A change in the behavior of `os.Rename` in Go 1.8 brought to light a
difference in the logic between `{Alloc,Task}Runner` and this test:
AllocRunner builds the alloc dir, moves dirs if necessary, and then lets
TaskRunner call TaskDir.Build().
This test called `TaskDir.Build` *before* `AllocDir.Move`, so in Go 1.8
it failed to `os.Rename over` the empty {data,local} dirs.
I updated the test to behave like the real code, but I defensively added
`os.Remove` calls as a subtle change in call order shouldn't break this
code. `os.Remove` won't remove a non-empty directory, so it's still
safe.
Fixes#2178 and allows using Docker and other image based drivers even
when nomad is run as a non-root user.
`client/allocdir` tests can be run as a non-root user to ensure this
behavior and tests that rely on root or non-root users properly detect
their effective user and skip instead of fail.
Many thanks to @iverberk for the original PR (#1609), but we ended up
not wanting to ship this implementation with 0.5.
We'll come back to it after 0.5 and hopefully find a way to leverage
filesystem accounting and quotas, so we can skip the expensive polling.
* Added the alloc dir move
* Moving allocdirs when starting allocations
* Added the migrate flag to ephemeral disk
* Stopping migration if the allocation doesn't need migration any more
* Added the GetAllocDir method
* refactored code
* Added a test for alloc runner
* Incorporated review comments
The following tests now check a whitelist for whether or not their
driver is present or not, or if the OS is supported or not.
* `TestAllocDir_MountSharedAlloc`
* `TestClient_Drivers_InWhitelist` (`exec` driver)
* `TestClient_Drivers` (`exec` driver)
* `TestJavaDriver_Fingerprint` (`java` driver)
