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53 lines
1.8 KiB
Markdown
53 lines
1.8 KiB
Markdown
# Hunting flaky tests in Kubernetes
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Sometimes unit tests are flaky. This means that due to (usually) race conditions, they will occasionally fail, even though most of the time they pass.
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We have a goal of 99.9% flake free tests. This means that there is only one flake in one thousand runs of a test.
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Running a test 1000 times on your own machine can be tedious and time consuming. Fortunately, there is a better way to achieve this using Kubernetes.
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_Note: these instructions are mildly hacky for now, as we get run once semantics and logging they will get better_
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There is a testing image ```brendanburns/flake``` up on the docker hub. We will use this image to test our fix.
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Create a replication controller with the following config:
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```yaml
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id: flakeController
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desiredState:
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replicas: 24
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replicaSelector:
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name: flake
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podTemplate:
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desiredState:
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manifest:
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version: v1beta1
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id: ""
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volumes: []
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containers:
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- name: flake
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image: brendanburns/flake
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env:
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- name: TEST_PACKAGE
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value: pkg/tools
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- name: REPO_SPEC
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value: https://github.com/GoogleCloudPlatform/kubernetes
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restartpolicy: {}
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labels:
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name: flake
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labels:
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name: flake
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```
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```./cluster/kubecfg.sh -c controller.yaml create replicaControllers```
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This will spin up 100 instances of the test. They will run to completion, then exit, the kubelet will restart them, eventually you will have sufficient
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runs for your purposes, and you can stop the replication controller:
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```sh
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./cluster/kubecfg.sh stop flakeController
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./cluster/kubecfg.sh rm flakeController
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```
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Now examine the machines with ```docker ps -a``` and look for tasks that exited with non-zero exit codes (ignore those that exited -1, since that's what happens when you stop the replica controller)
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Happy flake hunting!
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