open-consul/agent/util.go

149 lines
3.9 KiB
Go

package agent
import (
"bytes"
"crypto/md5"
"fmt"
"math"
"os"
"os/exec"
"os/signal"
osuser "os/user"
"strconv"
"time"
"github.com/hashicorp/consul/types"
"github.com/hashicorp/go-msgpack/codec"
)
const (
// This scale factor means we will add a minute after we cross 128 nodes,
// another at 256, another at 512, etc. By 8192 nodes, we will scale up
// by a factor of 8.
//
// If you update this, you may need to adjust the tuning of
// CoordinateUpdatePeriod and CoordinateUpdateMaxBatchSize.
aeScaleThreshold = 128
)
// msgpackHandle is a shared handle for encoding/decoding of
// messages
var msgpackHandle = &codec.MsgpackHandle{
RawToString: true,
WriteExt: true,
}
// aeScale is used to scale the time interval at which anti-entropy updates take
// place. It is used to prevent saturation as the cluster size grows.
func aeScale(interval time.Duration, n int) time.Duration {
// Don't scale until we cross the threshold
if n <= aeScaleThreshold {
return interval
}
multiplier := math.Ceil(math.Log2(float64(n))-math.Log2(aeScaleThreshold)) + 1.0
return time.Duration(multiplier) * interval
}
// decodeMsgPack is used to decode a MsgPack encoded object
func decodeMsgPack(buf []byte, out interface{}) error {
return codec.NewDecoder(bytes.NewReader(buf), msgpackHandle).Decode(out)
}
// encodeMsgPack is used to encode an object with msgpack
func encodeMsgPack(msg interface{}) ([]byte, error) {
var buf bytes.Buffer
err := codec.NewEncoder(&buf, msgpackHandle).Encode(msg)
return buf.Bytes(), err
}
// stringHash returns a simple md5sum for a string.
func stringHash(s string) string {
return fmt.Sprintf("%x", md5.Sum([]byte(s)))
}
// checkIDHash returns a simple md5sum for a types.CheckID.
func checkIDHash(checkID types.CheckID) string {
return stringHash(string(checkID))
}
// setFilePermissions handles configuring ownership and permissions
// settings on a given file. All permission/ownership settings are
// optional. If no user or group is specified, the current user/group
// will be used. Mode is optional, and has no default (the operation is
// not performed if absent). User may be specified by name or ID, but
// group may only be specified by ID.
func setFilePermissions(path string, user, group, mode string) error {
var err error
uid, gid := os.Getuid(), os.Getgid()
if user != "" {
if uid, err = strconv.Atoi(user); err == nil {
goto GROUP
}
// Try looking up the user by name
if u, err := osuser.Lookup(user); err == nil {
uid, _ = strconv.Atoi(u.Uid)
goto GROUP
}
return fmt.Errorf("invalid user specified: %v", user)
}
GROUP:
if group != "" {
if gid, err = strconv.Atoi(group); err != nil {
return fmt.Errorf("invalid group specified: %v", group)
}
}
if err := os.Chown(path, uid, gid); err != nil {
return fmt.Errorf("failed setting ownership to %d:%d on %q: %s",
uid, gid, path, err)
}
if mode != "" {
mode, err := strconv.ParseUint(mode, 8, 32)
if err != nil {
return fmt.Errorf("invalid mode specified: %v", mode)
}
if err := os.Chmod(path, os.FileMode(mode)); err != nil {
return fmt.Errorf("failed setting permissions to %d on %q: %s",
mode, path, err)
}
}
return nil
}
// ExecSubprocess returns a command to execute a subprocess directly.
func ExecSubprocess(args []string) (*exec.Cmd, error) {
if len(args) == 0 {
return nil, fmt.Errorf("need an executable to run")
}
return exec.Command(args[0], args[1:]...), nil
}
// ForwardSignals will fire up a goroutine to forward signals to the given
// subprocess until the shutdown channel is closed.
func ForwardSignals(cmd *exec.Cmd, logFn func(error), shutdownCh <-chan struct{}) {
go func() {
signalCh := make(chan os.Signal, 10)
signal.Notify(signalCh, os.Interrupt, os.Kill)
defer signal.Stop(signalCh)
for {
select {
case sig := <-signalCh:
if err := cmd.Process.Signal(sig); err != nil {
logFn(fmt.Errorf("failed to send signal %q: %v", sig, err))
}
case <-shutdownCh:
return
}
}
}()
}