File to trigger JMXFetch exit

Trigger JMXFetch exit when a specified file is created.
Usage: `--exit_file_location` or `-e` with the absolute path of the trigger
file to watch.

Author: yannmh

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

@@ -136,6 +136,12 @@ private static void clearInstances(List<Instance> instances) {
     void start() {
         // Main Loop that will periodically collect metrics from the JMX Server
         while (true) {
+            // Exit on exit file trigger
+            if (appConfig.getExitWatcher().shouldExit()){
+                LOGGER.info("Exit file detected: stopping JMXFetch.");
+                System.exit(0);
+            }
+
             long start = System.currentTimeMillis();
             if (instances.size() > 0) {
                 doIteration();
@@ -288,7 +294,7 @@ private void reportStatus(AppConfig appConfig, Reporter reporter, Instance insta
                                   instance.getServiceCheckTags());
 
         appConfig.getStatus().addInstanceStats(checkName, instance.getName(),
-                                               metricCount, reporter.getServiceCheckCount(checkName), 
+                                               metricCount, reporter.getServiceCheckCount(checkName),
                                                message, status);
         reporter.resetServiceCheckCount(checkName);
     }

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

@@ -2,6 +2,7 @@
 import java.util.Arrays;
 import java.util.List;
 
+import org.datadog.jmxfetch.converter.ExitWatcherConverter;
 import org.datadog.jmxfetch.converter.ReporterConverter;
 import org.datadog.jmxfetch.converter.StatusConverter;
 import org.datadog.jmxfetch.reporter.ConsoleReporter;
@@ -71,6 +72,12 @@ class AppConfig {
             required = false)
     private Status status = new Status();
 
+    @Parameter(names = {"--exit_file_location", "-e"},
+            description = "Absolute path of the trigger file to watch to exit. (default to null = no exit on file)",
+            converter = ExitWatcherConverter.class,
+            required = false)
+    private ExitWatcher exitWatcher = new ExitWatcher();
+
     @Parameter(description = "Action to take, should be in [help, collect, " +
             "list_everything, list_collected_attributes, list_matching_attributes, " +
             "list_not_matching_attributes, list_limited_attributes]",
@@ -93,6 +100,10 @@ public Status getStatus() {
         return status;
     }
 
+    public ExitWatcher getExitWatcher(){
+    	return exitWatcher;
+    }
+
     public int getCheckPeriod() {
         return checkPeriod;
     }

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

@@ -0,0 +1,37 @@
+package org.datadog.jmxfetch;
+
+import java.io.File;
+
+public class ExitWatcher {
+
+    private String exitFileLocation;
+    private boolean isEnabled;
+
+    public ExitWatcher(){
+        this(null);
+    }
+
+    public ExitWatcher(String exitFileLocation) {
+        this.exitFileLocation = exitFileLocation;
+        this.isEnabled = this.exitFileLocation != null;
+    }
+
+    public String getExitFileLocation() {
+        return exitFileLocation;
+    }
+
+    public boolean isEnabled() {
+        return isEnabled;
+    }
+
+    public boolean shouldExit(){
+        if (isEnabled()) {
+            File f = new File(exitFileLocation);
+            if(f.exists() && !f.isDirectory()) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+}

src/main/java/org/datadog/jmxfetch/converter/ExitWatcherConverter.java

@@ -0,0 +1,11 @@
+package org.datadog.jmxfetch.converter;
+
+import com.beust.jcommander.IStringConverter;
+import org.datadog.jmxfetch.ExitWatcher;
+
+public class ExitWatcherConverter implements IStringConverter<ExitWatcher> {
+
+    public ExitWatcher convert(String value) {
+        return new ExitWatcher(value);
+    }
+}

src/test/java/org/datadog/jmxfetch/TestApp.java

@@ -13,6 +13,7 @@
 import javax.management.MBeanServer;
 import javax.management.ObjectName;
 
+import java.io.File;
 import java.lang.management.ManagementFactory;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -401,12 +402,12 @@ public void testServiceCheckCounter() throws Exception {
 
         // Let's check that the counter is null
         assertEquals(0, repo.getServiceCheckCount("jmx"));
-        
+
         // Let's put a service check in the pipeline (we cannot call doIteration()
-        // here unfortunately because it would call reportStatus which will flush 
-        // the count to the jmx_status.yaml file and reset the counter. 
+        // here unfortunately because it would call reportStatus which will flush
+        // the count to the jmx_status.yaml file and reset the counter.
         repo.sendServiceCheck("jmx", Status.STATUS_OK, "This is a test", "jmx_test_instance", null);
-        
+
         // Let's check that the counter has been updated
         assertEquals(1, repo.getServiceCheckCount("jmx"));
 
@@ -430,6 +431,21 @@ public void testPrefixFormatter() throws Exception {
             assertEquals(data[i][1], Reporter.formatServiceCheckPrefix(data[i][0]));
     }
 
+    @Test
+    public void testExitWatcher() throws Exception {
+        // Test the ExitWatcher logic
+
+        // Create a temp file
+        File temp = File.createTempFile("exit-jmxfetch-file-name", ".tmp");
+        temp.deleteOnExit();
+
+        ExitWatcher exitWatcher = new ExitWatcher(temp.getAbsolutePath());
+        assertTrue(exitWatcher.shouldExit());
+
+        temp.delete();
+        assertFalse(exitWatcher.shouldExit());
+    }
+
     @Test
     public void testApp() throws Exception {
         // We expose a few metrics through JMX

src/test/java/org/datadog/jmxfetch/TestParsingJCommander.java

@@ -21,7 +21,8 @@ public class TestParsingJCommander {
     private static final String REPORTER_CONSOLE = "console";
     private static final String SINGLE_CHECK = "jmx.yaml";
     private static final List<String> MULTI_CHECK = Arrays.asList("jmx.yaml", "jmx-2.yaml");
-    private static final String STATUS_LOCATION = "/status/loaction";
+    private static final String STATUS_LOCATION = "/status/status_location";
+    private static final String EXIT_FILE_LOCATION = "/status/exit_locationt";
 
     private static AppConfig testCommand(String[] params) throws ParameterException {
         AppConfig appConfig = new AppConfig();
@@ -235,6 +236,21 @@ public void testParsingStatus() {
         assertTrue(appConfig.getStatus().isEnabled());
     }
 
+    @Test
+    public void testParsingExitWatcher() {
+        String[] params = new String[]{
+                "--reporter", REPORTER_CONSOLE,
+                "--check", SINGLE_CHECK,
+                "--conf_directory", CONF_DIR,
+                "--exit_file_location", EXIT_FILE_LOCATION,
+                AppConfig.ACTION_COLLECT
+        };
+        AppConfig appConfig = testCommand(params);
+        assertNotNull(appConfig.getExitWatcher());
+        assertEquals(EXIT_FILE_LOCATION, appConfig.getExitWatcher().getExitFileLocation());
+        assertTrue(appConfig.getExitWatcher().isEnabled());
+    }
+
     @Test
     public void testParsingAction() {
         // Positive cases