memcachedb 0.0.2 is released

Andreas Vierengel avierengel at
Fri Sep 21 14:09:59 UTC 2007

Steve Chu wrote:
> memcachedb is a better and simplified tugela, but more. It is designed
> for persistent, not for cache. It enables bdb's transaction(so never
> lost data) and no expiration concept exsited. For better performance,
> we use a fixed length of key and value. The code is simple and
> clear(about 1300+ lines), and also very internal, but already on our
> production for high traffic pageview countering.
> At the same time, we are testing memcachedb replication feature, and
> may ready on next release.
> Source code is available on:

I just downloaded it and quick-looked over the source.
If I have 1 client who rapidly get some key/values BDB which are in 
memory, and 1 client who get key/values which are not in memory => 
disk-access, the whole server would slow down for this disk-access 
because you have only the state-machine without using a worker-thread 
model for BDB-access. BDB blocks, at least for me :)


> Here comes the README file:
> What is memcachedb?
> *******************
> Memcachedb is a distributed storage system designed for persistent. We simplely
> hacked from memcached and tugela. But neither of them. Memcachedb is not a
> cache solution, it is a persistent solution for high-frequency writing
> and reading.
> It conforms to memcache protocol(not completed, see below), so any
> memcached client
> can have connectivity with memcachedb. Memcachedb uses Berkeley DB as a storing
> backend, so lots of features including transaction and replication are
> supported.
> memcachedb Features
> *******************
> High network performance, thanks to memcached and libevent(we using epoll).
> High storage performance, Using Berkeley DB BTREE Access Method, and
> bdb's own MPOOL.
> High availability, Berkeley DB Transaction supported, and replication
> will be ready later.
> Supported memcache command
> **************************
> get, set, add, replace
> incr, decr
> delete
> stats
> db_checkpoint, db_archive (not in memcache protocol)
> We Stand on the shoulders of giants, Memcachedb source code is based on:
> * Memcached:
> * Tugela:

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