Make JMXFetch know about its version number

pom.xml

@@ -164,6 +164,12 @@
         <url>[email protected]:Datadog/jmxfetch.git</url>
     </scm>
     <build>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
         <plugins>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>

src/main/java/org/datadog/jmxfetch/App.java

@@ -38,6 +38,7 @@
 import java.util.ListIterator;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Properties;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
@@ -118,15 +119,34 @@ public static void main(String[] args) {
             System.exit(1);
         }
 
+        // Display the version and quit
+        if (config.isVersion() || AppConfig.ACTION_HELP.equals(config.getAction())) {
+            JCommander.getConsole().println("JMX Fetch " + getVersion());
+            System.exit(0);
+        }
+
         // Display the help and quit
-        if (config.isHelp() || config.getAction().equals(AppConfig.ACTION_HELP)) {
+        if (config.isHelp() || AppConfig.ACTION_HELP.equals(config.getAction())) {
             commander.usage();
             System.exit(0);
         }
 
         System.exit(run(config));
     }
 
+    /**  Returns our own version number. */
+    public static String getVersion() {
+        try {
+            final Properties properties = new Properties();
+            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+            properties.load(classLoader.getResourceAsStream("project.properties"));
+            return properties.getProperty("version");
+        } catch (IOException e) {
+            e.printStackTrace();
+            return "?.?.?";
+        }
+    }
+
     /**
      * Main entry point of JMXFetch that returns integer on exit instead of calling {@code
      * System#exit}.
@@ -164,7 +184,7 @@ public static int run(AppConfig config) {
         // Set up the shutdown hook to properly close resources
         attachShutdownHook();
 
-        LOGGER.info("JMX Fetch has started");
+        LOGGER.info("JMX Fetch " + getVersion() + " has started");
 
         // set up the config status
         config.updateStatus();

src/main/java/org/datadog/jmxfetch/AppConfig.java

@@ -30,6 +30,7 @@ public class AppConfig {
     public static final String ACTION_LIST_NOT_MATCHING = "list_not_matching_attributes";
     public static final String ACTION_LIST_LIMITED = "list_limited_attributes";
     public static final String ACTION_HELP = "help";
+    public static final String ACTION_VERSION = "version";
     public static final HashSet<String> ACTIONS =
             new HashSet<String>(
                     Arrays.asList(
@@ -40,10 +41,10 @@ public class AppConfig {
                             ACTION_LIST_NOT_MATCHING,
                             ACTION_LIST_LIMITED,
                             ACTION_HELP,
+                            ACTION_VERSION,
                             ACTION_LIST_JVMS));
 
     private static final String AD_WIN_PIPE_PATH = "\\\\.\\pipe\\";
-    private static final String AD_LEGACY_PIPE_NAME = "dd-service_discovery";
     private static final String AD_PIPE_NAME = "dd-auto_discovery";
     private static final String AD_LAUNCH_FILE = "jmx.launch";
 
@@ -57,6 +58,12 @@ public class AppConfig {
             help = true)
     private boolean help;
 
+    @Parameter(
+            names = {"--version", "-v"},
+            description = "Display the version number and exit",
+            help = true)
+    private boolean version;
+
     @Parameter(
             names = {"--log_level", "-L"},
             description = "Level of verbosity",
@@ -216,7 +223,11 @@ public String getStatusLocation() {
         return this.statusLocation;
     }
 
+    /** Returns the action parameter of the app if any, or null otherwise. */
     public String getAction() {
+        if (this.action == null || this.action.isEmpty()) {
+            return null;
+        }
         return this.action.get(0);
     }
 
@@ -228,6 +239,10 @@ public boolean isHelp() {
         return help;
     }
 
+    public boolean isVersion() {
+        return version;
+    }
+
     public Status getStatus() {
         return status;
     }

src/main/resources/project.properties

@@ -0,0 +1 @@
+version=${project.version}