Why Spring Boot 2.2.3 Breaks pigx-gateway and How to Resolve It

Problem Description

After upgrading from Spring Boot 2.2 to 2.2.3, the

pigx-gateway

application fails to start.

Failure Log

<code>***************************
APPLICATION FAILED TO START
***************************
Description:
An attempt was made to call a method that does not exist. The attempt was made from the following location:
    org.springframework.cloud.gateway.config.GatewayAutoConfiguration$NettyConfiguration.gatewayHttpClient(GatewayAutoConfiguration.java:597)
The following method did not exist:
    reactor.netty.resources.ConnectionProvider.elastic(Ljava/lang/String;Ljava/time/Duration;)Lreactor/netty/resources/ConnectionProvider;
The method's class, reactor.netty.resources.ConnectionProvider, is available from the following locations:
    jar:file:/Users/lengleng/env/repository/io/projectreactor/netty/reactor-netty/0.9.3.RELEASE/reactor-netty-0.9.3.RELEASE.jar!/reactor/netty/resources/ConnectionProvider.class
It was loaded from the following location:
    file:/Users/lengleng/env/repository/io/projectreactor/netty/reactor-netty/0.9.3.RELEASE/reactor-netty-0.9.3.RELEASE.jar
Action:
Correct the classpath of your application so that it contains a single, compatible version of reactor.netty.resources.ConnectionProvider</code>

Investigation

The log points to a version conflict in the

reactor-netty

dependency.

<code>    +---------------------------+            +---------------------------+
    | Spring Boot 2.2.3.RELEASE |            | Spring Boot 2.2.2.RELEASE |
    +-------------+-------------+            +-------------+-------------+
                  |                                        |
+-----------------v----------------+     +-----------------v----------------+
|spring-boot-starter-reactor-netty |     |spring-boot-starter-reactor-netty |
|              2.2.3.RELEASE       |     |              2.2.2.RELEASE       |
+-----------------+----------------+     +-----------------+----------------+
                  |                                        |
          +-------+--------+                       +-------+--------+
          |  reactor-netty |                       |  reactor-netty |
          |  0.9.3.RELEASE |                       |  0.9.2.RELEASE |
          +----------------+                       +----------------+</code>

ConnectionProvider

Version 0.9.3 does not provide the method

ConnectionProvider.elastic(String, Duration)

. The method signature was changed to include an additional

maxLifeTime

parameter (see reactor/reactor-netty#922, #924).

<code>/**
 * Create a {@link ConnectionProvider} to cache and grow on demand {@link Connection}.
 *
 * An elastic {@link ConnectionProvider} will never wait before opening a new
 * connection. The reuse window is limited but it cannot starve an undetermined volume
 * of clients using it.
 *
 * @param name the channel pool map name
 * @param maxIdleTime the {@link Duration} after which the channel will be closed when idle (resolution: ms),
 *                    if {@code NULL} there is no max idle time
 * @param maxLifeTime the {@link Duration} after which the channel will be closed (resolution: ms),
 *                    if {@code NULL} there is no max life time
 * @return a new {@link ConnectionProvider} to cache and grow on demand {@link Connection}
 */
static ConnectionProvider elastic(String name, @Nullable Duration maxIdleTime, @Nullable Duration maxLifeTime) {
    ...
}</code>

Solution

Globally use reactor‑netty

0.9.4

(snapshot) or downgrade to

0.9.2

. Spring Boot 2.2.3 does not fix the reactor issue, so downgrading is currently the safest option.

<code>&lt;dependencyManagement&gt;
    &lt;dependencies&gt;
        &lt;dependency&gt;
            &lt;groupId&gt;io.projectreactor.netty&lt;/groupId&gt;
            &lt;artifactId&gt;reactor-netty&lt;/artifactId&gt;
            &lt;version&gt;0.9.2.RELEASE&lt;/version&gt;
        &lt;/dependency&gt;
    &lt;/dependencies&gt;
&lt;/dependencyManagement&gt;</code>