CachingDBStore.pm - collectd perl plugin which outputs to remote DB, or caches if remote DB not available

The perl module has only been tested with MySQL as the remote DB - there's nothing I can see which is MySQL 
specific, however there's no guarantees it will work elsewhere.

This was written due to a requirement for me to reliably, and centrally, store various metrics for many
servers.  This plugin is fault tolerant; the remote DB can some and go as it pleases without causing 
data loss.  When the remote DB does reappear after a period of absence the plugin will drain its local 
cache in a controlled manner.

Included in the sql directory is the SQL required to create the database, table and user in the remote
database, if you are using MySQL.  Additionally there is a MySQL procedure which will manage partitioning
the data into daily partitions.  You will need to set a scheduled event calling it with the retention
policy which you require.

Dependencies:
1. collectd
2. perl, compiled with threading and the following modules
    - DBI
    - DBD:mysql
    - DBD:SQLite
    - Data::UUID
    - DateTime
3. remote database


CollectD configuration:

collectd.conf:

LoadPlugin Perl

<Plugin perl>
    IncludeDir "path to this dir"
    LoadPlugin CachingDBStore
    <Plugin CachingDBStore>
        CacheTime 'time in seconds to cache in memory before flushing - defaults to 120'
        RemoteDBHost "hostname or ip"
        RemoteDBPort "port"
        RemoteDBName "name of db"
        RemoteDBUser "username"
        RemoteDBPassword "password"
        SQLiteDir "dir to write SQLite cache in - I would recommend not using /tmp"
        CommitEvery 'commit every x inserts - defaults to 1000'
        FlushSQLiteLimit 'stop adding to the write queue if we have retrieved this many from SQLite cache - defaults to 10,000'
    </Plugin>
</Plugin>


Depending on collectd version you may need to edit /etc/init.d/collectd and add the line:

export LD_PRELOAD=/usr/lib/libperl.so.5.10.1