Problems / Kubernetes and containers, medium

A release that never starts

At 30 s a release ships with a missing config value: the new pods start but the app never comes up. There is no readiness probe.

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Your goals

Keep success at 99% or more; the release may fail, the service may not.

Test cases

Like a coding problem, a solution has to pass every case, not just the one it was built for. Submit in the lab runs all 5; 2 of them are hidden until then.

  1. As given. The problem’s own traffic, scheduled failures and seed.
  2. Peak hour. 25% more traffic than the problem states, with the same failures.
  3. A slow dependency. The main data store or model answers twice as slowly for part of the run.

The traffic

150 requests a second for 150 seconds: 100% api (reads).

The system

What each component does in this design, and what calls it. The simulator mimics each one from these settings.

ComponentIts job hereSettings
Load balancerLoad balancerTraffic enters here.Calls API (pods).Layer 4 balancers route by IP and port; layer 7 balancers read HTTP and can route by path or header.–
API (pods)Container platformLoad balancer forwards to it.Calls Postgres.Kubernetes places pods on nodes by their CPU and memory requests, and only replaces a lost node's pods after about 5 minutes.20 slots
PostgresSQL databaseAPI (pods) calls it.Postgres runs one process per connection, which is why poolers like PgBouncer sit in front of busy databases.32 vCPU · 300 connections

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