I have a memcache backend and i want to add redis for adding the meta data of the keys of the memcache.
Meta data is as follows:
Miss_count: The number of times the data was not present in the memcache.
Hash_value: The hash value of the data corresponding to the key in the memcache.
Data in memcache : key1 ::: Data
Meta data (miss count) : key1_miss ::: 10
Meta data (hash value) : key1_hash ::: hash(Data)
Please provide help as in which data store is preferable as when i store the meta data in the memcache itself, the meta data is removed well before its expiry time as the size of the meta data is small and the slab allocation is allocating a small memory chuck to it.
If I understand your use case correctly I suspect Redis might be a good choice. Assuming you’ll be periodically updating the meta data miss counts associated with the various hashes over time, you’d probably want to use Redis sorted sets. For example, if you wanted the miss counts stored in a sorted set called “misscounts”, the Redis command to add/update those counts would be one and the same:
zadd misscounts misscount key1
… because zadd adds the entry if one doesn’t already exist or overwrites an existing entry if it does. If you have a hook into the process that fires each time a miss occurs, you could instead use:
zincrby misscounts 1 key1
Similar to the the zadd command behavior, zincrement will create a new entry (using the increment value as the count) if one doesn’t exist, or increment the existing count by the increment value you pass if an entry does exist.
Complete documentation of Redis commands can be found here. Descriptions of the different types of storage options in Redis is detailed here.
Oh, and a final note. In my experience, Redis is THE SHIT. Sorry to curse (in caps), but there’s simply no other way to do Redis justice. We call our Redis server “honey badger”, because when load starts increasing and our other servers start auto-scaling, honey badger just don’t give a shit.