10 Apr
2020
10 Apr
'20
3:56 p.m.
On Thu, 9 Apr 2020, John Mulligan wrote:
Hello ceph-devel,
I'm one of the members of the team currently maintaining, and hopefully
improving, go-ceph (ceph library bindings for Go) [1].
An issue I keep returning to is the nature of api calls such as:
- rados_mon_command
- rados_mgr_command
- ceph_mds_command
... etc
The argument named cmd for these functions is of type `const char **cmd` and
is followed by a `size_t cmdlen`. I'd like to better understand the rationale
for array-of-char* strings and how this is intended to be used.
It's purely historical. The command used to be an array of
strings/arguments directly from the CLI so that the parsing was done on
the mon. Way back when we changed it to JSON, but never cleaned up the
message strcture.
sage
>
> When I first saw the function I initially thought it was meant to support
> multiple "commands" getting issued at once but later started thinking that
a
> single command could be split across multiple strings, and experimentation
> demonstrated that this does indeed work. I've attempted reading the sources
> but nothing jumps out at me to explain this approach. Most callers of these
> functions seem to only use a single "command string".
>
> I also tried looking to see how the code makes use of the array (or vector
> after the transition to C++) but I will admit I'm not very familiar with C++
> and get a bit lost in some of the templates and overloading.
>
> Could someone who is familiar with this better explain how this argument and
> it's type is meant to be used?
> I want to make sure we're making good use of the apis that ceph provides in
> the wrapper library, or at the very least I want to make sure we're not mis-
> using the apis. :-)
>
> Thank you for your time.
>
> 1 - https://github.com/ceph/go-ceph
>
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