Process spawned by exec-maven-plugin blocks the maven process - maven

Question

I am trying to execute the following scenario using maven :
pre-integration-phase : Start a java based application using a main class (using exec-maven-plugin)
integration-phase : Run the integration test cases (using maven-failsafe-plugin)
post-integration-phase: Stop the application gracefully (using exec-maven-plugin)
Here is pom.xml snip:
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<executions>
<execution>
<id>launch-myApp</id>
<phase>pre-integration-test</phase>
<goals>
<goal>exec</goal>
</goals>
</execution>
</executions>
<configuration>
<executable>java</executable>
<arguments>
<argument>-DMY_APP_HOME=/usr/home/target/local</argument>
<argument>-Djava.library.path=/usr/home/other/lib</argument>
<argument>-classpath</argument>
<classpath/>
<argument>com.foo.MyApp</argument>
</arguments>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-failsafe-plugin</artifactId>
<version>2.12</version>
<executions>
<execution>
<goals>
<goal>integration-test</goal>
<goal>verify</goal>
</goals>
</execution>
</executions>
<configuration>
<forkMode>always</forkMode>
</configuration>
</plugin>
</plugins>
If I execute mvn post-integration-test, my application is getting started as a child process of the maven process, but the application process is blocking the maven process from executing the integration tests which comes in the next phase. Later I found that there is a bug (or missing functionality?) in maven exec plugin, because of which the application process blocks the maven process. To address this issue, I have encapsulated the invocation of MyApp.java in a shell script and then appended “/dev/null 2>&1 &” to spawn a separate background process. Here is the snip (this is just a snip and not the actual one) from runTest.sh:
java - DMY_APP_HOME =$2 com.foo.MyApp > /dev/null 2>&1 &
Although this solves my issue, is there any other way to do it? Am I missing any argument for exec-maven-plugin?

Answer 1

You can use the async configuration parameter to achieve what you require. Also see asyncDestroyOnShutdown which will shutdown the app on JVM exit by default.
https://www.mojohaus.org/exec-maven-plugin/exec-mojo.html#async
If set to true the child process executes asynchronously and build execution continues in parallel.
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.6.0</version>
<executions>
<execution>
<id>launch-myApp</id>
<phase>pre-integration-test</phase>
<goals>
<goal>exec</goal>
</goals>
</execution>
</executions>
<configuration>
<executable>java</executable>
<arguments>
<argument>-DMY_APP_HOME=/usr/home/target/local</argument>
<argument>-Djava.library.path=/usr/home/other/lib</argument>
<argument>-classpath</argument>
<classpath/>
<argument>com.foo.MyApp</argument>
</arguments>
<async>true</async>
</configuration>
</plugin>

Answer 2

(Unix only)
Use exec:exec and start a script.
This script should call
java -DMY_APP_HOME =$2 com.foo.MyApp > /dev/null 2>&1 &
first, and check the startup before the script finishes.
Did the program crash in 2 seconds?
When your java app needs some time to start you can add a script that waits for a complete startup.
retrymax=30
retry=0
RETURNCODE=1
while [ ${retry} -lt ${retrymax} ]; do
todo_your_test
RETURNCODE=$?
if [ ${RETURNCODE} -eq 0 ]; then
echo MyApp started
break
else
(( retry = retry + 1 ))
sleep 2
fi
done
exit ${RETURNCODE}

Answer 3

I am using the https://github.com/bazaarvoice/maven-process-plugin plugin while this issue is still open https://github.com/mojohaus/exec-maven-plugin/issues/18

Answer 4

There's a possible solution in this thread using Ant: Possible solution here: Maven and Exec: forking a process?
The same disadvantage as in your current solution is that it's platform dependent as well. Your current solution will only run in Unix/Linux-like environments, while the Ant-based solution is starting an instance of cmd, which only works on Windows. Using Maven profiles, one could create a configuration that uses the OS it's running on to determine which command shell to start, of course.