Cluster Monitoring

Overview

This guide shows you how to use the Rust driver to monitor topology events in a MongoDB instance, replica set, or sharded cluster. The driver creates topology events, also known as Server Discovery and Monitoring (SDAM) events, when there are any changes in the state of the instance or cluster that you are connected to.

You can use information about topology changes in your application, or you can monitor cluster changes to learn more about how they affect your application.

This guide includes the following sections:

• Event Descriptions describes the SDAM events that the driver can generate

• Event Subscription Example provides sample code that shows how to subscribe to an SDAM event

• Example Event Documents provides samples of each SDAM event

• Additional Information provides links to resources and API documentation for types and methods mentioned in this guide

Event Descriptions

You can subscribe to one or more of the following SDAM events:

Event Subscription Example

You can access one or more SDAM events by subscribing to them in your application. The following example connects to a MongoDB deployment and subscribes to the ServerOpeningEvent event type:

struct ServerOpenHandler;
impl SdamEventHandler for ServerOpenHandler {
    fn handle_server_opening_event(&self, event: ServerOpeningEvent) {
        eprintln!("Server opening: {:?}", event);
    }
}
let handler: Arc<dyn SdamEventHandler> = Arc::new(ServerOpenHandler);
client_options.sdam_event_handler = Some(handler);
let client = Client::with_options(client_options)?;
// ... perform actions with the client to generate events

Example Event Documents

The following sections show sample output for each type of SDAM event.

ServerDescriptionChangedEvent {
    address: ...,
    topology_id: ...,
    previous_description: ...,
    new_description: ...,
}

ServerOpeningEvent {
    address: ...,
    topology_id: ...,
}

ServerClosedEvent {
    address: ...,
    topology_id: ...,
}

TopologyDescriptionChangedEvent {
    topology_id: ...,
    previous_description: ...,
    new_description: ...,
}

TopologyOpeningEvent {
    topology_id: ...,
}

TopologyClosedEvent {
    topology_id: ...,
}

ServerHeartbeatStartedEvent {
    server_address: ...,
    awaited: false,
    driver_connection_id: 12,
    server_connection_id: ...,
}

ServerHeartbeatSucceededEvent {
    duration: ...,
    reply: ...,
    server_address: ...,
    awaited: false,
    driver_connection_id: 12,
    server_connection_id: ...,
}

ServerHeartbeatFailedEvent {
    duration: ...,
    failure: ...,
    server_address: ...,
    awaited: false,
    driver_connection_id: 12,
    server_connection_id: ...,
}

Additional Information

To learn more about monitoring a MongoDB deployment, see the How to Monitor MongoDB article.

To learn more about connecting to MongoDB, see the Connection Guide.