[Redis] [redis-db] keeping several (two or three) snapshot files.

Hello all

I will have a rather-small Redis store (typically 100 Megabytes to a few
Gigabytes) but I want to keep a few RDB snapshots.

I am working on the MELT monitor; MELT is a DSL to customize GCC (see
http://gcc-melt.org/ for more...); its monitor -in pre-alpha stage- will be
a *persistent* application
which would keep persistent compiler representation and provide a web
interface (my dream is a Coverity like free software tool based upon MELT &
GCC) . The persistent aspect could use REDIS. The monitor is checkpointing
(à la SBCL save-lisp-and-die
<http://www.sbcl.org/manual/index.html#Function-sb_002dext_003asave_002dlisp_002dand_002ddie>
primitive) its memory state into GDBM files and/or REDIS stores (so it
begins to erase the old REDIS store with FLUSHDB then regenerates that
store entirely with many SET commands; I am not able to do some incremental
checkpointing).

On my Debian/Sid machine, the default RDB snapshot (after some BGSAVE
command...) is going into /var/lib/redis/dump.rdb
I discovered on this forum that it is possible to slightly change that. If
I issue the two REDIS commands

    CONFIG SET dbname myredis.rdb
    BGSAVE

then the RDB snapshot is going into /var/lib/redis/myredis.rdb

However, I would like that before writing that RDB dump, the REDIS server
renames its previous version as /var/lib/redis/myredis.rdb~ or as
/var/lib/redis/myredis.rdb.1 and rename that previous backup as
/var/lib/redis/myredis.rdb~~ or as /var/lib/redis/myredis.rdb.2 (or perhaps
run logrotate on the backups).

How is that possible? The point is that I want the file rotation or
renaming to happen on the server side. Should I do some Lua scripting?

It is important for me to keep at least two or three last snapshot files of
the Redis store.

There is only one writing REDIS client application - the checkpointing MELT
monitor - (but it could be a remote one). Every other clients are read-only!

Regards.

PS. I don't want AOF persistence, I only want RDB.