From 9a1b78ee6316a93601584f3799aa2b0f8d69a891 Mon Sep 17 00:00:00 2001
From: Erik Brakkee <erik@brakkee.org>
Date: Wed, 14 Aug 2024 20:42:14 +0200
Subject: [PATCH] Eliminating copying of objects in the prometheus integration.

---
 cmd/converge/prometheus.go | 46 +++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/cmd/converge/prometheus.go b/cmd/converge/prometheus.go
index eaf1c6c..f8f46ad 100644
--- a/cmd/converge/prometheus.go
+++ b/cmd/converge/prometheus.go
@@ -143,18 +143,18 @@ func agentActive(agent *models.Agent) {
 }
 
 func findAgent(state *models.State, guid string) (*models.Agent, bool) {
-	for _, agent := range state.Agents {
-		if agent.Guid == guid {
-			return &agent, true
+	for i := range state.Agents {
+		if state.Agents[i].Guid == guid {
+			return &state.Agents[i], true
 		}
 	}
 	return nil, false
 }
 
 func findClient(state *models.State, guid string) (*models.Client, bool) {
-	for _, client := range state.Clients {
-		if client.Guid == guid {
-			return &client, true
+	for i := range state.Clients {
+		if state.Clients[i].Guid == guid {
+			return &state.Clients[i], true
 		}
 	}
 	return nil, false
@@ -219,12 +219,14 @@ func updateMetrics(state *models.State) {
 }
 
 func updateDurations() {
-	for _, agent := range lastState.Agents {
+	for i := range lastState.Agents {
+		agent := &lastState.Agents[i]
 		agentDuration.
 			With(prometheus.Labels{"agent_guid": agent.Guid}).
 			Set(float64(time.Now().Sub(agent.StartTime).Seconds()))
 	}
-	for _, client := range lastState.Clients {
+	for i := range lastState.Clients {
+		client := &lastState.Clients[i]
 		clientDuration.
 			With(prometheus.Labels{"client_guid": client.Guid}).
 			Set(float64(time.Now().Sub(client.StartTime).Seconds()))
@@ -232,43 +234,47 @@ func updateDurations() {
 }
 
 func updateMetricsImpl(state *models.State) {
-	agentGuids := make(map[string]models.Agent)
-	clientGuids := make(map[string]models.Client)
+	agentGuids := make(map[string]*models.Agent)
+	clientGuids := make(map[string]*models.Client)
 
 	agentCount.Set(float64(len(state.Agents)))
-	disconnectedAgents := make(map[string]models.Agent)
-	for _, agent := range lastState.Agents {
+	disconnectedAgents := make(map[string]*models.Agent)
+	for i := range lastState.Agents {
+		agent := &lastState.Agents[i]
 		disconnectedAgents[agent.Guid] = agent
 	}
-	for _, agent := range state.Agents {
+	for i := range state.Agents {
+		agent := &state.Agents[i]
 		if _, ok := findAgent(lastState, agent.Guid); !ok {
 			cumulativeAgentCount.Inc()
 		}
 		delete(disconnectedAgents, agent.Guid)
 		agentGuids[agent.Guid] = agent
-		agentActive(&agent)
+		agentActive(agent)
 	}
 	for _, agent := range disconnectedAgents {
-		removeAgentMetrics(&agent)
+		removeAgentMetrics(agent)
 	}
 
 	clientCount.Set(float64(len(state.Clients)))
 
 	// with this app
-	disconnectedClients := make(map[string]models.Client)
-	for _, client := range lastState.Clients {
+	disconnectedClients := make(map[string]*models.Client)
+	for i := range lastState.Clients {
+		client := &lastState.Clients[i]
 		disconnectedClients[client.Guid] = client
 	}
-	for _, client := range state.Clients {
+	for i := range state.Clients {
+		client := &state.Clients[i]
 		if _, ok := findClient(lastState, client.Guid); !ok {
 			cumulativeClientCount.Inc()
 		}
 		delete(disconnectedClients, client.Guid)
 		clientGuids[client.Guid] = client
-		clientActive(&client)
+		clientActive(client)
 	}
 	for _, client := range disconnectedClients {
-		removeClientMetrics(&client)
+		removeClientMetrics(client)
 	}
 
 	lastState = state