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-mesh
   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.

2. 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-mesh
   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).

2. 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-mesh
   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.

2. 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.org/v1alpha1
   kind: IOChaos
   metadata:
     name: io-mistake-example
     namespace: chaos-mesh
   spec:
     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.

2. 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	one
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	1
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
containerNames	[]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.