Prometheus metrics from collector server

Hi,

I’m looking into javamelody’s collector server and I’d like to know if there’s a way to obtain prometheus metrics from the collector server, similar to how we can query http://host/monitoring?format=prometheus. When I try to call http://collector-host/javamelody?format=prometheus, I get a 500 error java.lang.IllegalStateException: WRITER, (javamelody server 1.81).

The collector server is very useful when you use intermitent applications, and prometheus is a good time-series database to persist the centralized data from the collector server; if this isn’t possible, is there an alternative I could use to expose the javamelody collector server data to grafana?

Thank you for the good work!

[Barbiero]

my testing environment:

• JavaMelody collect server WAR 1.81.0
• Java: AdoptOpenJDK 11

Run as: java -server -jar -Djavamelody.storage-directory=/home/path/to/javamelody/storage javamelody-collector-server-1.81.0.war --httpPort=8090

Two instances of Spring Boot v1.5.22 with javamelody 1.72.0(latest for spring boot 1.5), which are registering themselves under the application name “backend”, running through AdoptOpenJDK 8

URL for javamelody is being accessed as http://localhost:8090/javamelody?format=prometheus&application=backend

Exception thrown:

fev 14, 2020 8:12:36 AM org.eclipse.jetty.util.log.JavaUtilLog warn
ADVERTÊNCIA: /javamelody
java.lang.IllegalStateException: WRITER
	at org.eclipse.jetty.server.Response.getOutputStream(Response.java:691)
	at net.bull.javamelody.internal.web.HtmlController.getWriter(HtmlController.java:131)
	at net.bull.javamelody.internal.web.MonitoringController.getWriter(MonitoringController.java:304)
	at net.bull.javamelody.internal.web.CollectorController.createWriterFromOutputStream(CollectorController.java:512)
	at net.bull.javamelody.internal.web.CollectorController.writeMessage(CollectorController.java:492)
	at net.bull.javamelody.internal.web.CollectorController.doMonitoring(CollectorController.java:178)
	at net.bull.javamelody.CollectorServlet.doGet(CollectorServlet.java:102)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:735)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
	at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:686)
	at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:501)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
	at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:533)
	at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
	at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1086)
	at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:428)
	at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
	at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1020)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
	at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
	at org.eclipse.jetty.server.Server.handle(Server.java:370)
	at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489)
	at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:949)
	at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:1011)
	at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:644)
	at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
	at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:668)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
	at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:834)

In order to register my spring-boot applications with the collector server, I use the following component, which waits until the server is up and running to try to register itself(apologies for pt-BR comments):

@Component
@ConditionalOnProperty(JavaMelodyCollectServerRegistrar.PROPERTY_JAVAMELODY_SERVER_URL)
public class JavaMelodyCollectServerRegistrar implements ApplicationListener<ApplicationReadyEvent> {
	private static final Logger LOGGER = LoggerFactory.getLogger(JavaMelodyCollectServerRegistrar.class);

	static final String PROPERTY_JAVAMELODY_SERVER_URL = "accountfy.javamelody.url";
	private static final String PROPERTY_JAVAMELODY_APPLICATION_NAME = "accountfy.javamelody.applicationName";

	@Value("${" + PROPERTY_JAVAMELODY_SERVER_URL + "}")
	private String javaMelodyUrl;

	@Value("${" + PROPERTY_JAVAMELODY_APPLICATION_NAME + "}")
	private String javaMelodyAppName;

	@Value("${server.port}")
	private String serverPort;

	@Override
	public void onApplicationEvent(ApplicationReadyEvent event) {
		String selfUrl = "";
		try {
			// Para registrar a aplicação no javamelody, precisamos de um ip para
			// comunicação.
			// O que é problemático quando consideramos que no k8s, pods têm IPs
			// intermitentes e variáveis.
			// Por isso vamos perguntar direto para o Java qual o nosso IP.
			String hostAddr = InetAddress.getLocalHost().getHostAddress();
			selfUrl = MessageFormat.format("http://{0}:{1}", hostAddr, serverPort);

			URL collectServerUrl = new URL(javaMelodyUrl);
			URL applicationNodeUrl = new URL(selfUrl);

			LOGGER.info("Registrando servidor \"{}\" de monitoramento com JavaMelody, URL: {} ; URL local: {}",
					javaMelodyAppName, collectServerUrl.toExternalForm(), applicationNodeUrl.toExternalForm());

			net.bull.javamelody.MonitoringFilter.registerApplicationNodeInCollectServer(javaMelodyAppName,
					collectServerUrl, applicationNodeUrl);
		} catch (UnknownHostException e) {
			LOGGER.error("Erro registrando monitoramento: Host desconhecido", e);
		} catch (MalformedURLException ex) {
			LOGGER.error("Erro registrando monitoramento: URL(s) malformada(s). Servidor: {} ; App: {}", javaMelodyUrl,
					selfUrl);
		}
	}

	@PreDestroy
	public void onDestroy() {
		LOGGER.info("Desregistrando do servidor do javamelody");
		try {
			net.bull.javamelody.MonitoringFilter.unregisterApplicationNodeInCollectServer();
		} catch (IOException e) {
			LOGGER.error("Erro ao desregistrar a aplicação do javamelody", e);
		}
	}
}

(in this instance, javaMelodyUrl = “http://localhost:8090” and javaMelodyAppName = “backend”)

Do note that I can access other information just fine. Also, this error occurs when the javamelody collector server is of the same version as the spring-boot counterparts (ie. 1.72.0). Using Chrome v80

Is it possible that the old versions from my servers are having trouble?

[evernat]

Enhancement registered in the issue above. Closing this one.