Do to some constraints with a client's system and setup, I am wondering if it is possible for SQL Server to fire off a web request?
I need to be able to send emails after a sql server column gets updated. I had a trigger with database mail but the database server on the client won't allow that. The alternative would have that figure fire off a web request when ready. I would do it via a web service on the web server and have it just poll the table, but that seems like a lot of wasteful cycles.
Any ideas?
You can execute managed code from SQL server. Create a windows service and let that do whatever you want in C# to fulful your need and SQL server call it.
Checkout this link for sample program
Do not call web services from SQLCLR, and especially do not call web services (or send email) via SQLCRL from triggers. There are many reasons why using SQLCLR for external http or smtp access is a bad idea, but doing it from a trigger is horrendous. Just think how will your application behave in a day when the web service responds with a 10 second latency...
You must do the mail interaction from an external application. You should decouple the interaction between your application and the emailer application via a queue. See Using Tables as Queues for how to use a SQL Server table as a queue. You can enqueue the mailing request directly from your application, or use a stored proc that both inserts the data and enqueue the request, or as the last resort, use a trigger on the table to enqueue the mailing request. You emailer application (a separate service) should monitor this queue and service it by doing the actual email send (or http web request , for the matter).
Related
Our company needs to write a web service which will use to submit data from remote site to HQ Servers. This web service will update more then 10 tables from both site(Remote and HQ).
We use SQL Server 2008 in both sides and one batch, will insert data into HQ Server and at the same time need to do some updates on the remote side as well.
The remote site will call the web service on HQ with required data.
Simply I need to commit or roll-back both servers when the web method executed.
What is the best way to handle the transaction block in this situation?
I want to control application (in my case it is corelDraw) ,I know I should use it's application object and I do this, but the issue now is I want to do this in webservice,
so as far as I understand if I put this code which control the application in the web-service ,my code will try to control the corel application which is on the server not on the client :(
so any hint/advice how could I do this, and control the application on the client not server ?!!!
As you already noticed web service runs on server and only result is passed to client.
Well you have a few options to control client machine over web service... Here is one of possible scenarios.
1. create web service that will provide commands for client
2. create windows service (client) that will consume your web service commands
3. inside windows service then just execute those commands in appropriate manner
Well I have to say this is not the prefered way I would take to automate corelDraw, but if you insist on using webservice as command provider it will do the job.
You need to ask yourself what is the difference between client and a server. Can a client be a server? Can a server be a client?
You make your client with CorelDraw installed to accept web-service request, i.e. effectively make it a web-service server, and then carry on as normal.
Although I would say web-service is not the best way to control such complex application as CorelDraw. I'd look in some other ways of communication between peers, like lower level network communication that would not have overhead of HTTP.
I am trying to write a monitoring tool to monitor some information
It will gonna work on azure normally. So i gonna host the database on azure also the webservice will be hosted at azure.
On the client's i read from the config file how many time's he need to update the information to the azure database ( with the webservice on azure ).
Now i want to send also some commands to the client itself. Like start service, .... what is the best way to do that?
How can i send it from a website that is hosted on the azure platform?
I think you should consider implementing a WCF service at the client as well. The Azure side of your software could call operations from this service when it needs to instruct the client to do something.
The WCF service at the client should be something simple,hosted in a Windows Service or in your actual client (whatever it is... win forms, console, etc).
Since you have no VPN, it sounds like you may have a problem with hosting a WCF service on the client. If the client is behind a firewall, you would have to modify the firewall configuration to allow your server to connect to this service.
Last time I had to do a service like this, I used Comet. The server maintains a queue of messages to be sent to the client. Your client connects to the web service and requests any available messages. If messages are available, the server returns them. If not, the server leaves the request open for some time. As soon as a message arrives, the server sends it down the already-open connection. The client will either periodically time out/reconnect or send a keep-alive message (perhaps once per minute) in order to keep the connection alive in the intervening firewalls.
I have a company network under my control and a couple of closed customer networks. I want to communicate from a web application in my network to a database inside a customer network. My first idea was:
Web application stores query in a database in the company network and waits for answer.
Windows service inside client network polls our database a couple of times every second through a (WCF) web service also in our company network.
If a query is available the Windows service executes it in it's local database and stores the answer in the company database.
I've been thinking about removing the polling idea and instead using persistent connection between a client in the customer network and a server in our company network. The client initiates the connection and then waits for queries from the server. What would be better or worse compared to polling through a web service? Would WCF be the right thing to use here?
you have few approaches:
WCF Duplex, Once the web application stores a query in database, you initiate a call to the client (in this case the Windows Service) instead of making the windows service polls every few seconds. net.tcp will be good choice but still you can use http.
Long polling, Instead of letting your Windows Service client sends a request every few seconds, let it send the request, the channel is open, set the timeout in both client and WCF service for longer time, let the server method loops and checks the database for new notifications. Once new notifications found, the method returns with them. At Client side, once you get a return send another request to the server and then process the data. If timeOut error occure, send another request. Just Google Long polling you will find a lot.
Regarding querying the database every few seconds, the better approach would be making a table for notifications, So instead of querying a large table with a complex sql string every few seconds you can let the client add the notifications in a separate table (after they are done adding them the main table), so your query will be much simpler and takes less resources. you can add direct pointers (Like Ids) in the notifications table to save time. Later clean up the notifications table..
i have the current scenario:
my app generates for each user an
valid system email address of form
lets say: uuid#website.com
when an user has a problem/question he can send an
email from any address to that
predefined system email address
the app should receive the emails sent by the user and process them(check for spam, insert in db)
in this scenario a possible first solution that i had in mind was to pool the emails addresses on a 15 minutes period, process them(spam or not spam) in an external desktop app(or similar) and insert them in a database.
because i want to do this in .net, C#, SQL server 2008, and it should run on a webserver is the below solution possible using WCF?
i create a WCF webservice that when an email is received by an email address it captures it and starts the processing procedure.
One problem i see with WCF from the start is that i don't think that it can auto react, the only way i used wcf until now was only for calling it directly and receiving a result. So i think another layer should be put between the email server and the wcf service and that layer should "react" when something is received.
the main idea is to process the emails as they arrive not to be pulled out of the inbox periodically.
any pointers? thank you
You are right. A web service cannot capture anything for you. You will have to call(using an .ashx/or etc) the web service. That is what the web services are for, to be called.
the app should receive the emails sent by the user and process them
It sounds like you are looking to develop an email client; if so, then how about:
Create an email client app (for instance here)
Create a windows service, to help process the mails.
Assuming that you've tailored the client program, the windows service would work-with the client, look for new messages, and processes them accordingly.
For email client examples, checkout:
This answer
And this article
If connecting to Exchange 2007 SP1 or later Exchange Web Services looks like the best approach:
Read MS Exchange email in C#