tumult-stress — CPU, Memory, and IO Stress

Script-based plugin for injecting resource stress via stress-ng.

Prerequisites

• stress-ng installed on the target host (apt install stress-ng / brew install stress-ng)

Actions

Action	Description	Key Variables
cpu-stress	Inject CPU stress	TUMULT_WORKERS, TUMULT_LOAD (0-100), TUMULT_TIMEOUT
memory-stress	Inject memory pressure	TUMULT_WORKERS, TUMULT_BYTES (e.g., 256m), TUMULT_TIMEOUT
io-stress	Inject IO stress	TUMULT_WORKERS, TUMULT_HDD_BYTES (e.g., 1g), TUMULT_TIMEOUT
combined-stress	CPU + memory + IO combined	TUMULT_CPU_WORKERS, TUMULT_CPU_LOAD, TUMULT_VM_WORKERS, TUMULT_VM_BYTES, TUMULT_HDD_WORKERS, TUMULT_TIMEOUT

Probes

Probe	Description	Output
cpu-utilization	Current CPU usage	Float 0-100
memory-utilization	Current memory usage	Float 0-100
io-utilization	Current IO wait	Float 0-100

Probes work on both Linux (/proc/stat, /proc/meminfo) and macOS (top, vm_stat, iostat).

Example Experiment

method[1]:
  - name: stress-cpu
    activity_type: action
    provider:
      type: process
      path: plugins/tumult-stress/actions/cpu-stress.sh
      env:
        TUMULT_WORKERS: 4
        TUMULT_LOAD: 80
        TUMULT_TIMEOUT: 60
    background: false

steady_state_hypothesis:
  title: CPU below 90%
  probes[1]:
    - name: check-cpu
      activity_type: probe
      provider:
        type: process
        path: plugins/tumult-stress/probes/cpu-utilization.sh
      tolerance:
        type: range
        from: 0.0
        to: 90.0