open-consul/agent/proxy/daemon.go

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package proxy
import (
"fmt"
"log"
"os"
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"os/exec"
"reflect"
"strconv"
"sync"
"time"
"github.com/hashicorp/consul/lib/file"
"github.com/mitchellh/mapstructure"
)
// Constants related to restart timers with the daemon mode proxies. At some
// point we will probably want to expose these knobs to an end user, but
// reasonable defaults are chosen.
const (
DaemonRestartHealthy = 10 * time.Second // time before considering healthy
DaemonRestartBackoffMin = 3 // 3 attempts before backing off
DaemonRestartMaxWait = 1 * time.Minute // maximum backoff wait time
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)
// Daemon is a long-running proxy process. It is expected to keep running
// and to use blocking queries to detect changes in configuration, certs,
// and more.
//
// Consul will ensure that if the daemon crashes, that it is restarted.
type Daemon struct {
// Command is the command to execute to start this daemon. This must
// be a Cmd that isn't yet started.
Command *exec.Cmd
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// ProxyID is the ID of the proxy service. This is required for API
// requests (along with the token) and is passed via env var.
ProxyID string
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// ProxyToken is the special local-only ACL token that allows a proxy
// to communicate to the Connect-specific endpoints.
ProxyToken string
// Logger is where logs will be sent around the management of this
// daemon. The actual logs for the daemon itself will be sent to
// a file.
Logger *log.Logger
// PidPath is the path where a pid file will be created storing the
// pid of the active process. If this is empty then a pid-file won't
// be created. Under erroneous conditions, the pid file may not be
// created but the error will be logged to the Logger.
PidPath string
// For tests, they can set this to change the default duration to wait
// for a graceful quit.
gracefulWait time.Duration
// process is the started process
lock sync.Mutex
stopped bool
stopCh chan struct{}
exitedCh chan struct{}
process *os.Process
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}
// Start starts the daemon and keeps it running.
//
// This function returns after the process is successfully started.
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func (p *Daemon) Start() error {
p.lock.Lock()
defer p.lock.Unlock()
// A stopped proxy cannot be restarted
if p.stopped {
return fmt.Errorf("stopped")
}
// If we're already running, that is okay
if p.process != nil {
return nil
}
// Setup our stop channel
stopCh := make(chan struct{})
exitedCh := make(chan struct{})
p.stopCh = stopCh
p.exitedCh = exitedCh
// Start the loop.
go p.keepAlive(stopCh, exitedCh)
return nil
}
// keepAlive starts and keeps the configured process alive until it
// is stopped via Stop.
func (p *Daemon) keepAlive(stopCh <-chan struct{}, exitedCh chan<- struct{}) {
defer close(exitedCh)
p.lock.Lock()
process := p.process
p.lock.Unlock()
// attemptsDeadline is the time at which we consider the daemon to have
// been alive long enough that we can reset the attempt counter.
//
// attempts keeps track of the number of restart attempts we've had and
// is used to calculate the wait time using an exponential backoff.
var attemptsDeadline time.Time
var attempts uint32
// Assume the process is adopted, we reset this when we start a new process
// ourselves below and use it to decide on a strategy for waiting.
adopted := true
for {
if process == nil {
// If we're passed the attempt deadline then reset the attempts
if !attemptsDeadline.IsZero() && time.Now().After(attemptsDeadline) {
attempts = 0
}
// Set ourselves a deadline - we have to make it at least this long before
// we come around the loop to consider it to have been a "successful"
// daemon startup and rest the counter above. Note that if the daemon
// fails before this, we reset the deadline to zero below so that backoff
// sleeps in the loop don't count as "success" time.
attemptsDeadline = time.Now().Add(DaemonRestartHealthy)
attempts++
// Calculate the exponential backoff and wait if we have to
if attempts > DaemonRestartBackoffMin {
exponent := (attempts - DaemonRestartBackoffMin)
if exponent > 31 {
exponent = 31
}
waitTime := (1 << exponent) * time.Second
if waitTime > DaemonRestartMaxWait {
waitTime = DaemonRestartMaxWait
}
if waitTime > 0 {
// If we are waiting, reset the success deadline so we don't
// accidentally interpret backoff sleep as successful runtime.
attemptsDeadline = time.Time{}
p.Logger.Printf(
"[WARN] agent/proxy: waiting %s before restarting daemon",
waitTime)
timer := time.NewTimer(waitTime)
select {
case <-timer.C:
// Timer is up, good!
case <-stopCh:
// During our backoff wait, we've been signalled to
// quit, so just quit.
timer.Stop()
return
}
}
}
p.lock.Lock()
// If we gracefully stopped then don't restart.
if p.stopped {
p.lock.Unlock()
return
}
// Process isn't started currently. We're restarting. Start it
// and save the process if we have it.
var err error
process, err = p.start()
if err == nil {
p.process = process
adopted = false
}
p.lock.Unlock()
if err != nil {
p.Logger.Printf("[ERR] agent/proxy: error restarting daemon: %s", err)
continue
}
}
var ps *os.ProcessState
var err error
if adopted {
// assign to err outside scope
_, err = findProcess(process.Pid)
if err == nil {
// Process appears to be running still, wait a bit before we poll again.
// We want a busy loop, but not too busy. 1 second between detecting a
// process death seems reasonable.
//
// SUBTELTY: we must NOT select on stopCh here since the Stop function
// assumes that as soon as this method returns and closes exitedCh, that
// the process is no longer running. If we are polling then we don't
// know that is true until we've polled again so we have to keep polling
// until the process goes away even if we know the Daemon is stopping.
time.Sleep(1 * time.Second)
// Restart the loop, process is still set so we effectively jump back to
// the findProcess call above.
continue
}
} else {
// Wait for child to exit
ps, err = process.Wait()
}
// Process exited somehow.
process = nil
if err != nil {
p.Logger.Printf("[INFO] agent/proxy: daemon exited with error: %s", err)
} else if ps != nil && !ps.Exited() {
p.Logger.Printf("[INFO] agent/proxy: daemon left running")
} else if status, ok := exitStatus(ps); ok {
p.Logger.Printf("[INFO] agent/proxy: daemon exited with exit code: %d", status)
}
}
}
// start starts and returns the process. This will create a copy of the
// configured *exec.Command with the modifications documented on Daemon
// such as setting the proxy token environmental variable.
func (p *Daemon) start() (*os.Process, error) {
cmd := *p.Command
// Add the proxy token to the environment. We first copy the env because it is
// a slice and therefore the "copy" above will only copy the slice reference.
// We allocate an exactly sized slice.
//
// Note that anything we add to the Env here is NOT persisted in the snapshot
// which only looks at p.Command.Env so it needs to be reconstructible exactly
// from data in the snapshot otherwise.
cmd.Env = make([]string, len(p.Command.Env), len(p.Command.Env)+2)
copy(cmd.Env, p.Command.Env)
cmd.Env = append(cmd.Env,
fmt.Sprintf("%s=%s", EnvProxyID, p.ProxyID),
fmt.Sprintf("%s=%s", EnvProxyToken, p.ProxyToken))
// Update the Daemon env
// Args must always contain a 0 entry which is usually the executed binary.
// To be safe and a bit more robust we default this, but only to prevent
// a panic below.
if len(cmd.Args) == 0 {
cmd.Args = []string{cmd.Path}
}
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// Perform system-specific setup. In particular, Unix-like systems
// shuld set sid so that killing the agent doesn't kill the daemon.
configureDaemon(&cmd)
// Start it
p.Logger.Printf("[DEBUG] agent/proxy: starting proxy: %q %#v", cmd.Path, cmd.Args[1:])
if err := cmd.Start(); err != nil {
return nil, err
}
// Write the pid file. This might error and that's okay.
if p.PidPath != "" {
pid := strconv.FormatInt(int64(cmd.Process.Pid), 10)
if err := file.WriteAtomic(p.PidPath, []byte(pid)); err != nil {
p.Logger.Printf(
"[DEBUG] agent/proxy: error writing pid file %q: %s",
p.PidPath, err)
}
}
return cmd.Process, nil
}
// Stop stops the daemon.
//
// This will attempt a graceful stop (SIGINT) before force killing the
// process (SIGKILL). In either case, the process won't be automatically
// restarted unless Start is called again.
//
// This is safe to call multiple times. If the daemon is already stopped,
// then this returns no error.
func (p *Daemon) Stop() error {
p.lock.Lock()
// If we're already stopped or never started, then no problem.
if p.stopped || p.process == nil {
// In the case we never even started, calling Stop makes it so
// that we can't ever start in the future, either, so mark this.
p.stopped = true
p.lock.Unlock()
return nil
}
// Note that we've stopped
p.stopped = true
close(p.stopCh)
process := p.process
p.lock.Unlock()
gracefulWait := p.gracefulWait
if gracefulWait == 0 {
gracefulWait = 5 * time.Second
}
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// Defer removing the pid file. Even under error conditions we
// delete the pid file since Stop means that the manager is no
// longer managing this proxy and therefore nothing else will ever
// clean it up.
if p.PidPath != "" {
defer func() {
if err := os.Remove(p.PidPath); err != nil && !os.IsNotExist(err) {
p.Logger.Printf(
"[DEBUG] agent/proxy: error removing pid file %q: %s",
p.PidPath, err)
}
}()
}
// First, try a graceful stop
err := process.Signal(os.Interrupt)
if err == nil {
select {
case <-p.exitedCh:
// Success!
return nil
case <-time.After(gracefulWait):
// Interrupt didn't work
p.Logger.Printf("[DEBUG] agent/proxy: graceful wait of %s passed, "+
"killing", gracefulWait)
}
} else if isProcessAlreadyFinishedErr(err) {
// This can happen due to races between signals and polling.
return nil
} else {
p.Logger.Printf("[DEBUG] agent/proxy: sigint failed, killing: %s", err)
}
// Graceful didn't work (e.g. on windows where SIGINT isn't implemented),
// forcibly kill
err = process.Kill()
if err != nil && isProcessAlreadyFinishedErr(err) {
return nil
}
return err
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}
// Close implements Proxy by stopping the run loop but not killing the process.
// One Close is called, Stop has no effect.
func (p *Daemon) Close() error {
p.lock.Lock()
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defer p.lock.Unlock()
// If we're already stopped or never started, then no problem.
if p.stopped || p.process == nil {
p.stopped = true
return nil
}
// Note that we've stopped
p.stopped = true
close(p.stopCh)
return nil
}
// Equal implements Proxy to check for equality.
func (p *Daemon) Equal(raw Proxy) bool {
p2, ok := raw.(*Daemon)
if !ok {
return false
}
// We compare equality on a subset of the command configuration
return p.ProxyToken == p2.ProxyToken &&
p.ProxyID == p2.ProxyID &&
p.Command.Path == p2.Command.Path &&
p.Command.Dir == p2.Command.Dir &&
reflect.DeepEqual(p.Command.Args, p2.Command.Args) &&
reflect.DeepEqual(p.Command.Env, p2.Command.Env)
}
// MarshalSnapshot implements Proxy
func (p *Daemon) MarshalSnapshot() map[string]interface{} {
p.lock.Lock()
defer p.lock.Unlock()
// If we're stopped or have no process, then nothing to snapshot.
if p.stopped || p.process == nil {
return nil
}
return map[string]interface{}{
"Pid": p.process.Pid,
"CommandPath": p.Command.Path,
"CommandArgs": p.Command.Args,
"CommandDir": p.Command.Dir,
"CommandEnv": p.Command.Env,
"ProxyToken": p.ProxyToken,
"ProxyID": p.ProxyID,
}
}
// UnmarshalSnapshot implements Proxy
func (p *Daemon) UnmarshalSnapshot(m map[string]interface{}) error {
var s daemonSnapshot
if err := mapstructure.Decode(m, &s); err != nil {
return err
}
p.lock.Lock()
defer p.lock.Unlock()
// Set the basic fields
p.ProxyToken = s.ProxyToken
p.ProxyID = s.ProxyID
p.Command = &exec.Cmd{
Path: s.CommandPath,
Args: s.CommandArgs,
Dir: s.CommandDir,
Env: s.CommandEnv,
}
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// FindProcess on many systems returns no error even if the process
// is now dead. We perform an extra check that the process is alive.
proc, err := findProcess(s.Pid)
if err != nil {
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return err
}
// "Start it"
stopCh := make(chan struct{})
exitedCh := make(chan struct{})
p.stopCh = stopCh
p.exitedCh = exitedCh
p.process = proc
go p.keepAlive(stopCh, exitedCh)
return nil
}
// daemonSnapshot is the structure of the marshalled data for snapshotting.
//
// Note we don't have to store the ProxyId because this is stored directly
// within the manager snapshot and is restored automatically.
type daemonSnapshot struct {
// Pid of the process. This is the only value actually required to
// regain management control. The remainder values are for Equal.
Pid int
// Command information
CommandPath string
CommandArgs []string
CommandDir string
CommandEnv []string
// NOTE(mitchellh): longer term there are discussions/plans to only
// store the hash of the token but for now we need the full token in
// case the process dies and has to be restarted.
ProxyToken string
ProxyID string
}