[GitHub] [pulsar] Shawyeok commented on a change in pull request #14564: Prometheus metric support label

[GitBox <gi...@apache.org>]

Shawyeok commented on a change in pull request #14564:
URL: https://github.com/apache/pulsar/pull/14564#discussion_r820115248



##########
File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/stats/prometheus/metrics/PrometheusTextFormatUtil.java
##########
@@ -167,4 +182,33 @@ public static void writeMetricsCollectedByPrometheusClient(Writer w, CollectorRe
             }
         }
     }
+
+    private static void writeLabels(Writer w, Map<String, String> labels) throws IOException {
+        if (labels.isEmpty()) {
+            return;
+        }
+
+        w.append('{');
+        writeLabelsNoBraces(w, labels);
+        w.append('}');
+    }
+
+    private static void writeLabelsNoBraces(Writer w, Map<String, String> labels) throws IOException {
+        if (labels.isEmpty()) {
+            return;
+        }
+
+        boolean isFirst = true;
+        for (Map.Entry<String, String> e : labels.entrySet()) {
+            if (!isFirst) {
+                w.append(',');
+            }
+            isFirst = false;
+            w.append(e.getKey())
+                .append("=\"")
+                .append(e.getValue())

Review comment:
       In the future, the label (key or value) could be user input or configuration, is it safer if we do the escape job for special characters before write out? e.g.  `\` `"` `\n`, reference `io.prometheus.client.exporter.common.TextFormat#writeEscapedLabelValue`




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