add test mode with CLI args

Author: SylvainJuge

jmx-scraper/src/main/java/io/opentelemetry/contrib/jmxscraper/JmxScraper.java

@@ -19,6 +19,7 @@
 import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -34,6 +35,7 @@
 public class JmxScraper {
   private static final Logger logger = Logger.getLogger(JmxScraper.class.getName());
   private static final String CONFIG_ARG = "-config";
+  private static final String TEST_ARG = "-test";
 
   private final JmxConnectorBuilder client;
   private final JmxMetricInsight service;
@@ -52,8 +54,11 @@ public static void main(String[] args) {
     // set log format
     System.setProperty("java.util.logging.SimpleFormatter.format", "%1$tF %1$tT %4$s %5$s%n");
 
+    List<String> effectiveArgs = new ArrayList<>(Arrays.asList(args));
+    boolean testMode = effectiveArgs.remove(TEST_ARG);
+
     try {
-      Properties argsConfig = parseArgs(Arrays.asList(args));
+      Properties argsConfig = parseArgsConfig(effectiveArgs);
       propagateToSystemProperties(argsConfig);
 
       // auto-configure and register SDK
@@ -78,16 +83,21 @@ public static void main(String[] args) {
       Optional.ofNullable(scraperConfig.getUsername()).ifPresent(connectorBuilder::withUser);
       Optional.ofNullable(scraperConfig.getPassword()).ifPresent(connectorBuilder::withPassword);
 
-      JmxScraper jmxScraper = new JmxScraper(connectorBuilder, service, scraperConfig);
-      jmxScraper.start();
+      if(testMode) {
+        System.exit(testConnection(connectorBuilder) ? 0 : 1);
+      } else {
+        JmxScraper jmxScraper = new JmxScraper(connectorBuilder, service, scraperConfig);
+        jmxScraper.start();
+      }
     } catch (ConfigurationException e) {
       logger.log(Level.SEVERE, "invalid configuration ", e);
       System.exit(1);
     } catch (InvalidArgumentException e) {
       logger.log(Level.SEVERE, "invalid configuration provided through arguments", e);
       logger.info(
-          "Usage: java -jar <path_to_jmxscraper.jar> "
-              + "-config <path_to_config.properties or - for stdin>");
+          "Usage: java -jar <path_to_jmxscraper.jar> [-test] [-config <conf>]");
+      logger.info("  -test           test JMX connection with provided configuration and exit");
+      logger.info("  -config <conf>  provide configuration, where <conf> is - for stdin, or <path_to_config.properties>" );
       System.exit(1);
     } catch (IOException e) {
       logger.log(Level.SEVERE, "Unable to connect ", e);
@@ -98,6 +108,24 @@ public static void main(String[] args) {
     }
   }
 
+  private static boolean testConnection(JmxConnectorBuilder connectorBuilder) {
+    try (JMXConnector connector = connectorBuilder.build()) {
+
+      MBeanServerConnection connection = connector.getMBeanServerConnection();
+      Integer mbeanCount = connection.getMBeanCount();
+      if (mbeanCount > 0) {
+        logger.log(Level.INFO, "JMX connection test OK");
+        return true;
+      } else {
+        logger.log(Level.SEVERE, "JMX connection test ERROR");
+        return false;
+      }
+    } catch (IOException e) {
+      logger.log(Level.SEVERE, "JMX connection test ERROR", e);
+      return false;
+    }
+  }
+
   // package private for testing
   static void propagateToSystemProperties(Properties properties) {
     for (Map.Entry<Object, Object> entry : properties.entrySet()) {
@@ -116,7 +144,7 @@ static void propagateToSystemProperties(Properties properties) {
    *
    * @param args application commandline arguments
    */
-  static Properties parseArgs(List<String> args) throws InvalidArgumentException {
+  static Properties parseArgsConfig(List<String> args) throws InvalidArgumentException {
 
     if (args.isEmpty()) {
       // empty properties from stdin or external file

jmx-scraper/src/test/java/io/opentelemetry/contrib/jmxscraper/JmxScraperTest.java

@@ -30,8 +30,8 @@ void shouldThrowExceptionWhenInvalidCommandLineArgsProvided() {
 
   @Test
   void emptyArgumentsAllowed() throws InvalidArgumentException {
-    assertThat(JmxScraper.parseArgs(Collections.emptyList()))
-        .describedAs("empty arguments allowed to use JVM properties")
+    assertThat(JmxScraper.parseArgsConfig(Collections.emptyList()))
+        .describedAs("empty config allowed to use JVM properties")
         .isEmpty();
   }
 
@@ -41,7 +41,7 @@ void shouldThrowExceptionWhenMissingProperties() {
   }
 
   private static void testInvalidArguments(String... args) {
-    assertThatThrownBy(() -> JmxScraper.parseArgs(Arrays.asList(args)))
+    assertThatThrownBy(() -> JmxScraper.parseArgsConfig(Arrays.asList(args)))
         .isInstanceOf(InvalidArgumentException.class);
   }
 
@@ -53,7 +53,7 @@ void shouldCreateConfig_propertiesLoadedFromFile() throws InvalidArgumentExcepti
     List<String> args = Arrays.asList("-config", filePath);
 
     // When
-    Properties parsedConfig = JmxScraper.parseArgs(args);
+    Properties parsedConfig = JmxScraper.parseArgsConfig(args);
     JmxScraperConfig config = JmxScraperConfig.fromConfig(TestUtil.configProperties(parsedConfig));
 
     // Then
@@ -72,7 +72,7 @@ void shouldCreateConfig_propertiesLoadedFromStdIn() throws InvalidArgumentExcept
       List<String> args = Arrays.asList("-config", "-");
 
       // When
-      Properties parsedConfig = JmxScraper.parseArgs(args);
+      Properties parsedConfig = JmxScraper.parseArgsConfig(args);
       JmxScraperConfig config =
           JmxScraperConfig.fromConfig(TestUtil.configProperties(parsedConfig));