Multi-Cluster Load Balancing in Kubernetes_ Strategies and Considerations.pptx

Multi-Cluster Load Balancing in Kubernetes:
Strategies and Considerations
Tamil Vanan
Tech Lead, Arcesium

Self Introduction
● I'm Tamil Vanan, with over 11 years of
experience in networking, automation,
development, and cloud-native technologies.
● My current role is as a Tech Lead at Arcesium.
● I have a keen interest in exploring and solving
cloud-native use cases.
● In my spare time, I enjoy playing badminton.
● You can reach out to me(@tamilhce) on
Twitter/Linkedin

Introduction
● What is Multi cluster Load balancing in Kubernetes?
● Use cases
● Importance of effective multi-cluster load balancing

Key Networking Constructs
1. Pods-to-pods communication without the need for proxies or
translations using IP addresses.
1. The service abstraction, which groups pods under a common
access policy, creating a virtual IP for transparently proxying
client requests to the pods.
1. Exposing services to the external world using Ingress, Gateway,
or services of type LoadBalancer.

Enabling External Access for Your Kubernetes
Application
How to make your application accessible outside the
kubernetes cluster
● Service of Type LB
● Ingress
● Gateway
Service Based Routing

Multi-Cluster Load Balancing Strategies
● GSLB (DNS-based Global Server Load Balancing)
● Service Mesh-based Multi-Cluster Load Balancing
● CNI-based Multi-Cluster Load Balancing

GSLB (DNS-based Global Server Load Balancing)
● Load balancing is based on timeproof
DNS protocol which is perfect for
global scope and extremely reliable
● No dedicated management cluster and
no single point of failure
● Reference: K8gb

GSLB (DNS-based Global Server Load Balancing)
● Pros
○ External Client Traffic
■ Ideal for applications with significant external traffic
○ Geographic Distribution
■ directing traffic to the nearest cluster or region based on the client’s location
■ minimizing latency
○ No Dependency
■ It doesn’t have any dependency on the vendor specific CNI, service mesh. Ingress
controller
■ Works with any existing clusters
● Cons
○ enabling fine-grained control over traffic patterns(traffic splitting, circuit breaking, retries, and
fault tolerance) is not applicable
○ DNS TTL

Service Mesh-based Multi-Cluster Load Balancing
● Service Mesh excels provides load balancing
services across multiple clusters, offering
precise control over traffic routing, load
balancing, and service discovery.
● References: Linkerd, Istio

Service Mesh-based Multi-Cluster Load Balancing
● Pros
○ East-West Traffic Handling
■ It’s perfect for east-west traffic, managing communication within and across clusters.
○ Advanced Traffic Management
■ Service Mesh offers advanced traffic management capabilities like traffic splitting, circuit breaking,
retries, and fault tolerance, enabling fine-grained control over traffic patterns
● Cons
○ Vendor Lock-in
■ Implies being tied to a specific service mesh provider, limiting flexibility
○ Scalability Challenges
■ As the number of clusters increases, inter-cluster service becomes more complex and has limitations
on scaling.
○ Increased Complexity and Overhead
■ Introduces additional complexity and overhead for routing external traffic.

CNI-based Multi-Cluster Load Balancing
● Multi-cluster load balancing based on CNI
leverages the underlying CNI for load distribution.
● Pod-to-Pod Communication
● Service Discovery

Requirements
● Ensure each Kubernetes worker node has a unique IP address and IP connectivity between all
worker nodes
● Achieve this through VPN tunneling for cross-region clusters or direct physical network connections
for clusters within the same region/DC.
● Assign unique PodCIDR ranges to all clusters.

Pros
● Ensure each Kubernetes worker node has a unique IP address and IP connectivity between all worker nodes
● Achieve this through VPN tunneling for cross-region clusters or direct physical network connections for clusters
within the same region/DC.
● Assign unique PodCIDR ranges to all clusters.
Cons
● Vendor Lock-in
○ Involves dependency on a particular CNI provider
● Adds extra overhead and cost implications: overlay networking via VPN, potentially resulting in added expenses and
latency

Selecting the Right Multi-Cluster Load Balancing
Strategy
● Why do you require multi-cluster load balancing?
● is it solely for achieving application high availability and disaster recovery?
● Is your application stateless?
● Does your application need service-to-service communications across clusters? why?
● Are you primarily dealing with HTTP-based applications, or do you also support UDP/TCP-based
services?
● Does your use case necessitate pod-to-pod service connectivity across clusters?

Conclusion
In summary, choosing the right multi-cluster load balancing strategy depends on
your specific requirements:
● DNS-based GSLB - For load balancing external traffic across clusters
spanning multiple regions.
● Service Mesh-based multi-cluster load balancing - When scaling services
across clusters and facilitating east-west communication.
● If your needs revolve around direct pod-to-pod communication across
clusters, opt for the CNI-based approach.

Q&A
● References
○ https://linkerd.io/2.14/features/multicluster
○ https://istio.io/latest/docs/setup/install/multicluster
○ https://cilium.io/blog/2019/03/12/clustermesh
○ https://github.com/k8gb-io/k8gb
● Contact: @tamilhce

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