fix prometheus metric provider bug and add test to cover label scope …

### Motivation
After add label for prometheus metric by apache#2650, it will cause prometheus metric format check failed when no label specified for a statsLogger. The metric list as follow.
```
replication_bookkeeper_client_bookkeeper_client_bookie_watcher_NEW_ENSEMBLE_TIME{success="false",quantile="0.9999", } NaN
```

### Modification
1. add label empty check for `PrometheusTextFormatUtil`
2. add label scope check test cover
3. add prometheus metric regex pattern check in test case

Reviewers: lipenghui <penghui@apache.org>, Andrey Yegorov <None>, Matteo Merli <mmerli@apache.org>, Jia Zhai <zhaijia@apache.org>, Addison Higham <None>, Enrico Olivelli <eolivelli@gmail.com>

This closes apache#2718 from hangc0276/chenhang/fix_bookeeper_metric_bug and squashes the following commits:

8590704 [hangc0276] format code
a6942d4 [chenhang] fix prometheus metric provider bug and add test to cover label scope and metric format check
bb8b1e0 [Andrey Yegorov] Include gradle files into the source artifact for releases, exclude site2/**
732b6cf [Andrey Yegorov] [maven-release-plugin] prepare for next development iteration
b0d9f10 [Andrey Yegorov] [maven-release-plugin] prepare branch branch-4.14
8dc108b [Matteo Merli] y
73e22ca [Don Inghram] ISSUE2620: RocksDB log path configurable
034ef85 [Shoothzj] Fix logger member not correct; (apache#2605)
b824a60 [hangc0276] fix always select the same region set bug for RegionAwareEnsemblePlacementPolicy (apache#2658)
683ad45 [Matteo Merli] Allow to attach labels to metrics (apache#2650)
8091096 [Matteo Merli] Allow to bypass journal for writes (apache#2401)
63867a9 [Matteo Merli] Impose a memory limit on the bookie journal (apache#2710)
87579b0 [Matteo Merli] Read entry error should print lastAddConfirmed in the log (apache#2707)

Author: hangc0276

bookkeeper-stats-providers/prometheus-metrics-provider/src/main/java/org/apache/bookkeeper/stats/prometheus/PrometheusTextFormatUtil.java

@@ -139,25 +139,34 @@ private static void writeQuantile(Writer w, DataSketchesOpStatsLogger opStat, St
         w.append(name)
                 .append("{success=\"").append(success.toString())
                 .append("\",quantile=\"").append(Double.toString(quantile))
-                .append("\", ");
-        writeLabelsNoBraces(w, opStat.getLabels());
+                .append("\"");
+        if (!opStat.getLabels().isEmpty()) {
+            w.append(", ");
+            writeLabelsNoBraces(w, opStat.getLabels());
+        }
         w.append("} ")
                 .append(Double.toString(opStat.getQuantileValue(success, quantile))).append('\n');
     }
 
     private static void writeCount(Writer w, DataSketchesOpStatsLogger opStat, String name, Boolean success)
             throws IOException {
-        w.append(name).append("_count{success=\"").append(success.toString()).append("\", ");
-        writeLabelsNoBraces(w, opStat.getLabels());
-        w.append("\"} ")
+        w.append(name).append("_count{success=\"").append(success.toString()).append("\"");
+        if (!opStat.getLabels().isEmpty()) {
+            w.append(", ");
+            writeLabelsNoBraces(w, opStat.getLabels());
+        }
+        w.append("} ")
                 .append(Long.toString(opStat.getCount(success))).append('\n');
     }
 
     private static void writeSum(Writer w, DataSketchesOpStatsLogger opStat, String name, Boolean success)
             throws IOException {
-        w.append(name).append("_sum{success=\"").append(success.toString()).append("\", ");
-        writeLabelsNoBraces(w, opStat.getLabels());
-        w.append("\"} ")
+        w.append(name).append("_sum{success=\"").append(success.toString()).append("\"");
+        if (!opStat.getLabels().isEmpty()) {
+            w.append(", ");
+            writeLabelsNoBraces(w, opStat.getLabels());
+        }
+        w.append("} ")
                 .append(Double.toString(opStat.getSum(success))).append('\n');
     }
 

bookkeeper-stats-providers/prometheus-metrics-provider/src/test/java/org/apache/bookkeeper/stats/prometheus/TestPrometheusFormatter.java

@@ -43,7 +43,7 @@
  */
 public class TestPrometheusFormatter {
 
-    @Test
+    @Test(timeout = 30000)
     public void testStatsOutput() throws Exception {
         PrometheusMetricsProvider provider = new PrometheusMetricsProvider();
         StatsLogger statsLogger = provider.getStatsLogger("test");
@@ -56,6 +56,12 @@ public void testStatsOutput() throws Exception {
         opStats.registerSuccessfulEvent(10, TimeUnit.MILLISECONDS);
         opStats.registerSuccessfulEvent(5, TimeUnit.MILLISECONDS);
 
+        OpStatsLogger opStats1 = statsLogger.scopeLabel("test_label", "test_value")
+                .getOpStatsLogger("op_label");
+        opStats1.registerSuccessfulEvent(10, TimeUnit.MILLISECONDS);
+        opStats1.registerSuccessfulEvent(5, TimeUnit.MILLISECONDS);
+        opStats1.registerFailedEvent(1, TimeUnit.MILLISECONDS);
+
         provider.rotateLatencyCollection();
 
         StringWriter writer = new StringWriter();
@@ -112,6 +118,52 @@ public void testStatsOutput() throws Exception {
         }
 
         assertTrue(found);
+
+        // test_op_label_sum
+        cm = (List<Metric>) metrics.get("test_op_label_sum");
+        assertEquals(2, cm.size());
+        m = cm.get(0);
+        assertEquals(2, m.tags.size());
+        assertEquals(1.0, m.value, 0.0);
+        assertEquals("false", m.tags.get("success"));
+        assertEquals("test_value", m.tags.get("test_label"));
+
+        m = cm.get(1);
+        assertEquals(15.0, m.value, 0.0);
+        assertEquals(2, m.tags.size());
+        assertEquals("true", m.tags.get("success"));
+        assertEquals("test_value", m.tags.get("test_label"));
+
+        // test_op_label_count
+        cm = (List<Metric>) metrics.get("test_op_label_count");
+        assertEquals(2, cm.size());
+        m = cm.get(0);
+        assertEquals(1, m.value, 0.0);
+        assertEquals(2, m.tags.size());
+        assertEquals("false", m.tags.get("success"));
+        assertEquals("test_value", m.tags.get("test_label"));
+
+        m = cm.get(1);
+        assertEquals(2.0, m.value, 0.0);
+        assertEquals(2, m.tags.size());
+        assertEquals("true", m.tags.get("success"));
+        assertEquals("test_value", m.tags.get("test_label"));
+
+        // Latency
+        cm = (List<Metric>) metrics.get("test_op_label");
+        assertEquals(14, cm.size());
+
+        found = false;
+        for (Metric mt : cm) {
+            if ("true".equals(mt.tags.get("success"))
+                    && "test_value".equals(mt.tags.get("test_label"))
+                    && "1.0".equals(mt.tags.get("quantile"))) {
+                assertEquals(10.0, mt.value, 0.0);
+                found = true;
+            }
+        }
+
+        assertTrue(found);
     }
 
     /**
@@ -126,6 +178,8 @@ private static Multimap<String, Metric> parseMetrics(String metrics) {
         // pulsar_subscriptions_count{cluster="standalone", namespace="sample/standalone/ns1",
         // topic="persistent://sample/standalone/ns1/test-2"} 0.0 1517945780897
         Pattern pattern = Pattern.compile("^(\\w+)(\\{([^\\}]+)\\})?\\s(-?[\\d\\w\\.]+)(\\s(\\d+))?$");
+        Pattern formatPattern = Pattern.compile("^(\\w+)(\\{(\\w+=[\\\"\\.\\w]+(,\\s?\\w+=[\\\"\\.\\w]+)*)\\})?"
+                + "\\s(-?[\\d\\w\\.]+)(\\s(\\d+))?$");
         Pattern tagsPattern = Pattern.compile("(\\w+)=\"([^\"]+)\"(,\\s?)?");
 
         Splitter.on("\n").split(metrics).forEach(line -> {
@@ -135,6 +189,7 @@ private static Multimap<String, Metric> parseMetrics(String metrics) {
 
             System.err.println("LINE: '" + line + "'");
             Matcher matcher = pattern.matcher(line);
+            Matcher formatMatcher = formatPattern.matcher(line);
             System.err.println("Matches: " + matcher.matches());
             System.err.println(matcher);
 
@@ -144,6 +199,7 @@ private static Multimap<String, Metric> parseMetrics(String metrics) {
             }
 
             checkArgument(matcher.matches());
+            checkArgument(formatMatcher.matches());
             String name = matcher.group(1);
 
             Metric m = new Metric();