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// Package rancher wraps Rancher commands necessary for K8s inspection.
package rancher
import (
"bytes"
"fmt"
"os/exec"
"check"
)
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="
cmdDockerCmdPsFormat = "--format"
cmdDockerCmdPsFormatArgs = "{{.Command}}"
)
// Rancher implements Informer interface.
type Rancher struct {
check.Informer
}
// GetAPIParams returns parameters of running Kubernetes API server.
// It queries default environment set in configuration file.
func (r *Rancher) GetAPIParams() ([]string, error) {
return getProcessParams(check.APIProcess, check.APIService)
}
func getProcessParams(process check.Command, service check.Service) ([]string, error) {
hosts, err := listHosts()
if err != nil {
return []string{}, err
}
for _, host := range hosts {
cmd, err := getPsCmdOutput(host, service)
if err != nil {
return []string{}, err
}
if len(cmd) > 0 {
i := bytes.Index(cmd, []byte(process.String()))
if i == -1 {
return []string{}, fmt.Errorf("missing %s command", process)
}
return btos(cmd[i+len(process.String()):]), 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
}
// getPsCmdOutput returns running Kubernetes service command with its parameters.
// It queries default environment set in configuration file.
func getPsCmdOutput(host string, service check.Service) ([]byte, error) {
// Following is equivalent to:
// $ rancher --host $HOST \
// docker ps --no-trunc \
// --filter "label=io.rancher.stack_service.name=$SERVICE" \
// --format "{{.Command}}"
cmd := exec.Command(bin, paramHost, host,
cmdDocker, cmdDockerCmdPs, cmdDockerCmdPsParams,
cmdDockerCmdPsFilter, cmdDockerCmdPsFilterArgs+service.String(),
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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