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|
package supervisor
import (
"fmt"
"io"
"os/exec"
"sync"
"time"
"github.com/kelseyhightower/envconfig"
"github.com/prometheus/client_golang/prometheus"
log "github.com/sirupsen/logrus"
)
// Config holds configuration for the circuit breaker of the respawn loop.
type Config struct {
// GITALY_SUPERVISOR_CRASH_THRESHOLD
CrashThreshold int `split_words:"true" default:"5"`
// GITALY_SUPERVISOR_CRASH_WAIT_TIME
CrashWaitTime time.Duration `split_words:"true" default:"1m"`
// GITALY_SUPERVISOR_CRASH_RESET_TIME
CrashResetTime time.Duration `split_words:"true" default:"1m"`
}
var (
startCounter = prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "gitaly_supervisor_starts_total",
Help: "Number of starts of supervised processes.",
},
[]string{"name"},
)
config Config
)
func init() {
envconfig.MustProcess("gitaly_supervisor", &config)
prometheus.MustRegister(startCounter)
}
// Process represents a running process.
type Process struct {
Name string
memoryThreshold int
events chan<- Event
healthCheck func() error
// Information to start the process
env []string
args []string
dir string
// Shutdown
shutdown chan struct{}
done chan struct{}
stopOnce sync.Once
}
// New creates a new proces instance.
func New(name string, env []string, args []string, dir string, memoryThreshold int, events chan<- Event, healthCheck func() error) (*Process, error) {
if len(args) < 1 {
return nil, fmt.Errorf("need at least one argument")
}
p := &Process{
Name: name,
memoryThreshold: memoryThreshold,
events: events,
healthCheck: healthCheck,
env: env,
args: args,
dir: dir,
shutdown: make(chan struct{}),
done: make(chan struct{}),
}
go watch(p)
return p, nil
}
func (p *Process) start(logger *log.Entry) (*exec.Cmd, error) {
startCounter.WithLabelValues(p.Name).Inc()
cmd := exec.Command(p.args[0], p.args[1:]...)
cmd.Env = p.env
cmd.Dir = p.dir
cmd.Stdout = logger.WriterLevel(log.InfoLevel)
cmd.Stderr = logger.WriterLevel(log.InfoLevel)
return cmd, cmd.Start()
}
func (p *Process) notifyUp(pid int) {
select {
case p.events <- Event{Type: Up, Pid: pid}:
case <-time.After(1 * time.Second):
// Timeout
}
}
func watch(p *Process) {
// Count crashes to prevent a tight respawn loop. This is a 'circuit breaker'.
crashes := 0
logger := log.WithField("supervisor.args", p.args).WithField("supervisor.name", p.Name)
// Use a buffered channel because we don't want to block the respawn loop
// on the monitor goroutine.
monitorChan := make(chan monitorProcess, config.CrashThreshold)
monitorDone := make(chan struct{})
go monitorRss(monitorChan, monitorDone, p.events, p.Name, p.memoryThreshold)
healthShutdown := make(chan struct{})
if p.healthCheck != nil {
go monitorHealth(p.healthCheck, p.events, p.Name, healthShutdown)
}
spawnLoop:
for {
if crashes >= config.CrashThreshold {
logger.Warn("opening circuit breaker")
select {
case <-p.shutdown:
break spawnLoop
case <-time.After(config.CrashWaitTime):
logger.Warn("closing circuit breaker")
crashes = 0
}
}
select {
case <-p.shutdown:
break spawnLoop
default:
}
cmd, err := p.start(logger)
if err != nil {
crashes++
logger.WithError(err).Error("start failed")
continue
}
pid := cmd.Process.Pid
go p.notifyUp(pid)
logger.WithField("supervisor.pid", pid).Warn("spawned")
waitCh := make(chan struct{})
go func(cmd *exec.Cmd, waitCh chan struct{}) {
err := cmd.Wait()
close(waitCh)
cmd.Stdout.(io.WriteCloser).Close()
cmd.Stderr.(io.WriteCloser).Close()
logger.WithError(err).Warn("exited")
}(cmd, waitCh)
monitorChan <- monitorProcess{pid: pid, wait: waitCh}
waitLoop:
for {
select {
case <-time.After(1 * time.Minute):
// We repeat this idempotent notification because its delivery is not
// guaranteed.
go p.notifyUp(pid)
case <-time.After(config.CrashResetTime):
crashes = 0
case <-waitCh:
crashes++
break waitLoop
case <-p.shutdown:
if cmd.Process != nil {
cmd.Process.Kill()
}
<-waitCh
break spawnLoop
}
}
}
close(healthShutdown)
close(monitorChan)
<-monitorDone
close(p.done)
}
// Stop terminates the process.
func (p *Process) Stop() {
if p == nil {
return
}
p.stopOnce.Do(func() {
close(p.shutdown)
})
select {
case <-p.done:
case <-time.After(1 * time.Second):
// Don't wait for shutdown forever
}
}
|
