TimeChaos Experiment

This document describe how to add TimeChaos experiments in Chaos Mesh.

TimeChaos is used to modify the return value of clock_gettime, which causes time offset on Go's time.Now() and Rust std's std::time::Instant::now() etc.

Configuration file

Below is a sample TimeChaos configuration file:

apiVersion: chaos-mesh.org/v1alpha1
kind: TimeChaos
metadata:
  name: time-shift-example
  namespace: chaos-testing
spec:
  mode: one
  selector:
    labelSelectors:
      'app.kubernetes.io/component': 'pd'
  timeOffset: '-10m100ns'
  clockIds:
    - CLOCK_REALTIME
  containerNames:
    - pd
  duration: '10s'
  scheduler:
    cron: '@every 15s'

For more sample files, see examples. You can edit them as needed.

Description:

• mode defines the mode to select pods.
• selector specifies the target pods for chaos injection. For more details, see Define the Scope of Chaos Experiment.
• timeOffset specifies the time offset. It is a duration string with specified unit, such as 300ms, -1.5h. Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
• clockIds defines all affected clk_id. clk_id refers to the first argument of clock_gettime call. For most application, CLOCK_REALTIME is enough.
• containerNames selects affected containers' names. If not set, the first container will be injected.
• duration defines the duration for each chaos experiment. In the sample file above, the time chaos lasts for 10 seconds.
• scheduler defines the scheduler rules for the running time of the chaos experiment. For more rule information, see robfig/cron.

Limitation

• Time modification can only be injected into the main process of container.
• Time chaos has no effect on pure system call clock_gettime.
• All injected vDSO calls use pure system calls to get the real time, so clock-related function calls can be much slower.