I have already established a Server-Client Application using UDP Sockets, but my Server is not capable of handling more than one Client at a time. Now I want to modify my applicaton in such a way that there are 10 Clients each running on different machines and my Server running on a separate machine. I want my Server to be able to communicate with each of the 10 Clients running on 10 different machines. I also don't want to miss the data coming from any of the Client.
What is the best possible way to do it? Kindly share some examples with me:(
I have been searching it on internet since a week, but was unable to find anything that may suit my application requirements.
Waiting for help.
Related
We have a real-time service, which gets binary messages from different sources (internal and external), then using a couple of NodeJS instances and one HAProxy instance, configured to route TCP traffic, we deliver them to our end-users and different services who consume the messages. HAProxy version is 1.8.14, NodeJS is 6.14.3, both hosted on a CentOS 7 machine.
Now we've got a complex problem with some "burst"s in the outbound interface of HAProxy instance. We are not sure whether the burst is real (e.g. some messages got stuck in Node and then network gets flooded with messages) or the problem is some kind of misconfig or an indirect effect of some other service (Both latter reasons are more likely, as sometimes we get these bursts during midnight, which we have minimal to zero load).
The issue is annoying right now, but it might get critical as it floods our outbound traffic so our real-time services experience a lag or a small downtime during working hours.
My question is, how can we track and record the nature or the content of these messages with minimum overhead? I've been reading through HAProxy docs to find a way to monitor this, which can be achieved by using a Unix socket, but we are worried about a couple of things:
How much is the overhead of using this socket?
Can we track what is going on in the servers using this socket? Or it only gives us stats?
Is there a way to "catch/echo" the contents of these messages, or find out some information about them? with minimum overhead?
Please let me know if you have any questions regarding this problem.
I am running WEB.API backend with Angular front end, using SignalR (2.2.0) with almost constant data changes.
My problem is that I am able to connect only 4 clients, 5th client would not connect. It will load all web page data, but SignalR won't connect. As soon as I disconnt
one of the 4 already connected clients, the 5th one would connect with not problems.
This is running on Windows 8.1 with IIS 8.5 on separate LAN.
IIS settings is default. Where shall I start looking to solve this?
Thank you.
update: in addition to below link provide by #thab, here is another one with concurent connection limits in IIS per Windows version: http://jpelectron.com/sample/WWW%20and%20HTML/IIS-%20OS%20Version%20Limits.htm
I think it's because you're using Windows 8.1 - there's a limit to the number of simultaneous connections that IIS supports on non-server versions of Windows:
http://weblogs.asp.net/owscott/windows-8-iis-8-concurrent-requests-limit
The problem relates to how SignalR holds a persistent connection (whether Forever Frames, Server Sent Events or Web Sockets) and if the limit is 10 connections, then you'll only be able to get a few users online at once...
I am trying to get as much network connections from one machine as I can, using few machines. I just want to be sure that establishing many connections between servers will give me similar results as having many connections with different server?
Yes, and some issues related to that are called the C10K problem !
However, a connection to localhost is not the same as a distant remote one: the latency and the bandwidth are quite different.
Maybe you want some web server benchmarking ? There are some tools for that!
I am trying to make a pub/sub infra using faye (nodejs). I wish to know whether horizontal scaling would be possible or not.
One nodejs process will run on single core, so when people are talking about clustering, they talk about creating multiple processes on the same machine, sharing a port, and sharing data through redis.
Like this:
http://www.davidado.com/2013/12/18/using-node-js-cluster-with-socket-io-for-push-notifications/
Firstly, I don't understand how we make sure that each of the forked processes goes to a different core. If I fork 10 node servers on a machine with 4 cores, is it taken care that they are equally distributed?
What if I wish to add is a new machine, and thus scale it. I have not seen any such support anywhere. I am not sure if it is even possible to do it.
Let's say somehow multiple nodes are being used and there is some load balancer. But one client will connect to only one server process. So when a client C1 publishes on a channel on which a client C2 has subscribed, and C1 is connected to process P1 and C2 is connected to process P2, how will P1 publish the message to C2 when it doesn't have the connection?
This would probably be possible in case of a single machine, because the cluster module enables all processes to share the same port and the connections too.
I am fairly new to the web world, as well as nodejs and faye. Please enlighten me if there is something wrong in the question.
You are correct in thinking that the cluster module allows multiple cores to be used on a single machine. The cluster module allows the same application to be spawned multiple times whilst listening to the same port. The distribution amongst the cores is down to the operating system, so if you have 10 processes and 4 cores then the OS will figure out how best to distribute them (as long as they haven't been spawned with a set affinity). By default this shouldn't be a concern for you.
Load-balancing can be done through node too but that is separate from clustering. Instead you would have a separate application that would grab the load statistics on each running server and proxy the http request to the most appropriate server (using http-proxy as an example). A very primitive load balancer will send one request to each running server instance incrementally to give an even distribution.
The final point about sharing messages between all the instances assumes that there is a single point where all the messages are held. In the article you linked to they assume that there is only one server and all the processes share access to the redis instance. As they all access the same redis instance, all processes will be able to receive the same messages. If we're going to start thinking about multiple servers that are in different locations in the world that all have different message stores (i.e. their own redis instances) then we get into the domain of 'replication'. Some data stores are built with this in mind and redis is one of them. You end up with a 'master' set of data and a set of 'slaves' that will periodically update with the master and grab anything they are missing. It is important to note here that messages will not be sent in 'real-time' here unless you have a very intensive replication process.
In conclusion, developers go through this chain of scaling for their applications. The first is to make the application multi-process (the cluster module). The second is to have a load balancer that proxies the http request to the appropriate server that is running the multi-process application. The third is to replicate the datastores so that the servers can run independently but keep in sync with each other.
I’m writing a small software component in order to download resources from a web Server (IIS).
But it seems like that system's performance is not acceptable. Now I’m planning to increase the number of connection to the web server by spawning multiple threads.
My question is, can I improve performance by using multiple threads? More over dose web server allow me to spawning several simultaneous connections?
Thanks
Upul
All properly configured web servers should be able to handle multiple connections from the same source. This allows, for example, a browser to download two images from a page at once.
Some servers may place an upper limit on the number of concurrent connections it will accept from one client, but this will usually be a high number. Using up to 6 connections is normally safe.
As for whether it will actually improve performance, that depends on your situation. If you have a very fast connection to an internet backbone, and find that the speed you are getting from the remote server is not taking advantage of the speed of your connection, then in many situations multithreading can improve speed. If the speed is already maxing out the speed of your connection to the internet, or the connection of the remote server, then it can't do anything.
Web servers are do allow simultaneous connections. There should not be any problem in opening one's unless the application logic prevents opening multiple connections for same client. To further clarify my point, if you require login before downloading resources and your application does not allow multiple simultaneous logins, then you will get stuck there. There are applications which do not allow lot of connections from same source for security reasons.