Fix tags concatenation in custom metric (#77)

Co-authored-by: vmakarevich <[email protected]>

Author: VitoMakarevich

src/main/java/com/datadoghq/datadog_lambda_java/MetricWriter.java

@@ -3,6 +3,8 @@
 import com.timgroup.statsd.NonBlockingStatsDClientBuilder;
 import com.timgroup.statsd.StatsDClient;
 
+import java.util.stream.Collectors;
+
 abstract class MetricWriter {
     private static MetricWriter IMPL;
     public static synchronized MetricWriter getMetricWriterImpl(){
@@ -59,14 +61,17 @@ public ExtensionMetricWriter() {
     @Override
     public void write(CustomMetric cm){
         if(null != client) {
-            StringBuilder tagsSb = new StringBuilder();
+            String tags = "";
             if (cm.getTags() != null) {
-                cm.getTags().forEach((k, val) ->
-                        tagsSb.append(k.toLowerCase())
-                                .append(":")
-                                .append(val.toString().toLowerCase()));
+                tags = cm
+                    .getTags()
+                    .entrySet()
+                    .stream()
+                    .map(
+                        entry -> entry.getKey().toLowerCase() + ":" + entry.getValue().toString().toLowerCase()
+                    ).collect(Collectors.joining(","));
             }
-            client.distribution(cm.getName(), cm.getValue(), tagsSb.toString());
+            client.distribution(cm.getName(), cm.getValue(), tags);
         } else {
             DDLogger.getLoggerImpl().error("Could not write the metric because the client is null");
         }

src/test/java/com/datadoghq/datadog_lambda_java/CustomMetricTest.java

@@ -90,7 +90,7 @@ public void run() {
                 if (null == text[0] || text[0].equals("notYetReceived")) {
                     Thread.sleep(1000);
                 } else {
-                    assertTrue(text[0].startsWith("foo:24.3|d|#firsttag:firsttagvaluesecondtag:100.34"));
+                    assertTrue(text[0].startsWith("foo:24.3|d|#firsttag:firsttagvalue,secondtag:100.34"));
                     break;
                 }
             }