README.md

ccTopology

The ccTopology package provides easy access to topology information, mainly for the local node. It loads the topology once through the hwloc library but stores it in own data structures for later access. Main purpose is to provide a common interface for various ClusterCockpit components to topology information.

Note: In order to use it, the environment variable CGO_LDFLAGS="-L/path/to/lib/directory/of/hwloc needs to be set to the library directory of hwloc.

For transmission of the whole topology of a node, ccTopology's Topology type can be marshaled to JSON:

func GetTopologyJSON() (json.RawMessage, error) {
    topo, err := ccTopology.LocalTopology()
    if err != nil {
        return nil, fmt.Errorf("Failed to init topology: %v", err.Error())
    }
    x, err := json.MarshalIndent(topo, "", "  ")
    if err != nil {
        return nil, fmt.Errorf("Failed to marshal topology: %v", err.Error())
    }
    return x, nil
}

On the receiving side, it can be unmarshaled to ccTopology's Topology type:

func GetNodeJSON(topologyJson json.RawMessage) (ccTopology.Topology, error) {
	topo, err := ccTopology.RemoteTopology(topologyJson)
	if err != nil {
		return nil, err
	}
    return topo, nil
}

There are additional helpers to get specific information out of node's topology:

type Topology interface {
	GetHwthreads() []uint
	GetHwthreadStrings() []string
	GetSockets() []uint
	GetSocketStrings() []string
	GetDies() []uint
	GetDieStrings() []string
	GetCores() []uint
	GetCoreStrings() []string
	GetPciDevices() []uint
	GetPciDeviceStrings() []string
	GetHwthreadsOfSocket(socket uint) []uint
	GetHwthreadStringsOfSocket(socket uint) []string
	GetHwthreadsOfMemoryDomain(memoryDomain uint) []uint
	GetHwthreadStringsOfMemoryDomain(memoryDomain uint) []string
	GetNumaNodeOfPciDevice(address string) int
	CpuInfo() CpuInformation
	MarshalJSON() ([]byte, error)
	UnmarshalJSON(in []byte) error
}

Testing

$ make test
CGO_LDFLAGS="-L/modules/hwloc-2.4.0/lib" /modules/go-1.23.2/bin/go test
PASS
ok  	github.com/cc-lib/ccTopology	0.093s
cd test && CGO_LDFLAGS="-L/modules/hwloc-2.4.0/lib" /modules/go-1.23.2/bin/go test
PASS
ok  	github.com/cc-lib/ccTopology/test	0.014s