[Tech] Swapping and datastore

[Ed Tomlinson]

On September 20, 2007, Matthew Toseland wrote:
> On Thursday 20 September 2007 17:37, Jusa Saari wrote:
> > What happens to the datastore when a node swaps its position? From what
> > I've understood, the requests are routed based on node locations, which
> > causes the contents of a node's datastore to reflect its position; if a
> > node changes its position to the other side of the position ring, it will
> > receive very few requests relevant to its datastore, which means that the
> > store will effectively get wiped clean every time the node swaps.
> > 
> > I tried to look at freenetproject.org for this, but the documentation
> > there (http://freenetproject.org/understand.html) seems to be describing
> > the routing algorithm which predated NGRouting.
> > 
> > So, given this, would it make sense to simply delete from the store any
> > keys not near the current location after a swap? They can't be accessed
> > anyway except by pure luck, and will simply waste store space which could
> > otherwise be used to fill the store up with relevant keys.
> 
> It's not necessary. They will be automatically deleted when new keys are 
> added, in accordance with the Least Recently Used cache replacement 
> algorithm. Until new data comes in we may as well keep the old data.
> 
> Also I'd expect *generally* that long range swaps occur mostly towards the 
> beginning of a node's lifetime, rather than later on.

I am not at all sure of that.  I know that is not the case here.  I have a node with
dynamic address.  My typical pattern is get ref to get myself 10 or more 'friends',
wait 2 weeks by which time I will be back down to 5 nodes or so.  When I add new
'friends' my nodes location shifts wildly...   I have a 4G datastore.   Question is, 
is this a common pattern?  If it is it could easily lead to low hit ratios.

I have always thought that the average location of the keys in the DS should 
influence the swap algorythm.

Ed Tomlinson