Incompatibility with Spring WebFlux 5.1 WebClient

[scottfrederick]

When CF Java Client is used in an application that also uses WebClient from Spring WebFlux 2.1.x.RELEASE, exceptions are thrown from Netty and connections to CF fail.

The relevant exception is:

Caused by: java.lang.IllegalArgumentException: 'httpRedirects' is already in use
	at io.netty.util.ConstantPool.createOrThrow(ConstantPool.java:113) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
	at io.netty.util.ConstantPool.newInstance(ConstantPool.java:95) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
	at io.netty.util.AttributeKey.newInstance(AttributeKey.java:55) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
	at reactor.netty.http.client.HttpClientOperations.<clinit>(HttpClientOperations.java:720) ~[reactor-netty-0.8.3.RELEASE.jar:0.8.3.RELEASE]

The root of the issue is clashing versions of reactor-netty.

• CFJC 3.x depends on io.projectreactor.ipc:reactor-netty:0.7.x.RELEASE (via spring-boot-dependencies:2.0.x).
• Spring WebFlux 2.1.x depends on io.projectreactor.netty.reactor-netty:0.8.x.RELEASE.

These versions of reactor-netty both have a class with a static initializer that registers a "constant" with Netty:

• reactor-netty:0.7.x.RELEASE: reactor.ipc.netty.http.client.HttpClientOperations
• reactor-netty:0.8.x.RELEASE: reactor.netty.http.client.HttpClientOperations

Whichever of these initializers runs first wins, and the second one fails. When the HttpClientOperations used by CFJC fails to initialize, the exception above appears in stdout but the app will start. Subsequent calls to CFJC result in long delays followed by a timeout.

[twoseat]

I have a branch outstanding to bring the client up to date with netty - unfortunately our use of it is extensive enough that the significant change between 0.7.x and 0.8.x has made for a tricky upgrade. Given that the upgrade should improve a number of other performance/reliability issues we have it was already a priority, but your issue makes it the priority for the next release.

[scottfrederick]

Thanks @twoseat! I did a quick version update in pom.xml along with a search-and-replace on exports just to see what the upgrade would look like, and I got scared :-). It does look like a big change to take on. I figured you were aware of the need to upgrade but I thought an issue with the exception would be useful in case anyone else tries to use the same combination of dependencies.

[idantr]

@twoseat can the 0.8.x be later than 0.8.6 this will fix additional bug we have that is still not reflected in cf-java-client
reactor/reactor-netty#413