Version: 1.0.0

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, all containers 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.