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：

  1. redis> MONITOR
  2. OK
  3. 1378822099.421623 [0 127.0.0.1:56604] "PING"
  4. 1378822105.089572 [0 127.0.0.1:56604] "SET" "msg" "hello world"
  5. 1378822109.036925 [0 127.0.0.1:56604] "SET" "number" "123"
  6. 1378822140.649496 [0 127.0.0.1:56604] "SADD" "fruits" "Apple" "Banana" "Cherry"
  7. 1378822154.117160 [0 127.0.0.1:56604] "EXPIRE" "msg" "10086"
  8. 1378822257.329412 [0 127.0.0.1:56604] "KEYS" "*"
  9. 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;}