web server outbound calls, from which tier?

[Secret Squirrel]

Hi,

We have a three tier architecture, but now we have received a third
party application that doesn't fit into it, and I am trying to find a
clean way to make it fit in nicely without rewritting it.

In our applications architecture, we have a presentation tier that is a
ASP.NET web server, accessible from the internet. This presentation
tier connects to a application tier, that is also accessible thru an
ASP.NET web server by web services. The web services in the application
tier access the Database tier, which simply is a database. Firewalls
between each server/tier.

Only our presentation tier is externally accessible. But it cannot
connect to the database directly due to firewall restrictions. The
presentation server/web server can only connect to the application
server. Our application tier can connect to the database, but cannot
connect to the internet due to firewall restrictions.

And now comes the bad news. A third party has given us an application
that we must host as well, that we cannot modify. This application will
connect to the database (directly), and it also wants to communicate
with a external web service via the internet. So it breaks our mold -
it won't go on the application tier because it needs to connect to the
internet, and we cannot place it at the presentation tier because it
needs to connect to the database.

Any suggestions, bearing in mind that we cannot rewrite the 3rd party
app? The application server CAN connect to the presentation tier's web
server- is there any way we could forward the requests from the
application server to the web server, and then have the web server
handle the request to the external web service, and return the response
to the application server? Any other ideas?

THanks,

Jon Paugh

 

[Ranjan Sakalley]

Hi,

Why don't you write another web service on your web server (Presentation
layer) , that can be called up from your application server (third party
component), and this service would just forward the calls to the external
webservice, and return back the results. Just a pure wrapper. My 2c.

HTH,
r.
http://codebetter.com/blogs/ranjan.sakalley/

 

[Javier G. Lozano]

I agree with Ranjan on the solution. Have the 3rd party app sit on the
app tier and have it connect to an endpoint on the webserver through
the port that's open between the two.

 

[Secret Squirrel]

thanks for suggestion.