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 SDAM events.

• 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 monitor the following SDAM events:

Event Monitoring Example

You can monitor SDAM events by assigning an EventHandler instance as the value of the sdam_event_handler client option. To construct an EventHandler, which processes all SDAM events, use the callback() or async_callback() method.

The following example connects to a MongoDB deployment, instructs the client to monitor SDAM events, and prints each event:

let mut client_options = ClientOptions::parse("<connection string>").await?;
client_options.sdam_event_handler = Some(EventHandler::callback(|ev| println!("{:?}", ev)));
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.