Periodically purge unconnected displays.

field/arena.go

@@ -873,6 +873,9 @@ func (arena *Arena) runPeriodicTasks() {
 		arena.EventStatusMessage = newEventStatusMessage
 		arena.EventStatusNotifier.Notify()
 	}
+
+	// Clean up the list of displays.
+	arena.purgeDisconnectedDisplays()
 }
 
 // Updates the string that indicates how early or late the event is running.

field/display.go

@@ -13,10 +13,12 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"time"
 )
 
 const (
-	minDisplayId = 100
+	minDisplayId       = 100
+	displayPurgeTtlMin = 30
 )
 
 type DisplayType int
@@ -58,12 +60,13 @@ var displayTypePaths = map[DisplayType]string{
 var displayRegistryMutex sync.Mutex
 
 type Display struct {
-	Id              string
-	Nickname        string
-	Type            DisplayType
-	Configuration   map[string]string
-	IpAddress       string
-	ConnectionCount int
+	Id                string
+	Nickname          string
+	Type              DisplayType
+	Configuration     map[string]string
+	IpAddress         string
+	ConnectionCount   int
+	lastConnectedTime time.Time
 }
 
 // Parses the given display URL path and query string to extract the configuration.
@@ -159,6 +162,7 @@ func (arena *Arena) RegisterDisplay(display *Display) {
 		} else {
 			display.ConnectionCount = 1
 		}
+		display.lastConnectedTime = time.Now()
 		arena.Displays[display.Id] = display
 	}
 	arena.DisplayConfigurationNotifier.Notify()
@@ -194,6 +198,25 @@ func (arena *Arena) MarkDisplayDisconnected(display *Display) {
 		} else {
 			existingDisplay.ConnectionCount -= 1
 		}
+		existingDisplay.lastConnectedTime = time.Now()
+		arena.DisplayConfigurationNotifier.Notify()
+	}
+}
+
+// Removes any displays from the list that haven't had any active connections for a while and don't have a nickname.
+func (arena *Arena) purgeDisconnectedDisplays() {
+	displayRegistryMutex.Lock()
+	defer displayRegistryMutex.Unlock()
+
+	deleted := false
+	for id, display := range arena.Displays {
+		if display.ConnectionCount == 0 && display.Nickname == "" &&
+			time.Now().Sub(display.lastConnectedTime).Minutes() >= displayPurgeTtlMin {
+			delete(arena.Displays, id)
+			deleted = true
+		}
+	}
+	if deleted {
 		arena.DisplayConfigurationNotifier.Notify()
 	}
 }

field/display_test.go

@@ -6,6 +6,7 @@ package field
 import (
 	"github.com/stretchr/testify/assert"
 	"testing"
+	"time"
 )
 
 func TestDisplayFromUrl(t *testing.T) {
@@ -123,3 +124,47 @@ func TestDisplayUpdateError(t *testing.T) {
 		assert.Contains(t, err.Error(), "doesn't exist")
 	}
 }
+
+func TestDisplayPurge(t *testing.T) {
+	arena := setupTestArena(t)
+
+	// Unnamed placeholder gets immediately purged upon disconnection.
+	display := &Display{Id: "254", Type: PlaceholderDisplay, Configuration: map[string]string{}}
+	arena.RegisterDisplay(display)
+	assert.Contains(t, arena.Displays, "254")
+	arena.MarkDisplayDisconnected(display)
+	assert.NotContains(t, arena.Displays, "254")
+
+	// Named placeholder does not get immediately purged upon disconnection.
+	display.Nickname = "Bob"
+	arena.RegisterDisplay(display)
+	assert.Contains(t, arena.Displays, "254")
+	arena.MarkDisplayDisconnected(display)
+	assert.Contains(t, arena.Displays, "254")
+
+	// Unnamed configured display does not get immediately purged upon disconnection.
+	display = &Display{Id: "1114", Type: FieldMonitorDisplay, Configuration: map[string]string{}}
+	arena.RegisterDisplay(display)
+	assert.Contains(t, arena.Displays, "1114")
+	arena.MarkDisplayDisconnected(display)
+	assert.Contains(t, arena.Displays, "1114")
+	arena.purgeDisconnectedDisplays()
+	assert.Contains(t, arena.Displays, "1114")
+
+	// Unnamed configured display gets purged by periodic task.
+	arena.RegisterDisplay(display)
+	assert.Contains(t, arena.Displays, "1114")
+	arena.MarkDisplayDisconnected(display)
+	arena.Displays["1114"].lastConnectedTime = time.Now().Add(-displayPurgeTtlMin * time.Minute)
+	arena.purgeDisconnectedDisplays()
+	assert.NotContains(t, arena.Displays, "1114")
+
+	// Named configured display does not get purged by periodic task.
+	display.Nickname = "Brunhilda"
+	arena.RegisterDisplay(display)
+	assert.Contains(t, arena.Displays, "1114")
+	arena.MarkDisplayDisconnected(display)
+	arena.Displays["1114"].lastConnectedTime = time.Now().Add(-displayPurgeTtlMin * time.Minute)
+	arena.purgeDisconnectedDisplays()
+	assert.Contains(t, arena.Displays, "1114")
+}

templates/setup_displays.html

@@ -30,7 +30,7 @@
 </div>
 
 <script id="displayTemplate" type="text/x-handlebars-template">
-  <tr>
+  <tr{{"{{#unless ConnectionCount}}"}} class="danger"{{"{{/unless}}"}}>
     <td>{{"{{Id}}"}}</td>
     <td>{{"{{ConnectionCount}}"}}</td>
     <td>{{"{{IpAddress}}"}}</td>