c441d51e05
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>
OCI Hooks Configuration
For POSIX platforms, the OCI runtime configuration supports hooks for configuring custom actions related to the life cycle of the container.
The way you enable the hooks above is by editing the OCI runtime configuration before running the OCI runtime (e.g. runc).
CRI-O and podman create create the OCI configuration for you, and this documentation allows developers to configure them to set their intended hooks.
One problem with hooks is that the runtime actually stalls execution of the container before running the hooks and stalls completion of the container, until all hooks complete.
This can cause some performance issues.
Also a lot of hooks just check if certain configuration is set and then exit early, without doing anything.
For example the oci-systemd-hook only executes if the command is init or systemd, otherwise it just exits.
This means if we automatically enabled all hooks, every container would have to execute oci-systemd-hook, even if they don't run systemd inside of the container.
Performance would also suffer if we exectuted each hook at each stage (pre-start, post-start, and post-stop).
The hooks configuration is documented in oci-hooks.5.