Andrejus Baranovski

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Blog about Oracle, Full Stack, Machine Learning and Cloud
Updated: 22 min 49 sec ago

Building Dynamic UI Form with Oracle JET

Mon, 2020-03-09 08:05
Dynamic form is a common requirement when building more advanced UIs. With Oracle JET you have all the tools available to build dynamic form. One of the examples of dynamic form requirements - report parameter capture screens. Building fixed forms to capture parameters for each report would be an overkill. A smarter approach is to build one dynamic form, which would handle a set of different UI components and render based on metadata received from the service.

Dynamic form example:


When values are changed, we can capture all changes while submitting the form - value printed in the log:


In the heart of dynamic form logic, we are using JET bind for each tag, it renders form elements from metadata:


Each element is checked and based on the type - UI field is rendered through JET if tag. Input field properties are fetched from metadata.

Example of metadata structure - array. It is important to use Knockout observable for value property. This will allow capturing user input. When we submit the form, we can iterate through the array and read value property:


Sample code available on GitHub.

Handy TensorFlow.js API for Client-Side ML Development

Thu, 2020-02-20 01:45
Let’s look into TensorFlow.js API for training data handling, training execution, and inference. TensorFlow.js is awesome because it brings Machine Learning into the hands of Web developers, this provides mutual benefit. Machine Learning field gets more developers and supporters, while Web development becomes more powerful with the support of Machine Learning.


Read more - Handy TensorFlow.js API for Client-Side ML Development.

Time-Series Prediction Beyond Test Data

Thu, 2020-01-23 12:13
I was working on the assignment to build a large scale time-series prediction solution. I end up using a combination of approaches in the single solution — Prophet, ARIMA and LSTM Neural Network (running on top of Keras/TensorFlow). With Prophet (Serving Prophet Model with Flask — Predicting Future) and ARIMA it is straightforward to calculate a prediction for future dates, both provide a function to return prediction for a given future horizon. The same is not obvious with LSTM, if you are new — this will require a significant amount of time to research how to forecast true future dates (most of the examples are showing how to predict against test dataset only).

I found one good example though which I was following and it helped me to solve my task — A Quick Example of Time-Series Prediction Using Long Short-Term Memory (LSTM) Networks. In this post, I will show how to predict shampoo sales monthly data, mainly based on the code from the above example.

Read more - Time-Series Prediction Beyond Test Data.


Publishing Keras Model API with TensorFlow Serving

Tue, 2019-12-24 11:40
Building a ML model is a crucial task. Running ML model in production is not a less complex and important task. I had a post in the past about serving ML model through Flask REST API — Publishing Machine Learning API with Python Flask. While this approach works, it certainly lacks some important points:

  • Model versioning 
  • Request batching 
  • Multithreading 

TensorFlow comes with a set of tools to help you run ML model in production. One of these tools — TensorFlow Serving. There is an excellent tutorial that describes how to configure and run it — TensorFlow Serving with Docker. I will follow the same steps in my example.

Read more in my Towards Data Science post.

Multiple Node.js Applications on Oracle Always Free Cloud

Thu, 2019-11-28 08:26
What if you want to host multiple Oracle JET applications? You can do it easily on Oracle Always Free Cloud. The solution is described in the below diagram:


You should wrap Oracle JET application into Node.js and deploy it to Oracle Compute Instance through Docker container. This is described in my previous post - Running Oracle JET in Oracle Cloud Free Tier.

Make sure to create Docker container with a port different than 80. To host multiple Oracle JET apps, you will need to create multiple containers, each assigned with a unique port. For example, I'm using port 5000:

docker run -p 5000:3000 -d --name appname dockeruser/dockerimage

This will map standard Node port 3000 to port 5000, accessible internally within Oracle Compute Instance. We can direct external traffic from port 80 to port 5000 (or any other port, mapped with Docker container) through Nginx.

Install Nginx:

yum install nginx

Go to Nginx folder:

cd etc/nginx

Edit configuration file:

nano nginx.conf

Add context root configuration for Oracle JET application, to be directed to local port 5000:

location /invoicingdemoui/ {
     proxy_pass http://127.0.0.1:5000/;
}

To allow HTTP call from Nginx to port 5000 (or other port), run this command (more about it on Stackoverflow):

setsebool -P httpd_can_network_connect 1

Reload Nginx:

systemctl reload nginx

Check Nginx status:

systemctl status nginx

That's all. Your Oracle JET app (demo URL) now accessible from the outside:

Getting Your Hands Dirty with TensorFlow 2.0 and Keras API

Thu, 2019-10-31 15:00
Diving into technical details of the regression model creation with TensorFlow 2.0 and Keras API. In TensorFlow 2.0, Keras comes out of the box with TensorFlow library. API is simplified and more convenient to use.


Read the complete article here.

SEO for Single Page Oracle (SPA) JET Application

Thu, 2019-10-24 02:49
This is a quick tip post related to Oracle JET.

SEO (search engine optimization) is a must for a public website or public-facing app. Search engines do indexing well for static HTML pages. Oracle JET on contrary follows SPA (single page application) approach with dynamic UI. This makes it harder for the search engines to build an index for such an app. The same applies to any other SPA implementations with Angular, React, Vue.js, etc.

If you want to build SEO support for Oracle JET, similar solutions as for Angular, React or Vue.js SPAs apps can be applied.

One of the simpler and reliable solutions - generate static HTML pages for Oracle JET SPA app. You can follow this article, it explains how the same can be done for Angular - SEO for Single Page Applications.

Machine Learning with SQL

Sat, 2019-10-19 10:25
Python (and soon JavaScript with TensorFlow.js) is a dominant language for Machine Learning. What about SQL? There is a way to build/run Machine Learning models in SQL. There could be a benefit to run model training close to the database, where data stays. With SQL we can leverage strong data analysis out of the box and run algorithms without fetching data to the outside world (which could be an expensive operation in terms of performance, especially with large datasets). This post is to describe how to do Machine Learning in the database with SQL.



Read more in my Towards Data Science post.

Running Oracle JET in Oracle Cloud Free Tier

Wed, 2019-09-25 13:09
OOW'19 stands up from recent years OOW conferences with important announcement - Oracle Cloud Free Tier offering. This offering includes two free DB instances and two free compute VM instances. What else you could wish for the side and hobby projects? This is a strong move by Oracle and it should boost Oracle Cloud. Read more about it in Oracle Cloud Free Tier page.



It was interesting to test how to deploy Oracle JET app to Oracle Always Free instance of compute VM. I will not go through the initial steps, related how to create VM instance and enable internet access (for the port 80). You can read all that in a nice write up from Dimitri Gielis post.

Assuming you already have created Oracle JET app and want to deploy it. One way would be to set up Node.js and Nginx on the compute VM and pull app source code from Git. I prefer another way - to go through Docker container, Nginx would act as HTTP server to redirect requests to Docker container port. But in this post for simplicity reasons, we are not going to look into Nginx setup - will focus only on JET deployment through Docker container.

1. Create an empty Node application (follow these steps):

express --view=pug

2. Add dependencies, go into the Node app and run:

npm install

3. Copy Oracle JET content from web folder into Node app public folder (remove existing files)

4. Inside Node app, adjust app.js file, comment out these lines:

var usersRouter = require('./routes/users');

app.set('view engine', 'pug');

app.use('/users', usersRouter);

5. Keep only index.js file in router folder

6. Remove template files from views folder

7. Update index.js file to redirect to Oracle JET index.html

router.get('/', function(req, res, next) {
  //res.render('index', { title: 'Express' });
  res.sendFile('index.html', {root: './public/'});
});

8. Note down port 3000 info from bin/www, this is the port Node app will run in Docker container

9. Create Dockerfile inside Node app folder (follow these steps). Content:

FROM node:10

# Create app directory
WORKDIR /usr/src/app

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ./

RUN npm install
# If you are building your code for production
# RUN npm ci --only=production

# Bundle app source
COPY . .

EXPOSE 3000
CMD [ "node", "./bin/www" ]

10. Create .dockerignore file. Content:

node_modules
npm-debug.log

11. Build Docker image locally, by running below command inside Node app:

docker build -t username/imagename -f ./Dockerfile .

12. Push Docker container to Docker Hub. This way we will be able to pull container from Oracle compute VM in the cloud:

docker push username/imagename

---

Next steps are executed inside Oracle compute VM. You should connect through SSH to run below commands.

13. Install Docker (run sudo su):

yum install docker-engine

14. Enable Docker:

systemctl enable docker

15. Start Docker:

systemctl start docker

16. Check Docker status:

systemctl status docker.service

17. Check Docker version:

docker version

18. Login into Docker Hub, to be able to pull the container with Node app. If login doesn't work (access permission issue), run this command: sudo usermod -a -G docker $USER

docker login

19. Run container:

docker run -p 80:3000 -d --name appname username/imagename

Node app with Oracle JET content can be accessed by port 80 using public IP of your Oracle container VM: http://130.61.241.30/index.html

Oracle JET app runs on Oracle container VM free tier:

Comprehensive TensorFlow.js Example

Mon, 2019-09-23 14:45
I have implemented an app which includes TensorFlow.js API usage. First I will walk you through the app functionality and then will dive into implementation details. This app implements a business report execution time prediction use case (this time in JavaScript), which was explained in my previous post — Report Time Execution Prediction with Keras and TensorFlow.

Read more in my Towards Data Science post.


Using Web Worker for Long Tasks in Oracle JET

Tue, 2019-09-10 02:42
JavaScript app runs in a single thread. This means if there is a long-running resource-intensive operation - the thread will be blocked and the page will stay frozen until operation completes. Obviously, this is not user-friendly and such behavior should be avoided. We can use Web Workers, through Web Workers we could run long-running operations in separate threads, without blocking the main thread. Code running in Web Worker doesn't have access to UI DOM, this means logic coded in Web Worker should operate with logic which is not directly related to UI.

Sample app contains commented code in dashboard.js. This code blocks main thread for 10 seconds, if you uncomment it - you will see that app becomes frozen for 10 seconds:


Web Worker is defined in dashboard.js. Web Worker is a separate JS file, which is being used for Worker object. API allows to send and receive messages, this way we can communicate to and from Web Worker (start a new task and receive message when task is completed):


Web Worker code - onmessage invoked when the message arrives from the main thread. postMessage sends message back to the main thread:


The sample app is available on GitHub repo.

Oracle JET - How To Reference JavaScript Module in HTML

Sun, 2019-08-11 07:06
I will explain how to reference JavaScript module function in Oracle JET HTML. In previous Oracle JET versions, we were using $root to access parent appController module. Syntax $root looks a bit like magic, it is better to reference module through a predefined variable. I will show you how.

Sample app comes with number converter, which helps to format numeric value. For convenience reasons and better reuse, number formatting function is moved to a separate module. Our goal is to call function self.convertNumericValue from converter module inside our module HTML:


Import the converter module into your target module. Make sure to define a variable for the import. Then define the local variable and assign it with the value pointing to the imported module. This will allow calling functions from the imported module, anywhere within our target module:


To demonstrate how it works, I will include a call to format number for the table column. I have defined a table column template for that reason:


Within the template, I'm calling converter (function is called by referencing local variable) to format number:


It works well, the column with salary values is formatted by function from the imported module:


A sample application is available on my GiHub repo.

Oracle JET Model ID Attribute

Tue, 2019-08-06 01:20
When building Oracle JET Model/Collection structure to render table, you should be careful defining ID attribute. This attribute must have unique values only, if there will be duplicates in ID, then table rows will be rendered incorrectly.

Take as example below structure for Employees REST endpoint. EmployeId attribute provides unique values and it should be defined as ID for JET model:


Let's try and see what happens when non-unique DepartmentId attribute is set for a key in JET model:


In this case, during data fetch and UI table rendering (specifically when navigating to the next page of the table) - JET runtime for the table will get confused and will fetch all of the records from the backend (definitely, not what we want):


Ok, change it to the proper one - use EmployeeId for the ID in JET model:


The table works as expected:


Lesson learned - make sure to use an attribute with unique values for JET model ID. If there is no single attribute with unique values, the concatenate multiple attributes on the backend to construct a single attribute with unique value.

Source code is available from my GitHub repo.

Report Time Execution Prediction with Keras and TensorFlow

Thu, 2019-08-01 01:03
The aim of this post is to explain Machine Learning to software developers in hands-on terms. Model is based on a common use case in enterprise systems — predicting wait time until the business report is generated.

Report generation in business applications typically takes time, it can be from a few seconds to minutes. Report generation requires time, because typically it would fetch and process many records, this process needs time. Users often get frustrated, they don’t know how long to wait until the report is finished and may go away by closing browser, etc. If we could inform user, before submitting the report request — how it long it will take to execute it, this would be great usability improvement.

I have implemented Machine Learning model using Keras regression to calculate expected report execution time, based on training data (logged information from the past report executions). Keras is a library which wraps TensorFlow complexity into simple and user-friendly API.

Python source code and training data is available on my GitHub repo. This code is based on Keras tutorial.

Fix for Oracle VBCS "Error 404--Not Found"

Tue, 2019-07-16 01:13
We are using Pay As You Go Oracle VBCS instance and had an issue with accessing VBCS home page after starting the service. The service was started successfully, without errors. But when accessing VBCS home page URL - "Error 404--Not Found" was returned.

I raised a support ticket and must say - received the response and help promptly. If you would encounter similar issue yourself, hopefully, this post will share some light.

Apparently "Error 404--Not Found" was returned, because VBCS instance wasn't initialized during instance start. It wasn't initialized, because of expired password for VBCS DB schemas. Yes, you read it right - internal system passwords expire in Cloud too.

Based on the instructions given by Oracle Support, I was able to extract logs from VBCS WebLogic instance (by connecting through SSH to VBCS cloud machine) and provide it to support team (yes, VBCS runs on WebLogic). They found password expire errors in the log, similar to this:

weblogic.application.ModuleException: java.sql.SQLException: ORA-28001: the password has expired

Based on provided instructions, I extracted VBCS DB schema name and connected through SQL developer. Then I executed SQL statement given by support team to reset all VBCS DB passwords in bulk. Next password expiry is set for 2019/January. Should it expire at all?

Summary: If you would encounter "Error 404--Not Found" after starting VBCS instance and trying to access VBCS home page, then most likely (but not always) it will be related to VBCS DB schema password expiry issue.

Forecast Model Tuning with Additional Regressors in Prophet

Mon, 2019-07-15 04:17
I’m going to share my experiment results with Prophet additional regressors. My goal was to check how extra regressor would weight on forecast calculated by Prophet.

Using dataset from Kaggle — Bike Sharing in Washington D.C. Dataset. Data comes with a number for bike rentals per day and weather conditions. I have created and compared three models:

1. Time series Prophet model with date and number of bike rentals
2. A model with additional regressor —weather temperature
3. A model with additional regressor s— weather temperature and state (raining, sunny, etc.)

We should see the effect of regressor and compare these three models.

Read more in my Towards Data Science post.

Oracle ADF A Status Update

Wed, 2019-07-03 14:11
Oracle posted information update for Oracle ADF - "With the continuous investment and usage of Oracle ADF inside Oracle we expect external customers will also continue to enjoy the benefits of Oracle ADF for many more years."

Read the complete post here: https://blogs.oracle.com/jdeveloperpm/oracle-adf-a-status-update

Happy to read the update, sounds positive. Thanks to Oracle for taking time and publishing this information. #adf #middleware #javascript #oracle #cloud #oraclefusion

Serving Prophet Model with Flask — Predicting Future

Wed, 2019-07-03 08:23
The solution to demonstrate how to serve Prophet model API on the Web with Flask. Prophet — Open-Source Python library developed by Facebook to predict time series data.

An accurate forecast and future prediction are crucial almost for any business. This is an obvious thing and it doesn’t need explanation. There is a concept of time series data, this data is ordered by date and typically each date is assigned with one or more values specific to that date. Machine Learning powered models could generate forecasts based on time series data. Such forecasts could be an important source of information for business decisions.

Read more in my Towards Data Science post.

Oracle Developer Tools - Do They Still Exist?

Wed, 2019-06-26 01:55
People are frustrated about @OracleADF @JDeveloper on social media - "ADF boat has no captain", etc. I agree @Oracle is to blame big time for such lame handling of its own Developer Tools stack. @Oracle please wake up and spend some budget on @OracleADF. Read more:

Oracle VBCS - right now this tool gets the most of Oracle focus. Supposed to offer declarative #JavaScript development experience in the Cloud. Not well received by the community. Are there any VBCS customers, please respond if yes?

Oracle APEX - comes with a very strong community (mostly backed by DB folks). But is not strategic for Oracle. More likely will be used by PL/SQL guys then by Java or Web developers. 

Oracle JET - highly promoted by Oracle. Set of opensource #JavaScript libs, glued by Oracle layer. Nice, but can't be used as a direct replacement for @OracleADF, JET is UI layer only. Oracle folks often confuse community by saying - Oracle JET is a great option to replace ADF

Oracle Forms - still alive, but obviously can't be strategic Oracle platform. A few years ago, Oracle was promoting Forms modernization to @OracleADF

Summary - Oracle Developer tools offering is weak. Lack of Oracle investment into development tools - makes Oracle developers community shrink.

Running Oracle JET as Progressive Web App

Sat, 2019-06-15 09:44
Progressive Web Apps (PWA) topic is a hot thing in web development these days. Read more about it - Progressive Web Apps. The beauty and power behind PWA - user can install a web app to his mobile device, without going through the app store. This simplifies update process too, when a new version of the app is available, the user will get it straight away, because it is essentially a Web page, wrapped to look like an installed app.

Inspired by this post - A Simple Progressive Web App Tutorial, I decided to add PWA config into Oracle JET app and test how it works (on Android, didn't test on iOS, but there is nothing JET specific, if PWA is supported on iOS, it should work).

Oracle JET PWA sample app is deployed on Heroku (PWA will work only if the app is coming through HTTPS) and available under this URL. The sample app is available on GitHub repo. Node.js wrapper for this sample is available in another GitHub repo, you can use it to deploy on Heroku or another service.

Access JET app URL, the app will be loaded and you should see Android notification in the bottom. Google Chrome mobile browser automatically is recognizing PWA app by manifest and offers to "install" it by adding to the home screen:


Select notification and you will get a confirmation message:


Select "Add" and Web app will be added to the home screen. It will look like a real mobile app for the user. For example, the user could get runtime stats for the app, check storage and data usage metrics:


The app is added to the home screen (look for Oracle  JET icon):


Select the app icon and app will be opened. There is no URL address bar in the header and indeed it looks like a mobile app, not a Web page:


The app will be recognized as PWA, if certain config steps were implemented. One of them - you need to add manifest file (add it in Oracle JET in the same folder as index.html) and provide app icons, name, etc.:


The manifest file must be included through a reference in the app entry point - index page (Oracle JET index.html page for example):


In addition to manifest, the app must define a service worker (same as manifest file, you can create this file in the same directory as Oracle JET index.html). PWA doesn't only bring the visual experience of the real app to the Web application. You can define a cache store for the app files, this means next time when offline - app files will load from local cache storage, there will be no need to download them from the internet:


Service worker can be registered from main.js file where Oracle JET context is initialized on the application initial load. Add service worker registration at the bottom of main.js:


The idea of this post was to share a simple example of PWA for Oracle JET. This should help you to get started quickly with PWA support config for Oracle JET app.

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