How to Setup Failover for DigitalOcean Static Routes Operator

Introduction

The main purpose of the Static Routes Operator is to offer greater flexibility and control over network traffic within your Kubernetes environment. It enables you to tailor the routing configuration to meet your application requirements and optimize network performance. It is deployed as a DaemonSet; hence, it will run on each node of your DigitalOcean Managed Kubernetes cluster.

In this tutorial, you will learn to manage the routing table of each worker node based on the CRD spec and set up a failing over gateway.

The main goal of this tutorial is to demonstrate how to manage the routing table of each worker node based on the CRD spec and Set up a failing over gateway.

Prerequisites

• Working DigitalOcean Managed Kubernetes cluster you have access to.

• Kubectl CLI installed on your local machine (configured to point to your DigitalOcean Managed Kubernetes cluster)

• NAT GW Droplets (2 or above) configured and running as detailed here.

• Create a system to detect failures in a gateway Droplet that fits the user’s needs and ensures clear and accurate detection with minimal false alarms. Use monitoring services like Prometheus or Nagios, set up health check endpoints on the Droplet, or alerting tools like Alertmanager for notifications. For this purpose, you can use a monitoring stack from our marketplace.

Below is the architectural Diagram:

Deploying the Kubernetes Static Routes Operator

Deploy the latest release of the static routes operator to your DigitalOcean Managed Kubernetes cluster using kubectl:

kubectl apply -f https://raw.githubusercontent.com/digitalocean/k8s-staticroute-operator/main/releases/v1/k8s-staticroute-operator-v1.0.0.yaml

Check if Operator Pods are up and running:

Let’s verify if the operator pods are up and running.

``bash kubectl get staticroutes -o wide -n staticroutes

The output looks similar to the below:

```bash
[secondary_label Output]
NAME                       AGE    DESTINATIONS         GATEWAY
static-route-ifconfig.me   119s   ["XX.XX.XX.XX"]     XX.XX.XX.XX
static-route-ipinfo.io     111s   ["XX.XX.XX.XX"]     XX.XX.XX.XX

Now let’s check the operator logs and no exceptions should be reported:

kubectl logs -f ds/k8s-staticroute-operator -n static-routes

You should observe the following output:

Output
Found 2 pods, using pod/k8s-staticroute-operator-498vv
[2023-05-15 14:12:32,282] kopf._core.reactor.r [DEBUG   ] Starting Kopf 1.35.6.
[2023-05-15 14:12:32,282] kopf._core.engines.a [INFO    ] Initial authentication has been initiated.
[2023-05-15 14:12:32,283] kopf.activities.auth [DEBUG   ] Activity 'login_via_pykube' is invoked.
[2023-05-15 14:12:32,285] kopf.activities.auth [DEBUG   ] Pykube is configured in cluster with service account.
[2023-05-15 14:12:32,286] kopf.activities.auth [INFO    ] Activity 'login_via_pykube' succeeded.
[2023-05-15 14:12:32,286] kopf.activities.auth [DEBUG   ] Activity 'login_via_client' is invoked.
[2023-05-15 14:12:32,287] kopf.activities.auth [DEBUG   ] Client is configured in cluster with service account.
[2023-05-15 14:12:32,288] kopf.activities.auth [INFO    ] Activity 'login_via_client' succeeded.
[2023-05-15 14:12:32,288] kopf._core.engines.a [INFO    ] Initial authentication has finished.
[2023-05-15 14:12:32,328] kopf._cogs.clients.w [DEBUG   ] Starting the watch-stream for customresourcedefinitions.v1.apiextensions.k8s.io cluster-wide.
[2023-05-15 14:12:32,330] kopf._cogs.clients.w [DEBUG   ] Starting the watch-stream for staticroutes.v1.networking.digitalocean.com cluster-wide.

To mitigate the impact of gateway failures, it is advisable to have a standby gateway Droplet prepared for failover when required. Although true high availability (HA) is not supported by the operator at the moment, performing failover helps minimize the duration of service disruption.

Suppose you have a designated destination IP address, 34.160.111.145, which represents the active or primary gateway, with an IP address of 10.116.0.4, responsible for transmitting traffic. This is stored in the primary.yaml file.

apiVersion: networking.digitalocean.com/v1
kind: StaticRoute
metadata:
  name: primary
spec:
  destinations: 
    - "34.160.111.145"
  gateway: "10.116.0.4"

Additionally, you will have a standby or secondary gateway with an IP address of 10.116.0.12, ready to handle traffic for the same destination IP address. The StaticRoute definition in secondary.yaml is identical to the primary one, except for the gateway IP address (and object name). This is stored in the file secondary.yaml.

apiVersion: networking.digitalocean.com/v1
kind: StaticRoute
metadata:
  name: secondary
spec:
  destinations: 
    - "34.160.111.145"
  gateway: "10.116.0.12"

The actual failover procedure then consists of the following steps:

• Identifying that the active gateway with IP address 10.116.0.5 is failing.
• Delete the currently active StaticRoute.
• Apply the standby StaticRoute.

Delete the Active StaticRoute

Now let’s delete the currently active StaticRoute.

kubectl delete -f primary.yaml

Wait 30 to 60 seconds to give each operator instance enough time to process the object deletion; that is, respond by removing the route from all nodes.

Apply the Standby StaticRoute

Let’s make the secondary StaticRoute active.

 kubectl apply -f secondary.yaml

The operator should pick up the new standby StaticRoute and enter the corresponding routing table entries. Afterward, the failover is completed.

Testing the Setup

Each sample CRD creates a static route to two websites reporting your public IP - ifconfig.me/ip, and ipinfo.io/ip. A typical static route definition looks like the below:

apiVersion: networking.digitalocean.com/v1
kind: StaticRoute
metadata:
  name: static-route-ifconfig.me
spec:
  destinations: 
    - "34.160.111.145"
  gateway: "10.116.0.5"

To test the setup, download a sample manifest from the example location:

Example for ifconfig.me & ipinfo.io-

curl -O https://raw.githubusercontent.com/digitalocean/k8s-staticroute-operator/main/examples/static-route-ifconfig.me.yaml

curl -O https://raw.githubusercontent.com/digitalocean/k8s-staticroute-operator/main/examples/static-route-ipinfo.io.yaml

After downloading the manifests, replace each manifest file’s <> placeholders. Then, apply each manifest using kubectl:

kubectl apply -f static-route-ifconfig.me.yaml

kubectl apply -f static-route-ipinfo.io.yaml

Finally, test if the curl-test pod replies to your NAT Gateway public IP for each route:

kubectl exec -it curl-test -- curl ifconfig.me/ip
kubectl exec -it curl-test -- curl ipinfo.io/ip

You would need to use the same test during the failover testing. During the primary gateway Droplet failure, the result should give NAT GW public IP of the primary Droplet and during the secondary gateway Droplet/failover. The result should give NAT Gateway’s public IP of the secondary Droplet.

Troubleshooting

• You need to check the StaticRoute object: If an error occurs, first look for errors in the static route event for each node where the rule is applied.

kubectl get StaticRoute <static-route-name> -o yaml

• Check logs: To dig deeper, you can check for errors in the static route operator logs.

kubectl logs -f ds/k8s-staticroute-operator -n static-routes

Clean up

To remove the operator and associated resources, please run the following kubectl command (make sure you’re using the same release version as in the install step):

kubectl delete -f deploy https://raw.githubusercontent.com/digitalocean/k8s-staticroute-operator/main/releases/v1/k8s-staticroute-operator-v1.0.0.yaml

The output looks similar to:

customresourcedefinition.apiextensions.k8s.io "staticroutes.networking.digitalocean.com" deleted
serviceaccount "k8s-staticroute-operator" deleted
clusterrole.rbac.authorization.k8s.io "k8s-staticroute-operator" deleted
clusterrolebinding.rbac.authorization.k8s.io "k8s-staticroute-operator" deleted
daemonset.apps "k8s-staticroute-operator" deleted

Now, if you test the same curl command, you will get the worker node IP as an output:

kubectl exec -it curl-test -- curl ifconfig.me/ip

kubectl exec -it curl-test -- curl ipinfo.io/ip 

Now check the worker node’s public IP:

kubectl get nodes -o wide

Conclusion

Implementing failover capabilities, even if true high availability (HA) is not fully supported, is a recommended approach to minimize the impact of gateway failures.

Organizations can significantly reduce the duration of service disruptions by having a standby gateway ready for failover when needed.

It is important to prepare a standby gateway droplet and ensure a smooth transition when failing over. While the implementation may vary depending on specific requirements, prioritizing failover readiness can contribute to maintaining reliable and uninterrupted service delivery.

Next Steps

You can refer to our documentation to configure Droplet as a gateway.

Our official Managed Kubernetes product documentation provides more information on the DigitalOcean Managed Kubernetes and its features.

You can contact our sales team to migrate to DigitalOcean or talk to our Solution Engineers.