[cl-memcached-devel] Some questions about cl-memcached

[quasi]

Renato Lucindo wrote:
> Hello,
> 
> I have a few questions about cl-memcached:
> 
> 1) Which object type is possible to store on memcached using
> cl-memcached? CLOS objects instances? Hash tables? Structures?

memcached stores just bytes.  We can retrieve these bytes by using a key
with which their storage is associated. We can store anything in
memcached, but the serialization etc. has to be our responsibility.  For
example using cl-store and flexi-streams we can store anything that
cl-store can serialize.

for example:

(defun cl-store-in-memcache (key obj &key (memcache *memcache*)
((:command command) :set) ((:timeout timeout) 0) ((:use-pool use-pool)
*use-pool*))
  "Serializes 'obj' with cl-store and stores in memcache"
  (let ((seq (flexi-streams:with-output-to-sequence (out)
	       (cl-store:store obj out))))
    (cl-memcached:mc-store key seq :memcache memcache :command command
:timeout timeout :use-pool use-pool)))


(defun cl-restore-from-memcache (keys-list &key (memcache *memcache*)
((:use-pool use-pool) *use-pool*))
  "Gets objects corresponding to keys from keys-list.  cl-store will
throw and RESTORE-ERROR if an object retrieved has not
been encoded by cl-store. i.e. if it cannot find a method to de-serialize it
Returned is an alist of key and objects"
  (mapcar #'(lambda (x)
	      (list (first x)
		    (flexi-streams:with-input-from-sequence (in (second x))
		      (cl-store:restore in))))
	  (cl-memcached:mc-get keys-list :memcache memcache :use-pool use-pool))))


> 2) When cl-memcached will support multiple servers (with weights) like
> others memcached clients?

Shortly.  :)  Am planning to work on this, but have had absolutely no
time.  Any help would be appreciated.  I also need replicated pairs support.


> 3) cl-memcached supports compression?

cl-memcached is supposed to be very simple library and as fast as
possible. You can very easily add a wrapper to use any compression
method you like to compress before you pass to cl-memcached.
e.g. http://common-lisp.net/project/gzip-stream/

Compression requires lots of CPU. But your specific needs may warrant
the use of compression in which case it is not too difficult to add.


> 4) cl-memcached will support other lisp implementations? (SBCL, CMUCL, CLISP??)

It already supports LW and SBCL.  I will upload an updated tarball by
this week end.


> 5) cl-memcached will deal with strings internally (this way won't be
> necessary pass :is-string parameter)?

I added this performance reasons.  Typically a memcached server just
sits and handles millions of requests.  Adding checks which may not be
used for most of the requests end up having an impact on performance
which IMHO we can avoid.  In case your app needs a specific setting, you
can write a wrapper for that.

I followed the same philosophy for cl-memcached as is followed for
memcached.  :)  do a simple job reliably and as fast as possible. I have
tried to get the best possible performance from this client.  Our
memcached servers have been up upwards of 60 days at a time and have
handled millions of requests per day.  cl-memcached has been quite
stable throughout the 12 months or so of its use till date.


> 
> Thanks!

thanks for writing in !!
 :)

quasi


> 
> Lucindo
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