Debugging Running Applications

How to access a running container?#

To interact with a running container on a worker node, use the ctr utility. This CLI tool is part of containerd, the runtime Oakestra uses for deploying containers. All Oakestra containers are placed in a custom namespace called oakestra.

In containerd, there are two key concepts:

• Containers: Represent the filesystem, environment, and associated metadata.
• Tasks: Represent the processes running inside those containers.

Listing Containers and Tasks#

sudo ctr -n oakestra container ls

To check all running tasks you can use the following:

sudo ctr -n oakestra task ls

Executing Commands Inside a Running Container#

To attach to a running container and execute commands inside it:

sudo ctr -n oakestra task exec --exec-id tty <your task name here> <the command you wish to execute>

For example, to use a shell inside the container x.y.z we can use

sudo ctr -n oakestra task exec --exec-id tty x.y.z /bin/sh

Where are the logfiles stored?#

The stdout and stderr of each container or unikernel is stored under /tmp/<appname>.<appns>.<servicename>.<servicens>.<instancenumber> of the worker node running the instance.

For example, to access the latest logs of instance 0 of x.y.z.y in my worker node I can run tail /tmp/x.y.z.y.0

What about Unikernels?#

You cannot attach directly to a running unikernel, but their logs are stored in the same way as containers. Check the /tmp directory structure as described above to access and review their logs.