How to check programmatically if Zookeeper is running? - java

I am using CuratorFramework (I'm still a newbie) in order to connect to a Zookeeper instance. I would like to import a configuration but before that I would like to test that my program is able to connect to Zookeeper. So far I have something like that:
public Boolean zookeeperRunning() {
CuratorFramework curatorFramework =
CuratorFrameworkFactory.newClient(zookeeperConn, new RetryOneTime(1));
curatorFramework.start();
CuratorZookeeperClient zkClient = curatorFramework.getZookeeperClient();
return zkClient.isConnected();
}
I've already started ZooKeeper on my local machine and I checked the connection with zkCli and the client is able to connect to it. The zookeeperCon variable is set to "127.0.0.1:2181" (I tried with localhost:2181 as well). The problem is that the above method always returns false despite the fact that zkServer is up n running. Most probably, the syntax is not correct but I could not find a solution online. Could you please help me with why the above code cannot find the zkServer which is up and running?

You can use a builder to create a configured client and setup a listener to monitor your zk instance's state:
// start client
client = CuratorFrameworkFactory.builder()
.connectString("localhost:2181")
.retryPolicy(new ExponentialBackoffRetry(1000, 3))
.namespace("heavenize")
.build();
client.getConnectionStateListenable().addListener(new ConnectionStateListener() {
#Override
public void stateChanged(CuratorFramework client, ConnectionState newState)
{
log.info("State changed to: "+newState);
}
});
}

You should first connect to zookeeper after you get the zkClient, if success, then check the isConnected status. Demo code below(Refer: here):
private static CuratorFramework buildConnection(String url) {
CuratorFramework curatorFramework = CuratorFrameworkFactory.newClient(url, new ExponentialBackoffRetry(100, 6));
// start connection
curatorFramework.start();
// wait 3 second to establish connect
try {
curatorFramework.blockUntilConnected(3, TimeUnit.SECONDS);
if (curatorFramework.getZookeeperClient().isConnected()) {
return curatorFramework.usingNamespace("");
}
} catch (InterruptedException ignored) {
Thread.currentThread().interrupt();
}
// fail situation
curatorFramework.close();
throw new RuntimeException("failed to connect to zookeeper service : " + url);
}

you should connect to zookeeper server then check it. for example:
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.test.TestingServer;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
import static org.junit.Assert.assertTrue;
public class ZkClientTest {
TestingServer zkServer;
#Before
public void startZookeeper() throws Exception {
zkServer = new TestingServer(2181);
zkServer.start();
}
#After
public void stopZookeeper() throws IOException {
zkServer.stop();
}
#Test
public void should_connect_to_zookeeper_server_when_config_use_default_localhost_2181()
throws InterruptedException {
CuratorFramework client = ZkClient.getInstance().getClient();
try {
client.blockUntilConnected(3, TimeUnit.SECONDS);
assertTrue(ZkClient.getInstance().getClient().getZookeeperClient().isConnected());
} finally {
ZkClient.getInstance().close();
}
}
}

Related

Jetty 9 WebSocket client issue when using secure connection

I'm writing a WebSocket client in a java application, using the Jetty 9.4.18 libraries.
I'm pretty new to WebSockets, so I started testing using the two sample classes from the Jetty documentation, connecting to echo.websocket.org
The test runs fine when I connect without SSL, but if fails when the connection is done to wss://echo.websocket.org
I always get the same exception:
java.io.EOFException: HttpConnectionOverHTTP#50371e9d::DecryptedEndPoint#6dc65fc2{echo.websocket.org/174.129.224.73:443<->/192.168.1.34:60521,OPEN,fill=-,flush=C,to=226/0}
at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.earlyEOF(HttpReceiverOverHTTP.java:338)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:1551)
at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.shutdown(HttpReceiverOverHTTP.java:209)
at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.process(HttpReceiverOverHTTP.java:147)
at org.eclipse.jetty.client.http.HttpReceiverOverHTTP.receive(HttpReceiverOverHTTP.java:73)
at org.eclipse.jetty.client.http.HttpChannelOverHTTP.receive(HttpChannelOverHTTP.java:133)
at org.eclipse.jetty.client.http.HttpConnectionOverHTTP.onFillable(HttpConnectionOverHTTP.java:155)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
at org.eclipse.jetty.io.ssl.SslConnection$DecryptedEndPoint.onFillable(SslConnection.java:411)
at org.eclipse.jetty.io.ssl.SslConnection.onFillable(SslConnection.java:305)
at org.eclipse.jetty.io.ssl.SslConnection$2.succeeded(SslConnection.java:159)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:118)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
at java.lang.Thread.run(Thread.java:748)
It looks like the server closes without answering to the handshake request.
I am aware of SslContextFactory, but my understanding is that it should be used only if you need your own TrustStore or KeyStore, or for other special cases.
Note also that after some failed attempt I downloaded another websocket implementation from https://github.com/TooTallNate/Java-WebSocket, and it works fine with both ws and wss, without setting anything specific for SSL.
However for this project I'm bind to use Jetty.
The code I'm using is exactly the sample from Jetty documentation at https://www.eclipse.org/jetty/documentation/9.4.x/jetty-websocket-client-api.html
the only change I did was to add an onError method to SimpleEchoSocket, that dumps the full exception stack.
Am I missing something?
Thanks in advance!
Unfortunately, websocket.org (and Kaazing host/proxy) has a bunch of TLS issues at this point in time, so using their public servers are not sane choice right now.
Here's a different demo, also using TLS and WebSocket, against a stackexchange server with a proper and sane TLS/SSL implementation.
This was written against Jetty 9.4.18.v20190429
package org.eclipse.jetty.demo;
import java.net.URI;
import java.util.concurrent.Future;
import org.eclipse.jetty.client.HttpClient;
import org.eclipse.jetty.util.component.LifeCycle;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.ssl.SslContextFactory;
import org.eclipse.jetty.websocket.api.Session;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
import org.eclipse.jetty.websocket.api.annotations.WebSocket;
import org.eclipse.jetty.websocket.client.WebSocketClient;
#WebSocket
public class SecureClientSocket
{
private static final Logger LOG = Log.getLogger(SecureClientSocket.class);
public static void main(String[] args)
{
String url = "wss://qa.sockets.stackexchange.com/";
SslContextFactory ssl = new SslContextFactory.Client();
ssl.setEndpointIdentificationAlgorithm("HTTPS");
HttpClient http = new HttpClient(ssl);
WebSocketClient client = new WebSocketClient(http);
try
{
http.start();
client.start();
SecureClientSocket socket = new SecureClientSocket();
Future<Session> fut = client.connect(socket, URI.create(url));
Session session = fut.get();
session.getRemote().sendString("Hello");
session.getRemote().sendString("155-questions-active");
}
catch (Throwable t)
{
LOG.warn(t);
}
finally
{
stop(http);
stop(client);
}
}
private static void stop(LifeCycle lifeCycle)
{
try
{
lifeCycle.stop();
}
catch (Exception e)
{
e.printStackTrace();
}
}
#OnWebSocketConnect
public void onConnect(Session sess)
{
LOG.info("onConnect({})", sess);
}
#OnWebSocketClose
public void onClose(int statusCode, String reason)
{
LOG.info("onClose({}, {})", statusCode, reason);
}
#OnWebSocketError
public void onError(Throwable cause)
{
LOG.warn(cause);
}
#OnWebSocketMessage
public void onMessage(String msg)
{
LOG.info("onMessage() - {}", msg);
}
}

Why do we need to restart Appium every time we run group of tests?

Why don't to set Appium running all the time? starting in the morning and stopping when day is complete, and running test scripts when we want.
Mac, Appium, Java.
You could do that, just start it in the morning and stop it at night, but you could also do something better: Check to see in your test script if it is running, and if not, start it. You could also then decide in your code whether or not to stop the service.
Below is the class I wrote for my own use with the help of many others by researching the net and putting it all together:
import java.io.IOException;
import java.net.ServerSocket;
import org.openqa.selenium.remote.DesiredCapabilities;
import io.appium.java_client.service.local.AppiumDriverLocalService;
import io.appium.java_client.service.local.AppiumServiceBuilder;
import io.appium.java_client.service.local.flags.GeneralServerFlag;
/**
* This class handles Appium Server
*
* #author Bill Hileman
*/
public class AppiumServer {
private AppiumDriverLocalService service;
private AppiumServiceBuilder builder;
private DesiredCapabilities cap;
private int port = 4723;
public void startServer() {
// Set Capabilities
cap = new DesiredCapabilities();
cap.setCapability("noReset", "false");
// Build the Appium service
builder = new AppiumServiceBuilder();
builder.withIPAddress("127.0.0.1");
builder.usingPort(port);
builder.withCapabilities(cap);
builder.withArgument(GeneralServerFlag.SESSION_OVERRIDE);
builder.withArgument(GeneralServerFlag.LOG_LEVEL, "error");
// Start the server with the builder
service = AppiumDriverLocalService.buildService(builder);
service.start();
}
public void stopServer() {
service.stop();
}
public boolean serverIsRunnning() {
boolean isServerRunning = false;
ServerSocket serverSocket;
try {
serverSocket = new ServerSocket(port);
serverSocket.close();
} catch (IOException e) {
// If control comes here, then it means that the port is in use
isServerRunning = true;
} finally {
serverSocket = null;
}
return isServerRunning;
}
}

Having trouble connecting android with MQTT to broker

I am trying to connect to an Apollo broker, this code works perfectly when I use it alone in a normal java project, everything is exactly the the same except now its in an android project and i try to run it when i click a button from MainActivity.
I have a text box that gets updated to "1" before i try to connect MQttClient however the second .setT("2") does not get run so I think the problem is with client.connect(opts) as if i just do client.connect() the text box gets updated to "2" but since i need the username and password it from opts the rest does not run
Just started using MQTT learning as I go along. Thanks for any help.
package com.example.androidmqtt;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.internal.MemoryPersistence;
public class Service {
MqttClient client;
MemoryPersistence persistence = new MemoryPersistence();
public Service()throws Exception{}
public static void main(String[] args) throws Exception {
new Service().doDemo();
}
public void doDemo() {
try {
client = new MqttClient("tcp://10.1.10.1:1883", "testingMyMQTT", persistence);
MainActivity.setT("2");
MqttConnectOptions opts = new MqttConnectOptions();
opts.setUserName("nabi");
opts.setPassword("M4rk3".toCharArray());
opts.setKeepAliveInterval(480);
MainActivity.setT("1");//sets the txt1 in main view to 1 so i know whats going on
client.connect(opts);
MainActivity.setT("2");
MqttMessage msg = new MqttMessage("Works".getBytes());
msg.setRetained(true);
msg.setQos(1);
MainActivity.setT("its working");
MqttTopic topic = client.getTopic("Android/Test");
MqttDeliveryToken token = topic.publish(msg);
} catch (MqttException e) {
e.printStackTrace();
}
}
}
Verify that android can connect to your local network 10.1.10.1 and if so, check the logs of the Apollo broker.

Oozie Java API Kerberos Authentication

I am trying to get an oozie job status using oozie java API. Currently it is failing with the message
Exception in thread "main" HTTP error code: 401 : Unauthorized
We are using a kerberos authentication in our cluster with a keytab file.
Please guide as how to proceed to implement the authentication.
My current program is:
import org.apache.oozie.client.OozieClient;
public class oozieCheck
{
public static void main(String[] args)
{
// get a OozieClient for local Oozie
OozieClient wc = new OozieClient(
"http://myserver:11000/oozie");
System.out.println(wc.getJobInfo(args[1]));
}
}
I figured a way to use kerberos in my java api.
First obtain kerberos tgt.
Then the below code works:
import java.io.BufferedReader;
import java.io.FileReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Properties;
import org.apache.log4j.Logger;
import org.apache.oozie.client.AuthOozieClient;
import org.apache.oozie.client.WorkflowJob.Status;
public class Wrapper
{
public static AuthOozieClient wc = null;
public static String OOZIE_SERVER_URL="http://localhost:11000/oozie";
public Wrapper ( String oozieUrlStr ) throws MalformedURLException
{
URL oozieUrl = new URL(oozieUrlStr);
// get a OozieClient for local Oozie
wc = new AuthOozieClient(oozieUrl.toString());
}
public static void main ( String [] args )
{
String lineCommon;
String jobId = args[0]; // The first argument is the oozie jobid
try
{
Wrapper client = new Wrapper(OOZIE_SERVER_URL);
Properties conf = wc.createConfiguration();
if(wc != null)
{
// get status of jobid from CLA
try
{
while (wc.getJobInfo(jobId).getStatus() == Status.RUNNING)
{
logger.info("Workflow job running ...");
logger.info("Workflow job ID:["+jobId+"]");
}
if(wc.getJobInfo(jobId).getStatus() == Status.SUCCEEDED)
{
// print the final status of the workflow job
logger.info("Workflow job completed ...");
logger.info(wc.getJobInfo(jobId));
}
else
{
// print the final status of the workflow job
logger.info("Workflow job Failed ...");
logger.info(wc.getJobInfo(jobId));
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
else
{
System.exit(9999);
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
You have to patch the oozie client if docs do not mention Kerberos.

What are the possible causes that let ActiveMQ application silently quit?

I have made a simple ActiveMQ application.
It listens to a queue. If a message comes, print out the dataId
Here is the code:
import javax.jms.Connection;
import javax.jms.ConnectionFactory;
import javax.jms.Destination;
import javax.jms.ExceptionListener;
import javax.jms.JMSException;
import javax.jms.MapMessage;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageListener;
import javax.jms.Session;
import org.apache.activemq.ActiveMQConnectionFactory;
public class MQ implements MessageListener {
private Connection connection = null;
private Session session = null;
private Destination destination = null;
private void errorOnConnection(JMSException e) {
System.out.println("MQ is having problems. Exception::"+ e);
}
private void init() throws JMSException {
String BROKER_URL = "failover:(tcp://myQueue001:61616,tcp://myQueue002:61616)?randomize=false";
ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(BROKER_URL);
connection = connectionFactory.createConnection("user", "password");
connection.setExceptionListener(
new ExceptionListener() {
#Override public void onException(JMSException e) {
errorOnConnection(e);
}
});
session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
destination = session.createQueue("myQueue");
MessageConsumer consumer = session.createConsumer(destination);
consumer.setMessageListener(this);
}
public boolean start() {
try {
if(connection==null )
init();
connection.start();
} catch (Exception e) {
System.out.println("MQListener cannot be started, exception: " + e);
}
return true;
}
#Override
public void onMessage(Message msg) {
try {
if(msg instanceof MapMessage){
MapMessage m = (MapMessage)msg;
int dataId = m.getIntProperty("dataId");
System.out.println(dataId);
}
} catch (JMSException e) {
System.out.println("Got an exception: " + e);
}
}
public static void main(String[] args) {
MQ mq = new MQ();
mq.start();
}
}
It works fine and does what it is meant to accomplish.
However, the problem is that it can run only for several days. After several days, it just quits silently without any exceptions or error.
The queue I am listening to is from 3rd party. From a guy there, the queue sometimes will be closed or restarted or interrupted.
But I think even if that happen, the default ActiveMQ settings will handle it by consistently reconnect to it, right? (according to http://activemq.apache.org/cms/configuring.html)
So any other possible causes which lead my code to quitting silently?
Depends on bit on your version. Since you are not doing anything yourself to keep the application running but instead depending on the ActiveMQ code to keep at least one non-deamon thread running. In some ActiveMQ versions the client wasn't always doing this so your application could quite while a failover was occurring. Best bet is to switch to v5.8.0 which I believe had some fixes for this.
You could add some polling code in main to read something from console or what not to ensure that the client stays up until you are sure you want it to go down.

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