I am hosting an on-premises website which I want to migrate to Windows Azure Virtual machine.I will be using multiple instances of Azure VMs. Currently I am using IN-Proc session management technique. Do I really need to change this session mode to migrate the website to cloud. Why??
If you want to have more than 1 Web Role Instance (for load balancing/scalability/redundancy purposes) then Yes you do need to change it. Just a reminder, but you need a minimum of 2 roles in order to be eligible for the 99.9% SLA.
InProc means that the session information is stored in that web roles process. a second web role instance, has no knowledge of that data contained in process in the first web role.
So if your first web request goes to WEBROLE_1 it has your session information.
If your second request goes to WEBROLE_2, it won't know that you already have some session data stored in the other role.
There are a number of other options for storing your session info including using TableStorage, SQL Azure or App Fabric Cache.
Related
We have several web applications using the same identity provider (which we also manage), most of them (including identity provider) are using .NET core.
Requirement is that if user is logged in in two or more applications at the same time (in one browser), and is actively using one app, it automatically extends the session lifetime in all of the applications.
So while he's using at least one application, he doesn't get logged out of neither of them. Which is another requirement: auto-logout after certain time of inactivity (this part is easy of course)
I thought of using Redis server to manage this shared session lifetime, using SessionId that each app would receive from identity server via claims. So each time user does some action, backend contacts Redis and check if user's session is still active and extend the session lifetime if it is. Logout user if it's not.
Problem is, applications are not allowed to access this Redis server directly (security reasons). So I thought of adding a separate web service for these apps to contact using standard HTTP endpoint. So basically just a middleman between Redis and web app.
Is there any better way to do it? Not sure how common of a requirement is this.
Redis usually belongs in the Distributed cache, which means that it is located on another server farm. Therefore, your application has restrictions because it is not allowed to access an external server.
If your application is under development or if it is still in the growth phase my recommendation is to use InMemory cache or consider response caching middleware.
Also, these are very small amounts of data, and if you are going to store only that in the cache for a start you would definitely consider InMemory.
Of course, I understand your need for a Redis and that is it:
Is coherent (consistent) across requests to multiple servers.
Survives server restarts and app deployments. And that's because
your cache is usually in a different location (e.g. Azure)
Doesn't use local memory.
Is scalable
etc.
For larger applications Consider replacing InMemory cache with the Distributed memory cache. It is mostly similar to the InMemory cache because both the InMemory and the Distributed cache are located on the server farm where the application was run. Only the InMemory cache requires a sticky session, and the Distributed memory cache does not.
Our plan is to migrate Azure Web Roles to Azure Web Sites. So far the Azure Web Roles were using Azure Caching that was shared across instances.
Our first thought was to switch to Redis Cache. But after a few other discussions we started discussing using just Http Runtime Cache as our data isn't big (we do not store any images or big data). It's all strings and numbers.
If go for Http Runtime Cache (using it on five instances of one Azure Web Site).
Could following scenario happen?:
Request comes to first instance that serves a content of freshly cached data.
User click's on an item but the request goes to second instance that has older cache at that moment that does not contain the item.
Would this result in an error? Is this a very possible situation? Can we be sure that the request will always go to that one instance?
By default Azure Websites implements sticky sessions, meaning that when a user makes a request and it gets routed to instance A, all future requests will also go to instance A for as long as instance A stays up
We have Windows Server 2008 R2 with IIS on in a web farm environment. I initiate a Classic ASP session and every so often, when refreshing the page, it doesn't show but then comes back again.
I go to http://mainurl.com but have two boxes called http://devbox1.com and http://devbox2.com
I put the files onto one of the DEV boxes which replicates to the other one.
After some reading, I guess this is down to a "common" issue with sharing sessions across a web farm instance.
Could someone please help me how to resolve this please?
Update:
As it's not clear in my post. Do not use the Session.SessionID as the identifier for the cookie as this will change across environments (Microsoft recommend never to store the SessionID in a database).
Quote from MSDN Library - Session.SessionID
You should not use the SessionID property to generate primary key values for a database application. This is because if the Web server is restarted, some SessionID values may be the same as those generated before the server was stopped. Instead, you should use an auto-increment column data type, such as IDENTITY with Microsoft® SQL Server™ or COUNTER with Microsoft Access.
Instead use a self generated id value that you then store in your cookie and the database. This way your Session object can be re-created.
There seems to be some discussion about solution using a database. Just to clarify Classic ASP uses Session object stored in memory this means the minute you switch machines load balanced or otherwise you still lose the session.
Interesting article on the IIS.net forums about this topic - iis 7 Load balancing
Quote from Bill Staples (who at the time was Product Unit Manager, IIS)
One thing to consider, however, is what to do with any application / session state. Classic ASP stores session state in memory that only one process can access. As soon as you scale the sites onto more than one machine, you can no longer guarantee that each incoming request for a particular user session is landing on the same machine, which means the client may suddenly 'lose state' between requests. This is why we recommend that you not use the built-in session support in ASP for these kinds of scenario. Instead we recommend you use SQL or another database to store this kind of data.
My recommendation would be to store the Session in a database create a cookie on the client machine then use this cookie to identify the session from the database.
Cookies can be changed so I would still recommend you use secure cookies across an SSL secured website, especially if data is of a sensitive nature.
You should create sticky sessions while working with web farms because most likely you have load balanced system which under standard configuration will point traffic to the lowest loaded node. As result your users will loose session from time to time.
Ask your network admin team to look how to create sticky session for your particular load balancers and network configuration, they should know exactly what this means.Here is one of the examples what this is and how to configure it: http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/US_StickySessions.html. But once again it is depend on what you are using.
**** solution with cookies or database entries not the best way to handle this situation because once again depend on your web farm configuration IIS may simple reject any attempt to overwrite session ID which you have stored in database or if security is tight enough even refuse to connect to page while connecting to other node.
Is the Application variable shared when the web application has multiple role instances in window azure? And I am using Dedicated cache worker role. Is Application Variable is preserved the cache? If not then how we can do it?
The Application variable is stored in-memory (see this MSDN reference article). There's no option to persist it or externalize it, so there's no way to share application state across web role instances. The article points this out, in terms of inability to share application state across servers in a web farm.
As this SO answer suggests, you'd need to use some shareable resource for application-level content. In other words, just don't use the Application variable. You could store app-level variables easily in a Windows Azure Table or Cache (either dedicated cache role or shared cache within your web role).
I'm researching some Windows Azure stuff, in order to make a decision whether to move to Azure or not.
Basic information
To answer the question, you'll need some basic understanding of my app so here goes.
The app is an ASP.NET MVC 3 application that connects to a SQL Server database.
It is a single instance application, meaning that every customer eventually has their own instance of the app running on our server, deployed to IIS 7 as a website.
I have one SQL Server, where each instance has its own database.
I also have a set of Windows Services to do some background processing. That should be straight forward, as I'll just rewrite those to use a Worker Role in Windows Azure - most of the logic in the services is located in their own class (library) anyway, so the service it self just calls one or more methods in a class.
Now to the question
Whenever someone signs up for a free trial, I add a record to an Admin database I have.
I then have a Windows Service that deploys a new instance of the ASP.NET MVC 3 app to IIS, grants permission to a few folders, runs the database deployment script and updates the record to reflect that it has now been deployed, and finally sends an e-mail to the prospect that their free trial has been created - here's how you access it.
So, how can I deploy a new instance in Windows Azure from a Worker Role? Preferably, I'd just add a new website to an existing Azure instance and create a new SQL Azure database for that particular site to use.
Does this require a lot of work to set up? Is it even possible?
Based on two quotes, I would like to suggest calling this a multi-tenant application:
It is a single instance application, meaning that every customer eventually has their own instance of the app running on our server,
And...
a Windows Service that deploys a new instance of the ASP.NET MVC 3 app to IIS, grants permission to a few folders
If I understand correctly, there is "one" IIS server (well, in Windows Azure, it's one Web Role, scalable to multiple instances), and with each new "tenant", you set up some new stuff to support that tenant.
If that's indeed the case, you can definitely do this from a worker role - just look at Nate Totten's multi-tenant web role blog post and related code. Look at the webdeploy code that actually manipulates IIS.
Further: take a look at Cloud Ninja, a project a few of my teammates published along with Fullscale180. This is a multi-tenant app that demonstrates how to manage multiple customers in a single deployment, as well as monitoring and scaling.
Finally: should you need to actually create brand new service hosts and storage accounts, the latest updates to the Windows Azure Management API support this.
I hope that helps a bit...
I think most of the things you want to achieve are possible.
It will definitely require some work to setup!
For some ideas on how to achieve what you are looking for, take a look at the MS SaaS example - http://www.fabrikamshipping.com/ - especially designed for porting existing apps to SaaS on Azure. Inside this app they have an "onboarding process" - and that process includes setting up new SQL connections and new portals.
There's lots of good blogging (watch the video) about this on http://blogs.msdn.com/b/vbertocci/archive/2010/10/07/new-online-demo-introducing-fabrikamshipping-saas.aspx