[jira] [Commented] (KUDU-2990) Kudu can't distribute libnuma (dependency of memkind)

["Adar Dembo (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-2990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16964654#comment-16964654 ] 

Adar Dembo commented on KUDU-2990:
----------------------------------

To be a little more pedantic, we currently provide Kudu in one source distribution and one binary distribution:
 * The source distribution does not include libnuma _per se_: it is downloaded as part of the thirdparty dependency build and either statically or dynamically linked into the Kudu binaries (depending on which the user asked for at build time). However, it is impossible to escape the dependency without editing the distributed build code. Moreover, if static linkage is selected, one ends up with Kudu binaries that statically link libnuma, which also violates the terms of the LGPL itself.
 * The binary distribution is available as a Maven artifact and is built in a CentOS 6.6 environment. The binaries are dynamically linked but the distribution also includes nearly all of the necessary dependencies, including libnuma.

> Kudu can't distribute libnuma (dependency of memkind)
> -----------------------------------------------------
>
>                 Key: KUDU-2990
>                 URL: https://issues.apache.org/jira/browse/KUDU-2990
>             Project: Kudu
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 1.10.0, 1.11.0, 1.12.0
>            Reporter: Adar Dembo
>            Priority: Blocker
>
> I noticed in [this commit|https://github.com/apache/kudu/commit/973e5cdf8fbcedcdcc659d980f3a3a69dc4f109f] 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|https://www.apache.org/legal/resolved.html#category-x].
> Some background: memkind was added as a new thirdparty dependency in 1.10.0. It replaced the libraries provided by [PMDK|https://pmem.io/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:
> # 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.
> # 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.
> # 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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