154 lines
3.1 KiB
Go
154 lines
3.1 KiB
Go
package satan
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import (
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"fmt"
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"log"
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"runtime/debug"
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"sync"
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"time"
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)
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// Satan is the master daemon.
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type Satan struct {
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SubscribeFunc SubscribeFunc
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Publisher Publisher
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daemons []Daemon
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queue chan *task
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shutdown chan struct{}
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wg sync.WaitGroup
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latency *statistics
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}
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// Actor is a function that could be executed by daemon workers.
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type Actor func()
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// SubscribeFunc is a function that is used by daemons to subscribe to messages.
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type SubscribeFunc func(consumer, topic string) Streamer
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// Streamer is the interface that wraps message consumers. Error handling
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// should be provided by the implementation. Feel free to panic.
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type Streamer interface {
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Messages() <-chan []byte
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Close()
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}
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// Publisher is the interface that wraps message publishers. Error handling
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// should be provided by the implementation. Feel free to panic.
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type Publisher interface {
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Publish(msg []byte)
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Close()
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}
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type task struct {
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daemon Daemon
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actor Actor
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createdAt time.Time
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system bool
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name string
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}
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const (
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defaultNumWorkers = 10
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)
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// Summon creates a new instance of Satan.
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func Summon() *Satan {
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return &Satan{
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queue: make(chan *task),
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latency: newStatistics(),
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shutdown: make(chan struct{}),
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}
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}
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// AddDaemon adds a new daemon.
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func (s *Satan) AddDaemon(d Daemon) {
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base := d.base()
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base.self = d
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base.subscribeFunc = s.SubscribeFunc
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base.publisher = s.Publisher
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base.queue = s.queue
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base.shutdown = make(chan struct{})
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base.stats = newStatistics()
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go d.Startup()
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s.daemons = append(s.daemons, d)
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}
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// StartDaemons starts all registered daemons.
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func (s *Satan) StartDaemons() {
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s.wg.Add(defaultNumWorkers)
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for i := 0; i < defaultNumWorkers; i++ {
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go func(i int) {
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s.runWorker(i)
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s.wg.Done()
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}(i)
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}
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}
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// StopDaemons stops all running daemons.
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func (s *Satan) StopDaemons() {
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for _, d := range s.daemons {
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close(d.base().shutdown)
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d.Shutdown()
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stats := d.base().stats.snapshot()
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log.Printf("%s daemon performace statistics:\n%s\n", d.base(), stats)
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}
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close(s.shutdown)
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s.wg.Wait()
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close(s.queue)
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log.Printf("Task processing latency statistics:\n%s\n", s.latency.snapshot())
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}
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func (s *Satan) runWorker(i int) {
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log.Printf("Starting worker #%d", i+1)
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defer log.Printf("Worker #%d has stopped", i+1)
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for {
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select {
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case t := <-s.queue:
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dur := time.Now().UnixNano() - t.createdAt.UnixNano()
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s.latency.add(time.Duration(dur))
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s.processTask(t)
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default:
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select {
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case <-s.shutdown:
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return
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default:
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}
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}
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}
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}
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func (s *Satan) processTask(t *task) {
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defer func(start time.Time) {
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dur := time.Now().UnixNano() - start.UnixNano()
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t.daemon.base().stats.add(time.Duration(dur))
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if err := recover(); err != nil {
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if t.system {
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log.Printf("System process %s recovered from a panic\nError: %v\n", t, err)
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debug.PrintStack()
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// Restarting system task
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s.queue <- t
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} else {
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t.daemon.base().handlePanic(err)
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}
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}
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}(time.Now())
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t.actor() // <--- THE ACTION HAPPENS HERE
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}
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func (t *task) String() string {
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if t.name == "" {
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return fmt.Sprintf("[unnamed %s process]", t.daemon.base())
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}
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return fmt.Sprintf("%s[%s]", t.daemon.base(), t.name)
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}
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