func GetGceConfig()

in prometheus-to-sd/config/gce_config.go [39:133]
83 lines of code
21 McCabe index (conditional complexity)

func GetGceConfig(project, cluster, clusterLocation, zone, node string) (*GceConfig, error) {
	if project != "" {
		glog.Infof("Using metadata all from flags")
		if cluster == "" {
			glog.Warning("Cluster name was not set. This can be set with --cluster-name")
		}
		if clusterLocation == "" {
			glog.Warning("Cluster location was not set. This can be set with --cluster-location")
		}
		if zone == "" {
			// zone is only used by the older gke_container
			glog.Info("Zone was not set. This can be set with --zone-override")
		}
		if node == "" {
			glog.Warning("Node was not set. This can be set with --node-name")
		}
		return &GceConfig{
			Project:         project,
			Zone:            zone,
			Cluster:         cluster,
			ClusterLocation: clusterLocation,
			Instance:        node,
		}, nil
	}

	if !gce.OnGCE() {
		return nil, fmt.Errorf("Not running on GCE.")
	}

	var err error
	if project == "" {
		project, err = gce.ProjectID()
		if err != nil {
			return nil, fmt.Errorf("error while getting project id: %v", err)
		}
	}

	if cluster == "" {
		cluster, err = gce.InstanceAttributeValue("cluster-name")
		if err != nil {
			return nil, fmt.Errorf("error while getting cluster name: %v", err)
		}
		cluster = strings.TrimSpace(cluster)
		if cluster == "" {
			return nil, fmt.Errorf("cluster-name metadata was empty")
		}
	}

	// instance/name endpoint is not available on the GKE metadata server.
	// Try GCE instance/name endpoint. If error, try instance/hostname.
	// If instance/hostname, remove domain to replicate instance/name.
	if node == "" {
		node, err = gce.InstanceName()
		if err != nil {
			node, err = gce.Hostname()
			if err != nil {
				return nil, fmt.Errorf("error while getting instance (node) name: %v", err)
			}
			node = strings.Split(node, ".")[0]
			glog.Warningf("using %s as instance/name", node)
		}
	}

	instanceId, err := gce.InstanceID()
	if err != nil {
		return nil, fmt.Errorf("error while getting instance id: %v", err)
	}

	if zone == "" {
		zone, err = gce.Zone()
		if err != nil {
			return nil, fmt.Errorf("error while getting zone: %v", err)
		}
	}

	if clusterLocation == "" {
		clusterLocation, err = gce.InstanceAttributeValue("cluster-location")
		if err != nil {
			return nil, fmt.Errorf("error while getting cluster location: %v", err)
		}
		clusterLocation = strings.TrimSpace(clusterLocation)
		if clusterLocation == "" {
			return nil, fmt.Errorf("cluster-location metadata was empty")
		}
	}

	return &GceConfig{
		Project:         project,
		Zone:            zone,
		Cluster:         cluster,
		ClusterLocation: clusterLocation,
		Instance:        node,
		InstanceId:      instanceId,
	}, nil
}