mon dependency on OSD MonClient using OSD's client_messenger

mon dependency on OSD MonClient using OSD's client_messenger

[Matt W. Benjamin]

Hi,

We noticed that OSDs use their client_messenger, rather than their potentially
dedicated cluster_messenger, to drive MonClient.  Then we found that the Mon's setup
of the OSDMap depends on this.

Can someone comment?  We assume this is well known, but what is the background?

Thanks,

Matt

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Matt Benjamin
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Re: mon dependency on OSD MonClient using OSD's client_messenger

[Gregory Farnum]

On Wed, Aug 6, 2014 at 9:40 AM, Matt W. Benjamin <matt@cohortfs.com> wrote:
> Hi,
>
> We noticed that OSDs use their client_messenger, rather than their potentially
> dedicated cluster_messenger, to drive MonClient.  Then we found that the Mon's setup
> of the OSDMap depends on this.
>
> Can someone comment?  We assume this is well known, but what is the background?

Right. The monitors are *strongly* identified with their single IP
address, which needs to be client-accessible, so it belongs on the
client network. Since every other daemon type is a client to the
monitors, adding a special cluster network for the monitors doesn't
really make sense and would be a fair bit of work.

At least, those are the good reasons for it being this way. I haven't
thought about it much previously because the OSD "cluster network" (or
any support for different networks/IPs at all) is a relatively new
thing in Ceph's life, and the monitors never got that treatment. ;) (I
am pretty sure the good reasons for it being that way actually do hold
even if we did have the patches, but maybe I'm missing something.)
-Greg
Software Engineer #42 @ http://inktank.com | http://ceph.com