Ash Tewari – Page 4

KeyNode with Node.js and Microsoft Azure

KeyNode is a application to issue and verify software license keys. Technology stack for KeyNode is Node.js, MongoDB and Microsoft Azure.

I had built this functionality with C9.io (a cloud-based IDE with a built-in source code repository and debugger), mongohq (MongoDB as a service – now part of compose.io) and appfog (Cloud PAAS built on top of CloudFoundry). It used SMTP/gmail to email license files. That was the version I created a couple of years ago to issue tamper-proof signed xml license files for CodeDemo (a code snippet tool for developers, presenters and instructors).

For KeyNode (open source) I switched to a different toolset : Visual Studio Code and Windows Azure, simplified the code to remove signed xml file and open-sourced it on GitHub. Signed xml allowed offline verification in CodeDemo (a Wpf/Desktop app). Removing signed xml requires verification to happen online. I am working on adding the web endpoint for verification of license keys. This version uses SendGrid to email license keys. KeyNode is deployed as a Windows Azure Web App. The Azure Web App is on Continuous Deployment feed from the source code repository on GitHub.

I created and tested this Node.js application locally without IIS and deployed it as an Azure Web App without making any changes to the code at all. Node.js applications are hosted in Azure under IIS with iisnode. Iisnode is a native IIS module that allows hosting of node.js applications in IIS on Windows. Read more about iisnode here. Iisnode architecture also makes it significantly easier to take advantages of scalability afforded by Azure.

KeyNode is a work in progress. My plan is to use this as the basis for further explorations in the following areas :

DevOps, Docker and Microservices (at miniature scale of course!)
Create a Web UI with Express (a Node.js web application framework)
Integrate with Azure Storage/Queues
and more…

I invite you to check out the live site on Azure and fork it for your own experiments : KeyNode on GitHub.

Resources :

Photo Credit : Piano Keyboard (www.kpmalinowski.pl)

Using Powershell with Splunk

Splunk Powershell Resource Kit is a convenient and very capable wrapper over Splunk REST API. You can use the Powershell commandlets exposed by this resource kit to deploy, check and manage splunk services as well as execute splunk searches. In this post, you will be introduced to the Splunk Powershell Resource Kit, you will learn how to use powershell commandlets to connect to a splunk instance and execute searches.

1. First, you will need to download the resource kit from github.
2. Installation is very simple. All you have to do is download and extract the files from the zip archive and double click on install.bat to install the splunk powershell module.
3. Open Windows Powershell console from Windows Start menu.
4. Verify that the Splunk module is installed by executing Get-Module commandlet.

Get-Module SplunkSearch

5. Import splunk resource kit commandlets using Import-Module command.

Import-Module -Name Splunk

6. Next, you need to use Get-Credentials and then Connect-Splunk commandlets to connect to splunk. You need to do this once per session or if you need to switch to a different splunk instance.

$credential = Get-Credential
Connect-Splunk -Credential $credential -ComputerName localhost

I have a local Splunk Enterprise instance running on my machine, so I am using localhost as the ComputerName to connect to it. If you have a SplunkCloud subscription you can use YourSubscriptionId.splunkcloud.com as the ComputerName to connect to your subscription. Like so –

Connect-Splunk -Credential $credential -ComputerName MySubscription.splunkcloud.com

7. Next, use Search-Splunk commandlet to execute searches –

Search-Splunk -Search "Error"

Here is a sample script:

$lastDay = ( get-date ).addDays( -1 ).toString( ‘s’ )

$searches = @(
    "ERROR"
    , "source=""tutorialdata.zip:*"" ERROR"
    , "CreditDoesNotMatch"
    ,"source=""tutorialdata.zip:.\\www3/access.log"" productId=WC-SH-G04"
)

Write-Output $lastDay
foreach($search in $searches)
{
    $qry = $search + " | stats count"
    Write-Output $qry
    Search-Splunk -Search $qry -StartTime $lastDay | Select-Object -ExpandProperty Count
}

The sample script executes multiple Splunk searches and outputs the count of results matching these search queries. Note that I am “-StartTime” parameter to scope the search to a narrower time window and “stats count” command to get the count of results. You can get this sample script as a github gist.

You can also use -EndTime and –MaxReturnCount to further constrain the query results and Format-List, Format-Table, Format-Wide commands to format the results. You can learn more about other Search parameters as well as other capabilities exposed in the resource kit documentation.

Resources :

Image credit : terminal by Andrea Mazzini from the Noun Project

PackRaft with Xamarin and Microsoft Azure

PackRaft is a cross-platform mobile application built with Xamarin. It integrates with Microsoft Azure services, such as Azure Table Storage and Azure App Service. It is created with Xamarin.Forms for iOS and Android (Windows version will be coming soon).

The purpose of creating this sample application was to expand expertise in cross-platform mobile development with Windows Azure integration, specifically with Xamarin.Forms and Azure App Service. With Xamarin.Forms, it is possible to achieve close to 100% code reuse across these platforms for certain type of apps. Azure App Service provide a set of rich cloud backend services for your mobile applications.

PackRaft allows the user to setup a fleet of vehicles of various seating capacities. Groups of riders are assigned to these rides according to the count of riders in each group. You can specify that certain groups be kept together on a single vehicle – and the app tries to honor those requests if possible. I did this via a rudimentary implementation of a bin packing algorithm. This implementation is deployed as an API App in Microsoft Azure.

PackRaft uses Azure Mobile Services SDK to persist Fleet data to Azure Table Storage and to authenticate users with Facebook and Microsoft accounts. Twitter and Google account authentication is also supported by Azure Mobile Services SDK out of the box and those will also be enabled in PackRaft soon.

PackRaft is available on Android, iPhone and iPad.

Does Xamarin have a future?

Xamarin‘s cross-platform mobile application framework has Xamarin.iOS and Xamarin.Android at its core. Both Xamarin.Android and Xamarin.iOS are based on Mono. Mono is an open source implementation of .NET (CLI and CLS). Xamarin’s customers are Microsoft (.NET) shops. Microsoft is open sourcing .NET itself. What does all this mean for Xamarin?

Is Xamarin’s competitive advantage going to be undermined by the open source .NET? Microsoft’s Universal Application Platform (UAP) and the promise of making .NET applications run on Mac and Linux seems to indicate that Microsoft may be emerging as a threat to Xamarin.

The formidable Microsoft has perhaps spelled death for Xamarin by standing up a competitor to Mono. If you are a developer getting started with Xamarin or already using Xamarin, should you be worried? After all Xamarin has a significant learning curve. Just because you are proficient with C# and Visual Studio does not mean that learning curve of cross-platform development with Xamarin is insignificant. I have worked with Xamarin platform for more than two years. As you get into Xamarin development, you quickly realize that you need to know and learn quite a lot about the platforms that you are developing for. So, should you put your time and money into Xamarin? Should you (continue to) invest in Xamarin? Does Xamarin have a future?

Xamarin’s core competitive advantage is not in competition with the (.NET Core) class libraries, SDKs and server frameworks being open sourced by Microsoft. Xamarin’s competitive advantage is in the ecosystem of development and testing tools as well as infrastructure that supports cross-platform mobile development, testing and monitoring. Xamarin marvelously simplifies creation of native apps on iOS and Android using C# (now F# also). The pace of innovation at Xamarin is breathtaking. There is nothing quite like it to enable cross-platform development of native mobile applications with Microsoft’s flagship programming language at its core and the incredible productivity allowed by Microsoft’s and 3rd party tool set.

I think both Microsoft and Xamarin are going to greatly benefit from the formation of .NET Foundation and open sourcing of .NET as well as cross-platform implementation of .NET. Keep in mind that while Mono is open source, Xamarin.Android and Xamarin.iOS are commercial products. Xamarin is going to benefit immensely by Mono closing the gaps with .NET BCL implementation and converged implementations of Mono and .NET in the near future, without giving up its core competitive advantages. Microsoft has seen the writing on the wall – The future belongs to Cloud and Mobile. Microsoft has a strong presence in Cloud, but not so much in Mobile. Microsoft is going to benefit from .NET running on Mac and Linux by expanding their customer base to those platforms in its cloud offerings in Azure. But Xamarin’s gains are also going to translate into broader and deeper mobile market penetration for Microsoft’s tools and technologies, benefiting Microsoft’s Cloud strategy even further. Xamarin’s success is strategically important to Microsoft. Now even more so.

I think that Xamarin will continue to gain strength and remain a viable cross-platform development framework as far as I can see. Xamarin’s future looks very bright to me.

Creating Android Apps using C# and Xamarin

You can create native Android and iOS applications using C#, with Xamarin. I explored the capabilities of Xamarin tools and the development experience with Xamarin to create an Android version of CensusMapper. CensusMapper displays U.S. Census data on a Map. I created the original application for Windows 8 (WinRT) using C#. I have since converted it to an MVVM (C#) application, HTML/Javascript (WinJS) version and more recently to a Universal Windows App running on Windows Phone 8.1 and Windows 8.1. In that tradition, now it is faithfully ported to run on Android devices, using C# and Xamarin. CensusMapper is available on Google Play Store.

CensusMapper.Android shows population of each U.S. State. User can tap on a location on the map to show the population (as per 2010 census) of the zip code containing the selected location. User can select a location to view the population compared to the containing geography, as a pie-chart.

This experimental project helped me expand my cross-platform mobile application development skillset in the following areas:

Using Xamarin/C# to create an Android app using Xamarin Studio on a PC and a Mac.
Structuring C#/.NET source code in a Portable Class Library to allow reuse on Windows, Windows Phone, Android and iOS platforms.
Converting the functionality of an existing Windows Universal App (Windows Phone/ WinRT) to an Android app.
Using GoogleMaps API (via Google Play Services) to display data retrieved from U.S. Census API.
Using Bing Maps API for reverse geocoding in an Android app.
Creating custom markers using low-level API in Android.Graphics namespace to display information on the map.
Charting with oxyplot cross-platform charting library.
Working with Android SDK, AVD Manager as well as developer documentation and resources on Android and Xamarin websites in the development lifecycle of the app.
Publishing an app on Google Play Store.

I started with Xamarin.Forms.Maps. It was quick and straight forward to create a Xamarin.Forms app. The tricky part was creating the custom markers (the shape of speech bubble) on the map, instead of using the default push-pin markers . I tried creating a CustomRender to create custom markers and built interactivity with the map elements, but it turned out to be too much hassle. All of that customization would be specific to Android platform only and not reusable on the iOS anyway. So, I decided against using Xamarin.Forms and work directly with Google Maps library. Xamarin.Forms also limits me to Windows Phone 8 compatibility in my PCL. I can’t use Windows Phone 8.1 in any PCL profile compatible with Xamarin.Forms. It also requires a minimum of Android 4.0. The PCL profile # 111 for sharing code between Windows 8, Windows Phone 8.1 as well as Android and iOS, is not compatible with Xamarin.Forms at the time of writing this.

Don’t use the Android emulator for testing. Get a real device. I stopped using the emulator while working on CensusMapper because GooglePlayServices (GPS) dependency was making me jump through way too many hoops. Debugging map functionality on the real device was a much more productive experience. Then I discovered Xamarin’s Android Player. It is awesome. By all means, use it! It is a pleasure to work with, especially on a Mac. Don’t be discouraged by the preview/beta status. It blows the Android SDK virtual devices out of the water, in terms of performance and usability.

I tested on Google Nexus 4 (Android 4.2), Samsung Galaxy SIII (Android 4.3) , BLU Dash JR (Android 4.4) and an older Coby Kyros tablet (Android 2.2). Google Play Services update, required for the app to work, could not be installed on BLU device because of the limited storage space. You must root the device in order to install the GPS updates on an SD card. It is advisable to have a root-friendly device. Google Nexus devices are excellent development devices, allowing you root access and the ability to load custom ROMs. However, it is very important for you to get a few different kinds of devices of various form factors and Android versions/API levels for testing your app’s functional and non-functional aspects.

Android device logs and the IDE build logs are the most important tools you have to resolve problems encountered in the Android app development with Xamarin. These should be the first places to look when troubleshooting issue.

Versions used in this project:
Xamarin 3.8.
Xamarin Studio 5.7
Xamarin Android 4.20.0

Universal Apps

The story of Windows Universal Apps is the result of advancements in three areas:

The platform convergence between Windows 8.1 and Windows Phone 8.1
The (ongoing) unification of Windows and Windows Phone stores.
Shared Projects and other enhancements in Visual Studio 2013 Update 2 to support cross-platform development.

I have written about my experience in converting an existing Windows 8 app, CensusMapper, to a Universal App on the AIS Blog. Read the article here. I have also created another Universal App, LRMS, using Windows App Studio. This app is available in both Windows and Windows Phone Stores.

I gave a presentation at the Raleigh Code Camp this past weekend : Creating Universal Apps for Windows Phone 8.1 and Windows 8.1. Thanks to everyone who attended the presentation. The session slides for this presentation are available here : Download Slides.