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App Virtualization Cloudburst

Added by Adam Marano , last edited by Craig Ellrod on May 19, 2011  (view change)


This blueprint documents how Citrix is using the Citrix Open Cloud lab to support the launch of Citrix Receiver for iPhone. A "private" cloud is created using Citrix Open Cloud – Citrix XenServer, Citrix NetScaler, Citrix Workflow Studio and Citrix XenApp hosted by Citrix partner Softlayer - to deliver Windows Application to the iPhone. The private cloud uses the Citrix Open Cloud Lab running in Amazon Web Services EC2 as an "overflow" cloud when demand exceeds the private cloud capacity. The blueprint documents the mechanics and workflow required to synchronize user data across clouds and load balancing across the cloud for optimal performance

The rest of this page further describes the Citrix technologies used to create this demo environment and some of the lessons learned during its creation. This type of scenario can be a compelling example of how ISVs can setup up similar demo environments using Citrix XenApp in the cloud.

Open Cloud Burst Demo Lab Blueprint



Technical Overview

In this scenario, there are a number of key requirements/problems to solve.

  • Provide an easy to use, internet accessible demo environment to showcase the Citrix Receiver and Citrix XenApp.
  • Make the capacity elastic to handle any load capacity.
  • Provide for 2 levels of users, standard and VIP users.
    • Standard users get a limited demo session timeframe and restricted access to additional resources (general public users).
    • VIP user accounts are not timed out and get extra access to additional resources(most are partners and Citrix employees so they can perform customer demos).
  • Leverage as many Citrix cloud enabling technologies as possible.
  • Build it fast and flexible to meet the daily changes to requirements.
  • Make the demo environment as automated as possible.
  • Create a secure data transfer connection between clouds.

Citrix also engaged partner AcXess to manage the cloud environments for the demo environment. AcXess also manages the Citrix Ready Virtual Lab , another example of Citrix technology being used in the cloud.

The core of the demo environment is Citrix XenApp. All of the demo applications that the user can access are hosted on the XenApp servers in Amazon EC2 and Softlayer. A decision was made, further details on this later, to design the demo environment using 2 seperate XenApp 5.0 farms, one in Softlayer and one in Amazon EC2. The same applications would be published on both farms to provide an identical user experience regardless of which environment the user was directed to.

All of the systems in Softlayer are running on XenServer virtual machines hosted on 4 physical servers.

All of the systems in Amazon EC2 are dynamically created Amazon EC2 instances, with the exception of a few key systems such as the Domain Controller.

The Softlayer Cloud and the Amazon EC2 Cloud are connected through Vyatta virtual appliances running in both locations, using an SSL site-to-site VPN. Active Directory, Domain and DNS information is synchronized and replicated over this secure connection.

Dynamic Online Registration and AD

AcXess provides an online registration system which allows demo users to self register for the demo environment. The registration system has different web based entry points, which creates the user account in different Active Directory OUs based on the demo requested:

  • Citrix Receiver for iPhones demo OU
  • Citrix Receiver for Windows Mobile OU

This design allows the applications being delivered to the demo user to be customized for the type of device they are using by allocating different configurations of the published demo apps to the different OU users. It also allows flexibility to add new OUs later to allow the demo environment to be expanded for other purposes at a later time.

VIP OUs for iPhone and Windows mobile were also added. Group Policies are used to grant different levels of resource access to standard and VIP users. Non-VIP accounts are scrubbed after 24 hours to limit resource utilization, VIP accounts are not deleted.

A Vyatta virtual appliance based site-to-site VPN is used to connect Softlayer and Amazon EC2 clouds. This allow for synchronization of the user accounts. This allows the registration system to reside only in Softlayer, and then the user account information is synchronized between the Domain Controller in Softlayer and the Domain Controller in Amazon EC2.

User Load Balancing

A Citrix NetScaler located in Softlayer is used to direct the user traffic to either the Amazon EC2 or Softlayer demo environment. Citrix Workflow Studio is used to monitor the load in Softlayer and trigger the NetScaler to redirect new XenApp requests to Amazon EC2 if the high load threshold is met in Softlayer. Citrix Workflow Studio is also used in the Amazon EC2 environment to start new Amazon EC2 Citrix XenApp servers dynamically if the max load on the EC2 XenApp farm is reached to expand the capacity of the Amazon EC2 XenApp farm. Citrix Workflow Studio will dynamically remove servers from the Amazon EC2 farm as the user load decreases. The Amazon EC2 XenApp server with the smallest load will be disabled from receiving new connections. Once this server has no more active sessions, the XenApp server instanced will be terminated and removed from the Amazon EC2 XenApp farm.

System Health Monitoring

Citrix Edgesight is used to monitor the health of the lab environments and provide debug and tuning data.

Component Configuration Tips & Tricks

The below sections provide Tips and Tricks on the configuration and setup of the Citrix Open Cloud components used in this solution.


Citrix XenApp

The XenApp farm in Softlayer and in Amazon EC2 are both using standard configurations, with authentication handled by the synchronized Active Directories.

There are 3 sub-categories of demos that the 2 farms are hosting:

  • Citrix Receiver for iPhones
  • Citrix Receiver for Windows Mobile devices
  • A private demo for select Netbook users at Synergy.
    To provide each demo group an experience "tuned" for their use case, the different groups are segregated into different OUs. This OU structure is then used to show a different set of applications "tuned" for the type of device they are using by publishing the different sets of applications to only the appropriate demo set of users. This allows the single XenApp infrastructure to meet the needs of the different demo groups. Folders were used in the Citrix Access Management Console to help manage the number of applications across the different demo groups. The folder structure used in the admin console we designed to mimic the folder structure the user would see on the devices UI when presented with the list of applications.


Citrix NetScaler

What does the Citrix NetScaler have in common with Cloud Computing? Quite a lot actually. The NetScaler is a powerful appliance, and we have used it in this scenario for load balancing between the two clouds - Softlayer & Amazon EC2. The NetScaler in this demo was configured using the Load Balancing Wizard for Citrix XenApp. The Amazon EC2 XenApp servers are brought online by having Workflow Studio send a command to the NetScaler to turn on the XenApp servers in Amazon EC2, when demand is signalled to Workflow Studio - Cloudburst. When you type the URL into your browser, the domain name resolves to a Virtual IP Address on the NetScaler (VIP). Inside the NetScaler, that VIP is load balanced across the XenApp Web Interfaces in Softlayer and EC2. Service characteristics of Web Interface in the Load Balancing Group:

  • HTTP
  • Port 80
  • LB Algorithm: Least Connections
  • Persistence: Cookie Insert & Source IP Address
  • Monitor: http-ecv
  • Down State Flush: Disabled


Vyatta SSL VPN

The Vyatta site-to-site SSL VPN connects the Domain Controller in the Softlayer lab to the Domain Controller in Amazon EC2 and allows the domain controllers to remain in sync. Using this method, the registration only needs to reside in Softlayer and all new users are synchronized to the EC2 domain, allowing the Citrix Netscaler to direct the demo user to either the Softlayer or Amazon EC2 Citrix XenApp farm as described in the Citrix NetScaler section.


Citrix Workflow Studio

Citrix Workflow Studio is used in both the Amazon ECW and Softlayer environments.

In Softlayer, Citrix Workflow Studio monitors the current load of the Citrix XenApp farm in Softlayer. If Workflow Studio determines that the XenApp farm is reaching capacity, it changes the configuration of the Citrix Netscaler to redirects all subsequent web requests to Web Interface or PN Agent to the Amazon EC2 site. Once the load in the Softlayer lab returns to lower levels of activity, Workflow Studio will change the Citrix Netscaler configuration again, to redirect Web Interface and PN Agent traffic back to the Softlayer lab.

In Amazon EC2, Citrix Workflow Studio is used to dynamically add and remove XenApp servers from the lab. Workflow Studio will monitor the load on the Amazon EC2 XenApp farm and start a new XenApp server in Amazon EC2 once the farm reaches the load threshold. As the Amazon EC2 XenApp farm decreases its load, it will disable connections to some of the XenApp servers in Amazon EC2. Once all of the existing connections on these servers have been ended, Workflow studio will terminate the instances of these XenApp servers, thus removing them from the farm.

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