[Gluster-devel] gluster source code help

[Ravishankar N]

On 02/03/2017 09:14 AM, jayakrishnan mm wrote:
>
>
> On Thu, Feb 2, 2017 at 8:17 PM, Ravishankar N <ravishankar at redhat.com 
> <mailto:ravishankar at redhat.com>> wrote:
>
>     On 02/02/2017 10:46 AM, jayakrishnan mm wrote:
>>     Hi
>>
>>     How  do I determine, which part of the  code is run on the
>>     client, and which part of the code is run on the server nodes by
>>     merely looking at the the glusterfs  source code ?
>>     I knew  there are client side  and server side translators which
>>     will run on respective platforms. I am looking at part of self
>>     heal daemon source  (ec/afr) which will run on the server nodes 
>>     and  the part which run on the clients.
>
>     The self-heal daemon that runs on the server is also a client
>     process in the sense that it has client side xlators like ec or
>     afr and  protocol/client (see the shd volfile
>     'glustershd-server.vol') loaded and talks to the bricks like a
>     normal client does.
>     The difference is that only self-heal related 'logic' get executed
>     on the shd while both self-heal and I/O related logic get executed
>     from the mount. The self-heal logic resides mostly in
>     afr-self-heal*.[ch] while I/O related logic is there in the other
>     files.
>     HTH,
>     Ravi
>
>
Hi JK,
> Dear  Ravi,
> Thanks for your kind explanation.
> So, each server node will have a separate self-heal daemon(shd) up and 
> running , every time a child_up event occurs, and this will  be an 
> index healer.
> And each daemon  will spawn  "priv->child_count " number of threads on 
> each server node . correct ?
shd is always running and yes those many threads are spawned for index 
heal when the process starts.
> 1. When exactly a full healer spawns  threads?
Whenever you run `gluster volume heal volname full`. See afr_xl_op(). 
There are some bugs in launching full heal though.
> 2. When can GF_EVENT_TRANSLATOR_OP & GF_SHD_OP_HEAL_INDEX happen 
> together (so that index healer spawns thread) ?
>     similarly when can GF_EVENT_TRANSLATOR_OP & GF_SHD_OP_HEAL_FULL 
>  happen ? During replace-brick ?
> Is it possible that index healer and full healer spawns threads 
> together (so that total number of  threads  is 2*priv->child_count)?
>
index heal threads wake up and run once every 10 minutes or whatever the 
cluster.heal-timeout is. They are also run when a brick comes up like 
you said, via afr_notify(). It is also run when you manually launch 
'gluster volume heal volname`. Again see afr_xl_op().
> 3. In /var/lib/glusterd/glustershd/glustershd-server.vol , why 
>  debug/io-stats  is chosen as the top xlator ?
>
io-stats is generally loaded as the top most xlator in all graphs at the 
appropriate place for gathering profile-info, but for shd, I'm not sure 
if it has any specific use other than acting as a placeholder as a 
parent to all replica xlators.

Regards,
Ravi
> Thanks
> Best regards
>
>>
>>     Best regards
>>     JK
>>
>>
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