rchapin – Page 13 – Ryan Chapin's Website

[SOLVED] Unable to Connect to ambari-metrics-collector Issues

Posted on September 2, 2016January 28, 2021 by rchapin

I was having some issues with the ambari-metrics family of services on a ‘pseudo-distributed’ cluster that I have installed on my workstation.

The symptoms were:

1. Ambari indicated the following CRITICAL errors in the Ambari Dashboard under the Ambari Metrics section

Connection failed: [Errno 111] Connection refused to rchapin-wrkstn:6188

2. After attempting to restart the ambari-metrics-collector via either the Ambari Dashboard or through the commandline (# ambari-metrics-collector [stop|start]) you see the following (similar) messages in the ambari-metrics-collector.log

2016-09-02 12:15:37,505 INFO

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Dynamically Instantiating Classes in Python

Posted on August 11, 2016January 28, 2021 by rchapin

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

Posted on August 9, 2016January 28, 2021 by rchapin

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”

Blacklisting Kernel Modules

Posted on June 12, 2016January 28, 2021 by rchapin

Following is a walkthrough on how to blacklist a kernel module. The specific example is blacklisting the nouveau driver so that I can install the OEM Nvidia driver.

1. First, blacklist the nouveau driver: Add a line to the textfile /etc/modprobe.d/nouveau-blacklist.conf that contains they keyword ‘blacklist’ and the name of the driver

blacklist nouveau

2. Rebuild the initramfs image file. First, backup existing initramfs

mv initramfs-3.10.0-327.18.2.el7.x86_64.img initramfs-3.10.0-327.18.2.el7.x86_64.img_2016-06-09.bak

Build new initramfs

dracut -v /boot/initramfs-$(uname -r).img $(uname -r)

3. Reboot the system → Continue reading “Blacklisting Kernel Modules”

How to Return Hive Query Results Similary to MySQL \G in One Vertical Column

Posted on June 9, 2016January 28, 2021 by rchapin

When trying to look at data in a database with really wide rows even just selecting 1 row to see the data is nearly impossible to understand when the single row wraps 7 or 8 times.

MySQL offers the ‘\G’ option to display the output in a single column.

The corresponding method in Hive is to execute the following set command:

!set outputformat vertical
SELECT something FROM some table;

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How to Configure a User Account in Active Directory So that the Password Never Expires

Posted on June 9, 2016January 28, 2021 by rchapin

Using ADSI Edit, navigate to the user in question. Right-click on the user and select Properties.

Then, scroll down to the ‘userAccountControl’ property and click the Edit button.

Enter 66048 into the field and then click ‘OK’ and then ‘Apply’.

After closing the edit window, scroll to the right to confirm that the value indicates the following

'0x10200 = (NORMAL_ACCOUNT|DONT_EXPIRE_PASSWORD)'

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Using netcat to Mock a RESTful Webservice that Returns JSON

Posted on May 10, 2016January 28, 2021 by rchapin

Let’s say that you are working on a part of a project that needs to consume some JSON data from a forthcoming HTTP service. That sub-system is being developed by one of your colleagues and is not yet ready for you to stand-up to develop against.

You can use netcat to mock the webservice and return some static JSON data for which you can develop and test against with a simple one-liner.

First, put together your JSON in a file, → Continue reading “Using netcat to Mock a RESTful Webservice that Returns JSON”

How to Use Credentials That Contain Special Characters with curl

Posted on May 2, 2016January 28, 2021 by rchapin

In order to execute curl commands to endpoints with passwords that contain special characters, the cleanest way that I have found to do so is to Base64 encode the authentication string for curl and then pass an Authorization request header along with the request.

In this example the credentials are uid ‘rchapin’ and passwd ‘abc123!@#’. Normally we would pass this to curl as follows:

$ curl -u rchapin:abc123!@# -X GET https://some-endpoint:443

However, this will not work and the password will → Continue reading “How to Use Credentials That Contain Special Characters with curl”

Solution for MySQL ERROR 1396 (HY000): Operation CREATE USER failed for

Posted on April 28, 2016January 28, 2021 by rchapin

This indicates that the user already exists, or did exist but that all of the data for that user has not been deleted.

As the mysql root user:

REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'user'@'hostname';
DROP USER 'user'@'hostname'

Then re-try creating the user.→ Continue reading “Solution for MySQL ERROR 1396 (HY000): Operation CREATE USER failed for”

How to Configure a Linux Client for Active Directory Authentication

Posted on April 26, 2016January 28, 2021 by rchapin

I am currently working on setting up multiple environments for a new project (DEV, QA, and PROD) and will be integrating all of the servers to an Active Directory Domain Controller for user management.

Following are notes from when I configured a Fedora Core 18 laptop to integrate with an AD server. It is likely things have changed some from then and I will update this as required for a current version of RHEL7/CentOS 7.

Install the following packages

yum

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