监视器¶
通过执行 MONITOR 命令， 客户端可以将自己变为一个监视器， 实时地接收并打印出服务器当前处理的命令请求的相关信息：
redis> MONITOR
OK
1378822099.421623 [0 127.0.0.1:56604] "PING"
1378822105.089572 [0 127.0.0.1:56604] "SET" "msg" "hello world"
1378822109.036925 [0 127.0.0.1:56604] "SET" "number" "123"
1378822140.649496 [0 127.0.0.1:56604] "SADD" "fruits" "Apple" "Banana" "Cherry"
1378822154.117160 [0 127.0.0.1:56604] "EXPIRE" "msg" "10086"
1378822257.329412 [0 127.0.0.1:56604] "KEYS" "*"
1378822258.690131 [0 127.0.0.1:56604] "DBSIZE"
每当一个客户端向服务器发送一条命令请求时， 服务器除了会处理这条命令请求之外， 还会将关于这条命令请求的信息发送给所有监视器， 如图 24-1 所示。
![digraph {
label = "\n 图 24-1 命令的接收和信息的发送";
rankdir = LR;
server [label = "服\n务\n器", shape = box, height = 3.0, width = 1.0];
node [shape = circle, width = 1.3];
client [label = "客户端"];
m1 [label = "监视器 1"];
m2 [label = "监视器 2"];
m3 [label = "监视器 3"];
client -> server [label = "发送命令请求"];
edge [label = "发送命令信息"];
server -> m1;
server -> m2;
server -> m3;
}](../../_images/graphviz-0a684588293c799f804995f27a2dd6f9da407f8e.png)