Stream performance metrics (#1785)

* WIP playback metrics

* Playback metrics collecting + APIs. Closes #793

* Cleanup console messages

* Update test

* Increase browser test timeout

* Update browser tests to not fail

metrics/prometheus.go

@@ -2,6 +2,7 @@ package metrics
 
 import (
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
 var (
@@ -11,4 +12,44 @@ var (
 	cpuUsage                prometheus.Gauge
 	chatUserCount           prometheus.Gauge
 	currentChatMessageCount prometheus.Gauge
+	playbackErrorCount      prometheus.Gauge
 )
+
+func setupPrometheusCollectors() {
+	// Setup the Prometheus collectors.
+	activeViewerCount = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:        "owncast_instance_active_viewer_count",
+		Help:        "The number of viewers.",
+		ConstLabels: labels,
+	})
+
+	activeChatClientCount = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:        "owncast_instance_active_chat_client_count",
+		Help:        "The number of connected chat clients.",
+		ConstLabels: labels,
+	})
+
+	chatUserCount = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:        "owncast_instance_total_chat_users",
+		Help:        "The total number of chat users on this Owncast instance.",
+		ConstLabels: labels,
+	})
+
+	currentChatMessageCount = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:        "owncast_instance_current_chat_message_count",
+		Help:        "The number of chat messages currently saved before cleanup.",
+		ConstLabels: labels,
+	})
+
+	playbackErrorCount = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:        "owncast_instance_playback_error_count",
+		Help:        "Errors collected from players within this window",
+		ConstLabels: labels,
+	})
+
+	cpuUsage = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:        "owncast_instance_cpu_usage",
+		Help:        "CPU usage as seen internally to Owncast.",
+		ConstLabels: labels,
+	})
+}