[Bitcoin-development] LevelDB benchmarking

[Mike Hearn]

> What problem does it solve?

Primarily that block verification and therefore propagation is too
slow because it's very CPU and IO intensive. The CPU work can be
multi-threaded. The IO work, not as much. As Bitcoin grows we need to
scale the nodes. Eventually there may be multi-machine nodes, but for
now we can buy more time by making the existing nodes faster.

I don't see this as a replacement for moving users to SPV clients.
Obviously, otherwise I would not be writing one ;)

> If the problem it will solve is the "too easy to get a DB_RUNRECOVERY
> error" because bdb is fragile when it comes to its environment... then
> LevelDB looks very interesting.

I have no experience with how robust LevelDB is. It has an API call to
try and repair the database and I know from experience that BigTable
is pretty solid. But that doesn't mean LevelDB is.

> If the problem is bdb is creaky and old and has obscure semantics and
> a hard-to-work-with API, then yes, lets switch (I'm easily seduced by
> a pretty API and blazing fast performance).

The code is a lot simpler for sure.

> As long as it compiles and runs on mac/windows/linux that doesn't
> really worry me.

It was refactored out of BigTable and made standalone for usage in
Chrome. Therefore it's as portable as Chrome is. Mac/Windows/Linux
should all work. Solaris, I believe, may need 64 bit binaries to avoid
low FD limits.

> Lack of infrastructure because it is new does worry me; for example,
> could I rework bitcointools to read the LevelDB blockchain?  (are
> there python bindings for LevelDB?)

Yes: http://code.google.com/p/py-leveldb/

First look at the code is here, but it's not ready for a pull req yet,
and I'll force push over it a few times to get it into shape. So don't
branch:

https://github.com/mikehearn/bitcoin/commit/2b601dd4a0093f834084241735d84d84e484f183

It has misc other changes I made whilst profiling, isn't well
commented enough, etc.