nomad/client/driver/utils.go

package driver

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	"github.com/armon/circbuf"
	"github.com/hashicorp/go-multierror"
	"github.com/hashicorp/go-plugin"
	"github.com/hashicorp/nomad/client/config"
	"github.com/hashicorp/nomad/client/driver/executor"
	cstructs "github.com/hashicorp/nomad/client/driver/structs"
	"github.com/hashicorp/nomad/helper/discover"
	"github.com/hashicorp/nomad/nomad/structs"
)

// cgroupsMounted returns true if the cgroups are mounted on a system otherwise
// returns false
func cgroupsMounted(node *structs.Node) bool {
	_, ok := node.Attributes["unique.cgroup.mountpoint"]
	return ok
}

// createExecutor launches an executor plugin and returns an instance of the
// Executor interface
func createExecutor(w io.Writer, clientConfig *config.Config,
	executorConfig *cstructs.ExecutorConfig) (executor.Executor, *plugin.Client, error) {

	c, err := json.Marshal(executorConfig)
	if err != nil {
		return nil, nil, fmt.Errorf("unable to create executor config: %v", err)
	}
	bin, err := discover.NomadExecutable()
	if err != nil {
		return nil, nil, fmt.Errorf("unable to find the nomad binary: %v", err)
	}

	config := &plugin.ClientConfig{
		Cmd: exec.Command(bin, "executor", string(c)),
	}
	config.HandshakeConfig = HandshakeConfig
	config.Plugins = GetPluginMap(w, clientConfig.LogLevel)
	config.MaxPort = clientConfig.ClientMaxPort
	config.MinPort = clientConfig.ClientMinPort

	// setting the setsid of the plugin process so that it doesn't get signals sent to
	// the nomad client.
	if config.Cmd != nil {
		isolateCommand(config.Cmd)
	}

	executorClient := plugin.NewClient(config)
	rpcClient, err := executorClient.Client()
	if err != nil {
		return nil, nil, fmt.Errorf("error creating rpc client for executor plugin: %v", err)
	}

	raw, err := rpcClient.Dispense("executor")
	if err != nil {
		return nil, nil, fmt.Errorf("unable to dispense the executor plugin: %v", err)
	}
	executorPlugin := raw.(executor.Executor)
	return executorPlugin, executorClient, nil
}

func createExecutorWithConfig(config *plugin.ClientConfig, w io.Writer) (executor.Executor, *plugin.Client, error) {
	config.HandshakeConfig = HandshakeConfig

	// Setting this to DEBUG since the log level at the executor server process
	// is already set, and this effects only the executor client.
	config.Plugins = GetPluginMap(w, "DEBUG")

	executorClient := plugin.NewClient(config)
	rpcClient, err := executorClient.Client()
	if err != nil {
		return nil, nil, fmt.Errorf("error creating rpc client for executor plugin: %v", err)
	}

	raw, err := rpcClient.Dispense("executor")
	if err != nil {
		return nil, nil, fmt.Errorf("unable to dispense the executor plugin: %v", err)
	}
	executorPlugin, ok := raw.(*ExecutorRPC)
	if !ok {
		return nil, nil, fmt.Errorf("unexpected executor rpc type: %T", raw)
	}
	// 0.6 Upgrade path: Deregister services from the executor as the Nomad
	// client agent now handles all Consul interactions.
	if err := executorPlugin.DeregisterServices(); err != nil {
		return nil, nil, err
	}
	return executorPlugin, executorClient, nil
}

// killProcess kills a process with the given pid
func killProcess(pid int) error {
	proc, err := os.FindProcess(pid)
	if err != nil {
		return err
	}
	return proc.Kill()
}

// destroyPlugin kills the plugin with the given pid and also kills the user
// process
func destroyPlugin(pluginPid int, userPid int) error {
	var merr error
	if err := killProcess(pluginPid); err != nil {
		merr = multierror.Append(merr, err)
	}

	if err := killProcess(userPid); err != nil {
		merr = multierror.Append(merr, err)
	}
	return merr
}

// validateCommand validates that the command only has a single value and
// returns a user friendly error message telling them to use the passed
// argField.
func validateCommand(command, argField string) error {
	trimmed := strings.TrimSpace(command)
	if len(trimmed) == 0 {
		return fmt.Errorf("command empty: %q", command)
	}

	if len(trimmed) != len(command) {
		return fmt.Errorf("command contains extra white space: %q", command)
	}

	return nil
}

// GetKillTimeout returns the kill timeout to use given the tasks desired kill
// timeout and the operator configured max kill timeout.
func GetKillTimeout(desired, max time.Duration) time.Duration {
	maxNanos := max.Nanoseconds()
	desiredNanos := desired.Nanoseconds()

	// Make the minimum time between signal and kill, 1 second.
	if desiredNanos <= 0 {
		desiredNanos = (1 * time.Second).Nanoseconds()
	}

	// Protect against max not being set properly.
	if maxNanos <= 0 {
		maxNanos = (10 * time.Second).Nanoseconds()
	}

	if desiredNanos < maxNanos {
		return time.Duration(desiredNanos)
	}

	return max
}

// GetAbsolutePath returns the absolute path of the passed binary by resolving
// it in the path and following symlinks.
func GetAbsolutePath(bin string) (string, error) {
	lp, err := exec.LookPath(bin)
	if err != nil {
		return "", fmt.Errorf("failed to resolve path to %q executable: %v", bin, err)
	}

	return filepath.EvalSymlinks(lp)
}

// getExecutorUser returns the user of the task, defaulting to
// cstructs.DefaultUnprivilegedUser if none was given.
func getExecutorUser(task *structs.Task) string {
	if task.User == "" {
		return cstructs.DefaultUnpriviledgedUser
	}
	return task.User
}

// execChroot executes cmd with args inside chroot if set and returns the
// output, exit code, and error. If chroot is an empty string the command is
// executed on the host.
func execChroot(ctx context.Context, chroot, name string, args []string) ([]byte, int, error) {
	buf, _ := circbuf.NewBuffer(int64(cstructs.CheckBufSize))
	cmd := exec.CommandContext(ctx, name, args...)
	cmd.Dir = "/"
	cmd.Stdout = buf
	cmd.Stderr = buf
	if chroot != "" {
		setChroot(cmd, chroot)
	}
	if err := cmd.Run(); err != nil {
		exitErr, ok := err.(*exec.ExitError)
		if !ok {
			// Non-exit error, return it and let the caller treat
			// it as a critical failure
			return nil, 0, err
		}

		// Some kind of error happened; default to critical
		exitCode := 2
		if status, ok := exitErr.Sys().(syscall.WaitStatus); ok {
			exitCode = status.ExitStatus()
		}

		// Don't return the exitError as the caller only needs the
		// output and code.
		return buf.Bytes(), exitCode, nil
	}
	return buf.Bytes(), 0, nil
}