Fix token metrics parsing (#199)

Fix #198

- use llama-server's `timings` info if available in response body
- send "-1" for token/sec when not able to accurately calculate
  performance
- optimize streaming body search for metrics information

misc/simple-responder/simple-responder.go

@@ -78,6 +78,14 @@ func main() {
 					"prompt_tokens":     25,
 					"total_tokens":      35,
 				},
+				// add timings to simulate llama.cpp
+				"timings": gin.H{
+					"prompt_n":             25,
+					"prompt_ms":            13,
+					"predicted_n":          10,
+					"predicted_ms":         17,
+					"predicted_per_second": 10,
+				},
 			}
 			c.SSEvent("message", finalData)
 			c.Writer.Flush()
@@ -102,6 +110,13 @@ func main() {
 					"prompt_tokens":     25,
 					"total_tokens":      35,
 				},
+				"timings": gin.H{
+					"prompt_n":             25,
+					"prompt_ms":            13,
+					"predicted_n":          10,
+					"predicted_ms":         17,
+					"predicted_per_second": 10,
+				},
 			})
 		}
 	})

proxy/metrics_middleware.go

@@ -67,51 +67,66 @@ func (rec *MetricsRecorder) processBody(body []byte) {
 	}
 }
 
-func (rec *MetricsRecorder) parseAndRecordMetrics(jsonData gjson.Result) {
-	if !jsonData.Get("usage").Exists() {
-		return
+func (rec *MetricsRecorder) parseAndRecordMetrics(jsonData gjson.Result) bool {
+	usage := jsonData.Get("usage")
+	if !usage.Exists() {
+		return false
 	}
 
+	// default values
 	outputTokens := int(jsonData.Get("usage.completion_tokens").Int())
 	inputTokens := int(jsonData.Get("usage.prompt_tokens").Int())
+	tokensPerSecond := -1.0
+	durationMs := int(time.Since(rec.startTime).Milliseconds())
 
-	if outputTokens > 0 {
-		duration := time.Since(rec.startTime)
-		tokensPerSecond := float64(inputTokens+outputTokens) / duration.Seconds()
+	// use llama-server's timing data for tok/sec and duration as it is more accurate
+	if timings := jsonData.Get("timings"); timings.Exists() {
+		tokensPerSecond = jsonData.Get("timings.predicted_per_second").Float()
+		durationMs = int(jsonData.Get("timings.prompt_ms").Float() + jsonData.Get("timings.predicted_ms").Float())
+	}
 
-		metrics := TokenMetrics{
+	rec.metricsMonitor.addMetrics(TokenMetrics{
 		Timestamp:       time.Now(),
 		Model:           rec.realModelName,
 		InputTokens:     inputTokens,
 		OutputTokens:    outputTokens,
 		TokensPerSecond: tokensPerSecond,
-			DurationMs:      int(duration.Milliseconds()),
-		}
-		rec.metricsMonitor.addMetrics(metrics)
-	}
+		DurationMs:      durationMs,
+	})
+
+	return true
 }
 
 func (rec *MetricsRecorder) processStreamingResponse(body []byte) {
+	// Iterate **backwards** through the lines looking for the data payload with
+	// usage data
 	lines := bytes.Split(body, []byte("\n"))
-	for _, line := range lines {
-		line = bytes.TrimSpace(line)
+
+	for i := len(lines) - 1; i >= 0; i-- {
+		line := bytes.TrimSpace(lines[i])
 		if len(line) == 0 {
 			continue
 		}
 
-		// Check for SSE data prefix
-		if data, found := bytes.CutPrefix(line, []byte("data:")); found {
-			data = bytes.TrimSpace(data)
+		// SSE payload always follows "data:"
+		prefix := []byte("data:")
+		if !bytes.HasPrefix(line, prefix) {
+			continue
+		}
+		data := bytes.TrimSpace(line[len(prefix):])
+
 		if len(data) == 0 {
 			continue
 		}
+
 		if bytes.Equal(data, []byte("[DONE]")) {
-				break
+			// [DONE] line itself contains nothing of interest.
+			continue
 		}
 
-			// Parse JSON to look for usage data
 		if gjson.ValidBytes(data) {
-				rec.parseAndRecordMetrics(gjson.ParseBytes(data))
+			if rec.parseAndRecordMetrics(gjson.ParseBytes(data)) {
+				return // short circuit if a metric was recorded
 			}
 		}
 	}

proxy/proxymanager_test.go

@@ -708,7 +708,9 @@ func TestProxyManager_MiddlewareWritesMetrics_NonStreaming(t *testing.T) {
 
 	// Check that metrics were recorded
 	metrics := proxy.metricsMonitor.GetMetrics()
-	assert.NotEmpty(t, metrics, "metrics should be recorded for non-streaming request")
+	if !assert.NotEmpty(t, metrics, "metrics should be recorded for non-streaming request") {
+		return
+	}
 
 	// Verify the last metric has the correct model
 	lastMetric := metrics[len(metrics)-1]
@@ -741,7 +743,9 @@ func TestProxyManager_MiddlewareWritesMetrics_Streaming(t *testing.T) {
 
 	// Check that metrics were recorded
 	metrics := proxy.metricsMonitor.GetMetrics()
-	assert.NotEmpty(t, metrics, "metrics should be recorded for streaming request")
+	if !assert.NotEmpty(t, metrics, "metrics should be recorded for streaming request") {
+		return
+	}
 
 	// Verify the last metric has the correct model
 	lastMetric := metrics[len(metrics)-1]

ui/src/pages/Activity.tsx

@@ -1,6 +1,18 @@
 import { useState, useEffect } from "react";
 import { useAPI } from "../contexts/APIProvider";
 
+const formatTimestamp = (timestamp: string): string => {
+  return new Date(timestamp).toLocaleString();
+};
+
+const formatSpeed = (speed: number): string => {
+  return speed < 0 ? "unknown" : speed.toFixed(2) + " t/s";
+};
+
+const formatDuration = (ms: number): string => {
+  return (ms / 1000).toFixed(2) + "s";
+};
+
 const ActivityPage = () => {
   const { metrics } = useAPI();
   const [error, setError] = useState<string | null>(null);
@@ -11,18 +23,6 @@ const ActivityPage = () => {
     }
   }, [metrics]);
 
-  const formatTimestamp = (timestamp: string) => {
-    return new Date(timestamp).toLocaleString();
-  };
-
-  const formatSpeed = (speed: number) => {
-    return speed.toFixed(2) + " t/s";
-  };
-
-  const formatDuration = (ms: number) => {
-    return (ms / 1000).toFixed(2) + "s";
-  };
-
   if (error) {
     return (
       <div className="p-6">
@@ -51,7 +51,7 @@ const ActivityPage = () => {
                 <th className="px-6 py-3 text-left text-xs font-medium uppercase tracking-wider">Model</th>
                 <th className="px-6 py-3 text-left text-xs font-medium uppercase tracking-wider">Input Tokens</th>
                 <th className="px-6 py-3 text-left text-xs font-medium uppercase tracking-wider">Output Tokens</th>
-                <th className="px-6 py-3 text-left text-xs font-medium uppercase tracking-wider">Processing Speed</th>
+                <th className="px-6 py-3 text-left text-xs font-medium uppercase tracking-wider">Generation Speed</th>
                 <th className="px-6 py-3 text-left text-xs font-medium uppercase tracking-wider">Duration</th>
               </tr>
             </thead>