Blobcached

Blobcached is a memcached protocol-compatible cache server for blob on SSD.

Supported commands

| Command | Format | | ------ | ------ | | get | get <key> [<key>]+\r\n | | set | set <key> <flags> <expiry> <datalen> [noreply]\r\n<data>\r\n | | delete | delete <key> [noreply]\r\n | | touch | touch <key> <expiry>[noreply]\r\n | | stats | stats\r\n |

How it works

concepts

| Name | | | ------ | ------ | | indexfile | an indexfile contains many of items powered by blotdb | | datafile | a regular file for storing values | | item | an item is made up of key, offset, term, size anchoring the value in datafile | | term | everytime the datafile is full, the term of datafile is increased |

Command: Set

• get the offset and term of datafile
• write value to the datafile
• write item with the offset, term and key to the indexfile

Command: Get

• get the item by key
• check term and offset of the item against datafile
• read value from the datafile

Command: Touch

• implemented by get & set

GC

• Blobcached scans and removes expired or invalid items in the indexfile
• by default, the rate up to 32k items/second