Wondering if there is a better option than a wcf callback.
When processing some data Invoices and printing them and I need to constantly show the user in a winform -"Invoice 1 Printed" invoice 2 printed etc....
I have put together a call back mechanism and all works but wondering if there is a better way of doing this .
Was thinking along the line if 2 services would be better than a callback.
One that loops at server side through the invoices and saves to the database the status ="Printed" and the other the queries it and check if it has printed and return to the user
.
Would that be better than a callback,faster and avoid timeouts etc..?
Just thinking as an alternative as a collegue who used callback extensively said" dont use callback use 2 services".
What would you do if you had to process 2000 invoices and notify the user for each one
Any suggestions?
On one project we have done the following:
All windows clients also host a WCF service
When the windows client starts it registers itself with the server, that this user is loggon with this IP address.
The server stores info on who is logged in where
Then we can send a message to the user whenever we want
When the client recieves the message we fire an event, then whatever part of the UI that is affected can update itself or show a message.
Related
I have a Silverlight app that uses WCF for communication with my SQL Server via Entity Framework. When I send multiple requests to the service it fails to send all. If I use the Callback event and send each request as the previous one completes all is well. How can I get this to work without this workaround?
Edited:
For i As Integer = 0 To someNumberOfTimesInLoop
serv.CloseElement_IncAsync(Params...)
Next
So I wonder if it's a concurrency problem as they hit at the same time and the Id fields for these tables are not incremented in time?
I have added this code in my App.xaml.vb based on this blog:
WebRequest.RegisterPrefix("http://", WebRequestCreator.ClientHttp)
Any ideas?
I'm building an application, it's easy and what I want to do is the following. I want a brainless client and all the work should be done on the server. So I want a way to change windows forms in my server application and not on the client itself.
So when I have an application like blackjack the user presses hit then the hit function on the server get called, he will calculate everything, send the result back to the client and then the client updates it buttons and GUI (like displaying cards, and so on).
Now how do you do this in WCF? I know how to call remote function but I can't get the windows forms part to work (can I add this in the contract, and how?)
Thanks!
Your client should handle all of its own UI. Your service shouldn't have anything to do with the UI.
Instead of having the service handle the UI, just have it send messages back to the client and let the client figure out which UI elements to show or not based on the messages.
So, when the server calculates some result, like BLACKJACK!, it'll send a message indicating that back to the client which will then show the proper UI elements.
Make sense?
I am trying to implement an API which uses the long-polling concept in Symfony framework.
Let's say that I have a table 'feeds' which can only grow (assume that users can insert thier feed from other interface).
I want to create a client-side real-time updated page. The idea is the following:
Client send an ajax request with timestamp of last modification (first time sends 0)
Server compares timestamp of client to timestamp, to retrieve all messages with bigger timestamp than the one sent by user
If there are newer messages, return them immediately to the client, with the timestamp of the latest one
On other hand, if there are no new messages, enter into a 2 minutes busy-wait loop, checking every 1-3 seconds (randomly) whether there are new messages.
When client receive servers answer, browser updates view and immediately sends a new ajax request.
In other words, instead of send an AJAX call every x seconds, the server holds the request till it has new information for us.
Having good experience with Symfony I tried to implement a simple demo of this api, and it works great. I had a problem of session blocking (the ajax call is held so access to the server is not possible), so I simply added the following to the action:
public function executeIndex(sfWebRequest $request)
{
session_write_close();
:
:
(see also this link)
Then I testes massive access to the API. 100 users works fine, 1000 everything crashes.
I realized that I have two problems:
For each access a new DB connection is opened
For each access the server executes a new process
For the first problem I tried to put persistent: true In my database.yml Doctrine connetor. When I monitored the server connections I saw that still each access to the API opens a new connection. So basically I am still blocked with the same two problems.
Does anyone have any idea or experience with this issue?? Or maybe I should give-up the idea of implementing my api with Symfony??
I think using symfony for this, is the wrong approach. Using Sockets would be much easier.
For example have a look at nodejs or ape-project (comet)
they both are able to handle much more current users than apache, lighttpd or nginx...
Apache creating different threads for each user and each thread have a separate database connection. that's why the db connection are high
My WCF service(hosted as Windows Service), has some 'SendEmail' methods, which sends out emails after doing some processing.
Now, I have got another requirement where client wants to preview emails before they are being sent out, so my WCF service needs to return whole email object to calling web app.
If client is happy with emails object, they can simply click 'Send out' which will then again call WCF service to send the emails.
Because at times it can take a bit longer for emails object processingy, I do not want calling application to wait until emails object is ready.
Can anyone please guide what changes I need to make to my WCF service (which currently has all one way operation)?
Also, please guide me whether I need to go for Asynch operation or message queuing or may be a duplex contract?
Thank you!
Based on your description I think you will have to:
Change current operation from sending email to storing email (probably in database).
Add additional operation for retrieving prepared emails for current user
Add additional method to confirm sending one or more emails and removing them from storage.
The process will be:
User will trigger some http request which will result in calling your WCF service for processing (first operation)
WCF service will initiate some processing (asynchronously or firt operation will be one-way so that client doesn't have to wait).
Processing will save email somehow
Depend on duration of processing you can either use AJAX to poll WebApp which will in turn poll WCF service for prepared emails or you will create separate page which will user have to access to see prepared emails. Both methods are using second operation.
User will check prepared email(s) and trigger http request which will result in calling third operation to send those emails.
You have multiple options:
Use Ladislav's approach. Only to add that service returns a token and then client uses the token to poll until a time out or a successful response. Also server keeps these temp emails for a while and after a timeout purges them.
Use duplex communication so that server also gets a way to callback the client and does so when it has finished processing. But don't do this - and here is my view why not.
Use an Asynchronous approach. You can find nice info here.
I have a vb.net 2.0 winforms project that is full of all kinds of business reports (generated with Excel interop calls) that can be run "on-demand". Some of these reports filter through lots of data and take a long time to run - especially on our older machines around the office.
I'd like to have a system where a report request can be made from the client machines, some listener sees it, locates a server with low-load, runs the report on that server, and emails the result to the user that requested it.
How can I design such a change? All our reports take different parameters, and I can't seem to figure out how to deal with this. Does each generator need to inherit from a "RemoteReport" class that does this work? Do I need to use a service on one of our servers to listen for these requests?
One approach you could take is to create a database that the clients can connect to, and have the client add a record that represents a report request, including the necessary parameters which could be passed in an xml field.
You can then have a service that periodically checks this database for new requests, and depending on how many other requests are current processing, submit the request to the least busy server.
The server would then be able to run the report and email the file to the user.
This is by no means a quick solution and will likely take some time to design the various elements and get them to work together, but its not impossible, especially considering that it has the possibility to scale rather well (adding more available/more powerful servers).
I developed a similar system where a user can submit a request for data from a web interface, that would get picked up by a request manager service that would delegate the request to the appropriate server based on the type of request, while providing progress indication to the client.
How about write a web service that accepts reporting requests. On completion the reports could be emailed to the users. The web service can provide a Status method that allows your WinForms app to interrogate the current status of the report requests.