You could say I am a fan of the Realm Mobile Platform. I'm using it and it seems to be working well.
However I am confused with how to operate it going to production. It seems to be deployed only to one server, and even the professional and enterprise editions are working on my single server.
Assuming Realm have thought of this (as Enterprise edition supports 'enterprise scaling) - how does this work if all clients point to my owned server URL?
Another question is how to monitor the load on that server.
Thanks!
The Professional Edition and the Enterprise Edition emit statsd compatible metrics which allow you to track the usage and load on each node in a Realm Object Server cluster. These metrics are also used internally inside the cluster in order to display statistics about the health of the cluster.
We are obviously still adding metrics as we understand more about our customer's use-cases, and fine-tuning the ones that we have.
With regards to the way the clustering works, we are currently implementing this according to an iterative process, where we add more and more features, and more and more resilience to the system with every passing day.
Basically, we have a logical load balancer process, which receives the incoming client connections, and then dispatches that to a node inside the cluster. This logical load balancer can be HA'd and LB'd itself as well, just like you would any regular WS connection handler. Handling many connections these days is easy. It's handling the quadratic merge algorithms that is expensive on the Realm Object Server, which is why the clustering is required for deployments at scale.
I just saw the Realm Mobile Platform. I'm curious what kind of redundancy is available outside of users having a full backup locally.
Can you have multiple Realm Object Servers?
It is possible to run multiple Realm Object Servers in various configurations for greater performance or reliability. This advanced functionality is part of the Enterprise Edition.
For the Developer Edition, you can run multiple Realm Object Servers but they all act independent of each other. For example you could split you user data across multiple servers with certain user groups using specific machines.
Since this question is from a user's (developer's) perspective I figured it might fit better here than on Server Fault.
I'd like an ASP.NET hosting that meets the following criteria:
The application seemingly runs on a single server (so no need to worry about e.g. session state or even static variables)
There is an option to scale storage, memory, DB size and CPU-power up and down on demand, in an "unlimited" way
I researched but there seems not to be such a platform, that completely abstracts the underlying architecture away and thus has the ease of use of a simple shared hosting but "unlimited" scalability.
"Single server" and "scalability" are mutually exclusive, I'm afraid. But a good load-balancer will apply affinity to requests so you don't need to needlessly double-cache data on multiple servers.
However, well-designed web applications are easy to port to a multiple-server scenario.
I think your best option is something like Windows Azure Websites (separate from Azure Web Workers) which run on a VM you don't have access to. The VM itself provides enough power as-is necessary to run your website, so you don't need to worry about allocating extra CPU power or RAM.
Things like SQL Server are handled separately, but is very cheap to run, and you can drag a slider to give yourself more storage space.
This can be still accomplished by using a cloud host like www.gearhost.com. Apps live in the cloud and by default get 1 node worker so session stickiness is maintained. You can then scale that application larger workers to accomplish what you need, all while maintaining HA and LB. Even further you can add multiple web workers. Each visitor is tied to a particular node to maintain session state even though you might have 10 workers for example. It's an easy and cheap way to scale a site with 100 visitors to many million in just a few clicks.
We have a web-application product that we sell to companies that is hosted at our servers.
The product contains couple of web applications, windows services and SQL server db.
Right now we have only one client that uses our product. We have two servers - one for the web apps and services and other for the db.
In order to add the product to another client, we have to 'duplicate' all the apps and db and run in separately.
As we started expanding and some companies will require more server power then others, I need to plan the servers infrastructure.
Having two servers for each client sounds ridiculous. Hosting costs will be huge. What will happen when I'll have 10 clients? And probably some servers will take more power than others, leaving servers using 30% from their capacity while others use 70%.
One thing I really care about is separating the DB from each product so in case of server compromise, only one db will be at risk.
So... I thought about Virtual Machines...
Does it sounds right?
Do I need two super servers to hold virtual machine instances? (one for web and other for db?)
What about Load balancing / etc..?
Will it require more maintenance time only because I use virtual machines?
Are there any hardware recommendations?
Any help will be appreciated
Many thanks
Virtual Machines is definitely the safest way to separate clients and will allow you the flexibility to allocate a specific percentage of resources to specific clients.
However, using separate processes on the same physical machine will perform better (but not always significantly) and will allow more dynamic use of resources (i.e., if one spikes, it will use the resources it needs). This setup will not allow you to control the resource allocation nearly as easily though. You'll also have to build your own monitoring tools to see and analyze what processes (clients) are using what resources (piggyback on perfmon).
Using separate processes also is dangerous if your application wasn't designed for this. Anywhere the application caches data on the file system or accesses anything besides memory and the database needs to be thoroughly scrubbed to make sure data from clients is not co-mingled or shared.
Separate virtual machines is more work to manage--each one is pretty much like it's own computer. So you have to manage all the VM's plus the physical machine.
You may also want to consider hosting in a more dynamic environment like Amazon AWS or Microsoft's Azure which will allow you to more easily scale up/down as necessary than a VM at a traditional host.
I am working on asp.net (newbie) and I am trying to understand what it means to do "load balancing" for the web site. The website will be used by multiple users and resources (database, web service,..).
If anyone could help me understanding the concept of the load balance for asp.net web site, I would really appreciate it.
Thanks.
One load-balancing-related issue you may want to be aware of at development time: where you store your session state. This MSDN article gives a good overview of your options.
If you implement your asp.net system using "out-of-process" or "sql-server-mode" session state management, that will give you some additional flexibliity later, if you decide to introduce a load-balancer to your deployed system:
Your load balancer needn't handle session affinity. As one poster mentioned above, all modern load-balancers handle it anyway, so this is a minor consideration in any case.
Web-gardens (a sort of IIS/server-implemented load-balancer) REQUIRES use of "out-of-process" or "sql-server-mode" session state management. So if your system is already configured that way, you'll be one step closer to being able to use web-gardens.
What is it?
Load balancing simply refers to distributing a workload between two or more computers. As a concept, it's not unique to asp.net. Although having separate machines for your database and web server could be called "load balancing" it more commonly refers to using multiple machines to serve a single role, such as having multiple web servers.
Should you worry about it? Probably not. Do you already have a performance problem? Are your database and web server on their own machines? If you do find that your server resources are strained, it would probably be easier to scale up (a more powerful single machine) than out (load balancing). These days, a dedicated box can handle a LOT of traffic if your code is decent.
Load Balancing, in the programming sense, does not apply to ASP.NET; it applies to a technique to try to distribute server load across two or more machines, rather than it all being used on one machine. Unless you will have many thousands (millions?) of users, you probably do not need to worry about it.
Check the Wikipedia article for more information.
Load balancing is not specific for any on technology stack be it asp.net, jsp etc. To load balance is to spread the incoming requests to a web site over more than one server. This is typically done with a software or hardware load balancer. The load balancer sits in front of two or more web servers and delegates the incoming traffic. Although this technique is not limited to web servers. Load Balancing
Enjoy!
I've never used it, but an option is IIS Application Request Routing.
IIS Application Request Routing (ARR)
2.0 enables Web server administrators, hosting providers, and Content
Delivery Networks (CDNs) to increase
Web application scalability and
reliability through rule-based
routing, client and host name
affinity, load balancing of HTTP
server requests, and distributed disk
caching
In a typical web server/database scenario, the db is almost always guaranteed to load up the machine first. This is because dealing with storing data requires more resources. Before you even start looking at load balancing your web server, you need to think about how to load balance the database.
Spreading one database across multiple servers is a lot harder than load balancing a web server. One of the techniques that can be used is sharding (or horizontal partitioning). This is where some records are stored on one server, and other records - on another server. For example records with ID 1-900000 are on server 1 and records 900001- are on server 2.
In comparison to DB load balancing, spreading the load across multiple ASP.NET servers is not overly complicated. Most of the session issues can be easily mitigated by using out of process session and/or never talking to Application.Cache directly. Data load balancing on the other hand is hard and requires a lot of planning and trial and error. In most cases, talking to a load balanced DB requires using an ORM which supports it (e.g. NHibernate) or your own Data Access Layer. The reason being is that you need to take out establishing a connection from the code that uses the database, so that the decision which DB to talk to is handled in one place.
the exact solution is to save session into the SQL Server with Stored Procedure. To read session call 'SessionCheck' stored Procedure.
I'd add that it really isn't something to worry about. By the time you need a load balancer, you can probably afford one of the neato newfangled ones with sticky sessions so you don't even have to deal with the session boogeyman.