From e4a61633c59d95d02b760bbc6a671568628a29a7 Mon Sep 17 00:00:00 2001
From: David Calavera <david.calavera@gmail.com>
Date: Tue, 1 Dec 2015 18:49:24 -0500
Subject: [PATCH] Add event subscribers.

- Add exit event for exec processes.

Signed-off-by: David Calavera <david.calavera@gmail.com>
---
 api/v1/server.go |  6 +-----
 event.go         |  1 +
 exit.go          | 25 +++++++++++++++++++++----
 supervisor.go    | 19 +++++++++++++++++--
 4 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/api/v1/server.go b/api/v1/server.go
index 3f93e7c..9ffe0aa 100644
--- a/api/v1/server.go
+++ b/api/v1/server.go
@@ -63,11 +63,7 @@ func (s *server) updateContainer(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *server) events(w http.ResponseWriter, r *http.Request) {
-	events, err := s.supervisor.Events()
-	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
+	events := s.supervisor.Events()
 	enc := json.NewEncoder(w)
 	for evt := range events {
 		var v interface{}
diff --git a/event.go b/event.go
index e5dd12f..a47a6fa 100644
--- a/event.go
+++ b/event.go
@@ -11,6 +11,7 @@ import (
 type EventType string
 
 const (
+	ExecExitEventType        EventType = "execExit"
 	ExitEventType            EventType = "exit"
 	StartContainerEventType  EventType = "startContainer"
 	DeleteEventType          EventType = "deleteContainerEvent"
diff --git a/exit.go b/exit.go
index b0a2a7c..25d0c33 100644
--- a/exit.go
+++ b/exit.go
@@ -6,17 +6,23 @@ type ExitEvent struct {
 	s *Supervisor
 }
 
+type ExecExitEvent struct {
+	s *Supervisor
+}
+
 func (h *ExitEvent) Handle(e *Event) error {
 	logrus.WithFields(logrus.Fields{"pid": e.Pid, "status": e.Status}).
 		Debug("containerd: process exited")
 	// is it the child process of a container
 	if container, ok := h.s.processes[e.Pid]; ok {
-		if err := container.RemoveProcess(e.Pid); err != nil {
-			logrus.WithField("error", err).Error("containerd: find container for pid")
-		}
-		delete(h.s.processes, e.Pid)
+		ne := NewEvent(ExecExitEventType)
+		ne.ID = container.ID()
+		ne.Pid = e.Pid
+		ne.Status = e.Status
+		h.s.SendEvent(ne)
 		return nil
 	}
+
 	// is it the main container's process
 	container, err := h.s.getContainerForPid(e.Pid)
 	if err != nil {
@@ -31,3 +37,14 @@ func (h *ExitEvent) Handle(e *Event) error {
 	h.s.SendEvent(ne)
 	return nil
 }
+
+func (h *ExecExitEvent) Handle(e *Event) error {
+	// exec process: we remove this process without notifying the main event loop
+	container := h.s.processes[e.Pid]
+	if err := container.RemoveProcess(e.Pid); err != nil {
+		logrus.WithField("error", err).Error("containerd: find container for pid")
+	}
+	delete(h.s.processes, e.Pid)
+	h.s.NotifySubscribers(e)
+	return nil
+}
diff --git a/supervisor.go b/supervisor.go
index c1717f9..bfc92c8 100644
--- a/supervisor.go
+++ b/supervisor.go
@@ -36,6 +36,7 @@ func NewSupervisor(stateDir string, concurrency int) (*Supervisor, error) {
 	}
 	// register default event handlers
 	s.handlers = map[EventType]Handler{
+		ExecExitEventType:        &ExecExitEvent{s},
 		ExitEventType:            &ExitEvent{s},
 		StartContainerEventType:  &StartEvent{s},
 		DeleteEventType:          &DeleteEvent{s},
@@ -63,16 +64,30 @@ type Supervisor struct {
 	events      chan *Event
 	tasks       chan *startTask
 	workerGroup sync.WaitGroup
+	subscribers map[subscriber]bool
 }
 
+type subscriber chan *Event
+
 // need proper close logic for jobs and stuff so that sending to the channels dont panic
 // but can complete jobs
 func (s *Supervisor) Close() error {
+	//TODO: unsubscribe all channels
 	return s.journal.Close()
 }
 
-func (s *Supervisor) Events() (<-chan *Event, error) {
-	return nil, nil
+func (s *Supervisor) Events() subscriber {
+	return subscriber(make(chan *Event))
+}
+
+func (s *Supervisor) Unsubscribe(sub subscriber) {
+	delete(s.subscribers, sub)
+}
+
+func (s *Supervisor) NotifySubscribers(e *Event) {
+	for sub := range s.subscribers {
+		sub <- e
+	}
 }
 
 // Start is a non-blocking call that runs the supervisor for monitoring contianer processes and