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  1. Kudu
  2. KUDU-2990

Kudu can't distribute libnuma (dependency of memkind)

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 1.10.0, 1.11.0, 1.12.0
    • Fix Version/s: 1.10.1, 1.12.0, 1.11.1
    • Component/s: util
    • Labels:
      None

      Description

      I noticed in this commit that libnuma (a dependency of memkind) is licensed under the LGPL. This means that we can't distribute it as per the ASF 3rd party license policy.

      Some background: memkind was added as a new thirdparty dependency in 1.10.0. It replaced the libraries provided by PMDK, and is used to power our generic non-volatile memory cache implementation, which can be configured as a replacement for the standard DRAM-based block cache.

      I spent some time looking into whether our use of memkind actually calls into libnuma and unfortunately I think the answer is yes: when we map a pmem region via memkind, it creates an arena with which to do allocations, and that allocates some per-CPU data structures. The precise number of structures is derived from a call into libnuma.

      We'll need to find a creative solution to this problem. Some ideas:

      1. Restrict libnuma to build time and expect it on the host system at runtime. We do this for some libraries already, like libsasl. I see libnuma installed on my laptop (Ubuntu 18) as well as on CentOS 6.6 and 7.3 machines we use for development. On my laptop the reverse dependencies look significant enough that it's likely installed by default, but I can't guarantee that everywhere, nor is it guaranteed for all sorts of funky container images users will no doubt put Kudu in.
      2. Like #1 but also patch memkind to dlopen() libnuma so that if it can't be found, whatever memkind function is currently running returns an error. That's a much better failure mode than "the Kudu process can't start", but it's unclear how much work this would be.
      3. Make the NVM cache implementation fully optional and excise it from the default Kudu distribution. I say "fully optional" because it's already somewhat optional: the CMake logic allows for it (and memkind, and libnuma) to not exist on macOS where that stuff apparently just doesn't work. Still, this would be frustrating for users who wish to use the NVM cache out of the box.

      I'm not sure what needs to happen to 1.10.0 (first release with the libnuma dependency) and with 1.11.0 (imminently releasing). Could someone with more experience in ASF legal matters weigh in?

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              • Assignee:
                adar Adar Dembo
                Reporter:
                adar Adar Dembo
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                • Created:
                  Updated:
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