How to Use Redis MONITOR for Real-Time Debugging and Performance Insights

Redis provides a MONITOR command. When a client issues MONITOR, it becomes a monitor and the server streams every command it executes to that client.

The MONITOR command is a debugging tool that helps understand what the server is doing.

For example, running MONITOR for 20 minutes captures all commands, allowing analysis such as:

Which commands are executed most frequently.

Which keys are hot.

Traffic volume derived from GET‑type commands.

Using the MONITOR Command

127.0.0.1:6379> monitor

OK

After execution, the client receives “OK” and enters a waiting state. When the server runs a command, the monitor automatically displays the execution info, e.g.:

1454886442.140044 [0 127.0.0.1:63773] "keys" "*"

1454886454.538036 [0 127.0.0.1:63773] "get" "user13"

1454886475.392050 [0 127.0.0.1:63773] "get" "mylist_score"

The parts mean: 1454886442.140044 – timestamp. [0 127.0.0.1:63773] – database number, client IP and port. "keys" "*" – the command executed.

Implementation Idea of MONITOR

When a client sends MONITOR, three main actions occur:

The client’s monitor flag is set to true.

The server adds the client to the end of the monitors list.

The server returns “OK” to the client.

After any client issues a command, the server, upon completing the command, sends the command information to every client in the monitors list.