Welcome!

Python Authors: Matt Davis, AppDynamics Blog, Pat Romanski, Donald Meyer, Liz McMillan

Related Topics: Perl, Linux Containers, Open Source Cloud, PHP, Ruby-On-Rails, Apache, Python

Perl: Article

Using a Perl Debugger with Server Side Triggers

This article describes a method to use a perl debugger on trigger scripts without advanced interprocess debugging tools

Introduction

This article describes a method to use a perl debugger on trigger scripts without advanced interprocess debugging tools.

Using a perl debugger with a V4.x server side trigger launched by the server is very difficult and encounters two known obstacles:

  1. The server will fire the trigger and the debugger will run in a thread of the detached server process; the debugger will start but will probably not communicate with you. However, if you manually started the server via a shell command then the perl debugger will start, accept input from the keyboard, then you will loose contact with the debugger; it does not have exclusive access to the keyboard because it is running in the context of the detached server process. The next command you type will go to the shell, not the debugger.  It gets messy from there.
  2. Debugging on your live server means another AccuRev command could launch the same trigger in debug mode and the AccuRev client that issued the command will appear to be “hung” because the server thread for that command has called the debugger.  Also, if you started the server from the shell command, you will now have two debuggers trying to communicate with you. Running two different triggers in debug mode will create madness for you and get your users very upset!

Summary

  • Trigger parameter files facilitate communication between the server process and triggers.
  • The AccuRev server does not provide a mechanism to preserve trigger parameter files; they are temporary and removed.
  • XML is used for most trigger parameter files but some still use flat files. Study the original trigger to know how to process the format.
  • Modify the trigger file to capture and preserver the trigger parameter files. There can be many parameter files per transaction. Compose the file name based upon the trigger name, sequence number, and epoch second.
  • Practice continuous process improvement! Use a semaphore file to activate and deactivate the feature to capture the parameter data to a file. You will enable the feature for a few minutes to collect samples then disable it.  The semaphore allows you to reuse the feature without editing the trigger script.
  • Once you have enabled the facility and have collected a few trigger parameter dump files, choose an interesting one and make a copy; the copy step is important because the trigger you are debugging will reinitialize the trigger parameter file to return data back to the server. NOTE: Some triggers expect both an XML and flat parameter files. Study the trigger to determine the correct calling arguments.
  • Use the copy of the parameter file and pass it as a command line parameter to the trigger you run with a Perl debugger.
  • You can now single step through your trigger.
  • You must make a new copy of the original parameter file before restarting the debugging session because the file you passed into your trigger was reinitialized. You do not need to exit the debugger, just make a new copy of the trigger file before you issue the debugger “R” (restart) command.

Details

I extend AccuRev functionality to support development processes and I create complex triggers that are easier to develop with a Perl debugger; this is especially true when your triggers are manipulating issue tracking data.  The AccuRev CLI manual provides good information about the triggers but you might need subtle details that are beyond the scope of the documentation. Walking through trigger execution with a debugger gives details about the content of the parameter files and what is passed from trigger to trigger.

I am not aware of any special options to allow the AccuRev server to run Perl triggers in debug mode and my attempts to do so create an unworkable environment. Since triggers are driven by parameter files, I’ve added routines to all the triggers to collect their parameter files. Once I have a collection of interesting parameter files I can launch the trigger scripts with my own Perl debugging tool of choice instead of them being launched by the AccuRev server.  I can also inject faulty data via the parameter file for testing.

The AccuRev server creates a temporary parameter file for each trigger it is calling.  The file name will be a relative path to a temporary directory and each filename will be a sequence number. Please note that a trigger can be fired more than once for a transaction. The temporary file name does not indicate the target trigger script; the trigger name and the AccuRev command that fired the script are embedded in the parameter file.

I embrace the concept of continuous improvement so I anticipate trigger debugging will used many times over the years.  I used a semaphore file to enable and disable the parameter dump functionality to eliminate edits to the trigger scripts on the live repository.  I’ve even attached captured parameter files to issue tickets I’ve submitted to AccuRev support.

Capturing Parameter Files

The AccuRev server determines what trigger to launch then creates one or more temporary files in the cache directory of the site slice and passes a relative directory name and file name(s) in the argument list to the trigger. The server process will ensure a unique sequence number when multiple threads launch the same trigger at the same time.

The steps I use are:

  1. Set up my environment:
    1. Define the semaphore file name
    2. Define a directory below the accurev root to store the trigger parameter files.
  2. Immediately after the trigger has parsed the XML data, call a utility function and pass it the “hook” name and the relative path to the temporary trigger parameter file that was created by the server. The server created file name will be a sequence number.
  3. The utility function will look for the semaphore file in the AccuRev root directory and will simply exit when not found. When the semaphore file is found, the function will compose a unique file name based upon
    1. The trigger “hook” name
    2. The  server supplied file name (minus the directory)
    3. The current epoch second
  4. The utility function will create the trigger dump directory as needed, create the file name composed in step #3, and write the trigger parameter data to the new file.

Appendix A has an excerpt of my server_admin_trig.pl and trigger utility module. I save off the parameter file immediately after the trigger has digested the XML data.

I strive to write my perl code to be operating system agnostic. I keep my common trigger code in a perl module that resides in the accurev “bin” directory. I like to avoid external environment dependencies so I explicitly state the lib path (in an OS agnostic way) to my trigger utility module.  I do this because the “use” is a compile time directive and is processed before variables are defined.

Debugging the Trigger with the Captured Parameter File

You must make a copy of the captured trigger parameter file before you use it. Triggers re-initialize the parameter file to pass data back to the server so your captured data will be lost.

  1. cd $HOME
  2. cp $ACCUREV/trigDumpDir/server_admin_trig-0_0-1246634816   test.dat.org

You launch a perl debugger and pass the trigger parameter file into the script as the first command line argument. Debug to your heart’s content.

  1. cd $HOME
  2. cp $ACCUREV/storage/site_slice/triggers/server_admin_trig.pl    funTime.pl
  3. cp test.dat.org test.dat
  4. perl -d funTime.pl test.dat

NOTE:  The script will reinitialize the parameter file for output. You must copy “test.dat.org” to “test.dat” before you restart the debugging session.

Appendix A:

Server_admin_trig.pl – You can download this script here

Click to download

Click to download

Trig_utils.pm – You can download this script here

Click to download this script

Click to download

Sample of Captured Trigger Data

Below is the trigger parameter file captured from server_admin_trig.pl for a “mkdepot” command.

This is a simple example. The parameter data gets much more interesting when your objective is to mine transaction or issue tracking details.

Capture file name is: /opt/accurev/ar6060/trigDumpDir/server_admin_trig-0_0-1248023869

<triggerInput>
<depot>test10</depot>
<hook>server_admin_trig</hook>
<command>mkdepot</command>
<principal>ar6060</principal>
<ip>127.0.0.1</ip>
</triggerInput>

More Stories By Wayne Blair

Wayne has extensive experience creating and extending software development, release, and installation environments. Background includes source control systems and builds management, networking and operating systems, clustered systems, hardware, and virtual machine management. Key skills include anticipating/addressing development group needs, detail oriented, communicating technical information, versatile, and supportive.

@ThingsExpo Stories
Rodrigo Coutinho is part of OutSystems' founders' team and currently the Head of Product Design. He provides a cross-functional role where he supports Product Management in defining the positioning and direction of the Agile Platform, while at the same time promoting model-based development and new techniques to deliver applications in the cloud.
Business professionals no longer wonder if they'll migrate to the cloud; it's now a matter of when. The cloud environment has proved to be a major force in transitioning to an agile business model that enables quick decisions and fast implementation that solidify customer relationships. And when the cloud is combined with the power of cognitive computing, it drives innovation and transformation that achieves astounding competitive advantage.
IoT is rapidly becoming mainstream as more and more investments are made into the platforms and technology. As this movement continues to expand and gain momentum it creates a massive wall of noise that can be difficult to sift through. Unfortunately, this inevitably makes IoT less approachable for people to get started with and can hamper efforts to integrate this key technology into your own portfolio. There are so many connected products already in place today with many hundreds more on the h...
In his session at Cloud Expo, Alan Winters, U.S. Head of Business Development at MobiDev, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to maximize project result...
Personalization has long been the holy grail of marketing. Simply stated, communicate the most relevant offer to the right person and you will increase sales. To achieve this, you must understand the individual. Consequently, digital marketers developed many ways to gather and leverage customer information to deliver targeted experiences. In his session at @ThingsExpo, Lou Casal, Founder and Principal Consultant at Practicala, discussed how the Internet of Things (IoT) has accelerated our abilit...
In his keynote at 19th Cloud Expo, Sheng Liang, co-founder and CEO of Rancher Labs, discussed the technological advances and new business opportunities created by the rapid adoption of containers. With the success of Amazon Web Services (AWS) and various open source technologies used to build private clouds, cloud computing has become an essential component of IT strategy. However, users continue to face challenges in implementing clouds, as older technologies evolve and newer ones like Docker c...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, discussed the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
No hype cycles or predictions of zillions of things here. IoT is big. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, Associate Partner at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He discussed the evaluation of communication standards and IoT messaging protocols, data analytics considerations, edge-to-cloud tec...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settl...
In his session at @ThingsExpo, Dr. Robert Cohen, an economist and senior fellow at the Economic Strategy Institute, presented the findings of a series of six detailed case studies of how large corporations are implementing IoT. The session explored how IoT has improved their economic performance, had major impacts on business models and resulted in impressive ROIs. The companies covered span manufacturing and services firms. He also explored servicification, how manufacturing firms shift from se...
IoT is at the core or many Digital Transformation initiatives with the goal of re-inventing a company's business model. We all agree that collecting relevant IoT data will result in massive amounts of data needing to be stored. However, with the rapid development of IoT devices and ongoing business model transformation, we are not able to predict the volume and growth of IoT data. And with the lack of IoT history, traditional methods of IT and infrastructure planning based on the past do not app...
Organizations planning enterprise data center consolidation and modernization projects are faced with a challenging, costly reality. Requirements to deploy modern, cloud-native applications simultaneously with traditional client/server applications are almost impossible to achieve with hardware-centric enterprise infrastructure. Compute and network infrastructure are fast moving down a software-defined path, but storage has been a laggard. Until now.
Digital Transformation is much more than a buzzword. The radical shift to digital mechanisms for almost every process is evident across all industries and verticals. This is often especially true in financial services, where the legacy environment is many times unable to keep up with the rapidly shifting demands of the consumer. The constant pressure to provide complete, omnichannel delivery of customer-facing solutions to meet both regulatory and customer demands is putting enormous pressure on...
The best way to leverage your CloudEXPO | DXWorldEXPO presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering CloudEXPO | DXWorldEXPO will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at CloudEXPO. Product announcements during our show provide your company with the most reach through our targeted audienc...
DXWorldEXPO LLC announced today that All in Mobile, a mobile app development company from Poland, will exhibit at the 22nd International CloudEXPO | DXWorldEXPO. All In Mobile is a mobile app development company from Poland. Since 2014, they maintain passion for developing mobile applications for enterprises and startups worldwide.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
JETRO showcased Japan Digital Transformation Pavilion at SYS-CON's 21st International Cloud Expo® at the Santa Clara Convention Center in Santa Clara, CA. The Japan External Trade Organization (JETRO) is a non-profit organization that provides business support services to companies expanding to Japan. With the support of JETRO's dedicated staff, clients can incorporate their business; receive visa, immigration, and HR support; find dedicated office space; identify local government subsidies; get...
DXWorldEXPO LLC announced today that the upcoming DXWorldEXPO | CloudEXPO New York event will feature 10 companies from Poland to participate at the "Poland Digital Transformation Pavilion" on November 12-13, 2018.
The current age of digital transformation means that IT organizations must adapt their toolset to cover all digital experiences, beyond just the end users’. Today’s businesses can no longer focus solely on the digital interactions they manage with employees or customers; they must now contend with non-traditional factors. Whether it's the power of brand to make or break a company, the need to monitor across all locations 24/7, or the ability to proactively resolve issues, companies must adapt to...
"We view the cloud not as a specific technology but as a way of doing business and that way of doing business is transforming the way software, infrastructure and services are being delivered to business," explained Matthew Rosen, CEO and Director at Fusion, in this SYS-CON.tv interview at 18th Cloud Expo (http://www.CloudComputingExpo.com), held June 7-9 at the Javits Center in New York City, NY.