hooks/exec/runtimeconfigfilter: Log config changes

To make it easier to notice and track down errors (or other surprising
behavior) due to precreate hooks.  With this commit, the logged
messages look like:

  time="2018-11-19T13:35:18-08:00" level=debug msg="precreate hook 0 made configuration changes:
  --- Old
  +++ New
  @@ -18,3 +18,3 @@
     Namespaces: ([]specs.LinuxNamespace) <nil>,
  -  Devices: ([]specs.LinuxDevice) (len=1) {
  +  Devices: ([]specs.LinuxDevice) (len=2) {
      (specs.LinuxDevice) {
  @@ -24,2 +24,11 @@
       Minor: (int64) 229,
  +    FileMode: (*os.FileMode)(-rw-------),
  +    UID: (*uint32)(0),
  +    GID: (*uint32)(0)
  +   },
  +   (specs.LinuxDevice) {
  +    Path: (string) (len=8) "/dev/sda",
  +    Type: (string) (len=1) "b",
  +    Major: (int64) 8,
  +    Minor: (int64) 0,
       FileMode: (*os.FileMode)(-rw-------),
  "
  time="2018-11-19T13:35:18-08:00" level=debug msg="precreate hook 1 made configuration changes:
  --- Old
  +++ New
  @@ -29,3 +29,3 @@
      (specs.LinuxDevice) {
  -    Path: (string) (len=8) "/dev/sda",
  +    Path: (string) (len=8) "/dev/sdb",
       Type: (string) (len=1) "b",
  "

Ideally those logs would include the container ID, but we don't have
access to that down at this level.  I'm not sure if it's worth
teaching RuntimeConfigFilter to accept a *logrus.Entry (so the caller
could use WithFields [1]) or to use a generic logging interface (like
go-log [2]).  For now, I've left the container ID unlogged here.

The spew/difflib implementation is based on stretchr/testify/assert,
but I think the ~10 lines I'm borrowing are probably small enough to
stay under the "all copies or substantial portions" condition in its
MIT license.

[1]: https://godoc.org/github.com/sirupsen/logrus#WithFields
[2]: https://github.com/go-log/log

Signed-off-by: W. Trevor King <wking@tremily.us>

0 files changed, 0 insertions, 0 deletions