concurrency for the expiry time

cmd/templaterender/render.go

@@ -92,8 +92,8 @@ func main() {
 				OS:       "linux",
 				Shell:    "/bin/bash",
 			},
-			ExpiryTime: time.Now().In(japan).Add(10 * time.Minute),
 		}
+		agent.SetExpiryTime(time.Now().In(japan).Add(10 * time.Minute))
 		state.Agents.Put(agent.Guid, &agent)
 		client := models.Client{
 			Guid:        models.ClientGuid(strconv.Itoa(rand.Int())),

pkg/models/state.go

@@ -3,9 +3,16 @@ package models
 import (
 	"git.wamblee.org/converge/pkg/comms"
 	"git.wamblee.org/converge/pkg/support/collections"
+	"sync/atomic"
 	"time"
 )
 
+// Concurrency design:
+// 1. State is immutable
+// 2. The MatchMakers uses copy-on-write and never modifies a state directly.
+// 3. the matchmaker modifies the expiry time of the agent. This is dealt with using the
+//    sync/atomic package by storing the expiry time as an int64 using time.Time.UnixNano()
+
 type RendezVousId string
 type AgentGuid string
 type ClientGuid string
@@ -22,7 +29,16 @@ type Agent struct {
 	// TODO add remote address.
 
 	EnvironmentInfo comms.EnvironmentInfo
-	ExpiryTime      time.Time
+	expiryTime      int64
+}
+
+func (agent *Agent) SetExpiryTime(t time.Time) {
+	atomic.StoreInt64(&agent.expiryTime, t.UnixNano())
+}
+
+func (agent *Agent) GetExpiryTime() time.Time {
+	t := atomic.LoadInt64(&agent.expiryTime)
+	return time.Unix(0, t)
 }
 
 type Client struct {

pkg/server/matchmaker/matchmaker.go

@@ -56,7 +56,7 @@ func (converge *MatchMaker) Register(publicId models.RendezVousId, conn io.ReadW
 				converge.admin.SetSessionType(models.ClientId(session.ClientId), models.SessionType(session.SessionType))
 			},
 			func(expiry comms.ExpiryTimeUpdate) {
-				agent.ExpiryTime = expiry.ExpiryTime
+				agent.SetExpiryTime(expiry.ExpiryTime)
 				converge.logStatus()
 			})
 	}()
@@ -137,7 +137,7 @@ func logStatusImpl(admin *models.State, notifier Notifier) {
 	for agent := range admin.Agents.RangeValues() {
 		lines = append(lines, fmt.Sprintf(format, agent.PublicId,
 			agent.StartTime.Format(time.DateTime),
-			agent.ExpiryTime.Format(time.DateTime),
+			agent.GetExpiryTime().Format(time.DateTime),
 			agent.EnvironmentInfo.Username,
 			agent.EnvironmentInfo.Hostname,
 			agent.EnvironmentInfo.OS))

pkg/server/templates/sessions.templ

@@ -39,7 +39,7 @@ templ State(state *models.State, location *time.Location) {
            <tr>
                <th>rendez-vous id</th>
                <th>start time</th>
-               <th>expiry time</th>
+               <th> time</th>
                <th>username</th>
                <th>host</th>
                <th>os</th>
@@ -50,7 +50,7 @@ templ State(state *models.State, location *time.Location) {
            <tr>
                <td>{string(agent.PublicId)}</td>
                <td>{agent.StartTime.In(location).Format(time.DateTime)}</td>
-               <td>{agent.ExpiryTime.In(location).Format(time.DateTime)}</td>
+               <td>{agent.GetExpiryTime().In(location).Format(time.DateTime)}</td>
                <td>{agent.EnvironmentInfo.Username}</td>
                <td>{agent.EnvironmentInfo.Hostname}</td>
                <td>{agent.EnvironmentInfo.OS}</td>