Gluster users - Jul 2016 - [Gluster-devel] Need a way to display and flush gluster cache ?

Hi,

Gluster stack has it's own caching mechanism , mostly on client side.
But there is no concrete method to see how much memory are consuming by
gluster for caching and if needed there is no way to flush the cache memory.

So my first question is, Do we require to implement this two features
for gluster cache?


If so I would like to discuss some of our thoughts towards it.

(If you are not interested in implementation discussion, you can skip
this part :)

1) Implement a virtual xattr on root, and on doing setxattr, flush all
the cache, and for getxattr we can print the aggregated cache size.

2) Currently in gluster native client support .meta virtual directory to
get meta data information as analogues to proc. we can implement a
virtual file inside the .meta directory to read  the cache size. Also we
can flush the cache using a special write into the file, (similar to
echoing into proc file) . This approach may be difficult to implement in
other clients.

3) A cli command to display and flush the data with ip and port as an
argument. GlusterD need to send the op to client from the connected
client list. But this approach would be difficult to implement for
libgfapi based clients. For me, it doesn't seems to be a good option.

Your suggestions and comments are most welcome.

Thanks to Talur and Poornima for their suggestions.

Regards

Rafi KC

+1 to option (2) which similar to echoing into /proc/sys/vm/drop_caches

 -Prashanth Pai

----- Original Message -----
> From: "Mohammed Rafi K C" <rkavunga at redhat.com>
> To: "gluster-users" <gluster-users at gluster.org>,
"Gluster Devel" <gluster-devel at gluster.org>
> Sent: Tuesday, 26 July, 2016 10:44:15 AM
> Subject: [Gluster-devel] Need a way to display and flush gluster cache ?
> 
> Hi,
> 
> Gluster stack has it's own caching mechanism , mostly on client side.
> But there is no concrete method to see how much memory are consuming by
> gluster for caching and if needed there is no way to flush the cache
memory.
> 
> So my first question is, Do we require to implement this two features
> for gluster cache?
> 
> 
> If so I would like to discuss some of our thoughts towards it.
> 
> (If you are not interested in implementation discussion, you can skip
> this part :)
> 
> 1) Implement a virtual xattr on root, and on doing setxattr, flush all
> the cache, and for getxattr we can print the aggregated cache size.
> 
> 2) Currently in gluster native client support .meta virtual directory to
> get meta data information as analogues to proc. we can implement a
> virtual file inside the .meta directory to read  the cache size. Also we
> can flush the cache using a special write into the file, (similar to
> echoing into proc file) . This approach may be difficult to implement in
> other clients.
> 
> 3) A cli command to display and flush the data with ip and port as an
> argument. GlusterD need to send the op to client from the connected
> client list. But this approach would be difficult to implement for
> libgfapi based clients. For me, it doesn't seems to be a good option.
> 
> Your suggestions and comments are most welcome.
> 
> Thanks to Talur and Poornima for their suggestions.
> 
> Regards
> 
> Rafi KC
> 
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