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Rohit is an investor, startup advisor and an Application Modernization Scale Specialist working at Google.

Thursday, June 9, 2016

Replatforming .NET applications to Cloud Foundry - Migrating .NET apps to Cloud Foundry

A lot of developers do not realize that Cloud Foundry can run a process from any runtime including .NET. Windows applications are managed side-by-side with Linux applications. .NET apps get support for key PCF features like scaling including autoscaling, monitoring, and high availability, logs and metrics, notifications, services including user-provided services and PCF set environment variables. BOSH and OpsManager now supports deployments on Microsoft Azure via pre-built ARM templates.This blog post provides details of the Windows support and provides guidance on migrating .NET apps to Cloud Foundry . This post build extensively on the work done by the Pivotal product engineering and the solutions team particularly Kevin Hoffman, Chris Umbel Zach Brown, Sam Cooper and Aaron Fortener.

There are two ways to run ASP.NET  apps on Cloud Foundry

1. Windows 2012 R2 Stack
 • Support Introduced in Nov. 2015
 • Supports.NET 3.5-4.5+
 • Requires Diego-Windows, Garden-Windows
 • BOSH-Windows support currently underway
 • App is pre-compiled, no detect. Leverage binary_buildpack  to push app
 • cf push mydotNetApp -s windows2012R2 -b binary_buildpack
 • Runs on Garden-Windows container
 • Win 2k12 provides process isolation primitives similar to those found in the Linux kernel
 • IronFrame abstracts these primitives into an API utilized byGarden-Windows
 • Win 2k12’s low-level API Linux kernel’s API
 • Therefore Garden-Windows process isolation functionality ≈ Garden-Linux
 • Developer OS is Windows

2. Linux cflinuxfs2 Stack
 • ASP.NET Core CLR only
 • Runs on Diego or DEA
 • Standard CF Ubuntu Stack
 • Community ASP.NET 5 Buildpack
 • cf push mydotNetApp -s cflinuxfs2 -b <asp.net5 bp>
 • Garden-Linux is the backing container
 • Garden-Linux containers are based on LXC (Linux cgroups)
 • Developer OS is Win, Mac OSX and Linux

ASP.NET Core vs ASP.NET 4.6

  • Web API
  • No Web Forms (yet)
  • No SignalR
  • Battle-tested, hardened
  • Many years of testing and improvement
  • MVC, Web Forms, SignalR, etc.

Migrating Existing Applications

• For Greenfield Applications Try “Core First” approach
• For Replatforming and migrating Existing Apps Probably ASP.NET 4.x
Dependencies and framework requirements will likely dictate choice
• All versions of the .NET SDK supported by Windows Server 2012 R2 are supported on PCF including 3.5, 4.5, 4.5.1 and 4.6

Here are some of the details on how Garden-Windows secures applications

Non Cloud-Native stuff you will want to change

 • Reading/Writing to the Registry.
•  Super old versions of ASP.NET. Upgrade to .NET core or ASP.NET 4.x
 • Reading/Writing to the local disk. File systems are ephemeral. Replace usage of the file system e.g. disk logging even temp files with a S3 compatible blob store or external file store.
 • Does the app use integrated Windows Authentication? Replace  Integrated Windows Auth. with ADFS/OAuth2 to leverage UAA and Pivotal SSO Tiles
 • In-Process Session State / Sticky Sessions. Replace InProc, StateServer with out-of-process data store e.g. Redis, SQL Server
 • Externalize  environment-specific config in web.config into VCAP environment variables. If value changes between environments, don’t get it from web.config. Don’t use externalization methods that only work in Azure. If app relies on machine.config or applicationHost.config, could have issues in PCF.
 • For MSI-Installed services or drivers, Bin deploy dependencies with app.
 • Nearly every app will need refactoring to use Console logging and tracing. Customers who mess with applicationHost.config can interfere with tracing, logging, etc.
 • 32 bit ASP-Net builds/References/Builds/apps depending on 32-bit libraries will not work. Use of 32-bit dependencies or when the app is itself a 32-bit app this is a red flag.
 • Does the app run as a service or a WCF Self-hosted services as opposed to IIS-hosted ? These services will need to be self-hosted in IIS as part of the replatforming to PCF.
 • Apps requiring assemblies in Global Assembly Cache won't work in CF.
 • Backing Service Drivers requiring native installers / DLLs may not work in CF.
 • On Demand Apps and ones triggered by job controller will need to be refactored to run in CF to use CF one-off task support coming in the CC v3 API.
• MSMQ and tight integration with other MSFT server products via on-server dependencies will need to be refactored to use external backing services. .NET Core is now supported in the RabbitMQ .NET client.
• Routing to non-HTTP WCF endpoints and listeners for third party middleware will not work since only HTTP based inbound traffic is routed to the windows containers.
• Reliance on Microsoft-specific infrastructure? (e.g. MSMQ, BizTalk, SharePoint, etc). These apps do NOT make good candidates to port to PCF.

.NET Application Selection Criteria


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