Image for a init container which may be used to write the libfaketime library to a shared volume - from which it may be loaded by an app container for "time travel".
libfaketime is a library which modifies the time for a process under Linux without affecting the rest of the system. It's ideal to let containers/pods travel in time by using the LD_PRELOAD mechanism.
Using this image for an init container, you don't need to modify your app image. Init and app container should share a volume into which the init container writes and from where the app container loads the library - et voilá, you don't need 1.21 GW of power to move a pod back to 1985.
For an example how exactly it's done please see our repository Marty McFly.
This project is published unter the GNU General Public License v3.0. For details please see the LICENSE file.
In the folder examples you'll find a docker compose file which demonstrates the principle of inserting libfaketime via an init container. It starts two containers:
- the init container which mounts the shared volume and copies libfaketime there. It runs first.
- the app container. It gets started after the init container is finished. The environment variable LD_PRELOAD is set to the path of libfaketime so that it gets loaded before the application, thus able to intercept system calls regerding time and to modify the "clock".
To test it simply run
# start
docker compose -f examples/docker-compose.yaml up
# break with ctrl-c; then remove containers:
docker compose -f examples/docker-compose.yaml down
The file k8s-deployment.yaml, to be found in the folder examples, shows how to use the libfaketime_init image to move your app container in time without modification of the apps image. Simply apply the manifest using kubectl:
$ kubectl apply -f examples/k8s-deployment.yaml
deployment.apps/libfaketime-init-demo created
$ # After some seconds, check the logs
$ kubectl logs libfaketime-init-demo-xxx-xxx inject-libfaketime
copying libfaketime library files to /lft_volume ...
'/usr/lib/x86_64-linux-gnu/faketime//libfaketime.so.1' -> '/lft_volume/libfaketime.so.1'
'/usr/lib/x86_64-linux-gnu/faketime//libfaketimeMT.so.1' -> '/lft_volume/libfaketimeMT.so.1'
$ kubectl logs libfaketime-init-demo-xxx-xxx main-app -f
Tue Aug 21 15:53:59 UTC 2029
Tue Aug 21 15:54:00 UTC 2029
Tue Aug 21 15:54:01 UTC 2029
$ kubectl delete -f examples/k8s-deployment.yaml
deployment.apps "libfaketime-init-demo" deleted
$
In the demo the FAKETIME parameter for libfaketime is set to a relative offset of 1234 days so that the application thinks it's roughly 3.5 years ahead.
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