[GitHub] [pulsar] marksilcox commented on a diff in pull request #15558: [fix][broker][functions-worker] Ensure prometheus metrics are grouped by type (#8407, #13865)

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

marksilcox commented on code in PR #15558:
URL: https://github.com/apache/pulsar/pull/15558#discussion_r936394736


##########
pulsar-broker/src/main/java/org/apache/pulsar/broker/stats/prometheus/PrometheusMetricStreams.java:
##########
@@ -0,0 +1,74 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pulsar.broker.stats.prometheus;
+
+import io.netty.buffer.ByteBufAllocator;
+import java.util.HashMap;
+import java.util.Map;
+import org.apache.pulsar.common.util.SimpleTextOutputStream;
+
+/**
+ * Helper class to ensure that metrics of the same name are grouped together under the same TYPE header when written.
+ */
+public class PrometheusMetricStreams {
+    private final Map<String, SimpleTextOutputStream> metricStreamMap = new HashMap<>();
+
+    /**
+     * Write the given metric and sample value to the stream. Will write #TYPE header if metric not seen before.
+     * @param metricName name of the metric.
+     * @param value value of the sample
+     * @param labelsAndValuesArray varargs of label and label value
+     */
+    void writeSample(String metricName, Number value, String... labelsAndValuesArray) {
+        SimpleTextOutputStream stream = initGaugeType(metricName);
+        stream.write(metricName).write('{');
+        for (int i = 0; i < labelsAndValuesArray.length; i += 2) {
+            stream.write(labelsAndValuesArray[i]).write("=\"").write(labelsAndValuesArray[i + 1]).write('\"');
+            if (i + 2 != labelsAndValuesArray.length) {
+                stream.write(',');
+            }
+        }
+        stream.write("\"} ").write(value).write(' ').write(System.currentTimeMillis()).write('\n');

Review Comment:
   @asafm @hangc0276 @merlimat @tjiuming 
   Assume removing of timestamp would be under a different PR as this one is specifically about grouping of metrics and removing of timestamp would affect a lot more metrics than the ones this PR touches.



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