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:

   

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

   

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

   

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

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.