Friday, February 4, 2022

Out now: Flows for APEX 22.1!

We are proud to announce the general availability of Flows for APEX 22.1. You can download a free copy of this open source software at https://flowsforapex.org.

Major new features of 22.1 include:

- declaratively sending an e-mail using the service task in BPMN

- support for repeating timers for non-interrupting boundary events

- timers supporting the Oracle date/interval format during modeling

- to prevent lost updates, we have introduced a "step key"

- the modeler having the Monaco text editor integrated

- APEX metadata being leveraged by the properties panel in the modeler

- support for a business rule task in BPMN

- an enhanced sample app "Expense Claims" to reflect most features of Flows for APEX 22.1

Have a look at the readme file in the software distribution to see a complete list of all enhancements.


To give you an overview of what is new in Flows for APEX 22.1 and how the upgrade path looks like, we invite everybody to join one of the following online sessions:

15-FEB 2022 15:00-16:30 SGT / 08:00-09:30 CET (EMEA/Asia Pacific area)

15-FEB 2022 12:00-13:30 EST / 18:00-19:30 CET (EMEA/America area)


You can register for these free sessions here:


EMEA/Asia Pacific area: https://zoom.us/meeting/register/tJIpdeivqDwoHtIIgAlf45zN8Gzy2u5YAfaa

EMEA/America area: https://zoom.us/meeting/register/tJEqf-qorj4jH9Xi52zSpQHSZzZvZB7f3lIf


Yours truly,

The Flows for APEX team

https://flowsforapex.org

Sunday, January 30, 2022

Protect your public server!

During the week, a DDoS attack with over 384 IP addresses from all over the world was started on our public Oracle APEX server. As we do like people (and proper bots) to make use of our free services to provide information about Oracle APEX, the bots managed to request an APEX page around 1.000 times a minute! With that many page views, the connection pool of Oracle REST Data Services (ORDS) with maximum 30 DB connections got full and people were starting to see an error message from ORDS. Of course we could scale up the connection pool with the database, but that would mean we had to scale up our hardware too, as ORDS was already taking up 100% CPU. Instead, my colleague Moritz Klein quickly found a way to throttle-down the requests in our proxy server installed in front of ORDS. We used a module called "event MPM". The configuration looks like this:

# event MPM
# StartServers: initial number of server processes to start
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestWorkers: maximum number of worker threads
# MaxConnectionsPerChild: maximum number of requests a server process serves
<IfModule mpm_event_module>
StartServers 2
MinSpareThreads 25
MaxSpareThreads 75
ThreadLimit 64
ThreadsPerChild 25
MaxRequestWorkers 75
MaxConnectionsPerChild    0
</IfModule>

What I like about this module, is that it doesn't reject requests, but it puts them in a queue instead. The user accessing the site has to wait longer before the application responds, but doesn't receive an error. After enabling this, the ORDS errors in the Tomcat log went away and the CPU load went down to 70%.

Of course, this didn't solve the problem. The question now was how to get rid of these requests? Nice bots, like Yanbot, just need a file called robots.txt and will respect this, but bad bots just ignore this standard.

We decided to install fail2ban and let it catch all incoming requests somewhere in the weekend (when normally very little traffic is expected) in order to block these directly at the firewall. After that, we set it to allow x requests in a certain time span, so that most people can still visit the site, but most new bots will be rejected at the firewall. For those of you that are not aware of what fail2ban is, it analyzes log files and blocks IP addresses for a certain time in the firewall (using iptables) based on criteria you define. Here is a great blog post about fail2ban: https://pipo.blog/articles/20210915-fail2ban-apache-dos

If you are not into Linux, you might want to use Cloudfare or Akamai and put their service in front of your server. For all Linux experts out there, I can also recommend mod_security, as it will give you even more possibilities to defend you from DDoS attacks, but it does require a 2-day training to get the hang of it. :)

Hope this helps to protect your public server before it hits you as well.

Tuesday, September 28, 2021

Flows for APEX 21.1: what's new

Flows for APEX is an extension for Oracle Application Express (APEX) that lets you model and run processes based on the BPMN 2.0 standard. This blog article will address some of the key features introduced with version 21.1.

Setting process variables before and/or after each step


With the help of process variables, information can be stored persistently in the database over the entire duration of a process instance. You can set a process variable through the PL/SQL API or, with 21.1, do this declarative for each step in the BPMN model. The variables are meant to be set at special trigger points in the model (e.g., after a task has been executed or before the process is split up at a gateway) and read out again at a later point in time without the need of an APEX session.

Restart failed tasks


Sometimes the execution of a step in a process fails, so that the process cannot continue. In this case, the transaction of the current step is rolled back, and the instance is set to an error state. With the help of the previously mentioned auditing capabilities, the error can be located and fixed. To restart the step, either execute the PL/SQL procedure flow_api_pkg.flow_restart_step or press the corresponding button on the Flow Monitor page.


More engine app enhancements


The Flows for APEX engine app is used to manage the BPMN models and process instances. With version 21.1, several enhancements have been made:

- Use of keyboard shortcuts in the modeler (copy, paste, save)

- Support for dark mode

- Layout adjustments to support different screen sizes

- Bulk export/import of models

- Export of a model or an instance as SVG


Process plug-ins for a true low-code experience

Next to the existing region plug-in “Flows for APEX viewer” for displaying BPMN models, 3 process plug-ins were introduced that can be used in your own APEX application to manage a flow instance without the need of custom coding: 

1. Management of the entire flow instance (start, stop, terminate, reset, delete)

2. Management of a single step within the flow instance (start, reserve, release, complete)

3. Management of process variables of a flow instance (setting / reading out the variables in conjunction with APEX page items)

The plugins are included in the distribution of the Flows for APEX application and can be easily exported and imported to be used in own applications.


Auditing

During the execution of a process flow, information is written to a logging table at various points in Flows for APEX. This includes events occurring at instance level as well as task-level together with a timestamp and the calling user. These can be called upon in the engine app via the detail page of a process instance for management and debugging purposes. Furthermore, logging information for a specific step in the instance can be displayed by simply clicking on it in the Flows for APEX Viewer.


Sample app “Expense Claims”

To demonstrate the integration of Flows for APEX in an APEX application, a new demo application comes with the distribution of Flows for APEX 21.1. This application covers a simple expense claim process and helps APEX developers to understand how to develop process-driven applications.

For those that want to learn the integration step-by-step, I can recommend our Flows for APEX tutorial, freely available at https://flowsforapex.mt-ag.com


Download your copy of Flows for APEX at https://flowsforapex.mt-ag.com

Project on Github: https://github.com/mt-ag/apex-flowsforapex