[GitHub] [ozone] adoroszlai commented on a change in pull request #2074: HDDS-5010 Fixing Prometheus duplicated TYPE definition

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

adoroszlai commented on a change in pull request #2074:
URL: https://github.com/apache/ozone/pull/2074#discussion_r599628973



##########
File path: hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/http/PrometheusMetricsSink.java
##########
@@ -64,43 +66,48 @@ public void putMetrics(MetricsRecord metricsRecord) {
         String key = prometheusName(
             metricsRecord.name(), metrics.name());
 
-        StringBuilder builder = new StringBuilder();
-        builder.append("# TYPE ")
-            .append(key)
-            .append(" ")
-            .append(metrics.type().toString().toLowerCase())
-            .append("\n");
-
-        StringBuilder prometheusMetricKey = new StringBuilder();
-        prometheusMetricKey.append(key)
-            .append("{");
-        String sep = "";
-
-        //add tags
-        for (MetricsTag tag : metricsRecord.tags()) {
-          String tagName = tag.name().toLowerCase();
-
-          //ignore specific tag which includes sub-hierarchy
-          if (!tagName.equals("numopenconnectionsperuser")) {
-            prometheusMetricKey.append(sep)
-                .append(tagName)
-                .append("=\"")
-                .append(tag.value())
-                .append("\"");
-            sep = ",";
-          }
+        String prometheusMetricKeyAsString =
+            getPrometheusMetricKeyAsString(metricsRecord, key);
+
+        String metricKey = "# TYPE "
+            + key
+            + " "
+            + metrics.type().toString().toLowerCase();
+
+        if (!metricLines.containsKey(metricKey)){
+          metricLines.put(metricKey, new TreeMap<>());
         }
-        prometheusMetricKey.append("}");
 
-        String prometheusMetricKeyAsString = prometheusMetricKey.toString();
-        builder.append(prometheusMetricKeyAsString);
-        builder.append(" ");
-        builder.append(metrics.value());
-        builder.append("\n");
-        metricLines.put(prometheusMetricKeyAsString, builder.toString());
+        metricLines.get(metricKey).put(prometheusMetricKeyAsString,

Review comment:
       Please use `computeIfAbsent` instead of `containsKey`, `put` and `get`.  Only individual calls are synchronized, so the sequence may lead to unexpected results.
   
   ```java
       metricLines.computeIfAbsent(metricKey, any -> synchronizedSortedMap(new TreeMap<>()))
           .put(prometheusMetricKeyAsString, builder.toString());
   ```




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