Tag Archives: elasticsearch

Scenario

In a spring-boot application that uses spring-boot-dependencies instead of spring-boot-starter-parent and a third party library that depends on elasticsearch version that is not comparable with version 6.x, elasticsearch dependency version get mixed up creating class loading issue.

Steps to reproduce

Create a spring-boot project and include spring-boot-dependencies in the dependency management section of the maven pom.xml

<properties>
  <spring.boot.version>2.1.6.RELEASE</spring.boot.version>
  <spring.cloud.version>Greenwich.RELEASE</spring.cloud.version>
</properties>

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-dependencies</artifactId>
      <version>${spring.boot.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>

    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-dependencies</artifactId>
      <version>${spring.cloud.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

Later, in the dependencies section include a third party library that depends on elastic search version 5.6.8

<dependnecies>
  <dependency>
    <groupId>com.netflix.conductor</groupId>
    <artifactId>conductor-es5-persistence</artifactId>
    <version>2.8.1</version>
  </dependency>
</dependnecies>

Note that conductor-es5-persistence depends on elasticsearch version 5.6.8

The try to run mvn dependency:tree on your project and observe the following:

[INFO] +- com.netflix.conductor:conductor-es5-persistence:jar:2.8.1:compile
[INFO] |  +- org.elasticsearch:elasticsearch:jar:6.4.3:compile
[INFO] |  |  +- org.elasticsearch:elasticsearch-core:jar:6.4.3:compile

Where 6.4.3 is coming from?

Diagnostic

Turns out mvn dependency:tree shows the issue, but it does not say where org.elasticsearch:elasticsearch:jar:6.4.3:compile is comming from. The best command for the job is:

mvn -Dverbose=true help:effective-pom

This command outputs effective POM that can be redirected to a file mvn -Dverbose=true help:effective-pom > ~/pom.xml and analysed. The effective pom will look something like this

...
<dependency>
  <groupId>org.elasticsearch</groupId>  <!-- org.springframework.boot:spring-boot-dependencies:2.1.6.RELEASE, line 1965 -->
  <artifactId>elasticsearch</artifactId>  <!-- org.springframework.boot:spring-boot-dependencies:2.1.6.RELEASE, line 1966 -->
  <version>6.4.3</version>  <!-- org.springframework.boot:spring-boot-dependencies:2.1.6.RELEASE, line 1967 -->
</dependency>
...

Magic! now we can see exactly where the problem is:

<!-- org.springframework.boot:spring-boot-dependencies:2.1.6.RELEASE, line 1967 -->

Solution

Lets look at this import dependency:

<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-dependencies</artifactId>
    <version>${spring.boot.version}</version>
    <type>pom</type>
    <scope>import</scope>
  </dependency>

spring-boot-dependencies is imported, so there is no easy way to exclude elasticsearch dependency that it pulls into our project. A simple maven <exclude> will not work here. The only way to solve the issue is to bring elasticsearch dependencies into your project dependency management block like this:

<properties>
  <spring.boot.version>2.1.6.RELEASE</spring.boot.version>
  <spring.cloud.version>Greenwich.RELEASE</spring.cloud.version>
  
  <elasticsearch.version>5.6.8</elasticsearch.version>
</properties>

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-dependencies</artifactId>
      <version>${spring.boot.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>

    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-dependencies</artifactId>
      <version>${spring.cloud.version}</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    
    <!-- Elasticsearch -->
    <dependency>
      <groupId>org.elasticsearch</groupId>
      <artifactId>elasticsearch</artifactId>
      <version>${elasticsearch.version}</version>
    </dependency>

    <dependency>
      <groupId>org.elasticsearch.client</groupId>
      <artifactId>transport</artifactId>
      <version>${elasticsearch.version}</version>
    </dependency>

    <dependency>
      <groupId>org.elasticsearch.distribution.integ-test-zip</groupId>
      <artifactId>elasticsearch</artifactId>
      <version>${elasticsearch.version}</version>
      <type>zip</type>
    </dependency>

    <dependency>
      <groupId>org.elasticsearch.plugin</groupId>
      <artifactId>transport-netty4-client</artifactId>
      <version>${elasticsearch.version}</version>
    </dependency>

  </dependencies>
</dependencyManagement>

Now run mvn -Dverbose=true help:effective-pom and confirm that the problem is fixed.