Running Kubernetes in Production: A Million Ways to Crash Your Cluster - DevOpsCon Munich 2018
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This document summarizes Henning Jacobs' talk on running Kubernetes in production and the many ways clusters can crash. It describes several incidents Zalando faced with their Kubernetes clusters that led to outages, including API server issues causing ingress problems, etcd deletion causing cluster downtime, EC2 networking issues, image pulling failures, and credential processing bottlenecks preventing deployments. Each incident highlighted lessons around disaster recovery planning, automated testing of upgrades, monitoring cloud infrastructure, and avoiding resource starvation.
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Running Kubernetes in Production: A Million Ways to Crash Your Cluster - DevOpsCon Munich 2018
- 1. Running Kubernetes in Production: A Million Ways to Crash Your Cluster HENNING JACOBS @try_except_ 2018-12-05
- 4. 4 ZALANDO AT A GLANCE ~ 4.5billion EUR revenue 2017 > 200 million visits per month > 15.000 employees in Europe > 70% of visits via mobile devices > 24 million active customers > 300.000 product choices ~ 2.000 brands 17 countries
- 5. Black Friday 2018 > 4,200 orders per minute
- 10. 10 INCIDENT #1: CUSTOMER IMPACT
- 11. 11 INCIDENT #1: IAM RETURNING 404
- 12. 12 INCIDENT #1: NUMBER OF PODS
- 13. 13 LIFE OF A REQUEST (INGRESS) Node Node MyApp MyApp MyApp EC2 network K8s network TLS HTTP Skipper Skipper ALB
- 14. 14 ROUTES FROM API SERVER Node Node MyApp MyApp MyApp Skipper ALBAPI Server Skipper
- 15. 15 API SERVER DOWN Node Node MyApp MyApp MyApp Skipper ALBAPI Server Skipper OOMKill
- 16. 16 INCIDENT #1: INNOCENT MANIFEST apiVersion: batch/v2alpha1 kind: CronJob metadata: name: "foobar" spec: schedule: "*/15 9-19 * * Mon-Fri" jobTemplate: spec: template: spec: restartPolicy: Never concurrencyPolicy: Forbid successfulJobsHistoryLimit: 1 failedJobsHistoryLimit: 1 containers: ...
- 17. 17 INCIDENT #1: FIXED CRON JOB apiVersion: batch/v2alpha1 kind: CronJob metadata: name: "foobar" spec: schedule: "7 8-18 * * Mon-Fri" concurrencyPolicy: Forbid successfulJobsHistoryLimit: 1 failedJobsHistoryLimit: 1 jobTemplate: spec: activeDeadlineSeconds: 120 template: spec: restartPolicy: Never containers:
- 18. 18 INCIDENT #1: LESSONS LEARNED • ALB routes traffic to ALL hosts if all hosts report “unhealthy” • Fix Ingress to stay “healthy” during API server problems • Fix Ingress to retain last known set of routes • Use quota for number of pods apiVersion: v1 kind: ResourceQuota metadata: name: compute-resources spec: hard: pods: "1500"
- 19. 19 INCIDENT #2: CLUSTER DOWN
- 20. 20 INCIDENT #2: MANUAL OPERATION % etcdctl del -r /registry-kube-1/certificatesigningrequest prefix
- 21. 21 INCIDENT #2: RTFM % etcdctl del -r /registry-kube-1/certificatesigningrequest prefix help: etcdctl del [options] <key> [range_end]
- 22. 22 Junior Engineers are Features, not Bugs https://www.youtube.com/watch?v=cQta4G3ge44
- 24. 24 INCIDENT #2: LESSONS LEARNED • Disaster Recovery Plan? • Backup etcd to S3 • Monitor the snapshots
- 25. 25 INCIDENT #3: API LATENCY SPIKES
- 26. 26 INCIDENT #3: CONNECTION ISSUES ... Kubernetes worker and master nodes sporadically fail to connect to etcd causing timeouts in the APIserver and disconnects in the pod network. ... Master Node API Server etcd etcd-member
- 27. 27 INCIDENT #3: STOP THE BLEEDING #!/bin/bash SLEEPTIME=60 while true; do echo "sleep for $SLEEPTIME seconds" sleep $SLEEPTIME timeout 5 curl http://localhost:8080/api/v1/nodes > /dev/null if [ $? -eq 0 ]; then echo "all fine, no need to restart etcd member" continue else echo "restarting etcd-member" systemctl restart etcd-member fi done
- 28. 28 INCIDENT #3: CONFIRMATION FROM AWS [...] We can’t go into the details [...] that resulted the networking problems during the “non-intrusive maintenance”, as it relates to internal workings of EC2. We can confirm this only affected the T2 instance types, ... [...] We don’t explicitly recommend against running production services on T2 [...]
- 29. 29 INCIDENT #3: LESSONS LEARNED • It's never the AWS infrastructure until it is • Treat t2 instances with care • Kubernetes components are not necessarily "cloud native" Cloud Native? Declarative, dynamic, resilient, and scalable
- 31. 31 INCIDENT #4: CLUSTER DOWN?
- 32. 32 INCIDENT #4: THE TRIGGER
- 35. 35 CLUSTER LIFECYCLE MANAGER (CLM) github.com/zalando-incubator/cluster-lifecycle-manager
- 36. 36 CLUSTER CHANNELS github.com/zalando-incubator/kubernetes-on-aws Channel Description Clusters dev Development and playground clusters. 3 alpha Main infrastructure cluster (important to us). 1 beta Product clusters for the rest of the organization (prod/test). 90+
- 37. 37 E2E TESTS ON EVERY PR github.com/zalando-incubator/kubernetes-on-aws
- 38. 38 RUNNING E2E TESTS (BEFORE) Control plane nodenode branch: dev Create Cluster Run e2e tests Delete Cluster Testing dev to alpha upgrade Control plane Control plane
- 39. 39 RUNNING E2E TESTS (NOW) Control plane nodenode Control plane nodenode branch: alpha (base) branch: dev (head) Create Cluster Update Cluster Run e2e tests Delete Cluster Testing dev to alpha upgrade Control plane Control plane
- 40. 40 INCIDENT #4: LESSONS LEARNED • Automated e2e tests are pretty good, but not enough • Test the diff/migration automatically • Bootstrap new cluster with previous configuration • Apply new configuration • Run end-to-end & conformance tests
- 41. 41 INCIDENT #5: IMPACT [4:59 PM] Marc: There is a error during build - forbidden: image policy webhook backend denied one or more images: X-Trusted header "false" for image pierone../ci/cdp-builder:234 .. [5:01 PM] Alice: Now it does not start the build step at all [5:02 PM] John: +1 [5:02 PM] John: Failed to create builder pod: … [5:02 PM] Pedro: +1 [5:04 PM] Damien: +1 [5:19 PM] Anton: We're currently having issues pulling images from our Docker registry which results in many problems… ...
- 43. 43 INCIDENT #5: A VERY INNOCENT PULL REQUEST
- 44. 44 INCIDENT #5: WHAT HAPPENED • Deployment caused rebuild with latest stable Go version • Library for signature verification was incompatible with Go 1.10, causing all verification checks to fail during runtime. • Lack of unit/smoke tests and alerting for one component • "Near miss": outage could have had large impact
- 45. 45 INCIDENT #6: IMPACT Error during Pod creation: MountVolume.SetUp failed for volume "outfit-delivery-api-credentials" : secrets "outfit-delivery-api-credentials" not found ⇒ All new Kubernetes deployments fail
- 46. 46 INCIDENT #6: CREDENTIALS QUEUE 17:30:07 | [pool-6-thread-1 ] | Current queue size: 7115, current number of active workers: 20 17:31:07 | [pool-6-thread-1 ] | Current queue size: 7505, current number of active workers: 20 17:32:07 | [pool-6-thread-1 ] | Current queue size: 7886, current number of active workers: 20 .. 17:37:07 | [pool-6-thread-1 ] | Current queue size: 9686, current number of active workers: 20 .. 17:44:07 | [pool-6-thread-1 ] | Current queue size: 11976, current number of active workers: 20 .. 19:16:07 | [pool-6-thread-1 ] | Current queue size: 58381, current number of active workers: 20
- 47. 47 INCIDENT #6: CPU THROTTLING
- 48. 48 INCIDENT #6: WHAT HAPPENED Scaled down IAM provider to reduce Slack + Number of deployments increased ⇒ Process could not process credentials fast enough
- 49. 49 CPU/memory requests "block" resources on nodes. Difference between actual usage and requests → Slack SLACK CPU Memory Node "Slack"
- 50. 50 DISABLING CPU THROTTLING [Announcement] CPU limits will be disabled ⇒ Ingress Latency Improvements kubelet … --cpu-cfs-quota=false
- 51. 51 A MILLION WAYS TO CRASH YOUR CLUSTER? • Switch to latest Docker to fix issues with Docker daemon freezing • Redesign of DNS setup due to high DNS latencies (5s), switch from kube-dns to node-local dnsmasq+CoreDNS • Disabling CPU throttling (CFS quota) to avoid latency issues • Quick fix for timeouts using etcd-proxy: client-go still seems to have issues with timeouts • 502's during cluster updates: race condition during network setup
- 52. 52 MORE TOPICS • Graceful Pod shutdown and race conditions (endpoints, Ingress) • Incompatible Kubernetes changes • CoreOS ContainerLinux "stable" won't boot • Kubernetes EBS volume handling • Docker
- 53. 53 RACE CONDITIONS.. • Switch to the latest Docker version available to fix the issues with Docker daemon freezing • Redesign of DNS setup due to high DNS latencies (5s), switch from kube-dns to CoreDNS • Disabling CPU throttling (CFS quota) to avoid latency issues • Quick fix for timeouts using etcd-proxy, since client-go still seems to have issues with timeouts • 502's during cluster updates: race condition • github.com/zalando-incubator/kubernetes-on-aws
- 54. 54 TIMEOUTS TO API SERVER.. github.com/zalando-incubator/kubernetes-on-aws
- 57. 57
- 58. 58 OPEN SOURCE Kubernetes on AWS github.com/zalando-incubator/kubernetes-on-aws AWS ALB Ingress controller github.com/zalando-incubator/kube-ingress-aws-controller Skipper HTTP Router & Ingress controller github.com/zalando/skipper External DNS github.com/kubernetes-incubator/external-dns Postgres Operator github.com/zalando-incubator/postgres-operator Kubernetes Resource Report github.com/hjacobs/kube-resource-report Kubernetes Downscaler github.com/hjacobs/kube-downscaler
- 61. 61 OTHER TALKS • Nordstrom: 101 Ways to Crash Your Cluster - KubeCon 2017 • Monzo: Anatomy of a Production Kubernetes Outage - KubeCon 2018 • Optimizing Kubernetes Resource Requests/Limits for Cost-Efficiency and Latency - HighLoad++ 2018 We need more failure talks!
- 62. QUESTIONS? HENNING JACOBS HEAD OF DEVELOPER PRODUCTIVITY henning@zalando.de @try_except_ Illustrations by @01k