nuster v3.1.0.19 released, now supports disk persistence, purging cache files, persistence cache stats

https://github.com/jiangwenyuan/nuster

There are four MODEs.

• off: default, disable disk persistence, data are stored in memory only
• only: save data to disk only, do not store in memory
• sync: save data to memory and disk(kernel), then return to the client
• async: save data to memory and return to the client, cached data will be saved to disk later by the master process

global
    master-worker
    nuster cache on data-size 10m dir /tmp/cache
    nuster nosql on data-size 10m dir /tmp/nosql
backend be
    nuster cache on
    nuster rule off   disk off   ttl 1m if { path_beg /disk-off }
    nuster rule only  disk only  ttl 1d if { path_beg /disk-only }
    nuster rule sync  disk sync  ttl 1h if { path_beg /disk-sync }
    nuster rule async disk async ttl 2h if { path_beg /disk-async }
    nuster rule others ttl 100

1. /disk-offwill be cached only in memory
2. /disk-onlywill be cached only in disk
3. /disk-syncwill be cached in memory and in disk, then return to the client
4. /disk-asyncwill be cached in memory and return to the client, cached data will be saved to disk later
5. other requests will be cached only in memory