feat: agent data cache to support connections to multiple hubs (#341)

beszel/internal/agent/agent_cache.go

@@ -0,0 +1,36 @@
+package agent
+
+import (
+	"beszel/internal/entities/system"
+	"time"
+)
+
+// Not thread safe since we only access from gatherStats which is already locked
+type SessionCache struct {
+	data           *system.CombinedData
+	lastUpdate     time.Time
+	primarySession string
+	leaseTime      time.Duration
+}
+
+func NewSessionCache(leaseTime time.Duration) *SessionCache {
+	return &SessionCache{
+		leaseTime: leaseTime,
+		data:      &system.CombinedData{},
+	}
+}
+
+func (c *SessionCache) Get(sessionID string) (stats *system.CombinedData, isCached bool) {
+	if sessionID != c.primarySession && time.Since(c.lastUpdate) < c.leaseTime {
+		return c.data, true
+	}
+	return c.data, false
+}
+
+func (c *SessionCache) Set(sessionID string, data *system.CombinedData) {
+	if data != nil {
+		*c.data = *data
+	}
+	c.primarySession = sessionID
+	c.lastUpdate = time.Now()
+}