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.
Related
I have a question about Service Layer(SL):
can I build cluster with several SL servers to load scaling?
Where can I read about it?
Technically you can create all the servesr with any number of server instances (service layers) you want - all running on the same database. That will work just fine.
However there is no built-in load balancing so you would have to handle that on your own.
The most common way of doing this is simply by providing different shortcuts to different groups of users. Each shortcut is linked to their own server instance and thus the users are directed to different servers.
I want to support the users of my Windows 10 desktop application with:
Local Data (not having to perform a fetch from the cloud every time they want new data)
Offline support
Replication with a cloud database
There can potentially be multiple users (in the order of 10-100 but not 1000) simultaneously editing the same database. I would run CouchDb as a service (ie. in a separate process to my app).
To achieve the above I am considering installing CouchDb on each client desktop PC (all replicating to a single main cloud CouchDb instance) together with my application to achieve the above goals.
One of the reasons I am pursuing this line of thinking is that it would allow my application code to mostly just be written in a manner that interacts with local data and the sync/replication (which is probably quite complex) can be taken care of by CouchDb.
I am using CouchDb as a replacement for something that I often see is done by sqlite but I really want the replication ability of CouchDb (which sqlite does not have).
Is the above a scenario in which I can expect CouchDb to perform well or is there something that I am not considering?
We have multiple clients doing this successfully. This is a recommended use-case for CouchDB. The limiting factor will be the cloud vm configuration, but 100s to 1000s of clients should be no problem on a decent vm setup.
CouchDB is sometimes called "A replication protocol with a database attached to it." This sounds appropriate for your use case. However, installing CouchDB (or any external database/service), particularly as part of a client application, isn't necessarily trivial. That doesn't mean it should be avoided--it's just complexity to consider when making a choice.
You might consider lighter-weight options for your client. PouchDB is the go-to solution for web apps, and often mobile apps, as it syncs with CouchDB, but has much lower resource requirements (at the cost of not being multi-tenant). For a desktop app, that may be appropriate.
Ultimately, whether CouchDB (or PouchDB, or PouchDB Server, etc) is appropriate for your use case depends on which trade-offs you're willing to make.
I want to create a program for my desktop and an app for my android. Both of them will do the same, just on those different devices. They will be something like personal assistants, so I want to put a lot of data into them ( for example contacts, notes and a huge lot of other stuff). All of this data should be saved on a server (at least for the beginning I will use my own Ubuntu server at home).
For the android app I will obviously use java and the database on the server will be a MySQL database, because that's the database I have used for everything. The Windows program will most likely be written in of these languages: Java, C#c C++, as these are the languages I am able to use quite well.
Now to the problem/question: The server should have a good backend which will be communicating with the apps/programs and read/write data in the database, manage the users and all that stuff. But I am not sure how I should approach programming the backend and the "network communication" itself. I would really like to have some relatively easy way to send secured messages between server and clients, but I have no experience in that matter. I do have programming experience in general, but not with backend and network programming.
side notes:
I would like to "scale big". At first this system will only be used by me, but it may be opened to more people or even sold.
Also I would really like to a (partly) self programmed backend on the server, because I could very well use this for a lot of other stuff, like some automation features in my house, which will be implemented.
EDIT: I would like to be able to scale big. I don't need support for hundreds of people at the beginning ;)
You need to research Socket programming. They provide relatively easy, secured network communication. Essentially, you will create some sort of connection or socket listener on your server. The clients will create Sockets, initialize them to connect to a certain IP address and port number, and then connect. Once the server receives these connections, the server creates a Socket for that specific connection, and the two sockets can communicate back and forth.
If you want your server to be able to handle multiple clients, I suggest creating a new Thread every time the server receives a connection, and that Thread will be dedicated to that specific client connection. Having a multi-threaded server where each client has its own dedicated Thread is a good starting point for an efficient server.
Here are some good C# examples of Socket clients and servers: https://msdn.microsoft.com/en-us/library/w89fhyex(v=vs.110).aspx
As a side note, you can also write Android apps in C# with Xamarin. If you did your desktop program and Android app both in C#, you'd be able to write most of the code once and share it between the two apps easily.
I suggest you start learning socket programming by creating very simple client and server applications in order to grasp how they will be communicating in your larger project. Once you can grasp the communication procedures well enough, start designing your larger project.
But I am not sure how I should approach programming the backend and
the "network communication" itself.
Traditionally, a server for your case would be a web server exposing REST API (JSON). All clients need to do http requests and render/parse JSON. REST API is mapped to database calls and exposes some data model. If it was in Java, it would be Jetty web server, Jackson Json parser.
I would really like to have some relatively easy way to send secured
messages between server and clients,
Sending HTTP requests probably the easiest way to communicate with a service. Having it secured is a matter of enabling HTTPS on the server side and implementing some user access authentication and action authorization. Enabling HTTPS with Jetty for Java will require few lines of code. Authentication is usually done via OAuth2 technique, and authorization could be based on ACL. You may go beyond of this and enable encryption of data at rest and employ other practices.
I would like to "scale big". At first this system will only be used by
me, but it may be opened to more people or even sold.
I would like to be able to scale big. I don't need support for
hundreds of people at the beginning
I anticipate scalability can become the main challenge. Depending on how far you want to scale, you may need to go to distributed (Big Data) databases and distributed serving and messaging layers.
Also I would really like to a (partly) self programmed backend on the
server, because I could very well use this for a lot of other stuff,
like some automation features in my house, which will be implemented.
I am not sure what you mean self-programmed. Usually a backend encapsulates some application specific business logic.
It could be a piece of logic between your database and http transport layer.
In more complicated scenario your logic can be put into asynchronous service behind the backend, so the service can do it's job without blocking clients' requests.
And in the most (probably) complicated scenario your backend may do machine learning (for example, if you would like you software stack to learn your home-being habits and automate house accordingly to your expectations without actually coding this automation)
but I have no experience in that matter. I do have programming
experience in general, but not with backend and network programming.
If you can code, writing a backend is not very hard problem. There are a lot of resources. However, you would need time (or money) to learn and to do it, what may distract you from the development of your applications or you may enjoy it.
The alternative to in-house developed of a backend could be a Backend-as-a-Service (BaaS) in cloud or on premises. There are number of product in this market. BaaS will allow you to eliminate the development of the backend entirely (or close to this). At minimum it should do:
REST API to data storage with configurable data model,
security,
scalability,
custom business-logic
Disclaimer: I am a member of webintrinsics.io team, which is a Backend-as-a-Service. Check our website and contact if you need to, we will be able to work with you and help you either with BaaS or with guiding you towards some useful resources.
Good luck with your work!
*If you think I should ask this question elsewhere, please let me know.
Background:
I need to build an application for converting weights into piece counts. The weights currently come from scales that are connected to PCs via serial ports. I am replacing PC based applications that connect to the scales via a serial connection. I am considering the feasibility of making the next generation of these applications into a web based solution. However, I do not want to do this if it is not a better solution than building an application that runs on the client. In addition, I do not want to use any sort of browser specific technology (ActiveX).
FYI, we currently run a Windows based environment.
What I have so far:
I am currently thinking that I will need some sort of client side “service” to allow the scale data to be retrieved by the web application. I have looked into creating a WCF service for this task and have determined that it would probably work. This would require that the scale be connected to some sort of Windows based computer that is on the network. I would then interface the WCF service (running as a Windows Service on the PC) from an ASP.NET web application running on an IIS web server. This would minimize the footprint on the client and allow us to use a web application.
I am looking for any constructive thoughts and ideas. I am open to reviewing any feasible option that would make this solution as simple and reliable as possible.
Answering my own question per request #honeycomb.
I discovered two viable options for this purpose. Following are high-level overviews of the techniques we leveraged.
Develop a scale reader to be run on a PC connected to the weigh scale device via an RS-232 connection. This reader will forward any information received from the scale into a database. Combined with technologies like change notifications and server-side push notifications, this option will allow data from a weigh scale to be pushed into a web page with little effort and no additional cost. (This option has performed well during testing but is not yet in production)
Invest in converting weigh scale devices to use ethernet connections and connect them to the network. Use an OPC server with a driver that can connect to the weigh scales you are using to read the data from these devices. Consider KEPWare's offering for this purpose. Use KEPWare's tools to forward this data to a database or wherever it is needed. Once again, you can leverage change notifications and server-side push technologies to push this data into web applications in near real-time without polling. (This option is currently working in a critical, production environment)
The second option is probably better in the long-term, but this may vary based on your specific situation. It has some up front costs and would be better suited to new implementations. For my system, I am using the first option because it will ease the transition between the new and old systems.
Note: I am not in any way associated with KEPWare. I am only suggesting their product because it is the only one I am aware of that supports this functionality. I am sure there are other OPC servers that support this type of device.
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.