after upgrade from jetcd 0.8.5 to 0.8.6 - java.lang.NoClassDefFoundError: io/netty/channel/MultiThreadIoEventLoopGroup

[jarekchr]

Versions

• etcd: 3.6.5 (this is not important at this moment)
• jetcd: 0.8.6
• java: 21/17

Describe the bug
After upgrade to jetcd 0.8.6 my tests throw exception:
java.lang.NoClassDefFoundError: io/netty/channel/MultiThreadIoEventLoopGroup

Error Message

io/netty/channel/MultiThreadIoEventLoopGroup

Stacktrace

java.lang.NoClassDefFoundError: io/netty/channel/MultiThreadIoEventLoopGroup
at io.vertx.core.spi.transport.Transport.eventLoopGroup(Transport.java:93)
at io.vertx.core.impl.VertxImpl.(VertxImpl.java:214)
at io.vertx.core.impl.VertxBootstrapImpl.instantiateVertx(VertxBootstrapImpl.java:231)
at io.vertx.core.impl.VertxBootstrapImpl.vertx(VertxBootstrapImpl.java:247)
at io.vertx.core.Vertx$1.build(Vertx.java:131)
at io.vertx.core.Vertx.vertx(Vertx.java:159)
at io.etcd.jetcd.impl.ClientConnectionManager.vertx(ClientConnectionManager.java:227)
at io.etcd.jetcd.impl.ClientConnectionManager.defaultChannelBuilder(ClientConnectionManager.java:162)
at io.etcd.jetcd.impl.ClientConnectionManager.defaultChannelBuilder(ClientConnectionManager.java:153)
at io.etcd.jetcd.impl.ClientConnectionManager.getChannel(ClientConnectionManager.java:74)
at io.etcd.jetcd.impl.ClientConnectionManager.newStub(ClientConnectionManager.java:106)
at io.etcd.jetcd.impl.KVImpl.(KVImpl.java:52)
at io.etcd.jetcd.impl.ClientImpl.lambda$new$0(ClientImpl.java:48)
at io.etcd.jetcd.support.MemorizingClientSupplier.get(MemorizingClientSupplier.java:37)
at io.etcd.jetcd.impl.ClientImpl.getKVClient(ClientImpl.java:65)
[...]

To Reproduce

Expected behavior

Additional context
I think that this is caused by use of new vertx.

[lburgazzoli]

do you have any direct or indirect netty dependencies?

[jarekchr]

yes, in pom.xml we're forcing netty 4.1.128.Final:

io.netty
netty-all
4.1.128.Final

[lburgazzoli]

That could be a problem, yes. can't you upgrade/downgrade ?

[jarekchr]

No - too many CVEs in previous versions of netty.
Actually this jetcd version updates indirect dependency of 2 new CVEs (CVE-2025-11965 and CVE-2025-11966) in vertx (1x high, 1x medium) that I hoped to be removed but it doesn't work.
I don't remember now exact issue but we also checked some time ago that with netty 4.2.x it doesn't work so we have to stay for a moment on 4.1.x.

[lburgazzoli]

Not sure what I can do honestly, I do have very little time and I'm barely able to keep up with dependencies and release, any help would be appreciated