Userver is used by hundreds of microservices only in our code base. Manual application of modifications to the whole code-base is a burden.
Rule of the thumb: we endeavor to change things only if the migration path is simple or there is a script to automate it.
Userver follows the two-part versioning since version 2.0:
major.minor
Examples: 2.0, 2.1_rc
We attempt to keep the API stable as long as it does not stand in the way of new features or better safety.
Note that framework internals located in *::impl::* and *::detail::* namespaces have no stability guarantees. You should not use those in your code directly.
Transitive includes could not be relied on. Even a change in patch version could remove some #include from header and break code that relies on transitive includes. However, we provide script ./scripts/add-missing-include.sh that helps to add missing includes in big code bases.
Avoid adding your own forward declarations for the framework types as the type could change to an alias or vice versa during the userver development process.
Userver is meant for usage mostly as a static library that is linked with the application. Because of that userver has no Application Binary Interface (ABI) stability guarantees. Binary interface may change on any commit.
However, you could redefine cmake options USERVER_NAMESPACE, USERVER_NAMESPACE_BEGIN and USERVER_NAMESPACE_END to place all the entities of the userver into versioned inline namespace. That would to allow you mixing different versions of userver in a single binary without ODR-violations.
