SYS-CON MEDIA Authors: Pat Romanski, Gary Arora, Zakia Bouachraoui, Yeshim Deniz, Liz McMillan

Blog Feed Post

20 Lines or Less # 54: Pools, Geo-IP, and Mobile

What could you do with your code in 20 Lines or Less? That's the question I ask (sometimes?) every week for the DevCentral community, and every week I go looking to find cool new examples that show just how flexible and powerful iRules can be without getting in over your head.

This week the forums provide us with more examples of iRules wizardry (or at least apprentice awesomeness) in a scant 20 lines or less each. The credit goes to the awesome community for providing such frequent and awesome examples. This week's installation of iRules goodness in particular is brought to you by hoolio, who despite the snow storm (perhaps because of it?) was iRuling away like the mad man he is. Showing off how to simplify geographical based redirection, how to smoothly access a particular pool given the right configuration, and how to do some fancy matching to search for strings of digits.

Mobile Redirects

In this example user Ruchir is looking to do some matching based on some mobile device needs. They have a somewhat complex set of requirements to strip out a set of 4 or 6 digits from a URI that could take multiple forms. Making clever use of the URI::path depth command and some intelligence built into switch, Aaron shows that this can be near trivial if you know what knobs to turn.


   1: when HTTP_REQUEST {
   2:     # Get the index of the last URI directory
   3:     set depth [URI::path [HTTP::uri] depth]
   5:     # Parse the last directory in the path
   6:     set last_dir [URI::path [HTTP::uri] $depth $depth]
   8:     # Parse everything after the last hyphen in the last directory
   9:     set digits [string trimleft [string range $last_dir [expr {[string last - $last_dir]}] end-1] -/]
  11:     log local0. "URI=[HTTP::uri], \$depth=$depth, \$last_dir=$last_dir, \$digits=$digits"
  13:     # Check if we parsed 4 or 6 digits
  14:     switch $digits {
  15:         [0-9][0-9][0-9][0-9] -
  16:         [0-9][0-9][0-9][0-9][0-9][0-9] {
  17:             # Found 4 or 6 digits, send a redirect
  18:             HTTP::redirect "$digits"
  19:         }
  20:     }
  21: }


Geo-IP Redirection

Geolocation is not a new concept in our products, but it is new to many users out there, and it's fantastic to see people bringing it up in the forums. In this example, the desire was to separate out several countries into their own landing pages. Aaron came through and made a much simpler version using switch and some cleaned up matching logic that shows this can be pretty easy indeed. I removed some of the country cases for brevity, but the idea remains intact.


   1: when HTTP_REQUEST {
   2:     if { [string tolower [HTTP::host]] equals "" && [HTTP::path] eq "/" }{
   3:         # Parse the client IP from the CDN header
   4:         set client_ip [HTTP::header value "Client-IP"]
   5:         if { $client_ip eq "" }{
   6:             # The header was empty/did not exist, so use the actual client IP
   7:             set client_ip [IP::client_addr]
   8:         }
   9:         set country [string tolower [whereis $client_ip abbrev]]
  10:         switch $country {
  11:             "af" -
  12:             "bh" -
  13:             "ye" { HTTP::redirect "${country}" } 
  14:             default {
  15:                 # Redirect all others
  16:                 HTTP::redirect ""
  17:             }
  18:         }
  19:     } else {
  20:         pool example_web_pool
  21:     }
  22: }


Pool Based on Inbound Port

Every so often we get a request from a user that wants to select a pool directly based off of something within the request. I.E. they want to add "/pool1" to the URI or they want to, as in this case, use the port number and append that to a pre-defined pool name and automatically direct traffic to a specific pool. In this case it is a way to specifically select a given node, as the user has one member per pool. That being said, we can do this, but not without one inherent issue in particular. If the pool doesn't exist, the connection will, understandably, fail. So what is a good way around this? The catch command! Aaron demonstrates how this works and gives a way for a backup plan in this snippet.


   3:     # Try assigning the pool based on the client destination port
   4:     # If the pool assignment fails, use the VS default pool
   5:     if {[catch {pool pool_[TCP::local_port]} result]}{
   6:         # Pool did not exist, so log the value for testing
   7:         # The VS default pool will be used
   8:         log local0. "pool_[TCP::local_port] doe not exist"
   9:     } else {
  10:         # Pool assignment succeeded
  11:     }
  12: }


Check back again next week, or better yet subscribe to the feed, for more examples of iRules less than 21 lines that you can add to your bag of tricks.



Read the original blog entry...

More Stories By Colin Walker

Coming from a *Nix Software Engineering background, Colin is no stranger to long hours of coding, testing and deployment. His personal experiences such as on-stage performance and the like have helped to foster the evangelist in him. These days he splits his time between coding, technical writing and evangalism. He can be found on the road to just about anywhere to preach the good word about ADCs, Application Aware networking, Network Side Scripting and geekery in general to anyone that will listen.

Colin currently helps manage and maintain DevCentral ( He is also a contributor in many ways, from Articles to Videos to numerous forum posts, to iRules coding and whatever else he can get his hands on that might benefit the community and allow it to continue to grow.

Latest Stories
Every organization is facing their own Digital Transformation as they attempt to stay ahead of the competition, or worse, just keep up. Each new opportunity, whether embracing machine learning, IoT, or a cloud migration, seems to bring new development, deployment, and management models. The results are more diverse and federated computing models than any time in our history.
On-premise or off, you have powerful tools available to maximize the value of your infrastructure and you demand more visibility and operational control. Fortunately, data center management tools keep a vigil on memory contestation, power, thermal consumption, server health, and utilization, allowing better control no matter your cloud's shape. In this session, learn how Intel software tools enable real-time monitoring and precise management to lower operational costs and optimize infrastructure...
"Calligo is a cloud service provider with data privacy at the heart of what we do. We are a typical Infrastructure as a Service cloud provider but it's been designed around data privacy," explained Julian Box, CEO and co-founder of Calligo, in this interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Isomorphic Software is the global leader in high-end, web-based business applications. We develop, market, and support the SmartClient & Smart GWT HTML5/Ajax platform, combining the productivity and performance of traditional desktop software with the simplicity and reach of the open web. With staff in 10 timezones, Isomorphic provides a global network of services related to our technology, with offerings ranging from turnkey application development to SLA-backed enterprise support. Leadin...
While a hybrid cloud can ease that transition, designing and deploy that hybrid cloud still offers challenges for organizations concerned about lack of available cloud skillsets within their organization. Managed service providers offer a unique opportunity to fill those gaps and get organizations of all sizes on a hybrid cloud that meets their comfort level, while delivering enhanced benefits for cost, efficiency, agility, mobility, and elasticity.
DevOps has long focused on reinventing the SDLC (e.g. with CI/CD, ARA, pipeline automation etc.), while reinvention of IT Ops has lagged. However, new approaches like Site Reliability Engineering, Observability, Containerization, Operations Analytics, and ML/AI are driving a resurgence of IT Ops. In this session our expert panel will focus on how these new ideas are [putting the Ops back in DevOps orbringing modern IT Ops to DevOps].
Darktrace is the world's leading AI company for cyber security. Created by mathematicians from the University of Cambridge, Darktrace's Enterprise Immune System is the first non-consumer application of machine learning to work at scale, across all network types, from physical, virtualized, and cloud, through to IoT and industrial control systems. Installed as a self-configuring cyber defense platform, Darktrace continuously learns what is ‘normal' for all devices and users, updating its understa...
Enterprises are striving to become digital businesses for differentiated innovation and customer-centricity. Traditionally, they focused on digitizing processes and paper workflow. To be a disruptor and compete against new players, they need to gain insight into business data and innovate at scale. Cloud and cognitive technologies can help them leverage hidden data in SAP/ERP systems to fuel their businesses to accelerate digital transformation success.
Concerns about security, downtime and latency, budgets, and general unfamiliarity with cloud technologies continue to create hesitation for many organizations that truly need to be developing a cloud strategy. Hybrid cloud solutions are helping to elevate those concerns by enabling the combination or orchestration of two or more platforms, including on-premise infrastructure, private clouds and/or third-party, public cloud services. This gives organizations more comfort to begin their digital tr...
Most organizations are awash today in data and IT systems, yet they're still struggling mightily to use these invaluable assets to meet the rising demand for new digital solutions and customer experiences that drive innovation and growth. What's lacking are potent and effective ways to rapidly combine together on-premises IT and the numerous commercial clouds that the average organization has in place today into effective new business solutions.
Keeping an application running at scale can be a daunting task. When do you need to add more capacity? Larger databases? Additional servers? These questions get harder as the complexity of your application grows. Microservice based architectures and cloud-based dynamic infrastructures are technologies that help you keep your application running with high availability, even during times of extreme scaling. But real cloud success, at scale, requires much more than a basic lift-and-shift migrati...
David Friend is the co-founder and CEO of Wasabi, the hot cloud storage company that delivers fast, low-cost, and reliable cloud storage. Prior to Wasabi, David co-founded Carbonite, one of the world's leading cloud backup companies. A successful tech entrepreneur for more than 30 years, David got his start at ARP Instruments, a manufacturer of synthesizers for rock bands, where he worked with leading musicians of the day like Stevie Wonder, Pete Townsend of The Who, and Led Zeppelin. David has ...
Darktrace is the world's leading AI company for cyber security. Created by mathematicians from the University of Cambridge, Darktrace's Enterprise Immune System is the first non-consumer application of machine learning to work at scale, across all network types, from physical, virtualized, and cloud, through to IoT and industrial control systems. Installed as a self-configuring cyber defense platform, Darktrace continuously learns what is ‘normal' for all devices and users, updating its understa...
Dion Hinchcliffe is an internationally recognized digital expert, bestselling book author, frequent keynote speaker, analyst, futurist, and transformation expert based in Washington, DC. He is currently Chief Strategy Officer at the industry-leading digital strategy and online community solutions firm, 7Summits.
Addteq is a leader in providing business solutions to Enterprise clients. Addteq has been in the business for more than 10 years. Through the use of DevOps automation, Addteq strives on creating innovative solutions to solve business processes. Clients depend on Addteq to modernize the software delivery process by providing Atlassian solutions, create custom add-ons, conduct training, offer hosting, perform DevOps services, and provide overall support services.