Added basic event queue machine

event.go

@@ -5,6 +5,7 @@ import (
   "errors"
   graphql "github.com/graph-gophers/graphql-go"
   "reflect"
+  "sort"
 )
 
 // Update the events listeners, and notify the parent to do the same
@@ -50,9 +51,13 @@ type Event interface {
   Parent() Event
   RegisterParent(parent Event) error
   RequiredResources() []Resource
-  CreatedResources() []Resource
+  DoneResource() Resource
   AddChild(child Event, info EventInfo) error
   FindChild(id graphql.ID) Event
+  Run() error
+  Abort() error
+  Lock() error
+  Unlock() error
 }
 
 // BaseEvent is the most basic event that can exist in the event tree.
@@ -63,11 +68,86 @@ type Event interface {
 // When starter, this event automatically transitions to completion and unlocks all it's resources(including created)
 type BaseEvent struct {
   BaseNode
-  created_resources []Resource
+  done_resource Resource
   required_resources []Resource
   children []Event
   child_info map[Event]EventInfo
+  actions map[string]func() (string, error)
   parent Event
+  signal chan string
+  abort chan string
+}
+
+func (event * BaseEvent) Abort() error {
+  event.signal <- "abort"
+  return nil
+}
+
+func (queue * EventQueue) Abort() error {
+  for _, event := range(queue.Children()) {
+    event.Abort()
+  }
+  queue.signal <- "abort"
+  return nil
+}
+
+func (event * BaseEvent) Lock() error {
+  locked_resources := []Resource{}
+  lock_err := false
+  for _, resource := range(event.RequiredResources()) {
+    err := resource.Lock(event)
+    if err != nil {
+      lock_err = true
+    }
+  }
+
+  if lock_err == true {
+    for _, resource := range(locked_resources) {
+      resource.Unlock(event)
+    }
+    return errors.New("failed to lock required resources")
+  }
+  return nil
+}
+
+func (event * BaseEvent) Unlock() error {
+  return event.DoneResource().Unlock(event)
+}
+
+func (event * BaseEvent) Run() error {
+  next_action := "start"
+  var err error = nil
+  for next_action != "" {
+    // Check if the edge exists
+    action, exists := event.actions[next_action]
+    if exists == false {
+      error_str := fmt.Sprintf("%s is not a valid action", next_action)
+      return errors.New(error_str)
+    }
+
+    // Run the edge function
+    next_action, err = action()
+    if err != nil {
+      return err
+    }
+
+    // Check signals
+    select {
+    case reason := <-event.abort:
+      error_str := fmt.Sprintf("State Machine aborted: %s", reason)
+      return errors.New(error_str)
+    default:
+    }
+
+    // Update the event after running the edge
+    event.Update()
+  }
+
+  err = event.DoneResource().Unlock(event)
+  if err != nil {
+    return err
+  }
+  return nil
 }
 
 // EventQueue is a basic event that can have children.
@@ -76,7 +156,7 @@ type EventQueue struct {
   BaseEvent
 }
 
-func NewEvent(name string, description string, required_resources []Resource) (* BaseEvent, Resource) {
+func NewEvent(name string, description string, required_resources []Resource) (* BaseEvent) {
   done_resource := NewResource("event_done", "signal that event is done", []Resource{})
   event := &BaseEvent{
     BaseNode: BaseNode{
@@ -88,17 +168,23 @@ func NewEvent(name string, description string, required_resources []Resource) (*
     parent: nil,
     children: []Event{},
     child_info: map[Event]EventInfo{},
-    created_resources: []Resource{done_resource},
+    done_resource: done_resource,
     required_resources: required_resources,
+    actions: map[string]func()(string, error){},
+    signal: make(chan string, 10),
   }
 
   // Lock the done_resource by default
   done_resource.Lock(event)
 
-  return event, done_resource
+  event.actions["start"] = func() (string, error) {
+    return "", nil
+  }
+
+  return event
 }
 
-func NewEventQueue(name string, description string, required_resources []Resource) (* EventQueue, Resource) {
+func NewEventQueue(name string, description string, required_resources []Resource) (* EventQueue) {
   done_resource := NewResource("event_done", "signal that event is done", []Resource{})
   queue := &EventQueue{
     BaseEvent: BaseEvent{
@@ -111,14 +197,83 @@ func NewEventQueue(name string, description string, required_resources []Resourc
       parent: nil,
       children: []Event{},
       child_info: map[Event]EventInfo{},
-      created_resources: []Resource{done_resource},
+      done_resource: done_resource,
       required_resources: required_resources,
+      actions: map[string]func()(string, error){},
+      signal: make(chan string, 10),
+      abort: make(chan string, 1),
     },
   }
 
-  done_resource.Lock(queue)
+  // Need to lock it with th BaseEvent since Unlock is implemented on the BaseEvent
+  done_resource.Lock(&queue.BaseEvent)
+
+  queue.actions["start"] = func() (string, error) {
+    return "queue_event", nil
+  }
+
+  queue.actions["queue_event"] = func() (string, error) {
+    // Sort the list of events by priority
+    // Keep trying to lock the highest priority event until the end of the list is reached, or an event is locked
+    // If an event is locked, transition it to "started" and start event in a new goroutine
+    // If the end of the queue is reached and there are no uncompleted events, transition to "done"
+    // If the end of the queue is reached and there are uncompleted events, transition to "wait"
+    copied_events := make([]Event, len(queue.Children()))
+    copy(copied_events, queue.Children())
+    less := func(i int, j int) bool {
+      info_i := queue.ChildInfo(copied_events[i]).(*EventQueueInfo)
+      info_j := queue.ChildInfo(copied_events[j]).(*EventQueueInfo)
+      return info_i.priority < info_j.priority
+    }
+    sort.SliceStable(copied_events, less)
+
+    wait := false
+    for _, event := range(copied_events) {
+      info := queue.ChildInfo(event).(*EventQueueInfo)
+      if info.state == "queued" {
+        wait = true
+        // Try to lock it
+        err := event.Lock()
+        // start in new goroutine
+        if err != nil {
+
+        } else {
+          info.state = "running"
+          go func(event Event, info * EventQueueInfo, queue * EventQueue) {
+            event.Run()
+            info.state = "done"
+            queue.signal <- "event_done"
+          }(event, info, queue)
+        }
+      } else if info.state == "running" {
+        wait = true
+      }
+    }
+
+    if wait == true {
+      return "wait", nil
+    } else {
+      return "", nil
+    }
+  }
+
+  queue.actions["wait"] = func() (string, error) {
+    // Wait until signaled by a thread
+    /*
+      What signals to take action for:
+       - abort : sent by any other thread : abort any child events and set the next event to none
+       - resource_available : sent by the aggregator goroutine when the lock on a resource changes : see if any events can be locked
+       - event_done : sent by child event threads : see if all events are completed
+    */
+    signal := <- queue.signal
+    if signal == "abort" {
+      queue.abort <- "aborted by signal"
+      return "", nil
+    }
+    return "queue_event", nil
+  }
 
-  return queue, done_resource
+  return queue
 }
 
 // Store the nodes parent for upwards propagation of changes
@@ -139,8 +294,8 @@ func (event * BaseEvent) RequiredResources() []Resource {
   return event.required_resources
 }
 
-func (event * BaseEvent) CreatedResources() []Resource {
-  return event.created_resources
+func (event * BaseEvent) DoneResource() Resource {
+  return event.done_resource
 }
 
 func (event * BaseEvent) Children() []Event {

main.go

@@ -32,7 +32,7 @@ func fake_data() * EventManager {
     }
   }
 
-  root_event, _ := NewEventQueue("root_event", "", []Resource{})
+  root_event := NewEventQueue("root_event", "", []Resource{})
 
   event_manager := NewEventManager(root_event, resources)
 

manager.go

@@ -5,7 +5,6 @@ import (
   "log"
   "errors"
   graphql "github.com/graph-gophers/graphql-go"
-  "context"
 )
 
 type EventManager struct {
@@ -35,9 +34,8 @@ func NewEventManager(root_event Event, dag_nodes []Resource) * EventManager {
   return manager;
 }
 
-func (manager * EventManager) Run(ctx context.Context) error {
-  //return manager.root_event.Run(ctx)
-  return nil
+func (manager * EventManager) Run() error {
+  return manager.root_event.Run()
 }
 
 func (manager * EventManager) FindResource(id graphql.ID) Resource {
@@ -97,14 +95,13 @@ func (manager * EventManager) AddEvent(parent Event, child Event, info EventInfo
     }
   }
 
-  for _, resource := range child.CreatedResources() {
+  resource := child.DoneResource()
   _, exists := manager.dag_nodes[resource.ID()]
   if exists == true {
     error_str := fmt.Sprintf("Created resource %s already exists in DAG, cannot add event %s", resource.ID(), child.ID())
     return errors.New(error_str)
   }
   manager.AddResource(resource)
-  }
 
   if manager.root_event == nil && parent != nil {
     error_str := fmt.Sprintf("EventManager has no root, so can't add event to parent")

manager_test.go

@@ -3,7 +3,7 @@ package main
 import (
   "testing"
   "time"
-  "context"
+  "fmt"
 )
 
 type graph_tester testing.T
@@ -51,7 +51,7 @@ func TestNewResourceAdd(t *testing.T) {
   description := "A resource for testing"
   children := []Resource{}
 
-  root_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
   test_resource := NewResource(name, description, children)
   event_manager := NewEventManager(root_event, []Resource{test_resource})
   res := event_manager.FindResource(test_resource.ID())
@@ -66,7 +66,7 @@ func TestNewResourceAdd(t *testing.T) {
 }
 
 func TestDoubleResourceAdd(t * testing.T) {
-  root_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
   test_resource := NewResource("", "", []Resource{})
   event_manager := NewEventManager(root_event, []Resource{test_resource})
   err := event_manager.AddResource(test_resource)
@@ -77,7 +77,7 @@ func TestDoubleResourceAdd(t * testing.T) {
 }
 
 func TestMissingResourceAdd(t * testing.T) {
-  root_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
   r1 := NewResource("r1", "", []Resource{})
   r2 := NewResource("r2", "", []Resource{r1})
 
@@ -89,7 +89,7 @@ func TestMissingResourceAdd(t * testing.T) {
 }
 
 func TestTieredResource(t * testing.T) {
-  root_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
   r1 := NewResource("r1", "", []Resource{})
   r2 := NewResource("r2", "", []Resource{r1})
 
@@ -100,7 +100,7 @@ func TestTieredResource(t * testing.T) {
 }
 
 func TestResourceUpdate(t * testing.T) {
-  root_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
   r1 := NewResource("r1", "", []Resource{})
   r2 := NewResource("r2", "", []Resource{})
   r3 := NewResource("r3", "", []Resource{r1, r2})
@@ -139,14 +139,14 @@ func TestResourceUpdate(t * testing.T) {
 }
 
 func TestAddEvent(t * testing.T) {
-  root_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
   r1 := NewResource("r1", "", []Resource{})
   r2 := NewResource("r2", "", []Resource{r1})
 
   name := "Test Event"
   description := "A test event"
   resources := []Resource{r2}
-  new_event, _ := NewEvent(name, description, resources)
+  new_event := NewEvent(name, description, resources)
 
   event_manager := NewEventManager(root_event, []Resource{r1})
   err := event_manager.AddResource(r2)
@@ -177,8 +177,8 @@ func TestAddEvent(t * testing.T) {
 }
 
 func TestLockResource(t * testing.T) {
-  root_event, _ := NewEvent("", "", []Resource{})
-  test_event, _ := NewEvent("", "", []Resource{})
+  root_event := NewEvent("", "", []Resource{})
+  test_event := NewEvent("", "", []Resource{})
   r1 := NewResource("r1", "", []Resource{})
   r2 := NewResource("r2", "", []Resource{})
   r3 := NewResource("r3", "", []Resource{r1, r2})
@@ -243,9 +243,9 @@ func TestLockResource(t * testing.T) {
 }
 
 func TestAddToEventQueue(t * testing.T) {
-  queue, _ := NewEventQueue("q", "", []Resource{})
-  event_1, _ := NewEvent("1", "", []Resource{})
-  event_2, _ := NewEvent("2", "", []Resource{})
+  queue := NewEventQueue("q", "", []Resource{})
+  event_1 := NewEvent("1", "", []Resource{})
+  event_2 := NewEvent("2", "", []Resource{})
 
   err := queue.AddChild(event_1, nil)
   if err == nil {
@@ -264,7 +264,8 @@ func TestAddToEventQueue(t * testing.T) {
 }
 
 func TestStartBaseEvent(t * testing.T) {
-  event_1, r := NewEvent("1", "", []Resource{})
+  event_1 := NewEvent("1", "", []Resource{})
+  r := event_1.DoneResource()
   manager := NewEventManager(event_1, []Resource{})
 
   e_l := event_1.UpdateChannel()
@@ -276,7 +277,7 @@ func TestStartBaseEvent(t * testing.T) {
     t.Fatal("r is not owned by event_1")
   }
 
-  err := manager.Run(context.Background())
+  err := manager.Run()
   if err != nil {
     t.Fatal(err)
   }
@@ -289,12 +290,50 @@ func TestStartBaseEvent(t * testing.T) {
   }
 }
 
+func TestAbortEventQueue(t * testing.T) {
+  root_event := NewEventQueue("", "", []Resource{})
+  r := root_event.DoneResource()
+  manager := NewEventManager(root_event, []Resource{})
+
+  r1 := NewResource("r1", "", []Resource{})
+  err := manager.AddResource(r1)
+  if err != nil {
+    t.Fatal(err)
+  }
+  r1.Lock(root_event)
+  e1 := NewEvent("1", "", []Resource{r1})
+  e1_info := NewEventQueueInfo(1)
+  // Add an event so that the queue doesn't auto complete
+  err = manager.AddEvent(root_event, e1, e1_info)
+  if err != nil {
+    t.Fatal(err)
+  }
+
+  // Now that an event manager is constructed with a queue and 3 basic events
+  // start the queue and check that all the events are executed
+  go func() {
+    time.Sleep(time.Second)
+    root_event.Abort()
+  }()
+
+  err = manager.Run()
+  if err == nil {
+    t.Fatal("event manager completed without error")
+  }
+
+  if r.Owner() == nil {
+    t.Fatal("root event was finished after starting")
+  }
+}
+
 func TestStartEventQueue(t * testing.T) {
-  root_event, r := NewEventQueue("", "", []Resource{})
+  root_event := NewEventQueue("", "", []Resource{})
+  r := root_event.DoneResource()
   rel := root_event.UpdateChannel();
   manager := NewEventManager(root_event, []Resource{})
 
-  e1, e1_r := NewEvent("1", "", []Resource{})
+  e1:= NewEvent("1", "", []Resource{})
+  e1_r := e1.DoneResource()
   e1_info := NewEventQueueInfo(1)
   err := manager.AddEvent(root_event, e1, e1_info)
   if err != nil {
@@ -302,7 +341,8 @@ func TestStartEventQueue(t * testing.T) {
   }
   (*graph_tester)(t).CheckForNil(rel)
 
-  e2, e2_r := NewEvent("1", "", []Resource{})
+  e2 := NewEvent("1", "", []Resource{})
+  e2_r := e2.DoneResource()
   e2_info := NewEventQueueInfo(2)
   err = manager.AddEvent(root_event, e2, e2_info)
   if err != nil {
@@ -310,7 +350,8 @@ func TestStartEventQueue(t * testing.T) {
   }
   (*graph_tester)(t).CheckForNil(rel)
 
-  e3, e3_r := NewEvent("1", "", []Resource{})
+  e3 := NewEvent("1", "", []Resource{})
+  e3_r := e3.DoneResource()
   e3_info := NewEventQueueInfo(3)
   err = manager.AddEvent(root_event, e3, e3_info)
   if err != nil {
@@ -322,16 +363,21 @@ func TestStartEventQueue(t * testing.T) {
   e2_l := e2.UpdateChannel();
   e3_l := e3.UpdateChannel();
 
+  // Abort the event after 5 seconds just in case
+  go func() {
+    time.Sleep(5 * time.Second)
+    root_event.Abort()
+  }()
+
   // Now that an event manager is constructed with a queue and 3 basic events
   // start the queue and check that all the events are executed
-  err = manager.Run(context.Background())
+  err = manager.Run()
   if err != nil {
     t.Fatal(err)
   }
 
-  time.Sleep( 5 * time.Second)
-
   if r.Owner() != nil {
+    fmt.Printf("root_event.DoneResource(): %p", root_event.DoneResource())
     t.Fatal("root event was not finished after starting")
   }