containerd

containerd API Python package

This repository provides a Python3 API to containerd's (gRPC) API, directly generated from the original containerd .proto API definitions. As it is generated from the protocol files, this Python package does not aim to be a fully Pythonesque package. In consequence, the usual idiosyncrasies of gRPC and protoc shine through.

Note: with Python2 going end-of-life in January 2020 we don't support Python2 in this package at this very late time in the lifecycle.

Versioning

The versioning of this package complies with PEP 440.

The version is composed of the version of the supported containerd API (e.g. 1.2 or 1.3) and an incremental number for each pycontainerd release for that specific containerd API version (starting from 0) connected with a '.' (a dot).

Ideally the Python containerd API has to be generated only once per containerd API version, resulting in x.y.0 package versions.

The result is version numbers like:

• 1.2.1 for the second release for API 1.2
• 1.3.0 for the first release for API 1.3

License

This project is licensed as Apache License, Version 2.0 (SPDX-License-Identifier: Apache-2.0).

You can obtain the full license text from the file License of this repository.

Installation

Installation depends on your starting point:

• You get the packages from https://pypi.org/project/containerd
• You have a pycontainerd Python Wheel package (something like containerd-x.y.z-py3-none-any.whl).
• You only have the source code (the result of cloning the git repository).

Dependencies

Python3 PIP is needed for Wheel installations (either from a ready Wheel package or from a self-built package). PIP takes care of installing all the Python packages listed as dependencies. Runtime dependencies are nevertheless listed below.

Installation from PyPI (AKA PIP)

Simply let PIP install the latest release for the corresponding containerd API version.

For example, for the container API version 1.5:

sudo pip3 install "containerd==1.5.*"

The quotes are important to avoid that the shell tries to resolve the "*" and passes it untouched to PIP.

Installation from Wheel package

Go to the directory where the wheel package is available and run:

sudo pip3 install containerd-<x.y.z>-py3-none-any.whl

Being containerd-<x.y.z>-py3-none-any.whl the filename of the wheel package.

NOTE: a global installation is required (or rather, more convenient) because the containerd API socket is usually only reachable for root.

Installation from source code

Additionally, if building from source code you'll also need make.

A Makefile is being provided that takes care of

• Building the Wheel package
• Installing the Wheel package

Get into the directory corresponding the API version of your containerd installation and run following:

make install

The second step is under the hood simply running the installation of the wheel package explained above. Including the global installation, therefore a sudo execution is asking for the user's password (assuming the user has that right).

Package Structure and Usage

The resulting Wheel package provides following Python packages (they have to be imported individually), providing multiple modules:

• containerd.events
• containerd.services.containers.v1
• containerd.services.content.v1
• containerd.services.diff.v1
• containerd.services.events.v1
• containerd.services.images.v1
• containerd.services.introspection.v1
• containerd.services.leases.v1
• containerd.services.namespaces.v1
• containerd.services.snapshots.v1
• containerd.services.tasks.v1
• containerd.services.version.v1
• containerd.types
• containerd.types.tasks
• containerd.protobuf (note: this is not a protobuf alias)
• containerd.vendor.gogoproto

In order to get the modules being provided by a package you can run:

python3 -c 'import <package> ; help(<package>)'

For example, for containerd.events:

python3 -c 'import containerd.events ; help(containerd.events)'

Examples

List All Namespaces

The following simple example queries containerd for its list of available containerd namespaces. Make sure you have the necessary privileges to connect to containerd; you may need to run this script as root:

import grpc
from containerd.services.namespaces.v1 import namespace_pb2_grpc, namespace_pb2

with grpc.insecure_channel('unix:///run/containerd/containerd.sock') as channel:
    namespacev1 = namespace_pb2_grpc.NamespacesStub(channel)
    namespaces = namespacev1.List(namespace_pb2.ListNamespacesRequest()).namespaces
    for namespace in namespaces:
        print('namespace:', namespace.name)

Usually, you want to add proper error handling. This is just a very simplistic example to illustrate the principle.

List Containers in a Specific Namespace

Several of containerd's APIs are namespaced. That is, they work only on a single namespace at a time. The namespace applies on the level of individual service calls and needs to be specified as an (additional) metadata element to these calls. If not specified, it the namespace will default to the namespace named default. The following example lists all containers in the "moby" namespace; this is the containerd namespace used by Docker.

import grpc
from containerd.services.containers.v1 import containers_pb2_grpc, containers_pb2

with grpc.insecure_channel('unix:///run/containerd/containerd.sock') as channel:
    containersv1 = containers_pb2_grpc.ContainersStub(channel)
    containers = containersv1.List(
        containers_pb2.ListContainersRequest(),
        metadata=(('containerd-namespace', 'moby'),)).containers
    for container in containers:
        print('container ID:', container.id)

Watch containerd Events Flowing

Containerd events can be easily read from the endless event stream via the containerd.services.events.v1 API, using the Subscribe service. The following example subscribes to all events and then prints their type and contents as the events come:

import grpc

from containerd.services.events.v1 import unwrap, events_pb2, events_pb2_grpc
from google.protobuf import any_pb2

with grpc.insecure_channel('unix:///run/containerd/containerd.sock') as channel:
    print("waiting for containerd events...")
    eventsv1 = events_pb2_grpc.EventsStub(channel)
    for ev in eventsv1.Subscribe(events_pb2.SubscribeRequest()):
        print('event type: ', ev.event.type_url)
        print('value: ', unwrap(ev))

Note: containerd.services.events.v1.unwrap(envelope) is a convenience function which unwraps the event object inside an event envelope returned by Subscribe(): the unwrapped event object is returned as a Python object of sub class containerd.events.* (as opposed to the arbitrary "any" binary value inside the event envelope).

Executable Programs

To help containerd client developers getting started, we've included two simple examples which are also made available as the CLI programs lsctr and watchctr (source code in examples/) when cloning the repository.

You first have to install the wheel package for the containerd package.

• lsctr lists all containerd containers in all namespaces. It is basically kind of an all-in-one combination of the ctr commands for namespaces, containers, and tasks in a single command.
• watchctr watches containerd events, such as container creation, start, stop, et cetera, and then prints them to the terminal.

To check that it works, run the lsctr command: this should list all available containerd containers, across all containerd namespaces (remember to use sudo in case you don't have the necessary privileges as an ordinary user to talk to containerd):

sudo lsctr

This should spit out something like this, when running on a recent Docker CE installation, which uses containerd under the hood:

moby
  ⤏ labels (0):
  ▩ container: 0eeb9e2862e9f68e832a2e2c60a2e44e74d54b05266532cf19b112f4d959e3fb
    ▷ PID: 3359 ⚐ status: RUNNING
    ⚙ runtime: io.containerd.runtime.v1.linux
    ⤏ labels (1):
        "com.docker/engine.bundle.path": "/var/run/docker/containerd/0eeb9e2862e9f68e832a2e2c60a2e44e74d54b05266532cf19b112f4d959e3fb"
    ◷ created: 2019-09-04 07:24:32.646856 ◷ updated: 2019-09-04 07:24:32.646856
  ▩ container: 1663afd0ddc6e0bba30b7fcc27b26044ece6022d970e32731db5dcb807b168df
    ▷ PID: 66062 ⚐ status: RUNNING
    ⚙ runtime: io.containerd.runtime.v1.linux
    ⤏ labels (1):
        "com.docker/engine.bundle.path": "/var/run/docker/containerd/1663afd0ddc6e0bba30b7fcc27b26044ece6022d970e32731db5dcb807b168df"
    ◷ created: 2019-08-16 08:08:21.471493 ◷ updated: 2019-08-16 08:08:21.471493
...

You can use lsctr -h to see the few CLI options available.

Package Requirements

The following Python packages are required:

• grpcio – gRPC for Python; required in order to communicate with containerd. This is a runtime dependency.
• protobuf – protobuf for Python; required in order to communicate with containerd. This is a runtime dependency.
• (optional) grpcio-tools – only required when re-generating the containerd API Python code using genpb2.sh.

Python ContainerD API

API Package (Re)Generation

In case you need to regenerate or update the Python code for the containerd API, in the top-level directory of this repository, run:

./genpb2.sh

Normally, you should not need to regenerate the grpc/pb2 Python modules unless you are a project contributor or maintainer.

Project Organization

The overall directory structure of the Python containerd API package is as follows (inside the api_1.x/ directories):

• containerd/ contains the Python modules generated by protoc as well as a very few hand-made modules. In order to avoid polluting the top-level package namespace with proto dependencies, genpb2.sh "vendorizes" dependencies only for such .proto files for which no PyPI packages are available, moving such dependencies inside the containerd top-level Python package namespace.
  • services/ contains the containerd service API v1.
  • events/ contains the containerd event definitions.
  • types/ contains containerd type definitions required by services and events.
  • protobuf/ internal dependency.
  • vendor/ contains the "vendorized" dependencies.
    • gogoproto/ modules not available as a PyPI package.
• genpb2.sh is a script to recreate or update the _pb2.py and _pb2_grpc.py Python modules from the containerd API .proto file definitions and dependencies. See genpb2.sh for more information on its workings.

Survival References

• gRPC Basics – Python.
• Protocol Buffers Python Reference: Python Generated Code.
• containerd API protocol definitions.