CASE 17 / KUBERNETES / RELEASE SAFETY / API CONTRACTS

Blue/Green and Canary Deployments.

Compare two release strategies for an API consumed by AEM: switch between validated blue/green environments or gradually expose a canary to selected traffic. Both require observable behavior and backward-compatible contracts, not simply a healthy container.

Representative engineering design, not a verified client delivery record. Implementation steps and validation checks describe the proposed approach; no measured results are claimed.

CONTEXTRepresentative engineering design
TECHNICAL FOCUSBlue/Green and Canary Deployments on Kubernetes
STATUSRepresentative case study
RELEASE CONTROL
  1. Stable API
  2. Candidate API
  3. Readiness
  4. Test traffic
  5. Traffic decision
  6. Promote / revert

Logical release stages, not a serial request path. Stable and candidate workloads coexist behind controlled routing.

01 / CONTEXT

Keep the consumer stable while the API changes

The integration service evolves independently of AEM components and OSGi clients. A candidate release must therefore accept requests from existing consumers throughout deployment and rollback.

02 / PROBLEM

Infrastructure health misses contract failures

A candidate may report ready while returning a changed payload, causing downstream errors or breaking session assumptions. A successful HTTP health response does not establish semantic compatibility with the consumer.

03 / ARCHITECTURE

Blue/green switches; canary observes

Blue/green uses separate workload labels and a controlled routing switch after candidate validation. A canary requires a routing layer that supports weighted or cohort-based traffic; a standard Service or Deployment alone is not a precise percentage-routing mechanism.

04 / ENGINEERING APPROACH

Define the rollback boundary before the rollout

Test old and new consumers against the candidate contract, and use additive data changes before removing fields. Configure startup and readiness checks for usable service behavior, while keeping liveness focused on recoverable process failure rather than every remote dependency.

  • Give stable and candidate revisions separate monitoring dimensions.
  • Document routing-controller behavior for retries, sticky sessions and long-lived connections.
  • Define acceptance and abort conditions before changing traffic; do not infer success from Pod counts.
05 / DEPLOYMENT FLOW

Advance traffic only with comparable evidence

For blue/green, validate the idle candidate and switch the route while retaining the previous revision for a bounded recovery window. For canary, increase exposure only after comparing meaningful request samples and error behavior.

CANDIDATE DECISION
  1. Deploy candidate
  2. Probe
  3. Contract tests
  4. Route traffic
  5. Observe
  6. Promote / rollback

Traffic policy belongs to the chosen ingress, gateway or service-routing implementation.

06 / OPERATIONAL CONSIDERATIONS

Rollback includes connections and state

Allow in-flight work to drain and align termination behavior with the routing layer. A route reversal cannot undo incompatible database writes, irreversible external side effects or an already-broken client contract.

07 / TRADEOFFS

Capacity, sampling and decision speed

Blue/green needs enough temporary capacity for both revisions but offers a clear switch point. Canary limits initial exposure, yet low traffic or biased cohorts can hide defects and prolong the decision window.

Continue with the complementary design in CI/CD Delivery to Kubernetes.

08 / WHAT I WOULD VALIDATE IN PRODUCTION

Rehearse a bad release deliberately

Reduced deployment risk is a target, not an asserted result. Test the abort path as carefully as the successful promotion path.

  • Inject an API contract mismatch that readiness alone would miss.
  • Verify observed traffic matches the intended routing policy and excludes synthetic probe traffic from comparisons.
  • Revert during active requests and check draining, client retries and duplicate side effects.
  • Exercise old and new service revisions against the same evolving data schema.
09 / LESSONS

Safe traffic needs a safe contract

Traffic control contains exposure; it does not repair incompatible application changes. Choose the release strategy after defining what can safely coexist and what evidence warrants promotion.

REFERENCE MATERIAL

Technical references

These sources document product behavior. The design and validation approach above are engineering proposals, not claims made by the vendors.

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TECHNOLOGY STACK
KubernetesDockerHTTP APIsReadiness ProbesTraffic RoutingCI/CD