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CSHARP-4327: Update Server Monitoring documentation #967

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Nov 23, 2022
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CSHARP-4327: Update Server Monitoring documentation #967

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7 changes: 6 additions & 1 deletion Docs/reference/content/reference/driver_core/index.md
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Expand Up @@ -23,7 +23,12 @@ Connection pooling is provided for every server that is discovered. There are a

### Server Monitoring

Each server that is discovered is monitored. By default, this monitoring happens every 10 seconds and consists of a `{ hello: 1 }` (or legacy hello) call followed by a `{ buildInfo: 1 }` call. When servers go down, the frequency of these calls will be increased to 500 milliseconds. See the [Server Discovery and Monitoring Specification](https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring-summary.rst) for more information.
Each server that is discovered is monitored.

MongoDB 4.4 or later: The `MongoClient` establishes an exhaust cursor to each discovered cluster node using `{ hello: 1 }` (or legacy hello). Cluster nodes push topology updates to `MongoClient`.
MongoDB 4.2 or ealier: The `MongoClient` polls each discovered cluster node every [heartbeatFrequencyMS](https://www.mongodb.com/docs/manual/reference/connection-string/#mongodb-urioption-urioption.heartbeatFrequencyMS) (default 10 seconds, MongoDB Atlas 5 seconds) using `{ hello: 1 }` (or legacy hello).

When servers go down, the frequency of these calls will be increased to 500 milliseconds. See the [Server Discovery and Monitoring Specification](https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring-summary.rst) for more information.
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do we have such logic about 500ms? :)

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Yes, we do:

public ServerMonitorSettings(TimeSpan connectTimeout, TimeSpan heartbeatInterval, Optional<TimeSpan> minHeartbeatInterval = default)
{
    _connectTimeout = connectTimeout;
    _heartbeatInterval = heartbeatInterval;
    _minHeartbeatInterval = minHeartbeatInterval.WithDefault(TimeSpan.FromMilliseconds(500));
}

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ah, I misunderstood, I meant that we don't wait if network error in streaming


### Server Selection

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