Apache Celix is a framework for C and C++14 to develop dynamic modular software applications using component and in-process service-oriented programming.
Add support for Apache Celix Features, inspired by Apache Karaf Features. This will allow users to select bundles and link the required libraries for the executable/container using a single entity.
Apache Karaf provides a simple and flexible way to provision applications.
In Apache Karaf, the application provisioning is an Apache Karaf "feature".
A feature describes an application as:
a name
a version
a optional description (eventually with a long description)
a set of bundles
optionally a set configurations or configuration files
optionally a set of dependency features
Proposed Solution
For Apache Celix, introducing a feature concept would be beneficial, especially for specifying additional linking requirements for the executable/container running the feature-based selected bundles. This is because some bundles depend on system-installed libraries rather than private bundle libraries.
Take the civetweb::civetweb library, for instance. Linking to this library is necessary if an executable/container uses the http_admin:
With the Apache Celix Features concept, this could be arranged by the feature if it supports library configuration. A feature could then be defined in CMake as:
add_celix_feature(celix_http_admin
NAME "Apache Celix HTTP Admin"
DESCRIPTION "Adds the Apache Celix HTTP Admin bundle so that the HTTP whiteboard pattern can be used to pick up HTTP and/or websocket services."
VERSION "1.0.0"
BUNDLES_LEVEL_3 Celix::http_admin
EXE_LINKING Celix::http_admin_api
Usage might look like:
add_celix_container(my_container
FEATURES celix_http_admin
)
# or
# celix_container_features(my_container celix_http_admin)
Downsides
The proposed solution relies on CMake, which further tightens the coupling between Apache Celix and CMake.
The add_celix_feature calls should either be "installable" or provided in the CelixConfig.cmake (or a Use.cmake file) to ensure they are usable downstream.
Apache Celix Features
Add support for Apache Celix Features, inspired by Apache Karaf Features. This will allow users to select bundles and link the required libraries for the executable/container using a single entity.
Background
Apache Karaf has a concept of "feature" to make it easier to add a selection of bundles.
Proposed Solution
For Apache Celix, introducing a feature concept would be beneficial, especially for specifying additional linking requirements for the executable/container running the feature-based selected bundles. This is because some bundles depend on system-installed libraries rather than private bundle libraries.
Take the civetweb::civetweb library, for instance. Linking to this library is necessary if an executable/container uses the http_admin:
With the Apache Celix Features concept, this could be arranged by the feature if it supports library configuration. A feature could then be defined in CMake as:
Usage might look like:
Downsides