Prevent remote JMX monitoring when started in agent mode (#675)

Signed-off-by: Fabian Stäber <fabian@fstab.de>
prometheus · Jan 16, 2022 · d2d8a22 · d2d8a22
1 parent 5c2c921
commit d2d8a22
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Showing 3 changed files with 22 additions and 19 deletions.
diff --git a/collector/src/main/java/io/prometheus/jmx/JmxCollector.java b/collector/src/main/java/io/prometheus/jmx/JmxCollector.java
@@ -29,7 +29,12 @@
 
 public class JmxCollector extends Collector implements Collector.Describable {
 
-    private final boolean jmxUrlRequired;
+    public enum Mode {
+      AGENT,
+      STANDALONE
+    }
+
+    private final Mode mode;
 
     static final Counter configReloadSuccess = Counter.build()
       .name("jmx_config_reload_success_total")
@@ -77,36 +82,34 @@ private static class Config {
     private final JmxMBeanPropertyCache jmxMBeanPropertyCache = new JmxMBeanPropertyCache();
 
     public JmxCollector(File in) throws IOException, MalformedObjectNameException {
-        this(in, false);
+        this(in, null);
     }
 
-    public JmxCollector(File in, boolean jmxUrlRequired) throws IOException, MalformedObjectNameException {
+    public JmxCollector(File in, Mode mode) throws IOException, MalformedObjectNameException {
         configFile = in;
-        this.jmxUrlRequired = jmxUrlRequired;
+        this.mode = mode;
         config = loadConfig((Map<String, Object>)new Yaml().load(new FileReader(in)));
         config.lastUpdate = configFile.lastModified();
-        exitIfJmxUrlMissing();
+        exitOnConfigError();
     }
 
     public JmxCollector(String yamlConfig) throws MalformedObjectNameException {
         config = loadConfig((Map<String, Object>)new Yaml().load(yamlConfig));
-        jmxUrlRequired = false;
+        mode = null;
     }
 
     public JmxCollector(InputStream inputStream) throws MalformedObjectNameException {
         config = loadConfig((Map<String, Object>)new Yaml().load(inputStream));
-        jmxUrlRequired = false;
+        mode = null;
     }
 
-    private void exitIfJmxUrlMissing() {
-        // If the jmxUrl configuration is missing, the JmxScraper implicitly monitors the JVM it runs in.
-        // This is good if the JmxCollector is used in the Java agent, because the Java agent should monitor the JVM
-        // it is attached to.
-        // However, if the JmxCollector is used in the WebServer, the intention is that it monitors another process.
-        // If the jmxUrl configuration is missing, it should not silently ignore this and start monitoring itself.
-        // The WebServer sets jmxUrlRequired to true so that we can verify this and terminate with a proper error message.
-        if (jmxUrlRequired && config.jmxUrl.isEmpty()) {
-            LOGGER.severe("configuration error: one of jmxUrl or hostPort is required");
+    private void exitOnConfigError() {
+        if (mode == Mode.AGENT && !config.jmxUrl.isEmpty()) {
+            LOGGER.severe("Configuration error: When running jmx_exporter as a Java agent, you must not configure 'jmxUrl' or 'hostPort' because you don't want to monitor a remote JVM.");
+            System.exit(-1);
+        }
+        if (mode == Mode.STANDALONE && config.jmxUrl.isEmpty()) {
+            LOGGER.severe("Configuration error: When running jmx_exporter in standalone mode (using jmx_prometheus_httpserver-*.jar) you must configure 'jmxUrl' or 'hostPort'.");
             System.exit(-1);
         }
     }
@@ -141,7 +144,7 @@ private synchronized Config getLatestConfig() {
               reloadConfig();
           }
       }
-      exitIfJmxUrlMissing();
+      exitOnConfigError();
       return config;
     }
 

diff --git a/jmx_prometheus_httpserver/src/main/java/io/prometheus/jmx/WebServer.java b/jmx_prometheus_httpserver/src/main/java/io/prometheus/jmx/WebServer.java
@@ -27,7 +27,7 @@ public static void main(String[] args) throws Exception {
      }
 
      new BuildInfoCollector().register();
-     new JmxCollector(new File(args[1]), true).register();
+     new JmxCollector(new File(args[1]), JmxCollector.Mode.STANDALONE).register();
      new HTTPServer(socket, CollectorRegistry.defaultRegistry);
    }
 }
diff --git a/jmx_prometheus_javaagent_java6/src/main/java/io/prometheus/jmx/JavaAgent.java b/jmx_prometheus_javaagent_java6/src/main/java/io/prometheus/jmx/JavaAgent.java
@@ -26,7 +26,7 @@ public static void premain(String agentArgument, Instrumentation instrumentation
             Config config = parseConfig(agentArgument, host);
 
             new BuildInfoCollector().register();
-            new JmxCollector(new File(config.file)).register();
+            new JmxCollector(new File(config.file), JmxCollector.Mode.AGENT).register();
             DefaultExports.initialize();
             server = new HTTPServer(config.socket, CollectorRegistry.defaultRegistry, true);
         }