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https://issues.apache.org/jira/browse/KUDU-2990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16964658#comment-16964658
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Adar Dembo commented on KUDU-2990:
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There's a clause in the ASF 3rd party license policy that talks about
["optional" features|https://www.apache.org/legal/resolved.html#optional]. I'll
quote it here verbatim:
{quote}
Apache projects can rely on components under prohibited licenses if the
component is only needed for optional features. When doing so, a project shall
provide the user with instructions on how to obtain and install the
non-included work. Optional means that the component is not required for
standard use of the product or for the product to achieve a desirable level of
quality. The question to ask yourself in this situation is:
"Will the majority of users want to use my product without adding the optional
components?"
{quote}
Under this criteria, the NVM cache can certainly be classified as an "optional"
feature. But, the wording of the policy ("...a project shall provide the user
with instructions...") suggests that to be compliant, these features must be
opt-in rather than opt-out. If that's true, it's tantamount to option #3 that I
listed in the bug summary.
Again, hoping someone with ASF legal background can advise on this.
> 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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