# CgroupGroup
`CgroupGroup` is an RAII guard that removes cgroups on drop. It
prevents cgroup leaks when workload spawning or other operations fail
between cgroup creation and cleanup.
```rust,ignore
use ktstr::prelude::*;
#[must_use = "dropping a CgroupGroup immediately destroys the cgroups it manages"]
pub struct CgroupGroup<'a> {
cgroups: &'a CgroupManager,
names: Vec<String>,
}
```
## Methods
**`new(cgroups: &CgroupManager) -> Self`** -- creates an empty group
bound to a `CgroupManager`.
**`add_cgroup(name, cpuset) -> Result<()>`** -- creates a cgroup and
sets its cpuset. The cgroup is tracked for removal on drop.
**`add_cgroup_no_cpuset(name) -> Result<()>`** -- creates a cgroup
without setting a cpuset. The cgroup is tracked for removal on drop.
**`names() -> &[String]`** -- returns the names of all tracked cgroups.
## Drop behavior
When the `CgroupGroup` is dropped, it calls
`CgroupManager::remove_cgroup()` on each tracked cgroup. Removal
errors are silently ignored (best-effort cleanup).
## Usage
`CgroupGroup` is the standard pattern for cgroup lifecycle management
in custom scenarios and in `run_scenario()` for data-driven scenarios.
```rust,ignore
fn custom_scenario(ctx: &Ctx) -> Result<AssertResult> {
let mut guard = CgroupGroup::new(ctx.cgroups);
guard.add_cgroup("cg_0", &cpuset_a)?;
guard.add_cgroup("cg_1", &cpuset_b)?;
// If WorkloadHandle::spawn() fails here, guard drops
// and both cgroups are removed automatically.
let mut h = WorkloadHandle::spawn(&config)?;
ctx.cgroups.move_tasks("cg_0", &h.tids())?;
h.start(); // workers block until start() is called
// ... run workload ...
// guard drops at end of scope, removing cg_0 and cg_1.
Ok(result)
}
```
The helper function `setup_cgroups()` returns a `CgroupGroup` alongside
the worker handles:
```rust,ignore
let (handles, _guard) = setup_cgroups(ctx, 2, &wl)?;
// _guard lives until end of scope; cgroups are cleaned up on drop.
```
See also: [CgroupManager](cgroup-manager.md) for filesystem operations,
[WorkloadHandle](workload-handle.md) for worker lifecycle,
[TestTopology](../concepts/topology.md) for cpuset generation.