We Keep Coding

Getting exception NoClassDefFoundError when connecting to Redis with lettuce 6.0.1

I'm new to java. Trying to connect to Redis with Lettuce.
Environment: openjdk - 15.0.1, Lettuce-core-6.0.1. RELEASE, Redis instance launched on RedisLabs (free tier), Dependency management as java Plain. IDE: IttelijIDEA.
I wrote this program code bellow, and when building its raises an Exception. Kindly asking for any suggestions how that could be fixed? Thanks a lot in advance to provided assistance.
import io.lettuce.core.RedisClient;
import io.lettuce.core.api.StatefulRedisConnection;
import io.lettuce.core.api.sync.RedisCommands;
public class redisConnect {
public static void main(String[] args) {
System.out.println("I remember how to create simple java program :)");
System.out.println("with this program I will connect to REDIS instance on ReidsLabs");
RedisClient redisClient = RedisClient.create("redis://password#host-name-from-redisLabs:port/dbname");
try (StatefulRedisConnection<String, String> connection = redisClient.connect()) {
RedisCommands<String, String> syncCommands = connection.sync();
syncCommands.set("key", "Hello, Redis!");
String str = syncCommands.get("key");
System.out.println(str);
connection.close();
}
redisClient.shutdown();
}
}
Exception value:
Exception in thread "main" java.lang.NoClassDefFoundError: io/netty/channel/group/ChannelGroup
at redisConnect.main(redisConnect.java:11)
Caused by: java.lang.ClassNotFoundException: io.netty.channel.group.ChannelGroup
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:606)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:168)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
... 1 more
Process finished with exit code 1
Lettuce Client has been uploaded from here: https://github.com/lettuce-io/lettuce-core/releases/download/6.0.1.RELEASE/lettuce-core-6.0.1.RELEASE-bin.zip
Code example has been taken from here: https://lettuce.io/core/6.0.1.RELEASE/reference/#getting-started.plain-java
Dependency to the project in intellij has been imported: like that:

How to display topics using Kafka Clients in Java?

public static void main(String [] args){
Properties config = new Properties();
config.put(AdminClientConfig.BOOTSRAP._SERVERS_CONFIG, "mybroker.ip.address:9092");
AdminClient admin = AdminClient.create(config);
ListTopicsResult ltr = admin.listTopics().names().get();
}
I am catching an ExecutionException with the error messages: org.apache.kafka.common.errors.TimeoutException: Call(callName:listTopics, deadlineMs=1599813311360, tries=1, nextAllowedTryMs=-9223372034707292162) timed out at 9223372036854775807 after 1 attempt(s)
StackTrace points to the class KafkaFutureImpl in wrapAndThrow.
I can't really paste the entire error since I am writing all of this through my mobile phone.
I am using Kafka Clients 2.6.0, JDK 1.8.0_191
this is very weird since the timeout happens instantly, and I have also tried passing arguments into get(time, timeunit) and I am getting the same result.
EDIT:
I was missing some dependencies in the POM. That resolved the issue.

Samza/Kafka Failed to Update Metadata

I am currently working on writing a Samza Script that will just take data from a Kafka topic and output the data to another Kafka topic. I have written a very basic StreamTask however upon execution I am running into an error.
The error is below:
Exception in thread "main" org.apache.samza.SamzaException: org.apache.kafka.common.errors.TimeoutException: Failed to update metadata after 193 ms.
at org.apache.samza.coordinator.stream.CoordinatorStreamSystemProducer.send(CoordinatorStreamSystemProducer.java:112)
at org.apache.samza.coordinator.stream.CoordinatorStreamSystemProducer.writeConfig(CoordinatorStreamSystemProducer.java:129)
at org.apache.samza.job.JobRunner.run(JobRunner.scala:79)
at org.apache.samza.job.JobRunner$.main(JobRunner.scala:48)
at org.apache.samza.job.JobRunner.main(JobRunner.scala)
Caused by: org.apache.kafka.common.errors.TimeoutException: Failed to update metadata after 193 ms
I not entirely sure how to configure or have the script write the required Kafka metadata. Below is my code for the StreamTask and the properties file. In the properties file I added the Metadata section to see if that would assist in the process afterwards but to no avail. Is that the right direction or am I missing something entirely?
import org.apache.samza.task.StreamTask;
import org.apache.samza.task.MessageCollector;
import org.apache.samza.task.TaskCoordinator;
import org.apache.samza.system.SystemStream;
import org.apache.samza.system.IncomingMessageEnvelope;
import org.apache.samza.system.OutgoingMessageEnvelope;
/*
* Take all messages received and send them to
* a Kafka topic called "words"
*/
public class TestStreamTask implements StreamTask{
private static final SystemStream OUTPUT_STREAM = new SystemStream("kafka" , "words"); // create new system stream for kafka topic "words"
#Override
public void process(IncomingMessageEnvelope envelope, MessageCollector collector, TaskCoordinator coordinator){
String message = (String) envelope.getMessage(); // pull message from stream
for(String word : message.split(" "))
collector.send(new OutgoingMessageEnvelope(OUTPUT_STREAM, word, 1)); // output messsage to new system stream for kafka topic "words"
}
}
# Job
job.factory.class=org.apache.samza.job.yarn.YarnJobFactory
job.name=test-words
# YARN
yarn.package.path=file://${basedir}/target/${project.artifactId}-${pom.version}-dist.tar.gz
# Task
task.class=samza.examples.wikipedia.task.TestStreamTask
task.inputs=kafka.test
task.checkpoint.factory=org.apache.samza.checkpoint.kafka.KafkaCheckpointManagerFactory
task.checkpoint.system=kafka
task.checkpoint.replication.factor=1
# Metrics
metrics.reporters=snapshot,jmx
metrics.reporter.snapshot.class=org.apache.samza.metrics.reporter.MetricsSnapshotReporterFactory
metrics.reporter.snapshot.stream=kafka.metrics
metrics.reporter.jmx.class=org.apache.samza.metrics.reporter.JmxReporterFactory
# Serializers
serializers.registry.string.class=org.apache.samza.serializers.StringSerdeFactory
serializers.registry.metrics.class=org.apache.samza.serializers.MetricsSnapshotSerdeFactory
# Systems
systems.kafka.samza.factory=org.apache.samza.system.kafka.KafkaSystemFactory
systems.kafka.samza.msg.serde=string
systems.kafka.consumer.zookeeper.connect=localhost:2181/
systems.kafka.consumer.auto.offset.reset=largest
systems.kafka.producer.bootstrap.servers=localhost:9092
# Metadata
systems.kafka.metadata.bootstrap.servers=localhost:9092

This question is about Kafka 0.8 which should be out of support if I am not mistaken.
This fact, combined with the context of people only running into this issue sometimes, but not all the time (and nobody seems to struggle with this in recent years), gives me very good confidence that upgrading to a more recent version of Kafka will resolve the problem.

Problem getting Java Streams in HP Tandem (Non-Stop)

We are porting a simple Java application between Tandem NonStop systems, from G-Series to H-Series. Java version is 1.5.0_02.
When performing basic I/O tasks like getting output stream from or opening a client socket, we receive exceptions like
java.io.IOException: Value out of range
or
java.net.SocketException: Value out of range
("value out of range" is Tandem native jargon for, well, quite everything I suppose).
Has anybody got similar issues? i.e. I/O corruption while for example messing with JNI?
I suppose there is something wrong with the system, but where might it be?
Thank you.
EDIT:
adding snippets as requested
sample snippet (a) - using Runtime.exec () (adapted)
Properties envVars = new Properties();
Process p = r.exec("/bin/env");
envVars.load(p.getInputStream());
Stack trace (a):
java.io.IOException: Value out of range (errno:4034)
at java.io.FileInputStream.readBytes(Native Method)
at java.io.FileInputStream.read(FileInputStream.java:194)
at java.lang.UNIXProcess$DeferredCloseInputStream.read(UNIXProcess.java:221)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:254)
at java.io.BufferedInputStream.read(BufferedInputStream.java:313)
at sun.nio.cs.StreamDecoder$CharsetSD.readBytes(StreamDecoder.java:411)
at sun.nio.cs.StreamDecoder$CharsetSD.implRead(StreamDecoder.java:453)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:183)
at java.io.InputStreamReader.read(InputStreamReader.java:167)
at java.io.BufferedReader.fill(BufferedReader.java:136)
at java.io.BufferedReader.readLine(BufferedReader.java:299)
at java.io.BufferedReader.readLine(BufferedReader.java:362)
at util.Environment.getVariables(Environment.java:39)
Last line fails, and output gets redirected to console (!).
sample snippet (b) - using HttpURLConnection:
public WorkerThread (HttpURLConnection conn, String requestData, Logger logger)
{
this.conn = conn;
...
}
public void run ()
{
OutputStream out = conn.getOutputStream ();
}
Stack trace (b):
java.net.SocketException: Value out of range (errno:4034)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.Socket.connect(Socket.java:507)
at sun.net.NetworkClient.doConnect(NetworkClient.java:155)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:365)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:477)
at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:280)
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:337)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:176)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:736)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:162)
at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:828)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java:230)
Case (a) can be avoided because it was a workaround for other issues with previous JRE version (!), but same behaviour with sockets is really nasty.

Error code 4034 seem to indicate that a specific server is not running in your NonStop cluster. Are you sure that your system is setup properly?

Update: The problem was caused by a spurious .so library.

Rmi connection refused with localhost

I have a problem using java rmi:
When I'm trying to run my server, I get a connectException (see below).
Exception happens when executing the rebind method:
Runtime.getRuntime().exec("rmiregistry 2020");
MyServer server = new MyServer();
Naming.rebind("//localhost:2020/RemoteDataPointHandler", server);
when using rmi://localhost:2020/RemoteDataPointHandler instead, it doesn't work either. Also using the default port does not work. I also tried using the 127.0.0.1 ip-address, but with the same effect.
my runtime args:
-Djava.security.policy=java.security.AllPermission
Exception in thread "main" java.rmi.ConnectException: Connection refused to host: localhost; nested exception is:
java.net.ConnectException: Connection refused
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:574)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:185)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:171)
at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:306)
at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
at java.rmi.Naming.rebind(Naming.java:160)
at be.fortega.knx.server.Main.(Main.java:25)
at be.fortega.knx.server.Main.main(Main.java:16)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:433)
at java.net.Socket.connect(Socket.java:524)
at java.net.Socket.connect(Socket.java:474)
at java.net.Socket.(Socket.java:371)
at java.net.Socket.(Socket.java:184)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:569)
... 7 more

had a simliar problem with that connection exception. it is thrown either when the registry is not started yet (like in your case) or when the registry is already unexported (like in my case).
but a short comment to the difference between the 2 ways to start the registry:
Runtime.getRuntime().exec("rmiregistry 2020");
runs the rmiregistry.exe in javas bin-directory in a new process and continues parallel with your java code.
LocateRegistry.createRegistry(2020);
the rmi method call starts the registry, returns the reference to that registry remote object and then continues with the next statement.
in your case the registry is not started in time when you try to bind your object

It seems to work when I replace the
Runtime.getRuntime().exec("rmiregistry 2020");
by
LocateRegistry.createRegistry(2020);
anyone an idea why? What's the difference?

You need to have a rmiregistry running before attempting to connect (register) a RMI service with it.
The LocateRegistry.createRegistry(2020) method call creates and exports a registry on the specified port number.
See the documentation for LocateRegistry

One difference we can note in Windows is:
If you use Runtime.getRuntime().exec("rmiregistry 1024");
you can see rmiregistry.exe process will run in your Task Manager
whereas if you use Registry registry = LocateRegistry.createRegistry(1024);
you can not see the process running in Task Manager,
I think Java handles it in a different way.
and this is my server.policy file
Before running the the application, make sure that you killed all your existing
javaw.exe and rmiregistry.exe corresponds to your rmi programs which are
already running.
The following code works for me by using Registry.LocateRegistry() or
Runtime.getRuntime.exec("");
// Standard extensions get all permissions by default
grant {
permission java.security.AllPermission;
};
VM argument
-Djava.rmi.server.codebase=file:\C:\Users\Durai\workspace\RMI2\src\
Code:
package server;
import java.rmi.Naming;
import java.rmi.RMISecurityManager;
import java.rmi.Remote;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class HelloServer
{
public static void main (String[] argv)
{
try {
if(System.getSecurityManager()==null){
System.setProperty("java.security.policy","C:\\Users\\Durai\\workspace\\RMI\\src\\server\\server.policy");
System.setSecurityManager(new RMISecurityManager());
}
Runtime.getRuntime().exec("rmiregistry 1024");
// Registry registry = LocateRegistry.createRegistry(1024);
// registry.rebind ("Hello", new Hello ("Hello,From Roseindia.net pvt ltd!"));
//Process process = Runtime.getRuntime().exec("C:\\Users\\Durai\\workspace\\RMI\\src\\server\\rmi_registry_start.bat");
Naming.rebind ("//localhost:1024/Hello",new Hello ("Hello,From Roseindia.net pvt ltd!"));
System.out.println ("Server is connected and ready for operation.");
}
catch (Exception e) {
System.out.println ("Server not connected: " + e);
e.printStackTrace();
}
}
}

it seems that you should set your command as an String[],for example:
String[] command = new String[]{"rmiregistry","2020"};
Runtime.getRuntime().exec(command);
it just like the style of main(String[] args).