Disaster Recovery on Kubernetes and Container Registry
Tags: disasterrecovery, kubernetes, containerregistry, containers
Published: 2023-07-28 16:51:52

**Disaster Recovery (DR)**
Disaster recovery is an integral cloud benefit. It is an essential advantage of adopting cloud architectures for business solutions. It is the ability to recover data, applications and IT infrastructures after a disaster or a disruptive occurrence. This occurrence may be natural or man-made. They include flood, hurricanes, earthquakes, hardware failures, cyber-attacks, non-compliance with best practices etc. Disaster recovery in cloud environment is accomplished with various tools, services and architectural builds which ensures resiliency and high availability.
Strategies employed for disaster recovery in on-premise environment differs greatly from what obtains in containerized environment. Granted, this is costlier than DR in containerized environment because backups for systems and data has to be kept safe in a physical data center (usually offsite). Investments in the maintenance and physically securing such infrastructure can be mind-blowing.

**Kubernetes and Container Registry**
Before diving into disaster recovery as it relates to Kubernetes and Containers Registry, let’s have a brief overview of what Kubernetes and Container Registry are.
First, **Containers** are lightweight packages that house the application code together with dependencies and configuration for specific application. Containers make deployment of application to any compute environment easy such that when there is higher demand for your application, it is not difficult to scale out to meet those demands by deploying additional container instances. This is depicted in the picture below

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/r9t5fxt0df3hlromlogv.png)

**Container image** is an executable code that can create a container on a computing system. It includes everything that a container needs to run. It is a snapshot of a specific application or service along with its dependencies and configurations. These images are stored and managed in Container Registry. 
**Container Registry** is a storage location where developers can push and pull container images and share them with their teams or the broader community. There are three main types of Container Registry:
(i)	Docker Hub - this is a public registry that make over 100,000 off-the-shelf images shared by software vendors, open source projects, and Docker’s community of users, accessible
(ii)	Self-hosted Registries- this is managed by individual organisation when they prefer to host their container images on their own on-premises infrastructure
(iii)	Third party Registry Services – these are Container Registry services provided by Cloud Service Providers. They are fully managed offerings that also give you control over how you manage your images but with no operational cost for infrastructure. These include Amazon Elastic Container Registry, Azure Container Registry and Google Container Registry.
These registries help in the containerization workflow. Containerization workflow is orchestrated such that it is easy for developers and operations teams to work with large-scale container deployments. A popular platform very useful here is Kubernetes.
**Kubernetes** is an open source platform for Container Orchestration. It is portable and extensible for automating deployment, scaling and management of containerized workload. It eliminates the complexity associated with management of containers. Containers are usually complex to manage because critical applications run in such environment. This necessitate the importance of having a very good and standard plan for disaster recovery in containerized environment. One that conforms to the best practices in the Industry. 

**Disaster Recovery on Kubernetes and Container Registry**
As explained above, in today’s technology world, Kubernetes and Container Registry play a crucial role in application development and deployment workflows. Therefore, having a robust disaster recovery plan for these components is essential for the following reasons
(i)	To maintain business continuity: When a disaster or any disruptive event occur, it affects the smooth running of business operations, slowing it down or stopping abruptly. But having disaster recovery plan in place will ensure business continuity
(ii)	To improve system security: Disaster recovery plans limit security risks. This is because most cloud based DR solutions have built-in security features that can detect and block cyber attacks
(iii)	To reduce cost of recovery: Business operations returns to normal state as early as possible after a disruption if there is an effective recovery plan. Thus, resulting in minimized loss due to the disaster
(iv)	To ensure customer retention: Customers always watch out for the capabilities of an organisation to recover after a disaster. This often affect their decision to continue their business relationship with the organisation. Imagine what can happen to a commercial bank that its Data centre was destroyed by fire and was unable to render the least of its services, like checking of account balance, for about a week after the fire outbreak.

Disaster recovery on Kubernetes and Container registry refers to the strategies and practices employed to ensure the availability, resilience, and recovery of containerized applications and container images in case of disruptive events or perils. 
Planning for these will basically be in three phases:
(i)	Identifying the potential risks on Kubernetes and Container Registry
(ii)	Preserving the applications and images before the occurrence of any disaster i.e. backup plans
(iii)	Recovering the applications and images after a disaster or disruptive event i.e. recovery plans

**What are the Potential Risks?**
These risks can be grouped into two:
1.Risks due to natural disasters
Natural disasters are acts of nature caused by the natural forces of the Earth where great damage and, sometimes, loss of life occurs. These include earthquakes, flood, hurricanes, volcanic eruptions, landslides, wildfires etc. These can cause an outright or partial destruction of data centres and other cloud infrastructures leading to disruption in availability of cloud applications and services.

2.Risks due to man made errors of system malfunctions. These are discussed below

a.<u>Security vulnerabilities:</u> Cyber attackers can gain unauthorized access to containerized applications if they are not regularly updated and patched. When deploying and managing Kubernetes components in-house, the Kubernetes API server and its components as open source tools have potential risk because both external and internal users connect to it. Also, RBAC is the Kubernetes-native method of managing and controlling authorization to Kubernetes resources. In the event of a security breach, attackers can quickly get high-level access to the clusters using the cluster admin role.
b.<u>Vulnerable container images:</u> Container images that are not scanned for vulnerabilities before deployment are detrimental to the cluster where they run. Images from untrusted source can have critical vulnerabilities like remote code execution.
c.<u>Security risk of Kubernetes secrets:</u> Kubernetes secrets are useful for securing sensitive data like passwords, certificates, or tokens and using them inside containers but they may not secure the cluster data against malicious cyber attacks. This is because they are not encrypted by default. Another massive threat to secrets is that any pod and any applications running inside the pod in the same namespace can access and read them.  In addition to this, any old or unused secrets can create confusion and let out vulnerable data.
d.<u>Runtime threats:</u> Containers are controlled by the host operating system in the runtime and these run on Worker nodes. If there are permissive policies or container images with vulnerabilities, they can permit unauthorized access into the whole cluster and this will be destructive.
e.<u>Risk through network access:</u> Network policies are used to manage and restrict the network access between pods, namespaces, and IP blocks. They also work with the labels on the pods. But when these labels are not used efficiently, it can lead to unauthorized access.
f.<u>Partial monitoring and audit logging:</u> Monitoring only the application metrics when an application is deployed to a Kubernetes cluster can predispose the whole system to unhealthy anomalies
g.<u>Unrestricted pods and namespaces:</u> This can give way to unwanted access to sensitive data inside your cluster.
h.<u>Cluster and Resource misconfiguration:</u> When online examples for Kubernetes resources are not edited using "kubectl edit" commands during configuration, the changes will be overwritten in the next deployment and you will not be able to track the modifications thus leading to unpredictable outcomes

**Major Elements of Disaster Recovery on Kubernetes and Container images in the Container Registry**
**1.Backup and Restore**
This is the process of making duplicate copies of critical data to be able to restore them when needed. 


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/72f1zp6vp9lp0con2mc0.png)
As seen in the image above, data are backed up and stored in an offsite location. This may be on physical secondary location or in private or public cloud.
Backup objectives has to be defined through metrics like the Recovery Point Objective (RPO) and Recovery Time Objective (RTO) to ensure that data is protected and minimize interruption in case of a data loss event. The RPO is the frequency at which backups are made while the RTO indicates the time it takes to restore data from backup. Organisation should strive to achieve the lowest metric in both the RPO and the RTO for the following reasons:
a)The smaller the RPO, the lesser the risk for data loss when recovering from a backup. 
b)A shorter RTO indicates that the recovery process should be able to restore data more rapidly after data loss and allow for the quicker continuation of business activities
For Kubernetes, regularly backing up the Kubernetes cluster's configuration and etcd database is essential to recover the cluster's state in case of failure.
Generally, backing up in Container registry bothers on regularly backing up the container images. This is usually automated with the built in features of the registry to be sure that the most recent image versions and metadata backed up consistently. Consulting the official documentation for the specific container registry solution you are using is very essential for more detailed and up-to-date instructions on how to perform backups and ensure data integrity.

**2.Data Replication**


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ksnd5cur1ijw3onm8eko.png)

The picture shows replication strategy for Kubernetes from Data Center 1 named **Active** which is the Primary location to a Data Center 2 named **Standby**, a Secondary location.
Processes involved in Replication of data are stated below:
- Running multiple replicas of critical application components 
  across different nodes in a Kubernetes cluster ensures 
  redundancy and high availability. If one replica fails, the 
  others can continue to handle the workload
- Geo-replication of data and applications across multiple 
  geographically dispersed data centers or availability zones 
  within a cloud provider's infrastructure ensures redundancy and 
  fault tolerance.
- Many container registry solutions offer built-in replication 
  features that can copy container images to multiple locations or 
  even across different cloud providers.

**3.Disaster Recovery Plan**
Outlining the steps and procedures (for various disaster scenarios) to follow in case of a disaster is very crucial to ensure proper implementation. This should include information on the followings:  
-  backup schedules
-  recovery point objectives (RPOs)
-  recovery time objectives (RTOs)
-  the responsibilities of different team members during a 
   recovery operation.

**4.Multi-cluster Set up**
-  Deploying Kubernetes clusters across multiple regions or data 
   centers can provide geographical   redundancy. If one data
   center experiences a disaster, applications can failover to 
   another cluster in a different location. This ensures 
   protection against regional outage.
-  Having a multi-cluster environment enables you to ensure that 
   workloads don’t experience downtime due to a problem within a 
   single cluster, as you can seamlessly transfer them to another 
   cluster.

**5.Load Balancers**
(a)In Kubernetes clusters, a Load Balancer service does the 
   following:
   -  Distributes network loads and service requests efficiently 
      across multiple instances
   -  Enables autoscaling in response to demand changes
   -  Ensures High Availability by sending workloads to healthy 
      Pods
   These actions mitigate the impact of potential failures and 
   spares users the annoyance of dealing with unresponsive 
   services and applications when a disaster occurs.

(b)For effective use of Load balancers for Disaster recovery plan 
   in Container Registry, the registry has to be replicated to a 
   secondary region. In Azure, Container Registry's has built-in 
   geo-replication feature that perform this task
Actions needed here are: 

i. deploy load balancers to both the primary and secondary regions
ii. set up health probes or monitoring checks on the container 
   registry instances behind the load balancers
iii. configure disaster recovery routing to ensure traffic are 
    redirected to secondary region in the event of disaster

**6.Monitoing and Alerting**
-  After setting up the backup process, regularly monitor the 
   backup logs 
-  Implementing effective monitoring and alerting systems can help 
   detect issues early and trigger recovery processes 
   automatically
-  This make it easy to detect security breaches or performance 
   problems

**7.Regular testing of Disaster Recovery plan**

Conduct periodic testing of the failover process to be sure that the disaster recovery plan will work as expected when there is need for it. It will help to identify and address any weaknesses in the recovery plan.  Here are some useful steps to take:-

a)Set up a separate environment specifically dedicated to testing disaster scenarios. This should be isolated from the production environment to prevent any accidental impact on live services.

b)Create a replica of your production Kubernetes cluster and container registry in the test environment using the same versions of Kubernetes, container images, configurations, and other dependencies to ensure consistency

c)Identify the potential disaster scenarios you want to simulate such as node failures, network outages, container image registry unavailability, or entire cluster outages

d)Utilize infrastructure-as-code (IAC) tools like Terraform to automate the provisioning of the test environment. This helps ensure that the test environment is reproducible and consistent for each test run

e)Set up load balancers in the test environment as you have in the production environment.

f)Intentionally trigger disaster scenarios and test your backup and restore procedures.

g)Deploy monitoring and logging tools in the test environment to closely observe the behavior of the system during each simulated disaster

h)Analyze the results and make necessary adjustments to improve the recovery plan

i)Create scripts or automation to clean up and reset the test environment after each simulation

j)Document the results of each disaster simulation and any improvements effected

k)Repeat testing regularly

**8.Security**	
(a)Access Control
- Apply strong access controls to limit who can manage and modify 
  resources in the Kubernetes cluster and container registry.
- Use Kubernetes RBAC (Role Based Access Control) to define 
  granular access levels based on roles, allowing only authorized 
  users to perform specific actions.

(b)Network Security
- Use Virtual LANs (VLANs) to segregate the disaster recovery 
  environment from the production environment
- Network Policies in Kubernetes can be used to control traffic 
  flow between pods and namespaces and enforce security rules.

(c)Secure Authentication and Authorization
-  Use authentication mechanisms such as TLS certificates or OAuth 
   tokens.
-  Integrate with an Identity Provider (IdP) for centralized user 
   management and single sign-on (SSO).
-  Enforce the use of Multi-Factor Authentication (MFA) for 
   accessing critical resources. This adds an extra layer of 
   security, making it difficult for unauthorized users to gain 
   access

(d)Encryption
-  Encrypt sensitive data at rest and in transit. 
-  Use encryption for etcd data, Kubernetes secrets, container 
   images, and communication channels.
-  Utilize TLS/SSL certificates for secure communication within 
   the Kubernetes cluster and with the container registry.

(e)Secure Container Images
-  Container images must be scanned for vulnerabilities before 
   deployment to ensure that only secure images are used in the DR 
   environment.
-  Use image signing and verification to prevent unauthorized 
   modifications.

(f)Regular Updates and Patching
   Consistently update the Kubernetes cluster, container runtime, 
   and other components with the latest security patches.

(g)Communication with External Services
-  These can be secured with VPNs or encrypted channels
-  Communication between the DR environment and external systems 
   must be authenticated and authorized 

(h)Security of the Disaster Recovery Site
-  This applies to organisation maintaining on premise  
   infrastructure
-  A separate site must be used for disaster recovery and you must 
   ensure that it meets the same security standards as the primary 
   site.
-  Securely transfer data between the primary and DR sites using 
   encrypted channels such as VPN, TLS/SSL Certificates, VLAN (for 
   Container registry) etc

**9.Create Disaster recovery team**
Creating a disaster recovery (DR) team for Kubernetes and the Container Registry is crucial for effectively handling and mitigating potential disasters. Note the following steps and criteria while creating the team

(a)	Members of the team should consist of skilled individuals who understand the infrastructure, applications, and data involved and stakeholders like the IT managers, DevOps leads, Cloud Administrators/Engineers, application owners, and security personnel
(b)	Define and assign specific roles and responsibilities of each team member based on their expertise and knowledge of Kubernetes, container orchestration, container registries, network management, and disaster recovery procedures systems involved
(c)	Select individuals who are available and accessible during potential disaster scenarios
(d)	Provide training and knowledge sharing sessions to the DR team to ensure that all members understand the disaster recovery plan and procedures and get familiar with the organization's infrastructure, applications, and data dependencies
(e)	Set up clear communication channels such as Google meet, Microsoft Teams, for the DR team to stay connected during both normal operations and disaster scenarios.
(f)	Organize regular disaster recovery drills and testing exercises for the team, to validate the effectiveness of the plan and identify any areas for improvement
(g)	All procedures, configurations, and contact information in the disaster recovery documentation must be kept up-to-date. And updated documentation must be circulated among DR team members
(h)	Set up alerts to notify the team about any suspicious or unauthorized activities.

**Real live Scenarios of disaster recovery on Kubernetes**
1.BlackRock, a global investment management firm, utilizes 
  Kubernetes to deploy its applications across multiple regions. 
  They set up a disaster recovery strategy where applications and 
  data are automatically replicated and failover to a secondary 
  Kubernetes cluster in case of a disaster in the primary region.

2.Adobe's Experience Manager (AEM), a content management solution, 
  uses Kubernetes for its disaster recovery strategy. They deploy 
  AEM in a highly available Kubernetes cluster with data 
  replication and automated failover across different regions or 
  data centers

3.Pinterest, a visual discovery and bookmarking platform, runs its 
  Kubernetes workloads on Amazon EKS. They have a multi- 
  Availability Zone EKS deployment to ensure redundancy and high 
  availability. In the event of a failure, their applications can 
  quickly recover in another Availability Zone.

**Real live Scenarios of disaster recovery on Container Registry**
  
1.Docker Hub, the official Docker image registry, employs robust 
  disaster recovery practices to ensure the availability of 
  container images for developers worldwide. They use a 
  combination of data replication, backups, and load balancing 
  across multiple regions to ensure high availability and data 
  redundancy. In the event of an outage in one region, users can 
  still access images from other available regions.

2.Microsoft Azure's Azure Container Registry (ACR) is designed for 
  high availability and disaster recovery. ACR replicates 
  container images across multiple regions, providing geographic 
  redundancy to ensure accessibility even during regional outages. 
  Additionally, ACR integrates with Azure Backup for image 
  registry backup and recovery.

3.Amazon Web Services (AWS) Elastic Container Registry (ECR) 
  offers container image storage with built-in redundancy and high 
  availability. ECR automatically replicates images across 
  multiple AWS Availability Zones within a region to ensure data 
  durability. Additionally, AWS provides multi-region replication 
  options to further enhance disaster recovery capabilities.

**Conclusion**
Disaster recovery on Kubernetes and container registry is a critical aspect of ensuring the high availability, resilience, and business continuity of modern cloud-native applications. Kubernetes has emerged as a dominant and popular orchestration platform for containerized workloads, offering flexibility and scalability to deploy applications across various environments. Along with it, Container registries play an essential role in securely storing and managing container images, making them an important part of the disaster recovery strategy.

This article have explored the key components of a robust disaster recovery plan for Kubernetes and Container Registry, together with strategies highlighted in view of best practices and real-life examples. We learned how to set up test environments to simulate disaster scenarios, the importance of encrypted channels for data transfer, and the significance of a well-prepared disaster recovery team.

As Cloud computing continues to evolve, organizations primary aim is to deliver seamless, reliable, and uninterrupted services to their customers. And this can be achieved by leveraging on the capabilities of Kubernetes, Container registries, and other cloud provider services while keeping on guard for potential disasters.

I hope you find this article helpful. Please leave your feedbacks in the comment section