Kubernetes Failure Stories - KubeCon Europe Barcelona
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Talk given on 2019-05-21 at KubeCon Barcelona: https://kccnceu19.sched.com/event/MPcM/kubernetes-failure-stories-and-how-to-crash-your-clusters-henning-jacobs-zalando-se Bootstrapping a Kubernetes cluster is easy, rolling it out to nearly 200 engineering teams and operating it at scale is a challenge. In this talk, we are presenting our approach to Kubernetes provisioning on AWS, operations and developer experience for our growing Zalando developer base. We will walk you through our horror stories of operating 100+ clusters and share the insights we gained from incidents, failures, user reports and general observations. Our failure stories will be sourced from recent and past incidents, so the talk will be up-to-date with our latest experiences. Most of our learnings apply to other Kubernetes infrastructures (EKS, GKE, ..) as well. This talk strives to reduce the audience's unknown unknowns about running Kubernetes in production.
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Kubernetes Failure Stories - KubeCon Europe Barcelona
- 4. 4 ZALANDO AT A GLANCE ~ 5.4billion EUR revenue 2018 > 250 million visits per month > 15.000 employees in Europe > 79% of visits via mobile devices > 26 million active customers > 300.000 product choices ~ 2.000 brands 17 countries
- 9. INCIDENT #1
- 10. 10 INCIDENT #1: CUSTOMER IMPACT
- 11. 11 INCIDENT #1: CUSTOMER IMPACT
- 12. 12 INCIDENT #1: INGRESS ERRORS
- 13. 13 INCIDENT #1: AWS ALB 502 github.com/zalando/riptide
- 14. 14 INCIDENT #1: AWS ALB 502 github.com/zalando/riptide 502 Bad Gateway Server: awselb/2.0 ...
- 15. 15 INCIDENT #1: ALB HEALTHY HOST COUNT 3 healthy hosts zero healthy hosts 2xx requests
- 16. 16 LIFE OF A REQUEST (INGRESS) Node Node MyApp MyApp MyApp EC2 network K8s network TLS HTTP Skipper Skipper ALB
- 17. 17 INCIDENT #1: SKIPPER MEMORY USAGE Memory Limit Memory Usage
- 18. 18 INCIDENT #1: SKIPPER OOM Node Node MyApp MyApp MyApp TLS HTTP Skipper Skipper ALB OOMKill
- 19. 19 INCIDENT #1: CONTRIBUTING FACTORS • Shared Ingress (per cluster) • High latency of unrelated app (Solr) caused high number of in-flight requests • Skipper creates goroutine per HTTP request. Goroutine costs 2kB memory + http.Request • Memory limit was fixed at 500Mi (4x regular usage) Fix for the memory issue in Skipper: https://opensource.zalando.com/skipper/operation/operation/#scheduler
- 20. INCIDENT #2
- 21. 21 INCIDENT #2: CUSTOMER IMPACT
- 22. 22 INCIDENT #1: IAM RETURNING 404
- 23. 23 INCIDENT #1: NUMBER OF PODS
- 24. 24 LIFE OF A REQUEST (INGRESS) Node Node MyApp MyApp MyApp EC2 network K8s network TLS HTTP Skipper Skipper ALB
- 25. 25 ROUTES FROM API SERVER Node Node MyApp MyApp MyApp Skipper ALBAPI Server Skipper
- 26. 26 API SERVER DOWN Node Node MyApp MyApp MyApp Skipper ALBAPI Server Skipper OOMKill
- 27. 27 INCIDENT #2: 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: ...
- 28. 28 INCIDENT #2: 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:
- 29. 29 INCIDENT #2: LESSONS LEARNED • 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" NOTE: we dropped quotas recently github.com/zalando-incubator/kubernetes- on-aws/pull/2059
- 30. INCIDENT #3
- 31. 31 INCIDENT #3: INGRESS ERRORS
- 32. 32 INCIDENT #3: COREDNS OOMKILL coredns invoked oom-killer: gfp_mask=0x14000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=994 Memory cgroup out of memory: Kill process 6428 (coredns) score 2050 or sacrifice child oom_reaper: reaped process 6428 (coredns), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB restarts
- 33. 33 STOP THE BLEEDING: INCREASE MEMORY LIMIT 4Gi 2Gi 200Mi
- 34. 34 SPIKE IN HTTP REQUESTS
- 35. 35 SPIKE IN DNS QUERIES
- 36. 36 INCREASE IN MEMORY USAGE
- 37. 37 INCIDENT #3: CONTRIBUTING FACTORS • HTTP retries • No DNS caching • Kubernetes ndots:5 problem • Short maximum lifetime of HTTP connections • Fixed memory limit for CoreDNS • Monitoring affected by DNS outage github.com/zalando-incubator/kubernetes-on-aws/blob/dev/docs/postmortems/jan-2019-dns-outage.md
- 38. INCIDENT #4
- 39. 39 INCIDENT #4: CLUSTER DOWN
- 40. 40 INCIDENT #4: MANUAL OPERATION % etcdctl del -r /registry-kube-1/certificatesigningrequest prefix
- 41. 41 INCIDENT #4: RTFM % etcdctl del -r /registry-kube-1/certificatesigningrequest prefix help: etcdctl del [options] <key> [range_end]
- 42. 42 Junior Engineers are Features, not Bugs https://www.youtube.com/watch?v=cQta4G3ge44
- 44. 44 INCIDENT #4: LESSONS LEARNED • Disaster Recovery Plan? • Backup etcd to S3 • Monitor the snapshots
- 45. INCIDENT #5
- 46. 46 INCIDENT #5: API LATENCY SPIKES
- 47. 47 INCIDENT #5: 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
- 48. 48 INCIDENT #5: STOP THE BLEEDING #!/bin/bash while true; do echo "sleep for 60 seconds" sleep 60 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
- 49. 49 INCIDENT #5: 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 [...]
- 50. 50 INCIDENT #5: 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
- 51. INCIDENT #6
- 53. 53 INCIDENT #6: CLUSTER DOWN?
- 54. 54 INCIDENT #6: THE TRIGGER
- 57. 57 CLUSTER LIFECYCLE MANAGER (CLM) github.com/zalando-incubator/cluster-lifecycle-manager
- 58. 58 CLUSTER CHANNELS github.com/zalando-incubator/kubernetes-on-aws Channel Description Clusters dev Development and playground clusters. 3 alpha Main infrastructure clusters (important to us). 2 beta Product clusters for the rest of the organization (non-prod). 57+ stable Product clusters for the rest of the organization (prod). 57+
- 59. 59 E2E TESTS ON EVERY PR github.com/zalando-incubator/kubernetes-on-aws
- 60. 60 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
- 61. 61 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
- 62. 62 INCIDENT #6: 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 github.com/zalando-incubator/kubernetes-on-aws/tree/dev/test/e2e
- 63. INCIDENT #7
- 64. 64 ⇒ all containers on this node down #7: KERNEL OOM KILLER
- 65. 65 INCIDENT #7: KUBELET MEMORY
- 67. 67 INCIDENT #7: THE PATCH https://github.com/kubernetes/kubernetes/issues/73587
- 68. INCIDENT #8
- 69. 69 INCIDENT #8: 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
- 70. 70 INCIDENT #8: 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
- 71. 71 INCIDENT #8: CPU THROTTLING
- 72. 72 INCIDENT #8: WHAT HAPPENED Scaled down IAM provider to reduce Slack + Number of deployments increased ⇒ Process could not process credentials fast enough
- 73. 73 CPU/memory requests "block" resources on nodes. Difference between actual usage and requests → Slack SLACK CPU Memory Node "Slack"
- 74. 74 DISABLING CPU THROTTLING [Announcement] CPU limits will be disabled ⇒ Ingress Latency Improvements kubelet … --cpu-cfs-quota=false
- 75. 75 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
- 76. 76 MORE TOPICS • Graceful Pod shutdown and race conditions (endpoints, Ingress) • Incompatible Kubernetes changes • CoreOS ContainerLinux "stable" won't boot • Kubernetes EBS volume handling • Docker
- 77. 77 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
- 78. 78 TIMEOUTS TO API SERVER.. github.com/zalando-incubator/kubernetes-on-aws
- 80. 80 WILL MANAGED K8S SAVE US? GKE: monthly uptime percentage at 99.95% for regional clusters
- 81. 81 WILL MANAGED K8S SAVE US? NO(not really) e.g. AWS EKS uptime SLA is only for API server
- 82. 82 PRODUCTION PROOFING AWS EKS List of things you might want to look at for EKS in production https://medium.com/glia-tech/productionproofing-e ks-ed52951ffd6c
- 83. 83 AWS EKS IN PRODUCTION https://kubedex.com/90-days-of-aws-eks-in-production/
- 86. 86
- 87. 87 KUBERNETES FAILURE STORIES A compiled list of links to public failure stories related to Kubernetes. k8s.af We need more failure talks! Istio? Anyone?
- 88. 88 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
- 89. QUESTIONS? HENNING JACOBS HEAD OF DEVELOPER PRODUCTIVITY henning@zalando.de @try_except_ Illustrations by @01k