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Why the connection is not closing when I call Close() method of EventHubClient?

This days I saw an interesting question on internet. The response is interesting and should be well known by everyone that is using Event Hub or other services from Service Bus over AMQP protocol.
Why the connection is not closing when I call eventHubClient.Close() method?
var factory = MessagingFactory
var client = factory.CreateEventHubClient("rveh");
client.Close(); // or client.CloseAsync()

By default, the communication protocol that is used by Event Hub is AMQP. AMQP protocol is using a connection over TCP. Opening and closing a AMQP connection is expensive, but the good part of AMQP is that we have a session that can be persisted and reused between different requests. When we are calling "Close" method, we are only notifying the MessageFactory that we don't need anymore the connection. It will not trigger a close/delete connection between our machine/system and EventHub. MessageFactory is smart enough to be able to reuse the TCP connection.
Taking this into account, calling the Create method can reuse an existing TCP connection. You cannot close the TCP connectio by yourself. The connection is created and managed by the MessageFactory. The connection will be recycled in the moment when GC (Garbage Collection) will run over the internal factory, but there is no control from our side.

Can I control the connection?
There are cases when you want to have control to the life cycle of the connection. A good example is when you need a high throughput to Event Hub from the same machine (sender). In this case you will want to create multiple connections and have a direct control to it.
For this scenario you will need to implement your own MessageFactory.

When the connection is reused?
The TCP connection is reused as long as the connection string is the same.

It is important to remember that "Close" method only notifies the MessageFactory that we don't need anymore the connection, it doesn't close immediately.


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