[SOLVED] Upgrading Apache Kafka 2.7 to Java 11 Changes authenticationID sent to ZooKeeper Enabling Only 1 Kafka Broker to r/w znodes

The title of this post is a bit of mouthful and requires a bit more explanation.

I am running a pure open-source version of Kafka (currently running 2.7) and am using SASL/GSSAPI connections between all of the brokers and ZooKeeper. Currently, the whole system, including ZooKeeper, is running Java 8 and it is long-overdue to be upgraded to Java 11.

Upgrading Kafka to Java 11 causes the server to send an incorrect authenticationID String to ZooKeeper which results in the → Continue reading “[SOLVED] Upgrading Apache Kafka 2.7 to Java 11 Changes authenticationID sent to ZooKeeper Enabling Only 1 Kafka Broker to r/w znodes”

message=class configured for SSLContext: sun.security.ssl.SSLContextImpl$TLSContext not a SSLContext When Mocking Static Methods in Class

When mocking static classes with Junit4, Mockito and PowerMock, you may see the following log messages after annotating your test class if the code that you are testing is making HTTP connections:

message=class configured for SSLContext: sun.security.ssl.SSLContextImpl$TLSContext not a SSLContext

Your annotations for the class (or method) typically include the following:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ SomeClassYouWantToMock.class })

This may cause some confusion, especially if whatever other code that you may have ONLY uses HTTP. Add the following to your annotations to tell → Continue reading “message=class configured for SSLContext: sun.security.ssl.SSLContextImpl$TLSContext not a SSLContext When Mocking Static Methods in Class”

Creating a Counter or Progress Bar for a Python Program

I’ve written a number of Python apps where I would like it to print some sort of counter or progress bar to STDOUT to let me know that it is still running instead of locked up or died somehow without me being able to see it.

I had tried using a couple of different existing progress bar related modules but none of them really worked except in a very specific use case.

So, after a bit of futzing around I → Continue reading “Creating a Counter or Progress Bar for a Python Program”

How To Spy and Verify a Static Void Method in Java

The Mockito and PowerMockito libraries for JUnit4 are not always the most intuitive.

Following is an example of how to spy and verify a static void method.

    @Test
    public void testAdd() {

        // Prepare the Utils class to be spied.
        PowerMockito.spy(Utils.class);

        // Run the test and get the actual value from the OUT
        int actualValue = App.add("Test1", 1, 1);

        /*
         * To verify the number of times that we called Utils.doSomething we
         * first need to tell the PowerMockito library 
Continue reading “How To Spy and Verify a Static Void Method in Java”

Configuring rsyslog to rotate log files from log messages streamed to it from a Systemd service

In general, I have moved to writing all of my applications to write their log output to STDOUT. This makes running them on the command line, in an IDE, on a bare metal box, VM, or in a container completely decoupled from how you store and view the logs. No more having multiple logging configs for each flavor of deployment.

In this particular case, I am running an application in a container (but it isn’t necessary that it is in → Continue reading “Configuring rsyslog to rotate log files from log messages streamed to it from a Systemd service”

Mocking Static Methods That Return void in Java

This is one of those things that I tend to do on a regular basis . . . but unfortunately don’t remember the details each time, so I am adding it for future reference.

Often, developers will want to mock static methods that return void.  The Mockito and PowerMockito frameworks provide for this, but the syntax isn’t immediately obvious.

Following is an example.

public class SomeClass {
    public static void doSomething(String arg1, int arg2) {
        // Method that does something...
    
Continue reading “Mocking Static Methods That Return void in Java”

Solution for Executing Native Process from Java that Requires sudo

If you are building a Java program that requires the ability to execute native commands on the machine which require sudo it requires some additional considerations other than just writing the Java code.

The problem is that sudo, by default, requires a tty for executing sudo such that a password can entered.  Even if you configure sudoers to grant NOPASSWD access to a specific command you will still get the following error

sudo: sorry, you must have a tty to 
Continue reading “Solution for Executing Native Process from Java that Requires sudo”

Dynamically Instantiating Classes in Python

A common design pattern is to define a class or list of classeses in configuration such that at runtime the classes can be dynamically instantiated.

I’ve done this before in many other languages and had need to do so today in Python (2.7.11)

It seems as though the clean way to do so is by using the Pyton importlib module.  By using it, it enables you to cleanly dynamically import sub modules

Following is an example:

import importlib

klass_1_module = 
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Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution

If you are using Mockito and PowerMock to build mocks for your Java tests and you run into the following error:

2016-05-05 17:31:20,204 main ERROR Could not reconfigure JMX java.lang.LinkageError: loader constraint violation: loader (instance of org/powermock/core/classloader/MockClassLoader) previously initiated loading for a different type with name "javax/management/MBeanServer"
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
        at org.powermock.core.classloader.MockClassLoader.loadUnmockedClass(MockClassLoader.java:238)
        at org.powermock.core.classloader.MockClassLoader.loadModifiedClass(MockClassLoader.java:182)
        at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:70)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

Simply add the following as a class level annotation:

@PowerMockIgnore( {"javax.management.*"} )

Continue reading “Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution”