Command Monitoring¶

These events are fired for commands directly to the wire and the response.

command_started

This event is sent just before a command is put one the wire. It will be followed by either a "command_succeeded" or "command_failed" event.

Fields:

• type: "command_started"
• databaseName: the name of the database to which the command applies
• commandName: the name of the command being executed; for legacy operations that don't use commands, the driver will convert them to appear as if they are in command form.
• command: a hash reference representing the full command to be sent
• requestId: the request identifier sent to the server
• connectionId: address and port of the destination server

command_succeeded

This event is sent just after a command reply is received, but only if the database reply document contains a non-false "ok" field. NOTE: write errors will have "ok:1" even though they have write errors; for writes, success indicates that the write attempt was valid, not that the write succeeded.

Fields:

• type: "command_succeeded"
• commandName: the name of the command being executed
• durationSecs: the elapsed time in seconds since the "command_started" event.
• reply: a hash reference representing the full database reply
• requestId: the request identifier sent to the server
• connectionId: address and port of the destination server

command_failed

This event is sent just after a command reply is received, but only if the database reply document contains a false "ok" field or if an exception occurred during send or receive operations.

Fields:

• type: "command_failed"
• commandName: the name of the command being executed
• durationSecs: the elapsed time in seconds since the "command_started" event.
• failure: a string with a error message about the failure
• eval_error: if an exception occurs, this contains the value of $@ when the exception was caught
• reply: a hash reference representing the full database reply or an empty hashref if the failure is due to an exception
• requestId: the request identifier sent to the server
• connectionId: address and port of the destination server

Server Discovery and Monitoring¶

These events are fired when servers and topology are amended.

server_opening_event

This event is sent when a new server is added to the topology.

Fields:

• type: "server_opening_event"
• topologyId: The topology refaddr
• address: address of the server

server_closed_event

This event is sent when a server is removed from the topology.

Fields:

• type: "server_closed_event"
• topologyId: The topology refaddr
• address: address of the server

server_description_changed_event

This event is sent when the server description changes, but does not include changes to the RTT.

Fields:

• type: "server_description_changed_event"
• address: address of the server
• topologyId: The topology refaddr
• previousDescription: Server Description before the change
• newDescription: Server Description after the change

topology_opening_event

This event is sent when the topology is created.

Fields:

• type: "topology_opening_event"
• topologyId: The topology refaddr

topology_closed_event

This event is sent when the topology is closed.

Fields:

• type: "topology_closed_event"
• topologyId: The topology refaddr

topology_description_changed_event

This event is sent when the topology description changes.

Fields:

• type: "topology_description_changed_event"
• topologyId: The topology refaddr
• previousDescription: Topology Description before the change
• newDescription: Topology Description after the change

server_heartbeat_started_event

This event is sent before the ismaster command is sent to the server.

Fields:

• type: "server_heartbeat_started_event"
• connectionId: address of the link to connect to

server_heartbeat_succeeded_event

This event is sent after the reply from the ismaster command arrives from a successful reply.

Fields:

• type: "server_heartbeat_succeeded_event"
• duration: time it took to send and receive a reply
• reply: the ismaster command reply
• connectionId: address of the server

server_heartbeat_failed_event

This event is sent if there is a failure from the ismaster command, which returns an error string of some sort.

Fields:

• type: "server_heartbeat_failed_event"
• duration: time it took to send and receive a reply
• failure: Returns an error string of the failure
• connectionId: address of the server