on the same public IP but on different ports, you can enable IP sharing by adding the metallb.universe.tf/allow-shared-ip annotation to services. The value of the annotation is a label of your choice. The services annotated with the same label will share the same IP. Here is an example configuration of two services that share the same IP address:

kind: Service
apiVersion: v1
metadata:
  name: mysqllb
  namespace: my-namespace
  annotations:
     metallb.universe.tf/allow-shared-ip: "label-to-share-1.2.3.4"
spec:
  ports:
    - protocol: TCP
      port: 33306
      targetPort: 3306
  allocateLoadBalancerNodePorts: false
  type: LoadBalancer
  selector:
    app: mysql

kind: Service
apiVersion: v1
metadata:
  name: httplb
  namespace: my-namespace
  annotations:
     metallb.universe.tf/allow-shared-ip: "label-to-share-1.2.3.4"
spec:
  ports:
    - protocol: TCP
      port: 30080
      targetPort: 80
  allocateLoadBalancerNodePorts: false
  type: LoadBalancer
  selector:
    app: httpd

Info

Just as a side note, in Rahti2, the way routes and external load balancer services manage traffic during deployment rollouts differently.

Routes, managed by OpenShift's HAProxy, are designed to quickly adjust and direct traffic as soon as a new pod starts and simultaneously cease routing to the old or terminating pods, ensuring rapid response to changes and minimizing service disruption.

In contrast, external load balancers distribute traffic not only to new pods but also continue to send requests to old or terminating pods. This behavior occurs because these services rely on periodic updates from EndpointSlices, which can delay the exclusion of terminating pods from traffic distribution. This difference in handling traffic can be useful to understand, as it affects how deployment strategies should handled for application updates.

For more information refer to the OpenShift documentation regarding route based deployment strategies. To avoid disruptions when using external load balancer services, you can adopt the principle of a blue-green deployment

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