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 80+ clusters and share the insights we gained from incidents, failures, user reports and general observations. 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. https://2018.container.camp/uk/schedule/running-kubernetes-in-production-a-million-ways-to-crash-your-cluster/

1. A Million Ways
to Crash Your Cluster
CONTAINER CAMP UK
HENNING JACOBS
@try_except_
2018-09-07

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
> 23
million
active customers
> 300.000
product choices
~ 2.000
brands
15
countries

5. 5
SCALE
95Clusters
378Accounts

6. INCIDENTS ARE FINE

7. 7
INCIDENT #1: CUSTOMER IMPACT

8. 8
INCIDENT #1: IAM RETURNING 404

9. 9
INCIDENT #1: NUMBER OF PODS

10. 10
LIFE OF A REQUEST (INGRESS)
DNS
my-app.example.org
ALB
aws-1234-lb.eu-central-1.elb.amazonaws.com
SERVICE
10.3.0.216
DEPLOYMENT
POD
10.2.0.1
POD
10.2.1.1
POD
10.2.2.1
POD
10.2.3.1
SKIPPER
172.31.1.1:9999
SKIPPER
172.31.2.1:9999
SKIPPER
172.31.3.1:9999
SKIPPER
172.31.4.1:9999
ALIAS Record

11. 11
INCIDENT #1: INNOCENT MANIFEST
apiVersion: batch/v2alpha1
kind: CronJob
metadata:
name: "foobar"
labels:
application: "foobar"
spec:
schedule: "*/15 9-19 * * Mon-Fri"
jobTemplate:
spec:
template:
metadata:
labels:
application: "foobar"
spec:
restartPolicy: Never
concurrencyPolicy: Forbid
successfulJobsHistoryLimit: 1
failedJobsHistoryLimit: 1
containers:
...

12. 12
INCIDENT #1: FIXED CRON JOB
apiVersion: batch/v2alpha1
kind: CronJob
metadata:
name: "foobar"
labels:
application: "foobar"
spec:
schedule: "7 8-18 * * Mon-Fri"
concurrencyPolicy: Forbid
successfulJobsHistoryLimit: 1
failedJobsHistoryLimit: 1
jobTemplate:
spec:
activeDeadlineSeconds: 120
template:
metadata:
labels:
application: "foobar"
spec:
restartPolicy: Never
containers:
...

13. 13
INCIDENT #1: LESSONS LEARNED
• ALB routes traffic to ALL hosts if all hosts report “unhealthy”
• Fix Skipper Ingress to stay “healthy” during API server problems
• Fix Skipper 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"

14. 14
INCIDENT #2: CLUSTER DOWN

15. 15
INCIDENT #2: MANUAL OPERATION
% etcdctl del -r /registry-kube-1/certificatesigningrequest prefix

16. 16
INCIDENT #2: RTFM
% etcdctl del -r /registry-kube-1/certificatesigningrequest prefix
help: etcdctl del [options] <key> [range_end]

17. 17
Junior Engineers are Features, not Bugs
https://www.youtube.com/watch?v=cQta4G3ge44

18. https://www.outcome-eng.com/human-error-never-root-cause/

19. 19
INCIDENT #2: LESSONS LEARNED
• Disaster Recovery Plan?
• Backup etcd to S3
• Monitor the snapshots

20. 20
INCIDENT #3: LATENCY SPIKES
...
Kubernetes worker and master nodes sporadically fail to connect to etcd
causing timeouts in the APIserver and disconnects in the pod network.
...

21. 21
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

22. 22
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
[...]

23. 23
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

24. 24
INCIDENT #4: IMPACT

25. 25
INCIDENT #4: CLUSTER DOWN?

26. 26
INCIDENT #4: THE TRIGGER

27. https://www.outcome-eng.com/human-error-never-root-cause/

28. 28
CLUSTER UPGRADE
FLOW

29. 29
CLUSTER LIFECYCLE MANAGER (CLM)
github.com/zalando-incubator/cluster-lifecycle-manager

30. 30
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+

31. 31
E2E TESTS ON EVERY PR
github.com/zalando-incubator/kubernetes-on-aws

32. 32
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

33. 33
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

34. 34
INCIDENT #4: LESSONS LEARNED
• Automated end-to-end tests are pretty good, but not enough
• Test the diff/migration automatically
• Bootstrap new cluster with the previous configuration
• Apply new configuration
• Run end-to-end & conformance tests

35. 35
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…
...

36. 36
INCIDENT #5: IMPACT

37. 37
INCIDENT #5: A VERY INNOCENT PULL REQUEST

38. 38
INCIDENT #5: WHAT HAPPENED
• Deployment caused rebuild with the 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

39. 39
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

40. 40
MORE TOPICS
• Graceful Pod shutdown and
race conditions (endpoints, Ingress)
• Incompatible Kubernetes changes
• CoreOS ContainerLinux "stable" won't boot
• Kubernetes EBS volume handling
• Docker

41. 41
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

42. 42
TIMEOUTS TO API SERVER..
github.com/zalando-incubator/kubernetes-on-aws

43. WELCOME TO
CLOUD NATIVE!

44. 44

45. 45
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

46. 46
KUBERNETES RESOURCE REPORT
github.com/hjacobs/kube-resource-report

47. https://github.com/hjacobs/kube-ops-view

48. 48
OTHER TALKS
• Nordstrom: 101 Ways to Crash Your Cluster - KubeCon 2017
• Monzo: Anatomy of a Production Kubernetes Outage - KubeCon 2018
• Inside Kubernetes Resource Management (QoS) - KubeCon 2018
We need more failure talks!

49. QUESTIONS?
HENNING JACOBS
HEAD OF
DEVELOPER PRODUCTIVITY
henning@zalando.de
@try_except_
Illustrations by @01k