MONITOR

Syntax

MONITOR

Available since: 1.0.0 Time complexity: ACL categories: ​​@admin​​​, ​​@slow​​​, ​​@dangerous​​

​​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.

$ redis-cli monitor
1339518083.107412 [0 127.0.0.1:60866] "keys" "*"
1339518087.877697 [0 127.0.0.1:60866] "dbsize"
1339518090.420270 [0 127.0.0.1:60866] "set" "x" "6"
1339518096.506257 [0 127.0.0.1:60866] "get" "x"
1339518099.363765 [0 127.0.0.1:60866] "eval" "return redis.call('set','x','7')" "0"
1339518100.363799 [0 lua] "set" "x" "7"
1339518100.544926 [0 127.0.0.1:60866] "del" "x"

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

$ telnet localhost 6379
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
MONITOR
+OK
+1339518083.107412 [0 127.0.0.1:60866] "keys" "*"
+1339518087.877697 [0 127.0.0.1:60866] "dbsize"
+1339518090.420270 [0 127.0.0.1:60866] "set" "x" "6"
+1339518096.506257 [0 127.0.0.1:60866] "get" "x"
+1339518099.363765 [0 127.0.0.1:60866] "del" "x"
+1339518100.544926 [0 127.0.0.1:60866] "get" "x"
QUIT
+OK
Connection closed by foreign host.

Manually issue the ​​QUIT​​​ or ​​RESET​​​ commands to stop a ​​MONITOR​​​ stream running via ​​telnet​​.

Commands not logged by MONITOR

Because of security concerns, no administrative commands are logged by ​​MONITOR​​​'s output and sensitive data is redacted in the command ​​AUTH​​.

Furthermore, the command ​​QUIT​​ is also not logged.

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 without ​​MONITOR​​ running:

$ src/redis-benchmark -c 10 -n 100000 -q
PING_INLINE: 101936.80 requests per second
PING_BULK: 102880.66 requests per second
SET: 95419.85 requests per second
GET: 104275.29 requests per second
INCR: 93283.58 requests per second

Benchmark result with ​​MONITOR​​​ running (​​redis-cli monitor > /dev/null​​):

$ src/redis-benchmark -c 10 -n 100000 -q
PING_INLINE: 58479.53 requests per second
PING_BULK: 59136.61 requests per second
SET: 41823.50 requests per second
GET: 45330.91 requests per second
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

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

Behavior change history