Re: [Gluster-devel] One Question about DHT

[Pavan T C]

On Wednesday 17 August 2011 09:18 AM, Daniel wrote:
> Hello Pavan,
>
> I came cross one question about DHT lookup.
>
> When dht_lookup process a fresh lookup, if the looked up target can not
> be found by hashed, why does it assert it as a directory and lookup on
> all the child nodes?

Not sure why you thought I should be the one to address this to. There 
are more knowledgeable engineers on this user group :)

I looked up the code a bit to answer your question and here is what I 
understand:

If it is a fresh lookup and the file hash computed for this entity did 
not fall into any of the pre-computed hashed ranges, a lookup_everywhere 
is triggered to go to the backend and see if it exists there. If it is 
not there too, this brings in a mechanism called "directory self heal".

The debug message does say - "see if it is a directory", but if you look 
at the dht_lookup_dir_cbk, a check is also made to see if it was *not* a 
directory. It might only be the debug messages that might have led you 
into thinking why a directory is being looked up in particular. That is 
not really the case.

Pavan

> Thanks
>
> Dan