server: limit number of samples kept in memory

3 files changed, 9 insertions, 4 deletions

diff --git a/server/building.go b/server/building.go
index c7d298f..8772374 100644
--- a/server/building.go
+++ b/server/building.go
@@ -7,7 +7,7 @@ type Building map[RoomID]Record[Humidity]
 func newBuilding(roomIDs []RoomID) Building {
 	b := make(Building)
 	for _, id := range roomIDs {
-		b[id] = newRecord[Humidity]()
+		b[id] = newRecord[Humidity](historySize)
 	}
 	return b
 }
diff --git a/server/record.go b/server/record.go
index 9051146..c2f38eb 100644
--- a/server/record.go
+++ b/server/record.go
@@ -15,13 +15,15 @@ type entry[T any] struct {
 	v T
 }
 
-func newRecord[T any]() Record[T] {
+// Create a record with the specified capacity.
+// If the capacity is exceeded, old entires will be discarded and new ones kept.
+func newRecord[T any](capacity int) Record[T] {
 	put := make(chan T)
 	get := make(chan chan T)
 	getRecent := make(chan chan T)
 
 	go func() {
-		var entries []entry[T]
+		entries := make([]entry[T], 0, capacity)
 
 		for {
 			select {
@@ -30,6 +32,9 @@ func newRecord[T any]() Record[T] {
 					return
 				}
 				entries = append(entries, entry[T]{time.Now(), v})
+				if len(entries) > capacity {
+					entries = entries[1:]
+				}
 			case c, ok := <-get:
 				if !ok {
 					return
diff --git a/server/server.go b/server/server.go
index fc19d94..4ef5151 100644
--- a/server/server.go
+++ b/server/server.go
@@ -9,7 +9,7 @@ import (
 
 const (
 	addr = ":9090"
-
+	historySize = 10000 // Number of old samples to keep in memory.
 	targetHumidityDefault = 35.0
 )