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simulate-io-chaos-on-kubernetes.md

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title
Simulate File I/O Faults

This document describes how to create IOChaos experiments in Chaos Mesh.

IOChaos introduction

IOChaos is a type of fault in Chaos Mesh. By creating an IOChaos experiment, you can simulate a scenario of file system fault. Currently, IOChaos supports the following fault types:

  • latency: delays file system calls
  • fault: returns an error for filesystem calls
  • attrOverride: modifies file properties
  • mistake: makes the file read or write a wrong value

For specific features, refer to Create experiments using the YAML files.

Notes

  1. Before creating an IOChaos experiment, make sure there is no Control Manager of Chaos Mesh running on the target Pod.

  2. IOChaos may damage your data. Use IOChaos with caution in the production environment.

Create experiments using Chaos Dashboard

  1. Open Chaos Dashboard, and click NEW EXPERIMENT on the page to create a new experiment:

    Create a New Experiment

  2. In the Choose a Target area, choose FILE SYSTEM INJECTION and select a specific fault type, such as LATENCY.

    ioChaos Experiments

  3. Fill out the experiment information, and specify the experiment scope and the scheduled experiment duration.

    Experiment Information

  4. Submit the experiment information.

Create experiments using the YAML files

Latency example

  1. Write the experiment configuration to the io-latency.yaml file, as shown below:
apiVersion: chaos-mesh.org/v1alpha1
kind: IOChaos
metadata:
  name: io-latency-example
  namespace: chaos-testing
spec:
  action: latency
  mode: one
  selector:
    labelSelectors:
      app: etcd
  volumePath: /var/run/etcd
  path: '/var/run/etcd/**/*'
  delay: '100ms'
  percent: 50
  duration: '400s'

In this configuration example, Chaos Mesh injects a delay into the directory /var/run/etcd and causes latency of 100 milliseconds to all file system operations (including read, writing, list contents, and so on) in this directory.

  1. After the configuration file is prepared, use kubectl to create an experiment:
kubectl apply -f ./io-latency.yaml

Fault example

  1. Write the experiment configuration to the io-fault.yaml file, as shown below:
apiVersion: chaos-mesh.org/v1alpha1
kind: IOChaos
metadata:
  name: io-fault-example
  namespace: chaos-testing
spec:
  action: fault
  mode: one
  selector:
    labelSelectors:
      app: etcd
  volumePath: /var/run/etcd
  path: /var/run/etcd/**/*
  errno: 5
  percent: 50
  duration: '400s'

In this example, Chaos Mesh injects a file fault into the directory /var/run/etcd, which gives a 50% probability of failure in all file system operations under this directory and returns error code 5 (Input/output error).

  1. After the configuration file is prepared, use kubectl to create an experiment:
kubectl apply -f ./io-fault.yaml

attrOverride example

  1. Write the experiment configuration to the io-attr.yaml file:
apiVersion: chaos-mesh.org/v1alpha1
kind: IOChaos
metadata:
  name: io-attr-example
  namespace: chaos-testing
spec:
  action: attrOverride
  mode: one
  selector:
    labelSelectors:
      app: etcd
  volumePath: /var/run/etcd
  path: /var/run/etcd/**/*
  attr:
    perm: 72
  percent: 10
  duration: '400s'

In this configuration example, Chaos Mesh injects /var/run/etcd directories attrOverride fault, giving a 10% probability that all file system operations in this directory will change the target file permissions to 72 (110 in octal), which will allow files to be executed only by the owner and their group and not authorized to perform other actions.

  1. After the configuration file is prepared, use kubectl to create an experiment:
kubectl apply -f ./io-attr.yaml

Mistake example

  1. Write the experiment configuration to the io-mistake.yaml file:
apiVersion: chaos-mesh. rg/v1alpha1
ind: IOChaos
metadata:
  name: io-mistake-example
  namespace: chaos-testing
special:
  action: mistake
  mode: one
  selector:
    labelSelectors:
      app: etcd
  volumePath: /var/run/etcd
  path: /var/run/etcd/**/*
  mistake:
    filling: zero
    maxOccurrences: 1
    maxLength: 10
  methods:
    - READ
    - WRITE
  percent: 10
  duration: '400s'

In this configuration example, Chaos Mesh injects read and write faults into the directory /var/run/etcd, which gives a 10% probability of failure in the read and write operations under this directory. During this process, one random position with a maximum length of 10 bytes will be replaced with 0 bytes.

  1. After the configuration file is prepared, use kubectl to create an experiment:
kubectl apply -f ./io-mistake.yaml

Field description

General fields

Parameter Type Description Default value Required Example
action string Indicates the specific type of faults. Only latency, fault, attrOverride, and mistake are supported. Yes latency
mode string Specifies the mode of the experiment. The mode options include one (selecting a Pod at random), all (selecting all eligible Pods), fixed (selecting a specified number of eligible Pods), fixed-percent (selecting a specified percentage of the eligible Pods), and random-max-percent (selecting the maximum percentage of the eligible Pods). None Yes 1
selector struct Specifies the target Pod. For details, refer to Define the experiment scope. None Yes
value string Provides parameters for the mode configuration, depending on mode. For example, when mode is set to fixed-percent, value specifies the percentage of Pods. No 2
volumePath string The mount point of volume in the target container. Must be the root directory of the mount. Yes /var/run/etcd
path string The valid range of fault injections, either a wildcard or a single file. Valid for all files by default No /var/run/etcd/*/
methods string[] Type of the file system call that requires injecting fault. For more information about supported types, refer to [Appendix A](#appendix-a: methods-type). All Types No READ
percent int Probability of failure per operation, in %. 100 No 100
ContainerName string Specifies the name of the container into which the fault is injected. No
duration string Specifies the duration of the experiment. Yes 30s

Fields related to action

The following are specific information about fields corresponding to action:

  • latency

    Parameter Type Description Default value Required Example
    delay string Specific delay time Yes 100 ms

  • fault

    Parameter Type Description Default value Required Example
    errno int returned error number Yes 22

    For common error numbers, see Appendix B.

  • attrOverride

    Parameter Type Description Default value Required Example
    attr AttrOverrideSpec Specific property override rules Yes As follows

    AttrOverrideSpec is defined as follows:

    Parameter Type Description Default value Required Example
    ino int ino number No
    size int File size No
    blocks int Number of blocks that the file uses No
    atime TimeSpec Last access time No
    mtime TimeSpec Last modified time No
    ctime TimeSpec Last status change time No
    kind string File type, see fuser::FileType No
    perm int File permissions in decimal No 72 (110 in octal)
    nlink int Number of hard links No
    uid int User ID of the owner No
    gid int Group ID of the owner No
    rdev int Device ID No

    TimeSpec is defined as follows:

    Parameter Type Description Default value Required Example
    sec int timestamp in seconds No
    nsec int Timestamp in nanoseconds No

    For the specific meaning of parameters, you can refer to man stat.

  • mistake

    Parameter Type Description Default value Required Example
    mistake MistakeSpec Specific error rules Yes

    MistakeSpec is defined as follows:

    Parameter Type Description Default value Required Example
    filling string The wrong data to be filled. Only zero (fill 0) or random (fill random bytes) are supported. Yes
    maxOccurrences int Maximum number of errors in each operation. Yes 1
    maxLength int Maximum length of each error (in bytes). Yes 1

::warning It is suggested that you only use mistake on READ and WRITE file system calls. Using mistake on other file system calls may lead to unexpected consequences, including but not limited to file system damage and program crashes. :::

Local debugging

If you are not sure about the effect of a certain Chaos, you can use toda to test the feature locally. Chaos Mesh also uses toda to implement IOChaos.

Appendix A: methods type

  • lookup
  • forget
  • getattr
  • setattr
  • readlink
  • mknod
  • mkdir
  • unlink
  • rmdir
  • symlink
  • rename
  • link
  • open
  • read
  • write
  • flush
  • release
  • fsync
  • opendir
  • readdir
  • releasedir
  • fsyncdir
  • statfs
  • setxattr
  • getxattr
  • listxattr
  • removexatr
  • access
  • create
  • getlk
  • setlk
  • bmap

For more information, refer to fuser::Filesystem.

Appendix B: Common Error Numbers

  • 1: Operation not permitted
  • 2: No such file or directory
  • 5: I/O error
  • 6: No such device or address
  • 12: Out of memory
  • 16: Device or resource busy
  • 17: File exists
  • 20: Not a directory
  • 22: Invalid argument
  • 24: Too many open files
  • 28: No space left on device

For more information, refer to Linux source code.