MONITOR

Available since 1.0.0.

MONITOR is a debugging command that streams back every command processed by the Redis server. It can help in understanding what is happening to the database. This command can both be used via redis-cli and via telnet.

The ability to see all the requests processed by the server is useful in order to spot bugs in an application both when using Redis as a database and as a distributed caching system.

  1. $ redis-cli monitor
  2. 1339518083.107412 [0 127.0.0.1:60866] "keys" "*"
  3. 1339518087.877697 [0 127.0.0.1:60866] "dbsize"
  4. 1339518090.420270 [0 127.0.0.1:60866] "set" "x" "6"
  5. 1339518096.506257 [0 127.0.0.1:60866] "get" "x"
  6. 1339518099.363765 [0 127.0.0.1:60866] "del" "x"
  7. 1339518100.544926 [0 127.0.0.1:60866] "get" "x"

Use SIGINT (Ctrl-C) to stop a MONITOR stream running via redis-cli.

  1. $ telnet localhost 6379
  2. Trying 127.0.0.1...
  3. Connected to localhost.
  4. Escape character is '^]'.
  5. MONITOR
  6. +OK
  7. +1339518083.107412 [0 127.0.0.1:60866] "keys" "*"
  8. +1339518087.877697 [0 127.0.0.1:60866] "dbsize"
  9. +1339518090.420270 [0 127.0.0.1:60866] "set" "x" "6"
  10. +1339518096.506257 [0 127.0.0.1:60866] "get" "x"
  11. +1339518099.363765 [0 127.0.0.1:60866] "del" "x"
  12. +1339518100.544926 [0 127.0.0.1:60866] "get" "x"
  13. QUIT
  14. +OK
  15. Connection closed by foreign host.

Manually issue the QUIT command to stop a MONITOR stream running via telnet.

*Commands not logged by MONITOR

For security concerns, certain special administration commands like CONFIG are not logged into the MONITOR output.

*Cost of running MONITOR

Because MONITOR streams back all commands, its use comes at a cost. The following (totally unscientific) benchmark numbers illustrate what the cost of running MONITOR can be.

Benchmark result withoutMONITOR running:

  1. $ src/redis-benchmark -c 10 -n 100000 -q
  2. PING_INLINE: 101936.80 requests per second
  3. PING_BULK: 102880.66 requests per second
  4. SET: 95419.85 requests per second
  5. GET: 104275.29 requests per second
  6. INCR: 93283.58 requests per second

Benchmark result withMONITOR running (redis-cli monitor > /dev/null):

  1. $ src/redis-benchmark -c 10 -n 100000 -q
  2. PING_INLINE: 58479.53 requests per second
  3. PING_BULK: 59136.61 requests per second
  4. SET: 41823.50 requests per second
  5. GET: 45330.91 requests per second
  6. INCR: 41771.09 requests per second

In this particular case, running a single MONITOR client can reduce the throughput by more than 50%. Running more MONITOR clients will reduce throughput even more.

*Return value

Non standard return value, just dumps the received commands in an infinite flow.