[Feature]: Configurable params for built-in workloads

[mrhillsman]

Problem Statement

Built-in workloads (CPU, memory, disk, database, network) have hardcoded values in their systemd unit constants (e.g., stress-ng --cpu 0 --cpu-method all). Some workloads (TPS, chaos-*) already read from WorkloadConfig.Params, but the core workloads do not. Users cannot tune workload behavior (e.g., CPU stress from 100% to 90%) without modifying source code.

Proposed Solution

Parameterize all built-in workloads using the existing getter-with-default pattern from chaos workloads (e.g., chaos_network.go:latencyMs()). Each workload gets param getter methods; systemd unit constants become methods that interpolate values via fmt.Sprintf.

Params per workload:

• CPU (internal/workloads/cpu.go): cpu-load-percent (default 100), cpu-method (default all)
• Memory (internal/workloads/memory.go): memory-percent (default 80), vm-stressors (default 1), vm-method (default all)
• Disk (internal/workloads/disk.go): block-size-rw (default 4k), block-size-seq (default 128k), rwmixread (default 70), numjobs (default 4), runtime (default 300)
• Database (internal/workloads/database.go): scale-factor (default 10), clients (default 4), duration (default 300)
• Network (internal/workloads/network.go): parallel-streams (default 4), test-duration (default 60)

Implementation pattern per workload:

1. Add param getter methods with defaults
2. Convert systemd unit constant → method with fmt.Sprintf
3. Unit tests for getter defaults/overrides and generated output

Alternatives Considered

Environment variable overrides in the systemd units — rejected because it bypasses the existing Params mechanism and doesn't compose with the config file.

Area

Workloads

Architecture Layer

Layer 3 - Workload Definitions (workloads, registry)

Additional Context

Affected files:

• internal/workloads/cpu.go
• internal/workloads/memory.go
• internal/workloads/disk.go
• internal/workloads/database.go
• internal/workloads/network.go
• Corresponding _test.go files

Verification:

1. go test ./internal/workloads/... — all param tests pass
2. go test ./... — full suite passes
3. Manual: run with params: {cpu-load-percent: "50"} and verify cloud-init output shows --cpu-load 50