[SUREFIRE-1587] Forked execution prevents correct ServerSocket closing

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.22.1
• Environment: Linux, problem becomes visible on archlinux and also on Travis CI
• Assignee: Unassigned
• Reporter: Johannes Wienke
• Created: 24/Oct/18 14:51
• Updated: 29/Aug/24 13:28

Description

The default mode of forked unit test execution (with JUnit) seems to interfere with socket operations. In our case, we see that with a surefire execution in forked mode, ServerSocket instances, despite returning from a close() call, are sometimes not correctly closed and a subsequent try to acquire a server socket on the same port then fails. This does not happen outside of surefire or when forkMode is set to none.

Here is a simple test case to try this. First the maven project pom.xml:

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>testing</groupId>
  <artifactId>testit</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>testit</name>
  <description>A simple testit.</description>
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.22.1</version>
      </plugin>
    </plugins>
  </build>

</project>

And here a test file to be placed into the test source tree:

AppTest.java

package testing;

import org.junit.Test;

import java.net.ServerSocket;

public class AppTest {

    @Test
    public void testSocketStuff() throws Exception {
        while (true) {
            System.out.println("Iteration");
            final ServerSocket socket = new ServerSocket(55444);
            socket.close();
        }
    }

}

Executing this with the default options (forking mode enabled) will pretty soon end up in the following exception after some iterations:

[ERROR] testSocketStuff(testing.AppTest)  Time elapsed: 1.376 s  <<< ERROR!
java.net.BindException: Address already in use (Bind failed)
        at testing.AppTest.testSocketStuff(AppTest.java:17)

Executing the same test with -DforkMode=none does not result in this failure and the loop runs endlessly.