[ccache] Using ccache with memcached

Martin Pool mbp at sourcefrog.net
Wed Dec 1 22:10:28 MST 2010

 Wilson Snyder <wsnyder at wsnyder.org> wrote:
>>I think it would be a pretty interesting idea.
>>Obviously you would need to trust all the other clients writing into
>>the cache, but that's probably feasible in this environment.
>>A shared cache kept entirely in ram might grow fairly big, but it's
>>not so expensive to get an 8GB or 16GB machine devoted to this.
> Why don't you just put the cache on a NFS (/CIFS) mounted
> volume?  With the most recent version this should work well.

Just to justify why I say it would be interesting:

memcached is becoming a semi-standard protocol for a distributed hash
map on a local network, which is pretty much what ccache wants.  There
are multiple implementations including load balancing, persistence,

clients using memcached will cache-miss or rebalance to other servers
if one is down.  nfs/cifs clients tend to hang or fail unless you have
a fairly complex or expensive server setup.

The protocol is pretty simple.  It doesn't necessarily require root
intervention on either end and it is pretty platform-independent.

Doing atomic get/set on NFS or CIFS is a bit of an abstraction
inversion, with almost certainly more round trips than memcached.  It
tends to fail in interesting ways when the client's caches incoherent

Regarding the value size limit, I would probably split the o file into
1MB chunks.


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