The personal view on the IT world of Johan Louwers, specially focusing on Oracle technology, Linux and UNIX technology, programming languages and all kinds of nice and cool things happening in the IT world.
When you start to develop your first application with Oracle JET the first thing you would like to understand is some of the basic ways on how to control parts of your application and influence some basic things provided by the template. The first place you can start looking is appController.js which is located at js/appController.js . The appController javascript is the simple control script which can be used to influence most part of the application.
What is provided in the base template (shown below) is a start for you to develop your own code. As you can see we have some hard values which are used in the examples. In a real world example it would not make any sense to have any (or most) of these in a hardcoded manner. You would rather fetch them from a REST API source.
If we look for example at line 19 in the above example;
This is used as a variable which is referred to in html pages within the Oracle JET application. This specific example if for example used to show the name of the application, you can see this in the screenshot below. The same is the case for the email address which is controlled in the appController.js script self.userLogin
If you want to understand how to call and include the values from appController.js you can refer to the basic examples provided by Oracle JET. You will see that there are data bindings included in the HTML code like for example the below:
The data-bind="text: appName" part will ensure that the value for appName from appController.js is used in this case.
As stated, there is no real good use for this model in real world applications, or at least the number of cases is limited. In reality you will fetch most data from a REST API in most cases. However, when starting with Oracle JET is a good to play around a bit with it to ensure you understand the basics and how to apply them as it will help you a lot when you develop your own custom code and extensions for appController.js in a later stage.
Whenever using the REST management API for Oracle Weblogic and you start to look into the JSON response files provided by Oracle Weblogic you will find that some (all) of the URL's in the JSON response are being constructed in a manner that slashes have been escaped in a generic manner. This is done, most likely, to ensure that nothing breaks when it is called by some other application. However, if you expect clean URL's this is a bit frustrating.
The example below showcases a part of the original JSON message as it it presented by the Weblogic REST API.
If you are using Oracle Linux and if you are using curl to get the content of the file you can pipe the result into sed to ensure you remove the unwanted slashes from the URL's in the reponse.
For this you pipe the result into the below sed command to get the expected output:
| sed 's|[\,]||g'
This will give you the below clean output as an example:
When using Oracle Weblogic there are a couple of ways on how you can manage and monitor your deployment. In the most basic form a Weblogic deployment comes with a management service providing you a web console to do most monitoring and management tasks. Additionally you can do everything from the Oracle Linux command line and you will have the option to hook things up to an Oracle Enterprise manager setup to do a more consolidated way of management and monitoring.
Even though all the options mentioned above are good and have their pros and cons, another option is available which, for some reason, is not that well known. You can also use the RESTful Management Services with Oracle Weblogic 12C.
In some versions the REST API is enabled and in some not. To ensure that it is enabled you will have to check the general configuration for your domain. Under the advanced section you will find the "enable RESTfull Management Services" which you will have to ensure is activated to be able to make use of it.
The REST API services can now be accessed via http://{IP}:{port}/management/ . Having the option to administer and monitor your Weblogic instance via a REST API will increase the options on including it in a more automated fashion a lot more.
Whenever you are looking into automation and custom building some management solutions for IT footprints that include Weblogic the REST API's are a must look into area.
When installing Oracle WebLogic server on Oracle Linux 7 one would expect an easy installation without any issues along the way. However, for some reason you might run into a strange error which is not that clear in the beginning on what the root cause might be. Installing the combination of Weblogic Server 12.2.1.3 on A Oracle Linux 4.1.12-61.1.28.el7uek.x86_64 machine in combiantion with Java 9.0.4 caused the below strange issue as soon as the universal installer was about to start:
After some research it became clear that the issue is being caused by something as simple as missing fonts. In case you do encounter this issue the solution is to create a file /etc/fonts/local.conf and ensure the below content is in the file.
This should ensure your installer is working fine.
for people who are not that big a fan of XML files and still need to use XML structures every now and than when they get data from another system the xml2json solution might be a good thing to look into. The xml2json util is an opensource utility written in Python which will convert XML data into JSON data, as well as the other way arround. Using this on the Oracle Linux commandline when you code bash scripting can save a lot of time. Especially if you use xml2json in combination with jq you can save a lot of time in most cases.
As an example, we take an example XML file we found on the Microsoft website. And for convenience I create a gist from it so you can more easily grab it from the command line. The XML contains a list of books and the details of the books.
If we now would like to do something with it in a JSON format we can can use the xml2sjon command as shown below to get a valid JSON structure we can work with.
As we have a JSON strcuture we can also use jq on it. You can find jq also on the Oracle YUM repository for your use. the xml2json utility is however not included in the Oracle YUM repository at this moment so you will have to grab it from github where you will find the xml2json.py file which you need to ensure is on your Oracle Linux system to be able to use it.
Some time ago the people from the Oracle Linux team have taken the time to build a Oracle Linux 7 version for the Raspberry pi. The Raspberry Pi is a series of small single-board computers developed in the United Kingdom by the Raspberry Pi Foundation to promote the teaching of basic computer science in schools and in developing countries. The original model became far more popular than anticipated, selling outside its target market for uses such as robotics. It does not include peripherals (such as keyboards, mice and cases).
The operating system you use will have to be placed on a single Micro SD card. Using a mac the below command was useful to place the downloaded Oracle Linux 7 distribution for the Raspberry Pi on the Micro SD card:
If you face the issue of the below error, you most likely have mounted the SD card to your operating system. You will have to unmount it (via the disk utility app) and retry the command. Do note this could take some time to complete.
dd: /dev/disk2: Resource busy
A bit of care is needed when executing the command. If your Micro SD card is NOT mounted on /dev/disk2 you might run into the issue that you damage an existing other disk. Meaning, you need to check if /dev/disk2 is indeed the SD card in your case. Using a Mac you can use the below command to check your disks:
diskutil list
When your dd command is finished and you place the SD card in your Raspberry Pi and start it you should end up with a running Oracle Linux 7 operating system on your Raspberry Pi.
When adopting Docker containers as a way to deploy applications and functionality in your landscape one of the tricks is to make sure you do not have to many different types of containers. Even though it is relatively simple to build a container and bake all configuration into it this might cause issues at a later stage. All container images need to be maintained and have some level of lifecycle management applied to them.
For this reason, it is better to limit the number of containers and ensure you can dynamically control the behaviour. This might cause a bit more work when developing the container image and will need to have some thinking about how to dynamically configure a container based upon a limited set of input parameters.
The reason you want to limit the number of parameters you provide a container during startup is that it is relative inflexible and will cause an additional burden on the teams responsible for ensuring the containers are always up and running in the right manner.
A better way is to store configuration data externally and have the container collect the configuration data based upon one (or max two) parameters. This can be for example the role of a container or the environment name where it will be deployed.
As an example, if we build a container for Oracle ORDS which will connect on one side to an Oracle database and on the other side provide a REST API interface to consumers you can make use of this principle. You do want to build a ORDS Docker container only once and would like to inform the container with a parameter which configuration details it needs to gather to start in the right role and manner within the landscape.
We have been building Oracle ORDS containers based upon Oracle Linux 7 Slim, as part of the script that starts ORDS in the container we have included parts that will ensure it will connect to a Consul Key Value store and collect the needed data to dynamically build the configuration files that are used by ORDS to start.
As an example, our ORDS container already knows it is an ORDS container, at startup we provide the input parameter that informs the container that the application name is “app0”. Based upon this knowledge the scripting will be able to fetch the needed configuration data from the Consul REST API.
In Consul we have provided all the needed KV pairs for the script to write the ORDS configuration. If we for example want to have the database hostname where an ORDS “app0” container needs to connect to we execute the below curl command to fetch the data:
The reason we use jq in the above example is to help with fetching "Value" from the JSON message we get returned by Consul. If we look at the full JSON message we get returned we see we get the below returned:
In our case we are only interested in "value", by adding jq '.[].Value' to the command we will only get the content of "Value" returned. However, value is between double quotes and is a base64 encoded string. If we want to decode the base64 encoded string we need to feed this into the base64 command which will not work if we still have it wrapped in the double quotes. This is the reason we pipe the result first into the tr command to strip off the double quotes. The result is a clear base64 encoded string which we can decode using the base64 --decode command.
Placing Consul in the center
By placing Consul in the center of your deployment you will add a KV store which can be used in combination with your Docker containers to play a vital role in how containers are started. By ensuring you have a way of controlling how Consul is positioned per environment (think development, test, acceptance & production like environments) you can influence extremely well how containers are behaving in relation to the environment they are running in.
Building the right and useable structure in the Consul KV store is vital for building the level of flexibility you need in a dynamic landscape.
Spending the right amount of time in thinking about the KV structure which can be used in every environment and thinking about how containers will fetch data from a central Consul KV store in your landscape will require some time and effort, however, will provide you with a lot of benefits in the longer run when operating a wider container based footprint.
In a previous post I showcased how to run Apache Kafka on Oracle Linux. This was intended as an example for testing purposes, the downside of this example was that you needed to start Zookeeper and Kafka manual. Adding it to the startup scripting of your Oracle Linux system makes sense. Not only in a test environment, also in a production environment (especially) you want to have Kafka started when you boot your machine. The below code snippet can be used for this.
You have to remember that, after you place this in /etc/init.d, you have to use chkconfig to add it as a service and you have to use the service command to start it for testing.
Apache Kafka is an open-source stream processing platform developed by the Apache Software Foundation written in Scala and Java. The project aims to provide a unified, high-throughput, low-latency platform for handling real-time data feeds. Its storage layer is essentially a "massively scalable pub/sub message queue architected as a distributed transaction log," making it highly valuable for enterprise infrastructures to process streaming data. Additionally, Kafka connects to external systems (for data import/export) via Kafka Connect and provides Kafka Streams, a Java stream processing library.
In this blogpost we will install Apache Kafka on Oracle Linux, the installation will be done in a test setup which is not ready for production environments however can very well be used to explore Apache Kafka running on Oracle Linux.
Apache Kafka is also provided as a service from the Oracle Cloud in the form of the Oracle Cloud Event Hub. This provides you a running Kafka installation that can be used directly from the start. The below video shows the highlights of this service in the Oracle Cloud.
In this example we will not use the Event Hub service from the Oracle Cloud, we will install Kafka from the ground up. This can be done on a local Oracle Linux installation or it can be done on a Oracle Linux installation in the Oracle Cloud, making use of the Oracle IaaS components in the Oracle Cloud.
Prepare the system for installation.
In esscence, the most important step you need to undertake is to ensure you have Java installed on your machine. The below steps outline how this should be done on Oracle Linux.
You can install the Java OpenJDK using YUM and the standard Oracle Linux repositories.
yum install java-1.8.0-openjdk.x86_64
You should now be able to verify that Java is installed in the manner shown below as an example.
[root@localhost /]# java -version
openjdk version "1.8.0_151"
OpenJDK Runtime Environment (build 1.8.0_151-b12)
OpenJDK 64-Bit Server VM (build 25.151-b12, mixed mode)
[root@localhost /]#
This however is not making sure you have set the JAVA_HOME and JRE_HOME as environment variables. To make sure you will have the following two lines in /etc/profile.
After you made the changes to this file you reload the profile by issuing a source /etc/profile command. This will ensure that the JRE_HOME and JAVA_HOME environment variables are loaded in the correct manner.
Downloading Kafka for installation
Before following the below instructions, it is good practice to check what the latest version is and download the latest stable Apache Kafka version. In our case we download the file kafka_2.11-1.0.0.tgz for the version we want to install in our example installation.
[root@localhost /]# cd /tmp
[root@localhost tmp]# wget http://www-us.apache.org/dist/kafka/1.0.0/kafka_2.11-1.0.0.tgz
--2017-12-27 13:35:51-- http://www-us.apache.org/dist/kafka/1.0.0/kafka_2.11-1.0.0.tgz
Resolving www-us.apache.org (www-us.apache.org)... 140.211.11.105
Connecting to www-us.apache.org (www-us.apache.org)|140.211.11.105|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 49475271 (47M) [application/x-gzip]
Saving to: ‘kafka_2.11-1.0.0.tgz’
100%[======================================>] 49,475,271 2.89MB/s in 16s
2017-12-27 13:36:09 (3.01 MB/s) - ‘kafka_2.11-1.0.0.tgz’ saved [49475271/49475271]
[root@localhost tmp]# ls -la *.tgz
-rw-r--r--. 1 root root 49475271 Nov 1 05:39 kafka_2.11-1.0.0.tgz
[root@localhost tmp]#
You can untar the downloaded file with a tar -xvf kafka_2.11-1.0.0.tgz and than move it to the location where you want to place Apache Kafka. In our case we want to place kafka in /opt/kafka so we undertake the below actions:
[root@localhost tmp]# mkdir /opt/kafka
[root@localhost tmp]#
[root@localhost tmp]# cd /tmp/kafka_2.11-1.0.0
[root@localhost kafka_2.11-1.0.0]# cp -r * /opt/kafka
[root@localhost kafka_2.11-1.0.0]# ls -la /opt/kafka/
total 48
drwxr-xr-x. 6 root root 83 Dec 27 13:39 .
drwxr-xr-x. 4 root root 50 Dec 27 13:39 ..
drwxr-xr-x. 3 root root 4096 Dec 27 13:39 bin
drwxr-xr-x. 2 root root 4096 Dec 27 13:39 config
drwxr-xr-x. 2 root root 4096 Dec 27 13:39 libs
-rw-r--r--. 1 root root 28824 Dec 27 13:39 LICENSE
-rw-r--r--. 1 root root 336 Dec 27 13:39 NOTICE
drwxr-xr-x. 2 root root 43 Dec 27 13:39 site-docs
[root@localhost kafka_2.11-1.0.0]#
Start Apache Kafka
The above steps should have placed Apache Kafka on your Oracle Linux system, now we will have to start it and test it for its working. Before we can start Kafka on our Oracle Linux system we first have to ensure we have ZooKeeper up and running. To do so, execute the below command in the /opt/kafka directory.
Depending on the sizing your machine you might want to change some things to the startup script for Apache Kafka. When, as in my case, you deploy Apache Kafka in an Oracle Linux test machine you might not have as much memory allocated to the test machine as you might have on a "real" server. The below line is present in the bin/kafka-server-start.sh file which sets the memory heap size that should be used.
export KAFKA_HEAP_OPTS="-Xmx1G -Xms1G"
in our case we changed the heap size to 128 MB which is more than adequate for testing purposes however migth be way to less when trying to deploy a production system. The below is an example of the setting as used for this test:
export KAFKA_HEAP_OPTS="-Xmx1G -Xms128M"
This should enable you to start Apache Kafka for the first time as a test on Oracle Linux. You can start Apache Kafka from the /opt/kafka directory using the below command:
You should be able to see a trail of messages from the startup routine and, if all is gone right the last message should be the one shown below. This shuuld be an indication that Kafka is up and running.
INFO [KafkaServer id=0] started (kafka.server.KafkaServer)
Testing Kafka
As we now have Apache Kafka up and running we could (should) test if Apache Kafka is working as expected. Kafka comes with a number of scripts that will make testing more easy. The below scrips come in use when starting to test (or debug) Apache Kafka;
bin/kafka-topics.sh
For taking actions on topics, for example creating a new topic
bin/kafka-console-producer.sh
Used for the role as producer of event messages
bin/kafka-console-consumer.sh
for the role as consumer for receiving event messages.
The first step in testing is to ensure we have a topic in Apache kafka to publish event messsage towards. For the we can use the kafka-topics.sh script. We will create the topic "test" as shown below;
[vagrant@localhost kafka]$
[vagrant@localhost kafka]$ bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic test
Created topic "test".
[vagrant@localhost kafka]$
To ensure the topic is really available in Apache Kafka we list the available topics with the below command:
[vagrant@localhost kafka]$ bin/kafka-topics.sh --list --zookeeper localhost:2181
test
[vagrant@localhost kafka]$
having a topic in Apache Kafka should enable you to start producing messages as a producer. The below example showcases starting the kafka-console-producer.sh script. This will give you an interactive commandline where you can type messages.
[vagrant@localhost kafka]$ bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test
hello 1
hello 2
thisisatest
this is a test
{test 123}
[vagrant@localhost kafka]$
As the whole idea is to produce messages on one side and recieve them at the other side we will also have to test the subscriber side of Apache Kafka to see if we can receive the messages on the topic "test" as a subscriber. The below command subscribes to the topic "test" and the --from-beginning options indicates we want to recieve not only event messages that are created as from this moment, we want to receive all messages from the beginning (creation) of the topic (as far as they are available in Apache Kafka).
[vagrant@localhost kafka]$ bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test --from-beginning
hello 1
hello 2
thisisatest
this is a test
{test 123}
As you can see the event messages we created as the producer are received by the consumer (subscriber) on the test topic.
Retail in general is changing, customers are more and more getting into the drivers seat and voice what they expect from a retailer. The situation where retailers are ensured from business based upon the location where their store is located are over. Customers more and more tend to use online retailers in combination with brick and mortar stores. Ensuring you provide exactly the services customers desire a the right survival tactic for most retailers. For those who are unable to make this change it is not uncommon to find themselves in a situation that they go bankrupt simply due to the fact that customers are overlooking them and do business with other retailers.
Next to providing customers what they know they want it is the tactic of being able to understand the customer in such a way that you can provide them services they did not knew they wanted. Surprising customers with unexpected services and options is vital for survival.
being able to deliver goods the same day to any location the customer might be or might visit, changing advertising screens based upon customers that are close to them, dynamically change pricing throughout the day, analyzing eye movement from customers to optimize shelving or deploying robots in stores to help customers.... all examples of retail innovations that more than real and are currently already used and tested by retailers.
Within this presentation a number of innovations are showcased and aligned with Oracle Cloud technology to support retailers to implement them. Leveraging the Oracle Cloud for retail innovation is something retailers should look into to ensure they are able to stay ahead of competition.
Security is becoming more and more a topic which is getting the attention it needs. Enterprises and C level executives start grasp the reality of the importance of security, legislation forcing enterprises to ensure the right level of security is in place to safeguard customer information and to ensure the safety of vital infrastructure services are pushing the topic in the right direction. Even though the topic is starting to get the correct level of attention the actual state of security at most enterprises is still lacking behind the reality of threads. The majority of enterprises are still relying on old and outdated mechanisms to secure their vital IT assets and data.
In this presentation an outline is given on the brutal truth of the state of security at the majority of enterprises. Additionally an insight is given in the solutions Oracle and the Oracle Cloud are providing to help enterprises to face the security challenges of today.
There will be almost no enterprise that will have all the systems in a single datacenter or with a single cloud provider. With the rise of hybrid cloud strategies and with the rise of cloud native and cloud born application we see more and more that application footprints become hybrid and span multiple cloud providers and in some cases also multiples clouds and customer datacenters. There are very good reasons for this and technically there are no issue in achieving this.
However, management and monitoring of systems and services in a distributed environment that is spanning multiple cloud vendors and private datacenters can become extremely difficult if you do not plan this and ensure you have a strategy for it. Planning for it and having a strategy for it can, and this is very advisable, include the use of one single and central management and monitoring application.
When you use the Oracle Cloud Management solution you can, for example, monitor an application as a single application even though it might span over multiple cloud vendors.
The screenshot above shows the automatically generated and updated application topology of an application spanning both the Oracle Public Cloud (OPC) and AWS. In this example we have servers and services that are consumed by both cloud providers, however, monitoring is done from a single solution.
Having the option to manage all your applications, regardless from the location where they reside is a big benefit for every company and can improve the stability of your IT footprint and lower the time needed to resolve incidents.
Base64 is a group of similar binary-to-text encoding schemes that represent binary data in an ASCII string format by translating it into a radix-64 representation. The term Base64 originates from a specific MIME content transfer encoding. For all clarity, Base64 encoding is NOT encryption and it will not make your message or data secure. However, a lot of good use cases for using a Base64 encoding exist and you will come across them frequently.
When working with Base64 encoded data (files, strings, etc) while developing scripting in Bash requires you to understand the basics of how to handle it. Under Oracle Linux the most common way is using the base64 command.
As an example, we have a string which we do want to apply base64 encoding on:
[vagrant@consul-dc2 tmp]$ echo "this is a clear text" | base64
dGhpcyBpcyBhIGNsZWFyIHRleHQK
[vagrant@consul-dc2 tmp]$
In the above example you will see that the clear text string is transformed into a base64 encoded string.
As an example, we have the base64 encoded string from the previous example and we want to decode this to clear text:
[vagrant@consul-dc2 tmp]$ echo "dGhpcyBpcyBhIGNsZWFyIHRleHQK" | base64 --decode
this is a clear text
[vagrant@consul-dc2 tmp]$
This, in effect, is all you have to do do handle base64 encoding under Oracle Linux.
Consul, developed by HashiCorp, is a tool commonly used for service discovery and service registration in microservice based landscapes. When running a distributed landscape spanning multiple datacenters or multiple Oracle Cloud zones you will, most likely, be running multiple cosul datacenter clusters. A consul datacenter cluster will take care of all service registration requests and all service discovery requests for this specific datacenter. Service discovery can be done based upon a REST API interface or it can be done based upon a DNS resolve mechanism.
Having stated that a Consul datacenter cluster takes care of all service registered in that datacenter is not fully true. You can connect the Consul clusters in the different datacenters or Oracle Cloud zones together with a concept called WAN gossip. Using WAN gossip the clusters will be aware of each other and you can use you local cluster to query services in the other datacenter.
An example of the construct of a FQDN is shown below. In this example we query a service named testservice in datacenter dc1. A DNS resolve on this FQDN will give you all the IP addresses for servers (or Docker containers) running this service.
testservice.service.dc1.consul
if we query the same Consul cluster without dc1 (testservice.service.consul) we will get exactly the same IP's as the DNS service from Consul will default the datacenter name to the name he is responsible for. however, if we query testservice.service.dc2.consul we will get a list of all IP's for instances for the testservice registered in the other datacenter.
In a lot of cases this is a very workable solution and it will solve most of the situations, it also gives a level of safeguard against cross-dc requests. However, in some cases you would like to have a full list of all IP's for a services without taking into consideration in which DC they reside.
In effect, Consul is not supporting this out of the box at this moment. If you use the API and not DNS the below command is the quickest way to get a list of all IP addresses for a service without taking into account in which datacenter they reside.
A similar command could be made using dig and leveraging the DNS way of doing things. However, for some reason it feels like this is a missing option in Consul.
Do note, we use JQ also, JQ is available from the Oracle Linux YUM repository, however, you will have to enable an additional channel as it is not available in the default enabled ones.
When writing scripting for Oracle Linux using Bash a very common scenario is that you want to write something to both the screen and to a file. In effect there is nothing that would prevent you from writing a line that will write to the screen and the other to write to a file. However, it is not that practical. You could decide to write a function that will take the line as input and will take both tasks. This will already limit the number of lines of code you might need. However a more gentle solution can be found in the tee command.
The tee command will read from standard input and write to standard output and files and can take the following flags:
-a, --append : append to the given FILEs, do not overwrite
so, in effect, if you want to write to screen and file in one single line of code you can use the tee command to achieve this. An example of this is shown below where we will write "Hello world" to both the screen and a file.
[root@docker consul]# echo "hello world" | tee /tmp/world.txt
hello world
[root@docker consul]# cat /tmp/world.txt
hello world
[root@docker consul]#
The nice thing about the tee command is that this will work for all output which is send to stdout. Meaning, you can spool almost everything to a file and show it on the screen at the same time.
