Re: gluster source code help

[Ravishankar N <ravishankar@xxxxxxxxxx>]

On 02/03/2017 09:14 AM, jayakrishnan mm wrote:

On Thu, Feb 2, 2017 at 8:17 PM, Ravishankar N <ravishankar@xxxxxxxxxx> 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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