[MESOS-8988] Allow for unbundled dependencies in CMake build.

• Type: Epic
• Status: In Progress
• Priority: Minor
• Resolution: Unresolved
• Component/s: build
• Labels: build, cmake
• Epic Name: cmake-unbundling
• Assignee: Unassigned
• Reporter: Till Toenshoff
• Created: 13/Jun/18 23:11
• Updated: 02/Jul/20 17:16

Description

Our CMake setup currently bundles all dependencies and does not allow for building against unbundled dependencies.

We should allow for unbundled dependencies as well.

Motivation;
a. It has proven to be problematic to enforce building against the bundled versions of our dependencies. Bundled versions may or may not be compatible with all of our supported platforms. Namely Libevent >= 2.1.x fails our libprocess tests on macOS and Ubuntu 17. This in turn prevents us from switching to SSL by default on all platforms.
b. Historically we tried to not enforce bundling and therefor allowing linux distros to supply Mesos packages.
c. Module authors need to link against the exact same dependency versions, where needed. Our autotools setup specifically allows for using unbundled dependencies, supporting module authors to cover this task.

Offering bundled dependencies is per-se a good thing as it eases the pain building Mesos - we just need to make that optional.

Issue Links

• blocks: MESOS-7866 CMake build system improvements
• blocks: MESOS-10145 Drop autotools build (or leave it as a thin wrapper around CMake).
• is related to: MESOS-9636 Autotools improvements