Adapt Version metric to a more flexible pattern

components/proxy/src/main/java/com/hotels/styx/Version.java

@@ -23,15 +23,21 @@
 import java.io.InputStreamReader;
 import java.io.Reader;
 import java.util.Objects;
+import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import static com.google.common.base.Objects.toStringHelper;
+import static java.lang.Integer.parseInt;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
  * Version of the current styx server.
  */
 public class Version {
     private static final Logger LOG = getLogger(Version.class);
+    private static final Pattern VERSION_FORMAT = Pattern.compile("(\\d+)\\.(\\d+)[-.](\\d+).*");
+
 
     private final String releaseTag;
 
@@ -74,7 +80,28 @@ public String releaseVersion() {
         return releaseTag.substring(firstDot + 1);
     }
 
+    public Optional<Integer> buildNumber() {
+        String releaseVersion = releaseVersion();
+        Optional<String> buildNumberAsString = extractFinalInt(releaseVersion);
+        return buildNumberAsString.flatMap(this::parseInteger);
+    }
+
+    private Optional<String> extractFinalInt(String versionString) {
+        Matcher m = VERSION_FORMAT.matcher(versionString);
+        if (!m.matches()) {
+            return Optional.empty();
+        } else {
+            return Optional.of(m.group(3));
+        }
+    }
 
+    private Optional<Integer> parseInteger(String string) {
+        try {
+            return Optional.of(parseInt(string));
+        } catch (NumberFormatException e) {
+            return Optional.empty();
+        }
+    }
 
     @Override
     public String toString() {

components/proxy/src/main/java/com/hotels/styx/proxy/ProxyConnectorFactory.java

@@ -71,7 +71,7 @@ class ProxyConnectorFactory implements ServerConnectorFactory {
                           MetricRegistry metrics,
                           HttpErrorStatusListener errorStatusListener,
                           String unwiseCharacters,
-                          ResponseEnhancer responseEnhancer, 
+                          ResponseEnhancer responseEnhancer,
                           boolean requestTracking) {
         this.serverConfig = requireNonNull(serverConfig);
         this.metrics = requireNonNull(metrics);

components/proxy/src/main/java/com/hotels/styx/startup/CoreMetrics.java

@@ -30,6 +30,7 @@
 
 import java.lang.management.RuntimeMXBean;
 import java.time.Duration;
+import java.util.Optional;
 
 import static java.lang.String.format;
 import static java.lang.management.ManagementFactory.getPlatformMBeanServer;
@@ -46,13 +47,23 @@ private CoreMetrics() {
     }
 
     public static void registerCoreMetrics(Version buildInfo, MetricRegistry metrics) {
-        registerVersionMetric(metrics, buildInfo.releaseVersion());
+        registerVersionMetric(buildInfo, metrics);
         registerJvmMetrics(metrics);
         metrics.register("os", new OperatingSystemMetricSet());
     }
 
-    private static void registerVersionMetric(MetricRegistry metricRegistry, String versionNumber) {
-        Gauge<String> versionGauge = () -> versionNumber;
+    private static void registerVersionMetric(Version buildInfo, MetricRegistry metrics) {
+        Optional<Integer> buildNumber = buildInfo.buildNumber();
+
+        if (buildNumber.isPresent()) {
+            registerVersionMetric(metrics, buildNumber.get());
+        } else {
+            LOG.warn("Could not acquire build number from release version: {}", buildInfo);
+        }
+    }
+
+    private static void registerVersionMetric(MetricRegistry metricRegistry, Integer buildNumber) {
+        Gauge<Integer> versionGauge = () -> buildNumber;
 
         metricRegistry.scope("styx").register("version.buildnumber", versionGauge);
     }

components/proxy/src/test/java/com/hotels/styx/VersionTest.java

@@ -17,9 +17,10 @@
 
 import org.testng.annotations.Test;
 
+import java.util.Optional;
+
 import static com.hotels.styx.Version.newVersion;
 import static com.hotels.styx.Version.readVersionFrom;
-import static com.hotels.styx.support.matchers.IsOptional.isPresent;
 import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -30,11 +31,12 @@ public class VersionTest {
     public void readBuildInfoFromTheSpecifiedPath() {
         Version version = readVersionFrom("/version.json");
         assertThat(version.releaseTag(), containsString("STYX"));
-        assertThat(version.releaseVersion(), is("0.0-125"));
+        assertThat(version.buildNumber(), is(Optional.of(125)));
     }
 
     @Test
     public void willCreateAnEmptyBuildInfoIfFailsToRead() {
         assertThat(readVersionFrom("version.txt"), is(newVersion()));
     }
+
 }

components/proxy/src/test/java/com/hotels/styx/startup/CoreMetricsTest.java

@@ -37,7 +37,7 @@ public void registersVersionMetric() {
 
         Gauge gauge = metrics.getGauges().get("styx.version.buildnumber");
 
-        assertThat(gauge.getValue(), is("1.2.3"));
+        assertThat(gauge.getValue(), is(3));
     }
 
     @Test