A root directory with installed packages can be shared between several local projects. If one local project triggers installation of a new third party package, then the root directory will be locked against modifications until the install has either finished or interrupted (i.e. Ctrl-C). Other local projects that try to run hunter_add_package for the same root at the same time will automatically wait for the root to be unlocked. Note that different root directories have independent locks, e.g. triggering a build of OpenSSL for iOS will not delay building of GTest for Android. Internally this is done using the file(LOCK ...) CMake command (available since 3.2).

Similar synchronization is done when initializing Hunter using the HunterGate command. This is a very handy feature for CI systems where an environment is shared between several jobs, e.g. Jenkins.