The RESP protocol was introduced in Redis 1.2, but it became the standard way for talking with the Redis server in Redis 2.0. This is the protocol you should implement in your Redis client.
RESP is actually a serialization protocol that supports the following data types: Simple Strings, Errors, Integers, Bulk Strings and Arrays.
The way RESP is used in Redis as a request-response protocol is the following:
Clients send commands to a Redis server as a RESP Array of Bulk Strings.
The server replies with one of the RESP types according to the command implementation.
In RESP, the type of some data depends on the first byte:
For Simple Strings the first byte of the reply is “+”
For Errors the first byte of the reply is “-”
For Integers the first byte of the reply is “:”
For Bulk Strings the first byte of the reply is “$”
For Arrays the first byte of the reply is “*”
Additionally RESP is able to represent a Null value using a special variation of Bulk Strings or Array as specified later.
In RESP different parts of the protocol are always terminated with “\r\n” (CRLF).
快照保存方式为操作系统fork出主进程的一个子进程，父进程继续处理client请求，子进程读取全部数据写入到临时文件中，由于os的copy on write机制，父子进程会共享相同的物理页面，当父进程处理写请求时os会为父进程要修改的内存页创建副本，而不是写共享的页。所以子进程的地址空间内的数据是fork时整个数据库的一个快照。
-h, –help : this help
-V, –version : show version and exit
-t, –test-conf : test configuration for syntax errors and exit
-d, –daemonize : run as a daemon
-D, –describe-stats : print stats description and exit
-v, –verbose=N : set logging level (default: 5, min: 0, max: 11)
-o, –output=S : set logging file (default: stderr)
-c, –conf-file=S : set configuration file (default: conf/nutcracker.yml)
-s, –stats-port=N : set stats monitoring port (default: 22222)
-a, –stats-addr=S : set stats monitoring ip (default: 0.0.0.0)
-i, –stats-interval=N : set stats aggregation interval in msec (default: 30000 msec)
-p, –pid-file=S : set pid file (default: off)
-m, –mbuf-size=N : set size of mbuf chunk in bytes (default: 16384 bytes)
