[java.net.http.HttpClient] Active monitoring of resolved IP addresses

[Nicolas Henneaux]

Hi,



I am not sure it is the right mailing list. If it’s not, I apologize in
advance and could you tell me which is one the more appropriate?



*I am trying to build an HTTP client based on java.net.http.HttpClient and
I would like to have some control on the IP addresses resolved under the
hood.*



I would like such mechanism to use all the IP addresses behind the host of
the request. The underlying problem, I am trying to solve, is to react as
soon as possible to an unavailability of a target IP. It could be done by
doing active monitoring for each IP and use only the addresses available
(at TCP, TLS or HTTP level) when sending an HTTP request. I also would like
to load balance the traffic between all the IP’s and actively detect change
in the DNS resolution. I am maintaining a long live connection to an
external HTTPS service.



At the moment, only one IP address is used by the HTTP java client and pool
of connections is maintained to target this IP.



I have built a work-around by using the IP address in the URL provided to
the HTTP client and using a specific trust manager matching the expected
name to keep the TLS validation. It has several limitation. In particular
it changes the HTTP request which could impact the response you received
depending on the server you target. It also forces to use one HTTP client
by host you want to target. I have created a small GitHub repository
<https://github.com/nhenneaux/resilient-httpclient> to illustrate this
workaround.



I explored a bit the HTTP client implementation and so far I have not found
any way to implement such mechanism. In particular, I am stuck in
jdk.internal.net.http.HttpRequestImpl#getAddress which is package visible
and prevents any extension.



Such mechanism exists in Jetty HTTP client (see
org.eclipse.jetty.util.SocketAddressResolver) or in HTTP Apache client.



*Is there any existing mechanism I could use to properly solve such
problem? If none, is there a way to contribute or to submit a request of
improvement? *



Thank you in advance for your help!



Best regards,



*Nicolas Henneaux*