Can I modify/extend a production web service without affecting existing clients?

Question

I am currently calling a web service that returns a service defined class which I am interpreting in my application. I'm considering asking the vendor of this web service to add a property to this class which will make my life as well as their other clients lives a lot easier. To be clear I'm not asking them to modify existing behaviour or properties, so this would extend existing functionality.

My question is, if they add this property to the class, will it adversely affect existing clients' applications?

Answer 1

Yes, it could mean you get serialization errors if you haven't updated your proxies. Its better to version the service interface even if that means supporting multiple versions at once.

Answer 2

Aside from the fact that you are asking a third party to shoulder the development, (which they are often not excited to do). The modifying/extending of the web service could require downtime, which may matter a great deal. It also would interfere with the backwards compatibility of their API.

There is also a performance consideration if the property contains a lot of additional data which will be propagated to all clients unnecessarily.

Answer 3

It can potentially be a problem, yes:

• the old client may barf when receiving the unexpected property from the server
• the server may barf when not receiving the expected property from old clients

It can also work... it just needs testing / planning.

A safer option (if you have complex deployment that can't all go at once) is to consider the API sealed and add a new "v2" end-point etc.