I have a windows service which monitors a directory and whenever it detects a new file it will send that file to my web service for processing. I've now noticed that it's become a bit of a bottle neck sending the file using the web service request, so I was trying to work out what the alternatives are?
I've thought of having the Windows Service doing the processing directly (which I'd ideally like), but this isn't an option. Would it be better to be using WCF? In 90% of deployments the Web Service is on the same server as the Windows Service, but there is that 10% where it's on different servers. Just not sure what the best approach would be here...
EDIT: I'm sending the file as a byte[] to the Web Service, this is what I am wanting to somehow speed up. So the question I have is, would using another approach help speed this up, such as using WCF and a different protocol? I understand there is always an overhead, but trying to minimize this.
WCF & Bindings: Changing to WCF offers several bindings you can use that are more efficient to transmit data in a LAN, e.g. NetTcpBinding or Named Pipes (local only). So using WCF is a good step if you don't want to introduce bigger changes into your application.
Hybrid approach:
However, the best way to speed up at least for the 90% of deployments that host both components on the same machine is to remove the process boundary in these cases. As you mention, you've already thought about that. So just in case that the reason for putting the idea aside are the 10% of deployments that would require a distributed installation: By using an interface with an implementation for local procession and one for remote transmission, you could implement a configurable approach that supports both scenarios (90% very efficient, 10% at least not slower as before).
Scaling down data sizes:
Another - obvious - way to speed things up is to filter or compress the file contents before transmitting them to the service.
File path instead of contents:
As I understand your environment, the machines that host the services are at least close to each other (LAN, no firewall issues, ...). So it might also be a viable option not to transmit the file contents to the service, but to notify the service of the file path and have the web service access the file directly. Though not a very beautiful way with certain downsides (e.g. account of web service must be able to access the file, path must also be accessible from the web service) you'd at least get rid of the inefficient transmission of the files and substitute that with a protocol that is built for file access. Also in the 90% of installations where both services run on the same machine, the web service would do a local file access that should be very fast.
Related
I am currently working on an Owin self-hosted web service that runs on my machine and that allows peers (other machines) to download files from its virtual directory with microsoft's BITS. The downloads will work with relatively small files, but whenever I have to download large files (over 2Go) I get this error from BITS:
"The server does not support the necessary HTTP protocol. Background
Intelligent Transfer Service (BITS) requires that the server support
the Range protocol header."
I was wondering if there was a way to enable the Range Requests in Owin or if I have to implement manually the "data chunking" in the requests I receive. Because changing the content of every request to have the header "Accept-Ranges: bytes" doesn't seem to work (I assumed it would not magically worked, but I tried it anyway).
I couldn't find a lot of information on what I am trying to do besides finding out how to know if a server is supporting the range requests.
There was this question that seemed to look similar to mine, but was more focussed on setting the headers properly. It doesn't really show if/how the code splits the file before returning the response. There was also something about IIS, but my web service doesn't run on IIS, it runs on the client's machine and is instanciated by a windows service.
I found a solution to my problem. With a little bit more research on the subject, I discovered this article which sums up really well the problem I had, which is that requests going trough ASP.NET Http Handlers do not support Range-specific requests. So I will have to manually implement support for the range specific requests in my web service.
I am trying to create a monitoring application for our operations department to be proactive when dealing with systems that are encountering problems. I created an app that does the job but it has some draw backs:
Each copy of the app running serves individual pings to the systems, when 1 ping would suffice.
I have 3 different api's for getting the status of our systems depending whether its hosted IIS, WCF or desktop.
To fix the first issue i was going to create a database which an interim service(app)(monitor) would make the pings, then the app would query the database for updates. After thinking about this I realized the second issue and decided it is a future problem.
So my thought was to, rather than have the interim application pinging the systems, simply have each system have one interface in which it posts it status to the database every x time. But then I ran into a problem with the WCF and IIS services we have. These services can sit for days without anyone actually using the service. How would I make these services continue to post its data?
My questions are:
Is it better to have data REQUESTED or PUSHED in this type of situation?
If REQUESTED, what is a suggested practice for maintaining a single API across mulitple platforms(IIS, WCF, Desktop)?
If PUSHED, how would you handle the case of the Web services which are instance based and not continuously running?
For web services, one solution might be to implement a health-check end point , something that you can simply call like: webservice/isServiceUp?
I prefer that this information is PULLED. If a service / web Service/ Application is down, then you can't possibly rely on it to write something to the DB... it would be possible but highly risky and unreliable.
In a real world situation, it is a little more complicated than that because something might happen between your service host and the consumer (DNS problem for example), in which case, you would want to consider the case of not getting anything back from the isServiceUp (no true no false, just a 400 lvl error)...
Consider using your load balancer for checking on APPS / web services and proactively switching to a different IP in case of issues... it is a possibility.
I am working on a project in which a WCF service will be consumed by iOS apps. The number of hits expected on the webserver at any given point in time is around 900-1000. Every request may take 1-2 seconds to complete. The same number of requests are expected on every second 24/7.
This is what my plan:
Write WCF RESTful service (the instance context mode will be percall).
Request/Response will be in Json.
There are some information that needs to be persisted in the server - this information is actually received from another remote system - which is shared among all the requests. Since using a database may not be a good idea (response time is very important - 2 seconds is the max the customer can wait), would it be good to keep it in server memory (say a static Dictionary - assume this dictionary will be a collection of 150000 objects - each object consists of 5-7 string types and their keys). I know, this is volatile!
Each request will spawn a new thread (by using Threading.Timers) to do some cleanup - this thread will do some database read/write as well.
Now, if there is a load balancer introduced sometime later, the in-memory stored objects cannot be shared between requests routed through another node - any ideas?
I hope you gurus could help me by throwing your comments/suggestions on the entire architecture, WCF throttling, object state persistence etc. Please provide some pointers on the required Hardware as well. We plan to use Windows 2008 Enterprise Edition server, IIS and SQL Server 2008 Std edition database.
Adding more t #3:
As I said, we get some information to the service from a remote system. On the web server where the the WCF is hosted, a client of the remote system will be installed and WCF references one of this client dlls to get the information, in the form of a hashtable(that method returns a hashtable - around 150000 objects will be there in this collection). Would you suggest writing this information to the database, and the iOS requests (on every second) which reach the service retrieves this information from the database directly? Would it perform better than consuming directly from this hashtable if this is made static?
Since you are using Windows Server 2008 I would definitely use the Windows Server App Fabric Cache to store your state:
http://msdn.microsoft.com/en-us/library/ff383813.aspx
It is free to use, well supported and integrated and is (more or less) API compatible with the Windows Azure App Fabric Cache if you every shift your service to Azure. In our company (disclaimer: not my team) we used to use MemCache but changed to the App Fabirc Cache and don't regret it.
Let me throw some comments/suggestions based on my experience in serving a similar amount or request under the WCF framework, 3.5 back in the days.
I don't agree to #3. Using a database here is the right thing to do. To address response time, implement caching and possibly cache dependency in order to keep the data synchronized across all instances (assuming that you are load balanced)(also see App Fabric suggested above/below). In real world scenarios, data changes, often, and you must minimize the impact.
We used Barracuda hardware and software to handle scalability as far as I can tell.
Consider indexing keys/values with Lucene if applicable. Lucene delivers extremely good performances when it comes to read/write. Do not use it to store your entire data, read on it. A life saver if used correctly. Note that it could be complicated to implement on a load balanced environment.
Basically, caching might be the only necessary change to your architecture.
I have an application that is built as a Windows Service and a c# library assembly (.dll.) In order to manage and maintain this service, I'd like to add the ability to run a command-line application that tells the last time the service archived files, the next time it's scheduled to do so, the status of the last run, and the location of a file created by the service.
What's the best architecture for writing a service and library that can share data with another application? I'm using .net 2.0.
The way that inter-process communication happens in .net is through remoting (even if both processes are on the same machine). Other responses have suggested alternatives to inter-process communication which would not require remoting.
The best architecture is probably to make your service be a "server" that can report on it's status (and whatever information you want). Using WCF for this like ocdecio suggested would make it pretty simple.
I use WCF for that and create a contract definition for the commands/events I want to support.
Options that spring to mind that I've applied in the past:
Save the information to a database
(if you have one to hand)
Implement a
"status monitor" type thread on the
service that the client can connect
to and query via TCP/IP etc.
A fairly simple approach is to store that information in either a local config / text file which both apps have access to. Or even to place it in a registry key.
+1 for just having the service provide that (and any other data) when it is queried (simple tcp, RPC, web service, or whatever)
I'd make it pretty generic - like
QueryInfo(some identifier)
with a response as some string and a return value or other indicator that the service does not know what you are talking about, cannot get the info, or give back the info
I have 50+ kiosk style computers that I want to be able to get a status update, from a single computer, on demand as opposed to an interval. These computers are on a LAN in respect to the computer requesting the status.
I researched WCF however it looks like I'll need IIS installed and I would rather not install IIS on 50+ Windows XP boxes -- so I think that eliminates using a webservice unless it's possible to have a WinForm host a webservice?
I also researched using System.Net.Sockets and even got a barely functional prototype going however I feel I'm not skilled enough to make it a solid and reliable system. Given this path, I would need to learn more about socket programming and threading.
These boxes are running .NET 3.5 SP1, so I have complete flexibility in the .NET version however I'd like to stick to C#.
What is the best way to implement this? Should I just bite the bullet and learn Sockets more or does .NET have a better way of handling this?
edit:
I was going to go with a two way communication until I realized that all I needed was a one way communication.
edit 2:
I was avoiding the traditional server/client and going with an inverse because I wanted to avoid consuming too much bandwidth and wasn't sure what kind of overhead I was talking about. I was also hoping to have more control of the individual kiosks. After looking at it, I think I can still have that with WCF and connect by IP (which I wasn't aware I could connect by IP, I was thinking I would have to add 50 webservices or something).
WCF does not have to be hosted within IIS, it can be hosted within your Winform, as a console application or as windows service.
You can have each computer host its service within the winform, and write a program in your own computer to call each computer's service to get the status information.
Another way of doing it is to host one service in your own computer, and make the 50+ computers to call the service once their status were updated, you can use a database for the service to persist the status data of each node within the network. This option is easier to maintain and scalable.
P.S.
WCF aims to replace .net remoting, the alternatives can be net.tcp binding or net.pipe
Unless you have plans to scale this to several thousand clients I don't think WCF performance will even be a fringe issue. You can easily host WCF services from windows services or Winforms applications, and you'll find getting something working with WCF will be fairly simple once you get the key concepts.
I've deployed something similar with around 100-150 clients with great success.
There's plenty of resources out on the web to get you started - here's one to get you going:
http://msdn.microsoft.com/en-us/library/aa480190.aspx
Whether you use a web service or WCF on your central server, you only need to install and configure IIS on the server (and not on the 50+ clients).
What you're trying to do is a little unclear from the question, but if the clients need to call the server (to get a server status, for example), then they just call a method on the webservice running on the server.
If instead you need to have the server call the clients from time to time, then you'll need to have each client call a sign-in method on the server webservice each time the client starts up. The sign-in method would take a delegate method from the client as a parameter. The server would then call this delegate when it needed information from the client.
Setting up each client with its own web service would represent an inversion of the traditional (one server, multiple clients) client/server architecture, and as you've already noted this would be impractical.
Do not use remoting.
If you want robustness and scalability you end up ruling out everything but what are essentially stateless remote procedure calls. Since this is exactly the capability of web services, and web services are simpler and easier to build, remoting is an essentially pointless technology.
Callbacks with remote delegates are on the performance/reliability forbidden list, so if you were thinking of using remoting for that, think again.
Use web services.
I know you don't want to be polling, but I don't think you need to. Since you say all your units are on a single network segment then I suggest UDP for broadcast change notifications, essentially setting a dirty flag, and allowing the application to (re-)fetch on demand. It's still not reliable but it's easy and very fast because it's broadcast.
As others have said you don't need IIS, you can self-host. See ServiceHost class for details on how to do this.
I'd suggest using .NET Remoting. It's quite easy to implement and doesn't require anything else.
For me its is better to learn networking.. or the manual way of socket communication.. web services are mush slower because it contains metadata..
your clients and the servers can transform to multithreaded application. just imitate the request and response architecture. it is much easy to implement a network application like this..
If you just need a status update, you can use much simpler solution, such as simple tcp server/client messaging or like orrsella said, remoting. WCF is kinda overkill here.
One note though, if all your 50+ kiosk is connected via internet, then you might need use VPN or have an open port on each kiosk(which is a security risk) so that your server can retrieve status update from each kiosk.
We had a similiar situation, but the status is send to our server periodically, so we only have 1 port to protect/secure. The frequency of the update is configurable as to accomodate slower clients.
As someone who implemented something like this with over 500+ clients and growing:
Message Queing is the way to go.
We have gone from an internal developed TCP server and client to WCF polling and ended up with Message queing. It's the only guaranteed way to get data to and from clients and servers over the internet. As a bonus, many of these solutions have an extensive framework makeing it trivial to implement publish-subscribe, Send-one-way, point-to-point sending, Request-reply. Some of these are possible with WCF but it will involve crying, shouting, whimpering and long nights not to mention gallons of coffee.
A couple of important remarks:
Letting a process poll the clients instead of the other way around = Bad idea.. it is not scalable at all and you will soon be running in to trouble when the process is take too long to complete.. Not to mention having to handle all the ip addresses ( do you have access to all clients on the required ports ? What happpens when the ip changes etc..)
what we have done: The clients sends status updates to a central message queue on a regular interval ( you can easily implement live updates in the UI), it also listens on it's own queue for a GetStatusRequest message. if it receives this, it answers ( has a timeout).. this way, we can see overal status of all clients at all times and get a specific status of a specific client when needed.
Concerning bandwidth: kiosk usually show images/video etc.. 1Kb or less status messages will not be the big overhead.
I CANNOT stress enough that the current design you present will have a very intensive development cycle AND will not scale or extend well ( trust me, we have learned this lesson). Next to this, building a good client/server protocol for this type of stuff is a hard job that will be totally useless afterwards if you make a design error ( migrating a protocol is not easy)
We have built our solution ontop of ActiveMQ ( using NMS library c#) and are currently extending Simple Service Bus for our internal workings.
We only use WCF for the communication between our winforms app and the centralized service(s)