[GitHub] [kafka] dajac commented on a diff in pull request #12121: KAFKA-13846: Adding overloaded metricOrElseCreate method

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

dajac commented on code in PR #12121:
URL: https://github.com/apache/kafka/pull/12121#discussion_r875156714


##########
clients/src/main/java/org/apache/kafka/common/metrics/Metrics.java:
##########
@@ -524,6 +524,58 @@ public void addMetric(MetricName metricName, MetricValueProvider<?> metricValueP
         addMetric(metricName, null, metricValueProvider);
     }
 
+    /**
+     * Create or get an existing metric to monitor an object that implements Measurable.
+     * This metric won't be associated with any sensor. This is a way to expose existing values as metrics.
+     *
+     * This method is kept for binary compatibility purposes, it has the same behaviour as
+     * {@link #metricOrElseCreate(MetricName, MetricConfig, MetricValueProvider)}.
+     *
+     * @param metricName The name of the metric
+     * @param config The configuration to use when measuring this measurable
+     * @param measurable The measurable that will be measured by this metric
+     * @return Existing KafkaMetric if already registered or else a newly created one
+     */
+    public KafkaMetric metricOrElseCreate(MetricName metricName, MetricConfig config, Measurable measurable) {

Review Comment:
   I wonder if we really need all these overloads. Do we have use cases for all of them? I have the impression that the last one would be sufficient.



##########
clients/src/main/java/org/apache/kafka/common/metrics/Metrics.java:
##########
@@ -563,10 +615,15 @@ public synchronized void removeReporter(MetricsReporter reporter) {
         }
     }
 
-    synchronized void registerMetric(KafkaMetric metric) {
+    synchronized void registerMetric(KafkaMetric metric, boolean raiseIfMetricExists) {

Review Comment:
   I am wonder if this change is really necessary. Is it?



##########
clients/src/main/java/org/apache/kafka/common/metrics/Metrics.java:
##########
@@ -524,6 +524,58 @@ public void addMetric(MetricName metricName, MetricValueProvider<?> metricValueP
         addMetric(metricName, null, metricValueProvider);
     }
 
+    /**
+     * Create or get an existing metric to monitor an object that implements Measurable.
+     * This metric won't be associated with any sensor. This is a way to expose existing values as metrics.
+     *
+     * This method is kept for binary compatibility purposes, it has the same behaviour as
+     * {@link #metricOrElseCreate(MetricName, MetricConfig, MetricValueProvider)}.
+     *
+     * @param metricName The name of the metric
+     * @param config The configuration to use when measuring this measurable
+     * @param measurable The measurable that will be measured by this metric
+     * @return Existing KafkaMetric if already registered or else a newly created one
+     */
+    public KafkaMetric metricOrElseCreate(MetricName metricName, MetricConfig config, Measurable measurable) {
+        return metricOrElseCreate(metricName, config, (MetricValueProvider<?>) measurable);
+    }
+
+    /**
+     * Create or get an existing metric to monitor an object that implements MetricValueProvider.
+     * This metric won't be associated with any sensor. This is a way to expose existing values as metrics.
+     * This method takes care of synchronisation while updating/accessing metrics by concurrent threads.
+     *
+     * @param metricName The name of the metric
+     * @param metricValueProvider The metric value provider associated with this metric
+     * @return Existing KafkaMetric if already registered or else a newly created one
+     */
+    public KafkaMetric metricOrElseCreate(MetricName metricName, MetricValueProvider<?> metricValueProvider) {
+        return metricOrElseCreate(metricName, null, metricValueProvider);
+    }
+
+    /**
+     * Create or get an existing metric to monitor an object that implements MetricValueProvider.
+     * This metric won't be associated with any sensor. This is a way to expose existing values as metrics.
+     * This method takes care of synchronisation while updating/accessing metrics by concurrent threads.
+     *
+     * @param metricName The name of the metric
+     * @param metricValueProvider The metric value provider associated with this metric
+     * @return Existing KafkaMetric if already registered or else a newly created one
+     */
+    public KafkaMetric metricOrElseCreate(MetricName metricName, MetricConfig config, MetricValueProvider<?> metricValueProvider) {

Review Comment:
   Instead of updating ‘registerMetric’, did we consider using synchronized?



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