NullPointerException since 5.19.0 (Add support for Micrometer Observation)

[assopt]

Describe the bug

java.lang.NullPointerException: Cannot invoke "java.net.InetAddress.getHostAddress()" because the return value of "com.rabbitmq.client.impl.FrameHandler.getAddress()" is null
	at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:445)
	at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:1251)
	at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:1198)
        ...

The code at line 445 was added in 5.19.0 (Add support for Micrometer Observation).

Other code in the class AMQConnection is null safe. toString() for example uses the method getHostAddress() which explicitly handles the case of the address being null.

Reproduction steps

We know that the address is null because the hostname cannot be resolved. As we have a proxy in between there is no need to resolve the hostname in the first place.

Expected behavior

No NPE even if the hostname cannot be resolved to an address.

Use getHostAddress() instead of this._frameHandler.getAddress().getHostAddress().

Additional context

Including 5.18.0 everything worked. With the update to a newer version as the only change on our side we get the NPE.

[lukebakken]

Thanks for the report. Since you understand the issue well, a pull request with a fix (and tests) would be appreciated.

[michaelklishin]

As we have a proxy in between there is no need to resolve the hostname in the first place

we will not guess what specifically your environment or client configuration looks like. We do not guess in this community.

Please submit a PR and/or a set of steps to reproduce.

[assopt]

I will submit a pull request next week.

[acogoluegnes]

@assopt I pushed a fix. Can you tell us more about your environment? I'd be curious to know how the address can be null at this point.

[assopt]

In that specific environment we initialize the connection from a server where no hostname resolution is available. So that server uses a socks proxy via its IP address to reach the rabbitmq server via its hostname. The hostname is then resolved by the socks proxy. We cannot use the IP address of the rabbitmq server directly as it may change in the future.
In the code we put the socks proxy in between via delegation.

[acogoluegnes]

OK, thanks for the context. Can you try the latest snapshot to make sure the issue is fixed in your environment?

[assopt]

Works :-) Thank you!