[crossfire] Handling massive loot

[Mark Wedel]

On 3/22/21 11:58 AM, Nicolas Weeger wrote:
> Hello.
> 
> One issue that happens is server delays when dealing with big loot.
> 
> For instance a player selling some thousands rods can stuck the server for
> some seconds... Or even dropping many items on a big pile can be quite slow.
> 
> 
> So to handle that correctly, I was thinking of changing the server code like
> that:
> 
> - split data/commands reception and processing - have one loop that reads from
> the socket, put commands in a waiting queue, then another function later
> processes those commands
> 
> - for commands like pick/drop/examine, enable them to work on multiple
> processing loops instead of a single. So for instance the command would drop
> 100 items, then store its status, put itself back on top of the command
> waiting queue, and exit - this way the server can process something else.

Being multi threaded would help some things out.

It has been a while, by my recollection is the drop (and pickup) problem is that these are in fact handled by the server, eg, 'drop all' is done on the server, dropping everything of matching criteria.  And likewise, pickup all is done on the server, so slowing down the command processing from the client doesn't help out.

It is also my recollection in that the reason this is slow that each time an object is moved (ground to player or vice versa), it has to check the destination for duplicates to merge them (otherwise, you could have 20 different entries for silver coins).  This becomes an O(n^2) operation, so when dropping a few items, it is pretty fast, but when dropping a stack of 100 different items, that takes a lot of time.

There are a couple ways to deal with this:
- A thought I had a while back is once a space gets too many items on it, items fall over to neighboring spaces - this would reduce the upper threshhold over that operation (never too many items to examine on a space), but this could basically result in an entire shop being filled to a level of 25 items deep.
- For items going to the floor, marking the space as needing 'merging' later on could be done (one could even imagine something like a shop keeper standing on the space as this merging is done, preventing players from interacting with it)
- For items going into the players inventory (they step onto a pile of junk), deferred merging could be done, but would result in new items getting send to the client, and then and update down the road that the new item does not exist and in fact item X has a different quantity.  I'm not sure how visually that works out.
- Maybe limit the number of items picked up at once, even with pickup all, to something like 25 or other number where performance is still reasonable.  This makes it harder to clean up everything in the dungeon, but is somewhat more realistic (you can only pick up stuff so quickly).
- I can't remember if the gold insertion when selling a bunch of items is intelligent.  That is to say, if you sell 100 items, does is calculate the net proceeds and inserts it once (intelligent) or inserts the coinage 100 items (1/each item, keeping in mind that there could actually be several different coins being inserted for each item).  So changing that (deferred gold updating) could also have some benefit.