Develop Reference

Unable to push message into ActiveMQ

I'm successfully pushing message into ActiveMQ from local Eclipse setup. However, the same code does not push message when I try to execute from server as a cron job. It does not even throw an exception during code execution.
Java environment - 1.8
Supporting jars used:
slf4j-api-1.8.0-beta2.jar
javax.annotation-api-1.2.jar
javax.jms-api-2.0.1.jar
management-api-1.1-rev-1.jar
activemq-core-5.7.0.jar
Code:
try {
map = getMessageDetails(session,"MessageQueueEmail");
userName = map.get("userName");
password = map.get("password");
hostName = map.get("mqHostName");
queue = map.get("queueName");
// Create a ConnectionFactory
ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(userName, password, hostName);
// Create a Connection
connection = factory.createConnection();
// start the Connection
connection.start();
System.out.println("MQ started connection");
// Create a Session
sessionMQ = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
// Create the destination Queue
Destination destination = sessionMQ.createQueue(queue);
// Create a MessageProducer from the Session to the Queue
messageProducer = sessionMQ.createProducer(destination);
messageProducer.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
// Create a message
Message message = sessionMQ.createTextMessage(textMsg);
System.out.println("MQ Message sent successfully");
// Tell the producer to send the message
messageProducer.send(message);
} catch(Exception e) {
e.printStackTrace();
System.out.println("\n::::::::::::Error occurred sendEmailMessageToIntranet::::::::::::: " + e.getMessage());
}

Thanks everyone for response. The issue is resolved after importing correct certificate file to the server. Wondering, why MQ attempts failure notification had not logged

Your code looks ok except you might have expiration going. Try with PERSISTENT and most likely is the issues that you are not redirecting stderr in your cronjob ? Make sure you do something like this:
*/1 * * * * /something/send.sh &>> /something/out.log
And then check in the morning.

NullPointerException when making XMPP connection through Smack 4.2.0

I intend to use Smack to send messages through Firebase CCS. I modified a simple CCS client for my Web App but when I try to make connection, it results in exception.
I am using Smack 4.2.0
Here is the process of connection.
1) The connection method which is in my client:
public void connect() throws XMPPException{
try{
config = XMPPTCPConnectionConfiguration.builder()
.setPort(Config.FCM_PORT)
.setHost("fcm-xmpp.googleapis.com")
.setXmppDomain("googleapis.com")
.setSecurityMode(/*Default; Explicit setting for emphasis*/SecurityMode.ifpossible)
.setSendPresence(true)
.setUsernameAndPassword(fcmServerUsername, mApiKey)
.setSocketFactory(SSLSocketFactory.getDefault())
.setDebuggerEnabled(mDebuggable)/* Launch a window with info about packets sent and received */
.build();
}
catch(XmppStringprepException e){
e.printStackTrace();
}
connection = new XMPPTCPConnection(config);
// Configuring Automatic reconnection
ReconnectionManager manager = ReconnectionManager.getInstanceFor(connection);
manager.setReconnectionPolicy(ReconnectionManager.ReconnectionPolicy.RANDOM_INCREASING_DELAY);
manager.enableAutomaticReconnection();
// Connect now then login
try{
connection.connect();
connection.login();
}
// TODO: Handle the exceptions if possible appropriately
catch(SmackException sme){
logger.severe(sme.getMessage());
sme.printStackTrace();
}
catch(IOException ioe){
logger.severe(ioe.getMessage());
ioe.printStackTrace();
}
catch(InterruptedException ie){
logger.severe("Connection got interrupted!!");
ie.printStackTrace();
}
}
2) I traced the exception and I got it here: (Smack's source)
At the line - HostAddress hostAddress = DNSUtil.getDNSResolver().lookupHostAddress(config.host, config.port, failedAddresses, config.getDnssecMode());
// AbstractXMPPConnection.java
protected List<HostAddress> populateHostAddresses() {
List<HostAddress> failedAddresses = new LinkedList<>();
if (config.hostAddress != null) {
hostAddresses = new ArrayList<>(1);
HostAddress hostAddress = new HostAddress(config.port, config.hostAddress);
hostAddresses.add(hostAddress);
}
else if (config.host != null) {
hostAddresses = new ArrayList<HostAddress>(1);
HostAddress hostAddress = DNSUtil.getDNSResolver().lookupHostAddress(config.host, config.port, failedAddresses, config.getDnssecMode());
if (hostAddress != null) {
hostAddresses.add(hostAddress);
}
} else {
// N.B.: Important to use config.serviceName and not AbstractXMPPConnection.serviceName
hostAddresses = DNSUtil.resolveXMPPServiceDomain(config.getXMPPServiceDomain().toString(), failedAddresses, config.getDnssecMode());
}
// Either the populated host addresses are not empty *or* there must be at least one failed address.
assert(!hostAddresses.isEmpty() || !failedAddresses.isEmpty());
return failedAddresses;
}
The exception is NullPointerException and I found that getDNSResolver() returns null. Of all the sources I have referenced, there wasn't anything related to DNS resolver as it is supposed to be internally handled by Smack. So my question is, have I missed out some crucial configuration or step in making the connection?
EDIT: I asked here because Smack is vast lib and there might some config someone knows that I might have missed. I am unable to set DNSResolver directly

EDIT : ANSWER UPDATE
This is NOT a bug in Smack's source as their Upgrade Guide for 4.2.0 explicitly mentions:
**
API Changes
**
Warning: This list may not be complete
Introduced ConnectionConfiguration.setHostAddress(InetAddress)
In previous versions of Smack,
ConnectionConfiguration.setHost(String) could be used to set the
XMPP service's host IP address. This is no longer possible due to the
added DNSSEC support. You have to use the new connection configuration
ConnectionConfiguration.setHostAddress(InetAddress) instead.
This seems to be a bug because I solved it by providing the Host Address (which was supposed to be inferred from {Host, Domain}). So, how did I know to provide the host address?
The trick lies here: (Smack' source)
// AbstractXMPPConnection.java
if (config.hostAddress != null) {
hostAddresses = new ArrayList<>(1);
HostAddress hostAddress = new HostAddress(config.port, config.hostAddress);
hostAddresses.add(hostAddress);
}
else if (config.host != null) {
hostAddresses = new ArrayList<HostAddress>(1);
HostAddress hostAddress = DNSUtil.getDNSResolver().lookupHostAddress(config.host, config.port, failedAddresses, config.getDnssecMode());
if (hostAddress != null) {
hostAddresses.add(hostAddress);
}
} else {
// N.B.: Important to use config.serviceName and not AbstractXMPPConnection.serviceName
hostAddresses = DNSUtil.resolveXMPPServiceDomain(config.getXMPPServiceDomain().toString(), failedAddresses, config.getDnssecMode());
}
You can see the if, else-if blocks here and since the exception arises in the else if (config.host != null) block, I provided hostAddress so that it never enters that block and it worked.
I know this is sort of a hack around the actual problem but this seems to be a bug in Smack 4.2.0 unless someone disproves me otherwise.
Bonus info: If after rectifying this problem, you get another exception in Base 64 encoding during login, refer to this - XMPP client using Smack 4.1 giving NullPointerException during login

Not sure in 4.2.0 but in 4.2.2 (and newer), you will need smack-resolver-dnsjava-4.2.2.jar to be in your classpath, smack calls DNSUtil which is included in the package, if the class doesn't exist it returns NullPointerException.
Hope this help!
David

SNMP response is null [SNMP4j]

I've hit kind of a brick wall. I got a small system that communicate with DSLAM's by SNMP.
Everything has worked fine for a couple of months, but when I recently added a new DSLAM to the system, I couldn't get an answer from it. Tried the other IP's and didn't have a problem.
After an hour or so, suddenly on of the other DSLAM's stopped answering me too. So now I've got two units without any communication, which kinda sucks. So of course I checked the units, and didn't find a problem. By my MIB-browser, I can reach all of the units... But not via my software. So the error lies somewhere in my software. So I checked Wireshark, and see that the getNext requests are going out, but I don't seem to get an answer. When I do it via the MIB browser, there comes an answer. But the funny thing is: the two requests are identical. So I must not be listening - and yes, it is listening.
Why in the world is this specific to some IP's, and dear Lord why do they contaminate eachother?
Let's look at some code:
public String GetNextValue(String OID, Dslam dslam) throws IOException {
Snmp snmp = new Snmp(new DefaultUdpTransportMapping());
snmp.listen();
CommunityTarget target = initializeTarget(dslam);
PDU request = new PDU();
request.setType(PDU.GETNEXT);
OID oid= new OID(OID);
request.add(new VariableBinding(oid));
PDU responsePDU=null;
ResponseEvent responseEvent;
responseEvent = snmp.send(request, target);
if (responseEvent != null){
System.out.println("resonse event not null..");
responsePDU = responseEvent.getResponse();
if ( responsePDU != null){
System.out.println("pdu not null..");
#SuppressWarnings("unchecked")
Vector <VariableBinding> tmpv = (Vector<VariableBinding>) responsePDU.getVariableBindings();
if(tmpv != null){
System.out.println("tmpv not null..");
VariableBinding vb = (VariableBinding) tmpv.get(0);
if(!vb.isException()){
return vb.getVariable().toString()
}
}
}
}
_errorHandler.criticalError("Response error in DSLAM communication");
return null;
}
And the initializer:
private CommunityTarget initializeTarget(Dslam dslam){
Address addr = new UdpAddress(dslam.getAddress() + "/" + dslam.getManagementPort() );
System.out.println("IP: " + dslam.getAddress() + " port: " + dslam.getManagementPort());
CommunityTarget target = new CommunityTarget(addr, new OctetString("public"));
target.setVersion(SnmpConstants.version2c);
target.setTimeout(3000);
target.setRetries(3);
return target;
}
And if we run a test upon a working DSLAM:
#Test
public void Lowtest() throws IOException{
SnmpController snmpController = SnmpController.GetInstance();
DslamGrabber dslamGrabber = new DslamGrabber();
Dslam dslam = dslamGrabber.getByDslamId("test5xda5");
String result = snmpController.GetNextValue(".1.3.6.1.4.1.637.61.1.39.3.3.1.1.2", dslam);
System.out.println(result);
}
Result:
IP: 195.215.96.135 port: 161
resonse event not null..
pdu not null..
tmpv not null..
OID: 1.3.6.1.4.1.637.61.1.39.3.3.1.1.2.1
BF512_2048
The we try against test5xda9 (the second one to succumb to this hideous disease-like error)
We get 3 retries in Wireshark, and the following output:
IP: 192.215.96.139 port: 161
resonse event not null..
Response error in DSLAM communication
null
I really hope somebody here can help me. I'm a few hours away to either break down in tears or break a DSLAM..
Best regards
Ben

Well, as a friend pointed out 192 does not equal 195.

ActiveMQ browser needs long time for last .hasMoreElements()

I try to implement a queue browser for ActiveMQ.
The code shown below should display the text messages in the queue named 'Q1'. There are two messages in there. In general it works but the last e.hasMoreElements() call needs up to 20 seconds. I wanted to update the list every 500 millis. Why is that so slow?When i press 'update' in the browser view for http://localhost:8161/admin/browse.jsp?JMSDestination=Q1 e.hasMoreElements() returns immediately. What's going on here? How to achieve a 'realtime' view?
//init:
ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://localhost:61616");
Connection connection = connectionFactory.createConnection();
connection.start();
Session session = connection.createSession(true, Session.CLIENT_ACKNOWLEDGE);
Queue queue = session.createQueue("Q1");
boolean run = true;
while (run) {
LOG.info("--------------------------------------------------------------------------------");
QueueBrowser browser = session.createBrowser(queue);
Enumeration e = browser.getEnumeration();
while (e.hasMoreElements()) { //<- very slow before returning false after last message. why?
Object o = e.nextElement();
if (o instanceof ActiveMQTextMessage) {
LOG.info(((ActiveMQTextMessage) o).getText());
} else {
LOG.info(o.toString());
}
}
Thread.sleep(500);
browser.close();
}
session.close();
connection.close();

After my previous comment, I've discovered that calling setTransactedIndividualAck(true) on the connection factory solves the problem
ActiveMQConnectionFactory cf2 = new ActiveMQConnectionFactory(...);
cf2.setTransactedIndividualAck(true);
I'm not sure that this is the right thing to do for the problem but at least it works now. See the message on the ActiveMQ user forum here:
http://activemq.2283324.n4.nabble.com/JMS-browser-getEnumeration-hasMoreElements-takes-15s-on-last-element-td4709969.html

I had the same issue. But changing the acknowledgment on the session eliminated the delay.
Try this:
Session session = connection.createSession(true, Session.AUTO_ACKNOWLEDGE);

I found that calling Session.commit() within my hasMoreElements() loop stopped the hanging using activemq-broker version 5.14.5:
while(enumeration.hasMoreElements()) {
final Message message = (Message)enumeration.nextElement();
final TextMessage textMessage = (TextMessage)message;
session.commit();
}
I did more research to see if this was a bug with ActiveMQ or not and found that activemq-broker version 5.15.1 did not hang, even without calling commit() after each iteration. All prior versions of the broker hanged on the final call to hasMoreElements(). It doesn't seem like the contributors deliberately fixed this particular issue, since the bug report on JIRA that the change referenced was for something different. The change that fixed this issue changed part of the iterate() method of the org.apache.activemq.broker.region.Queue class from:
// are we done browsing? no new messages paged
if (!added || browser.atMax()) {
browser.decrementQueueRef();
browserDispatches.remove(browserDispatch);
}
to
// are we done browsing? no new messages paged
if (!added || browser.atMax()) {
browser.decrementQueueRef();
browserDispatches.remove(browserDispatch);
} else {
wakeup();
}
To confirm this was the change that fixed the issue, I went to the previous version, 5.15.0 and forced wakeup() to be called using a debugger and the call to hasMoreElements() did not hang.

After some research and try i switched to the more up-to-date JMX technology. There are no performance issues while walking through the queues.
Some code:
JMXServiceURL url = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi");
JMXConnector connector = JMXConnectorFactory.connect(url, null);
connector.connect();
connection = connector.getMBeanServerConnection();
ObjectName name = new ObjectName(getObjectNameByBrokerName(brokerName));
brokerMBean = (BrokerViewMBean) MBeanServerInvocationHandler.newProxyInstance(connection, name, BrokerViewMBean.class, true);
ObjectName[] objNames = brokerMBean.getQueues();
for (ObjectName objName : objNames) {
QueueViewMBean queueMBean = (QueueViewMBean) MBeanServerInvocationHandler.newProxyInstance(connection, objName, QueueViewMBean.class, true);
System.out.println(queueMBean.getName());
}
You have to activate jmx in the configuration. It's de-activated by default.

Identify server on Tomcat (HttpServletRequest.getLocalAddr() fails)

With Tomcat setup behind Apache, how can an id (IP address ideally) of the server be easily determined?
The specific situation is that multiple servers are setup behind a load balancer, thus the incoming request host name is non-unique and insufficient to identify a particular server for logging purposes. Using HttpServletRequest.getLocalAddr() is unfortunately returning the same hostname instead of the IP address as would be expected (I am assuming this is related to this very old issue here: https://issues.apache.org/bugzilla/show_bug.cgi?id=46082).
Is there a way to make getLocalAddr() perform as documented, or are other methods required to query the IP address of the server?

On our project, we use JMX to get all the config information.
It takes a few steps, because it is like navigating down the server.xml file
This link has some info: http://oss.wxnet.org/mbeans.html
It is probably overkill if all you want is the IP, but I thought I'd throw it out there.
MBeanServer mbeanServer = ManagementFactory.getPlatformMBeanServer();
Set<ObjectName> theConnectors = mbeanServer.queryNames(
new ObjectName("Catalina:type=Connector,*"),
null);
if (theConnectors != null)
{
for (ObjectName nextConnectorName : theConnectors)
{
InetAddress theInetAddress = (InetAddress) mbeanServer.getAttribute(
nextConnectorName,
"address");
if (theInetAddress != null)
{
ipAddress = theInetAddress.getHostAddress();
}
if (!StringUtil.isEmpty(ipAddress))
{
// found the IP address
break;
}
}
}

For my situation, the solution was to get the IP address of the server directly instead of attempting to get the local address via HttpServleRequest.
I cached the IP for use in my filter via:
private static final String serverIp;
static {
String addressString = null;
try
{
InetAddress address = InetAddress.getLocalHost();
addressString = address.getHostAddress();
} catch (Exception e)
{
logger.error("Exception while attempting to determine local ip address",e);
}
if (addressString != null) serverIp = addressString;
else serverIp = "unknown";
}

I had a similar issue recently (a few years after the original question) and found this question and answers. The issue in my case was that the ServletRequest#getLocalAddr() implementation was returning the remote address instead of the local address. The issue was caused by a regression in Tomcat v9.0.22. It was fixed in v9.0.23. See the question and answer here:
https://stackoverflow.com/a/57725039/9602527