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// Package rancher wraps Rancher commands necessary for K8s inspection.
package rancher
import (
"bytes"
"errors"
"os/exec"
)
const (
bin = "rancher"
paramHost = "--host"
cmdHosts = "hosts"
cmdHostsParams = "--quiet"
cmdDocker = "docker"
cmdDockerCmdPs = "ps"
cmdDockerCmdPsParams = "--no-trunc"
cmdDockerCmdPsFilter = "--filter"
cmdDockerCmdPsFilterArgs = "label=io.rancher.stack_service.name=kubernetes/kubernetes"
cmdDockerCmdPsFormat = "--format"
cmdDockerCmdPsFormatArgs = "{{.Command}}"
k8sProcess = "kube-apiserver"
)
// GetK8sParams returns parameters of running Kubernetes API server.
// It queries default environment set in configuration file.
func GetK8sParams() ([]string, error) {
hosts, err := listHosts()
if err != nil {
return []string{}, err
}
for _, host := range hosts {
cmd, err := getK8sCmd(host)
if err != nil {
return []string{}, err
}
if len(cmd) > 0 {
i := bytes.Index(cmd, []byte(k8sProcess))
if i == -1 {
return []string{}, errors.New("missing " + k8sProcess + " command")
}
return btos(cmd[i+len(k8sProcess):]), nil
}
}
return []string{}, nil
}
// listHosts lists IDs of active hosts.
// It queries default environment set in configuration file.
func listHosts() ([]string, error) {
cmd := exec.Command(bin, cmdHosts, cmdHostsParams)
out, err := cmd.Output()
if err != nil {
return nil, err
}
return btos(out), nil
}
// getK8sCmd returns running Kubernetes API server command with its parameters.
// It queries default environment set in configuration file.
func getK8sCmd(host string) ([]byte, error) {
// Following is equivalent to:
// $ rancher --host $HOST \
// docker ps --no-trunc \
// --filter "label=io.rancher.stack_service.name=kubernetes/kubernetes" \
// --format "{{.Command}}"
cmd := exec.Command(bin, paramHost, host,
cmdDocker, cmdDockerCmdPs, cmdDockerCmdPsParams,
cmdDockerCmdPsFilter, cmdDockerCmdPsFilterArgs,
cmdDockerCmdPsFormat, cmdDockerCmdPsFormatArgs)
out, err := cmd.Output()
if err != nil {
return nil, err
}
return out, nil
}
// btos converts slice of bytes to slice of strings split by white space characters.
func btos(in []byte) []string {
var out []string
for _, b := range bytes.Fields(in) {
out = append(out, string(b))
}
return out
}
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