When I run a parallel build which invokes multiple goals Maven multiplies the work e.g. when I run
Every phase is executed once as expected. However when I run
install sonar:sonar -T 4
Every phase is executed twice.
The problem can be reproduced with a single simple Java project (of course parallel builds are useless with a single module). Debugging showed that every Mojo is really called twice per project.
Find attached a simple project and two build outputs, where you can see that the parallel build is doing everything twice (you can ignore that Sonar fails in the end, due to no server is up).