Migrating telemetry and security agents from dockershim
Kubernetes' support for direct integration with Docker Engine is deprecated, and will be removed. Most apps do not have a direct dependency on runtime hosting containers. However, there are still a lot of telemetry and monitoring agents that has a dependency on docker to collect containers metadata, logs and metrics. This document aggregates information on how to detect these dependencies and links on how to migrate these agents to use generic tools or alternative runtimes.
Telemetry and security agents
Within a Kubernetes cluster there are a few different ways to run telemetry or security agents. Some agents have a direct dependency on Docker Engine when they as DaemonSets or directly on nodes.
Why do some telemetry agents communicate with Docker Engine?
Historically, Kubernetes was written to work specifically with Docker Engine. Kubernetes took care of networking and scheduling, relying on Docker Engine for launching and running containers (within Pods) on a node. Some information that is relevant to telemetry, such as a pod name, is only available from Kubernetes components. Other data, such as container metrics, is not the responsibility of the container runtime. Early yelemetry agents needed to query the container runtime and Kubernetes to report an accurate picture. Over time, Kubernetes gained the ability to support multiple runtimes, and now supports any runtime that is compatible with the container runtime interface.
Some telemetry agents rely specifically on Docker Engine tooling. For example, an agent
might run a command such as
docker ps
or docker top to list
containers and processes or docker logs
to receive streamed logs. If nodes in your existing cluster use
Docker Engine, and you switch to a different container runtime,
these commands will not work any longer.
Identify DaemonSets that depend on Docker Engine
If a pod wants to make calls to the dockerd running on the node, the pod must either:
- mount the filesystem containing the Docker daemon's privileged socket, as a volume; or
- mount the specific path of the Docker daemon's privileged socket directly, also as a volume.
For example: on COS images, Docker exposes its Unix domain socket at
/var/run/docker.sock This means that the pod spec will include a
hostPath volume mount of /var/run/docker.sock.
Here's a sample shell script to find Pods that have a mount directly mapping the
Docker socket. This script outputs the namespace and name of the pod. You can
remove the grep '/var/run/docker.sock' to review other mounts.
kubectl get pods --all-namespaces \
-o=jsonpath='{range .items[*]}{"\n"}{.metadata.namespace}{":\t"}{.metadata.name}{":\t"}{range .spec.volumes[*]}{.hostPath.path}{", "}{end}{end}' \
| sort \
| grep '/var/run/docker.sock'
/var/run may be mounted instead of the full path (like in this
example).
The script above only detects the most common uses.
Detecting Docker dependency from node agents
In case your cluster nodes are customized and install additional security and telemetry agents on the node, make sure to check with the vendor of the agent whether it has dependency on Docker.
Telemetry and security agent vendors
We keep the work in progress version of migration instructions for various telemetry and security agent vendors in Google doc. Please contact the vendor to get up to date instructions for migrating from dockershim.