Fix race condition in config maven plugin

The race occur during Maven parallel build where multiple threads will
race to create the output directory.

2 files changed, 4 insertions, 2 deletions

diff --git a/config-class-plugin/src/main/java/com/yahoo/vespa/ConfigGenMojo.java b/config-class-plugin/src/main/java/com/yahoo/vespa/ConfigGenMojo.java
index 941f8afc648..17eb557ace0 100644
--- a/config-class-plugin/src/main/java/com/yahoo/vespa/ConfigGenMojo.java
+++ b/config-class-plugin/src/main/java/com/yahoo/vespa/ConfigGenMojo.java
@@ -20,7 +20,7 @@ import java.util.ArrayList;
 /**
  * Goal which generates config classes from def-files.
  */
-@org.apache.maven.plugins.annotations.Mojo(name = "config-gen", defaultPhase = LifecyclePhase.GENERATE_SOURCES)
+@org.apache.maven.plugins.annotations.Mojo(name = "config-gen", defaultPhase = LifecyclePhase.GENERATE_SOURCES, threadSafe = true)
 public class ConfigGenMojo extends AbstractMojo {
     @Component
     private MavenProject project;
diff --git a/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala b/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala
index c346338e543..f2ee4f74157 100644
--- a/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala
+++ b/configgen/src/main/scala/com/yahoo/config/codegen/JavaClassBuilder.scala
@@ -166,7 +166,9 @@ object JavaClassBuilder {
     val subDirs: Array[String] = (PackagePrefix + namespace).split("""\.""")
     for (subDir <- subDirs) {
       dir = new File(dir, subDir)
-      if (!dir.isDirectory && !dir.mkdir) throw new CodegenRuntimeException("Could not create " + dir.getPath)
+      this.synchronized {
+        if (!dir.isDirectory && !dir.mkdir) throw new CodegenRuntimeException("Could not create " + dir.getPath)
+      }
     }
     dir
   }