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Eclipse Vert.x 4 beta 1 released!

We are extremely pleased to announce the first 4.0 beta release of Eclipse Vert.x .

Vert.x 4 is the evolution of the Vert.x 3.x series that will bring key features to Vert.x.

SQL client metrics

Vert.x 4 supports metrics for clients which are critical for monitoring application performance.

While the capabilities are generic and can apply to any client, each client needs a specific integration. Obviously the SQL client was the perfect candidate in mind for this new feature.

Micrometer metrics will report these metrics as

  • vertx_sql_queue_pending: number of requests scheduled but not yet executed
  • vertx_sql_queue_time: time spent in queue before processing
  • vertx_sql_processing_pending: number of request being processed
  • vertx_sql_processing_time: requests latencies

A better API for JDBC Client

Our JDBC client will not go away in Vert.x 4, we do recknognize that JDBC is important because it supports the most important number of databases in the ecosystem.

When we designed the SQL client API we strived a lot to come with the simplest and most powerful API for asynchonous SQL client.

This release brings an implementation of the SQL client API for JDBC.

The 3.x API series will continue to be supported for the lifetime of Vert.x 4.

Event loop affinity

Using Vert.x from a non Vert.x thread is a very common use case we have been supporting since Vert.x 3.

When you use a Vert.x resource (like a client) from a non Vert.x thread, Vert.x 3 obtains a new event-loop everytime it happens.

In Vert.x 4 we decided to pin the first event loop to the non Vert.x thread. The goal is to prevent some data races and also makes reasonning about this easier.

Vertx vertx = Vertx.vertx();

for (int i = 0;i < 4;i++) {
  String msg = "Message " + i;
  vertx.runOnContext(v -> {

Running this with Vert.x 3 will print the 4 lines but they are likely to not be reordered, this code could also be running in parallel (that is two different threads running at the same time on a different CPU core).

Running this with Vert.x 4 will print the 4 lines in the correct order and always with the same thread. This eliminates some potential data races and also allows to reason about what will happen at runtime.

Vert.x Json Schema supports Draft2019-09

The new vertx-json-schema module now supports the latest Json Schema Draft2019-09 spec. You can finally play with the new $recursiveRef to build extensible recursive schemas and with unevaluatedProperties/unevaluatedItems to define strict schemas. Look at the module documentation to start using it.

Clustering configuration simplified

In Vert.x 3, cluster host was set to localhost by default in EventBusOptions. Consequently, a lot of new users were confused about why event bus consumers and producers were not able to communicate even if the underlying cluster manager was configured correctly.

Also, when using the CLI tool or the Launcher class, Vert.x tried to find a host among available network interfaces if none was provided with the -cluster-host argument. Sometimes, the host chosen by the cluster manager and Vert.x were not the same.

Starting with Vert.x 4 beta 1, the cluster host default has been removed and, if users don’t provide any, Vert.x will ask the cluster manager which one it picked before trying to find one itself. This applies whether Vert.x is embedded in any Java program or started with the CLI tool or with the Launcher class.

So far, only vertx-hazelcast and vertx-infinispan cluster managers can provide Vert.x with a cluster host. When other cluster managers are used, Vert.x will choose one itself.

Cluster manager upgrades

vertx-hazelcast has been upgraded to Hazelcast 4.0.2 and vertx-infinispan to Infinispan 11.0.1.Final.


This is the Beta1 relase of Vert.x 4, you can of course expect more betas as we get feedback from the community and fix issues that we failed to catch before.

You can also read the milestone announces to know more about the overral changes:

The deprecations and breaking changes can be found on the wiki.

For this release there are no Docker images.

The release artifacts have been deployed to Maven Central and you can get the distribution on Maven Central.

You can bootstrap a Vert.x 4.0.0.Beta1 project using

The documentation has been deployed on this preview web-site

That’s it! Happy coding and see you soon on our user or dev channels.