Rolling out new versions of your apps on Kubernetes can be tricky, but knowing the different deployment options is important for keeping your services running smoothly with little to no downtime. This rabbithole of Kubernetes deployment methods may seem daunting and difficult to comprehend (there’s a lot of options), but we're here to help. This guide covers the most common deployment techniques available in Kubernetes along with recommendations on when to use each.
With Kubernetes, you don't have to replace all your application instances at once in a disruptive way. Instead, you can use more gradual deployment models like rolling updates, canary deployments, blue-green splits, and more. Each approach has pros and cons in terms of risk, infrastructure needs, application complexity, and business priorities. Understanding the nuances of each deployment method will help find the one that best fits your needs. Based on these factors and capabilities, you will then be able to select a deployment method that best suits the needs for your delivery pipelines and application architecture while balancing speed with stability.
By the end, you’ll understand the various deployment options at your disposal in Kubernetes as well as strategies for leveraging them effectively. This will set you up for faster, lower-risk delivery of containerized workloads on Kubernetes.
Now, let’s begin by reviewing what deployments are and how they work in Kubernetes.
A Kubernetes deployment represents the desired state for your application pods and ReplicaSets. These deployments allow you to declare how many replicas of a pod should be running at a given time. If pods fail or need to be updated, the deployment ensures the desired state is maintained by starting new pods.
When you implement or update a Kubernetes deployment, the deployment controller manages transitioning to the new application version. This might involve spinning up new pods on nodes with available capacity or gracefully shutting down old pods.
Deployments enable a controlled rollout process for releasing new pod updates. Without them, pods would need to be manually managed, thus making it difficult to rollback issues. By leveraging deployments, you can easily release and iterate on applications deployed to a Kubernetes cluster while minimizing downtime or stability issues.
The controlled rollout abilities of Kubernetes deployments make them essential for maintaining availability during application updates. However, you need an intentional deployment strategy to utilize them effectively.
Choosing the right approach can help minimize downtime during releases. Strategies like rolling and blue/green deployments maintain capacity and availability even as new pods are spun up or old ones terminated. This prevents gaps in service.
A sound deployment strategy also ensures alignment with business requirements for application availability and uptime. Based on factors like traffic patterns and peak seasons, you can select a Kubernetes deployment technique that balances new releases with end user impact.
Finally, having an intentional deployment plan enables faster rollbacks if issues emerge. Techniques like canary releases minimize the blast radius from new version problems. Kubernetes can quickly rollback a portion of traffic to the previous stable version while you remediate the situation. This is far preferable to suddenly switching all users back or dealing with extensive downtime.
Kubernetes offers several deployment strategies to roll out updates, test in production, and shift traffic in a controlled manner. Each technique has its own pros, cons, and use cases in terms of risk tolerance, infrastructure requirements, and rollback capabilities. Major deployment options include:
Rolling deployments update older application versions with new ones in a gradual, controlled process. New pods with code changes are incrementally created while old instances are terminated. This approach leverages health checks and configurable parameters like "max unavailable" and "max surge" to shift load methodically. It aims to validate updates without large drops in capacity.
Rolling releases are best suited for stateless applications that can handle some temporary instance loss during upgrades. The gradual rollout reduces, but does not eliminate, the risk of issues. The tradeoff is that rollouts can take more time for large pod clusters, with potential uneven performance during upgrades. So rolling deployments may not suit mission critical systems with little headroom.
The recreate strategy terminates all old pods before new code is deployed. It first scales down existing application versions, then deploys fresh pods to match the desired state. This approach causes downtime and disruption for users during upgrade events as existing pods go abruptly offline. But it allows you to validate application changes independently and modify environment variables or configuration requirements.
Recreate deployments work best for stateful applications that need to sync data or reading volumes before the newly released version goes live. It also enables dependency and architectural changes automatically across the entire system. The lack of capacity during upgrades may be problematic, however, for clusters supporting production workloads. Downtime windows must be planned with business needs in mind. Recreate works when validation or environment control outweighs constant availability concerns.
The ramped deployment strategy gradually increases the number of new pods at a controlled rate to validate stability and performance. Additional instances get added over time until reaching the target scale.
This approach prevents large resource spikes that can occur when spinning up full copies of large applications instantly. The incremental scaling places less simultaneous load on infrastructure. New code can also be canceled quickly if issues emerge. Ramped rollouts work well for large monolithic apps or those with significant background processing demands before becoming ready to receive traffic. It offers a middle ground between all-at-once recreate and instance-by-instance rolling deployments.
The tradeoff is lengthier rollout timeframes, especially for apps that must scale up significantly. The gradual validation process also provides limited feedback on wide scale Kubernetes deployment readiness until later in the release
The best-effort controlled strategy defines key parameters upfront but gives Kubernetes flexibility to optimize the rollout event. Custom tuning allows setting limits on things like max unavailable instances or pod termination rates.
Within the guardrails provided, Kubernetes handles the details of the rollout dynamically based on cluster conditions. This balances some predictability in the process while still allowing automation optimizations. Defining best-effort parameters works well when precise control over every upgrade step is not required. It can handle rolling deployments more efficiently without onerous scripting. You still limit the blast radius for issues.
However, if guaranteed SLAs or visibility into each rollout phase is needed, a pure best-effort approach may be lacking. There is also reliance on Kubernetes to make good decisions autonomously within the provided constraints.
The blue-green deployment strategy launches the new application version on duplicate infrastructure alongside the old version. Once validated, traffic gets switched from original “blue” pods to fresh “green” ones instantly. This facilitates rapid rollback to existing apps in case of issues while reducing downtime for upgrades. Validation can happen via tested traffic on the green cluster prior to cutting over all users simultaneously.
Blue-green deployments work well for components with complex dependency changes or machines relying on rapid failover recovery. The separate environment enables decoupling updates from stability risks on live apps.
The drawback is the resource overhead of running independent application stacks. Advanced traffic management capabilities are also required to seamlessly transition users during the cutover event to avoid requests being dropped.
The canary deployment strategy shifts a small portion of traffic to a new Kubernetes pod version while the bulk sees no change initially. If stable, the new “canary” release gets progressively exposed to more users. This enables extensive production testing before fully rolling out updates. Issues can also be caught early with minimal user impact since only a slice of traffic goes to new code. Failing canaries provide actionable rollback signals.
Canary deployments are ideal for risk-averse teams wanting phased test flights and analysis at scale. It offers the most flexibility to assess new versions while controlling failure blast radius if unstable.
The complexity of managing and assessing incremental rollout steps can slow down the release cycle, however. More advanced metrics and monitoring are also required to determine canary health during each stage before proceeding.
Shadow deployments, sometimes called “Dark Launches”, emulate production infrastructure and flows but do not serve live users. Instead, replicated traffic verifies performance before broadcast to all end users. This technique validates architecture decisions, database interactions, and downstream dependencies without direct customer impact. However, running duplicate production systems is resource heavy and potentially cost prohibitive at scale.
Shadow launches work in highly complex distributed systems needing layered integration testing between old and new modular components. Teams assess holistically rather than risk incremental consumer exposure.
The cost and synchronization across cloned production environments makes shadow testing challenging, however. Teams also receive limited live data feedback even when emulating workflows. It may discover issues late compared to incremental rollout.
A/B testing deployments launch two (or more) versions of an application side-by-side then examine differences in usage and metrics. This helps compare versions like old vs new homepage experiences to judge what users prefer. Kubernetes facilitates the concurrent launches and weight shifting needed to route subsets of traffic to each variant. Teams gain data insights on alternatives without impacting operations of the existing stable release.
A/B analyses shine when teams need usage statistics tied to proposed changes rather than just internal app diagnostics. The production-derived data quantifies impact more accurately compared to internal testing.
However, this technique increases infrastructure overhead to host and monitor duplicate releases. Steering production samples to variants can also complexify traffic routing logic and may have compliance implications depending on data sensitivity.
Selecting the right Kubernetes deployment strategy requires weighing key decision criteria across categories like business needs, technical parameters, and organizational maturity. There are several important considerations to factor to determine optimal fit:
Analyze Application Architecture
Application architecture directly influences technical strategy options. Assess attributes like:
Set Acceptable Failure Thresholds
No release process is risk-free, but consequences vary across techniques. Define acceptable thresholds like:
Confirm Monitoring & Validation Capabilities
More progressive techniques like canary analysis, A/B testing, or blue/green rely on validation at each stage by monitoring for leading indicators of problems.
Optimize Gradually
Start stringent with reactive safeguards, then optimize towards progressive delivery techniques as organizational maturity allows. Leverage Kubernetes' flexibility to institute release processes aligned to your stability confidence. This can transition over time based on factors like:
Regularly reevaluating business and technical factors as priorities evolve enables designing an optimal Kubernetes application deployment strategy fitting current needs.
Kubernetes provides extremely versatile options for deploying containerized applications leveraging built-in controls like health checks, traffic shifting, and rolling updates.
Carefully choosing a deployment strategy aligned to your use case ensures releasing new versions with minimal disruption. We covered popular techniques from using basic rolling updates to more advanced models like canary, blue/green, and shadow launches - each with their own strengths and weaknesses.
With the power of Kubernetes, teams can implement customized application deployment workflows fitting their precise technical and business needs while minimizing release risks. As priorities change over time, reevaluate which deployment strategies offer the right fit.
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