Container Orchestration in CSIT¶
Overview¶
Linux Containers¶
Linux Containers is an OS-level virtualization method for running multiple isolated Linux systems (containers) on a compute host using a single Linux kernel. Containers rely on Linux kernel cgroups functionality for controlling usage of shared system resources (i.e. CPU, memory, block I/O, network) and for namespace isolation. The latter enables complete isolation of applications’ view of operating environment, including process trees, networking, user IDs and mounted file systems.
LXC combine kernel’s cgroups and support for isolated namespaces to provide an isolated environment for applications. Docker does use LXC as one of its execution drivers, enabling image management and providing deployment services. More information in [lxc], [lxcnamespace] and [stgraber].
Linux containers can be of two kinds: privileged containers and unprivileged containers.
Unprivileged Containers¶
Running unprivileged containers is the safest way to run containers in a production environment. From LXC 1.0 one can start a full system container entirely as a user, allowing to map a range of UIDs on the host into a namespace inside of which a user with UID 0 can exist again. In other words an unprivileged container does mask the userid from the host, making it impossible to gain a root access on the host even if a user gets root in a container. With unprivileged containers, non-root users can create containers and will appear in the container as the root, but will appear as userid <non-zero> on the host. Unprivileged containers are also better suited to supporting multi-tenancy operating environments. More information in [lxcsecurity] and [stgraber].
Privileged Containers¶
Privileged containers do not mask UIDs, and container UID 0 is mapped to the host UID 0. Security and isolation is controlled by a good configuration of cgroup access, extensive AppArmor profile preventing the known attacks as well as container capabilities and SELinux. Here a list of applicable security control mechanisms:
- Capabilities - keep (whitelist) or drop (blacklist) Linux capabilities, [capabilities].
- Control groups - cgroups, resource bean counting, resource quotas, access restrictions, [cgroup1], [cgroup2].
- AppArmor - apparmor profiles aim to prevent any of the known ways of escaping a container or cause harm to the host, [apparmor].
- SELinux - Security Enhanced Linux is a Linux kernel security module that provides similar function to AppArmor, supporting access control security policies including United States Department of Defense–style mandatory access controls. Mandatory access controls allow an administrator of a system to define how applications and users can access different resources such as files, devices, networks and inter- process communication, [selinux].
- Seccomp - secure computing mode, enables filtering of system calls, [seccomp].
More information in [lxcsecurity] and [lxcsecfeatures].
Linux Containers in CSIT
CSIT is using Privileged Containers as the sysfs is mounted with RW
access. Sysfs is required to be mounted as RW due to VPP accessing
/sys/bus/pci/drivers/uio_pci_generic/unbind. This is not the case of
unprivileged containers where sysfs is mounted as read-only.
Orchestrating Container Lifecycle Events¶
Following Linux container lifecycle events need to be addressed by an orchestration system:
- Acquire - acquiring/downloading existing container images via docker pull or lxc-create -t download.
- Build - building a container image from scratch or another container image via docker build <dockerfile/composefile> or customizing LXC templates in GitHub.
- (Re-)Create - creating a running instance of a container application from anew, or re-creating one that failed. A.k.a. (re-)deploy via docker run or lxc-start
- Execute - execute system operations within the container by attaching to running container. THis is done by lxc-attach or docker exec
- Distribute - distributing pre-built container images to the compute nodes. Currently not implemented in CSIT.
Container Orchestration Systems Used in CSIT¶
Current CSIT testing framework integrates following Linux container orchestration mechanisms:
- LXC/Docker for complete VPP container lifecycle control.
- Combination of Kubernetes (container orchestration), Docker (container images) and Ligato (container networking).
LXC¶
LXC is the well-known and heavily tested low-level Linux container runtime [lxcsource], that provides a userspace interface for the Linux kernel containment features. With a powerful API and simple tools, LXC enables Linux users to easily create and manage system or application containers. LXC uses following kernel features to contain processes:
- Kernel namespaces: ipc, uts, mount, pid, network and user.
- AppArmor and SELinux security profiles.
- Seccomp policies.
- Chroot.
- Cgroups.
CSIT uses LXC runtime and LXC usertools to test VPP data plane performance in a range of virtual networking topologies.
Known Issues
- Current CSIT restriction: only single instance of lxc runtime due to the cgroup policies used in CSIT. There is plan to add the capability into code to create cgroups per container instance to address this issue. This sort of functionality is better supported in LXC 2.1 but can be done is current version as well.
- CSIT code is currently using cgroup to control the range of CPU cores the LXC container runs on. VPP thread pinning is defined vpp startup.conf.
Docker¶
Docker builds on top of Linux kernel containment features, and offers a high-level tool for wrapping the processes, maintaining and executing them in containers [docker]. Currently it using runc a CLI tool for spawning and running containers according to the OCI specification
A Docker container image is a lightweight, stand-alone, executable package of a piece of software that includes everything needed to run it: code, runtime, system tools, system libraries, settings.
CSIT uses Docker to manage the maintenance and execution of containerized applications used in CSIT performance tests.
- Data plane thread pinning to CPU cores - Docker CLI and/or Docker configuration file controls the range of CPU cores the Docker image must run on. VPP thread pinning defined vpp startup.conf.
Kubernetes¶
Kubernetes [k8sdoc], or K8s, is a production-grade container orchestration platform for automating the deployment, scaling and operating application containers. Kubernetes groups containers that make up an application into logical units, pods, for easy management and discovery. K8s pod definitions including compute resource allocation is provided in .yaml files.
CSIT uses K8s and its infrastructure components like etcd to control all phases of container based virtualized network topologies.
Ligato¶
Ligato [ligato] is an open-source project developing a set of cloud-native tools for orchestrating container networking. Ligato integrates with FD.io VPP using goVPP [govpp] and vpp-agent [vppagent].
Known Issues
- Currently using a separate LF Jenkins job for building csit-centric prod_vpp_agent docker images vs. dockerhub/ligato ones.
Implementation¶
CSIT container orchestration is implemented in CSIT Level-1 keyword Python libraries following the Builder design pattern. Builder design pattern separates the construction of a complex object from its representation, so that the same construction process can create different representations e.g. LXC, Docker, other.
CSIT Robot Framework keywords are then responsible for higher level lifecycle control of of the named container groups. One can have multiple named groups, with 1..N containers in a group performing different role/functionality e.g. NFs, Switch, Kafka bus, ETCD datastore, etc. ContainerManager class acts as a Director and uses ContainerEngine class that encapsulate container control.
Current CSIT implementation is illustrated using UML Class diagram:
- Acquire
- Build
- (Re-)Create
- Execute
+-----------------------------------------------------------------------+
| RF Keywords (high level lifecycle control) |
+-----------------------------------------------------------------------+
| Construct VNF containers on all DUTs |
| Acquire all '${group}' containers |
| Create all '${group}' containers |
| Install all '${group}' containers |
| Configure all '${group}' containers |
| Stop all '${group}' containers |
| Destroy all '${group}' containers |
+-----------------+-----------------------------------------------------+
| 1
|
| 1..N
+-----------------v-----------------+ +--------------------------+
| ContainerManager | | ContainerEngine |
+-----------------------------------+ +--------------------------+
| __init()__ | | __init(node)__ |
| construct_container() | | acquire(force) |
| construct_containers() | | create() |
| acquire_all_containers() | | stop() |
| create_all_containers() | 1 1 | destroy() |
| execute_on_container() <>-------| info() |
| execute_on_all_containers() | | execute(command) |
| install_vpp_in_all_containers() | | system_info() |
| configure_vpp_in_all_containers() | | install_supervisor() |
| stop_all_containers() | | install_vpp() |
| destroy_all_containers() | | restart_vpp() |
+-----------------------------------+ | create_vpp_exec_config() |
| create_vpp_startup_config|
| is_container_running() |
| is_container_present() |
| _configure_cgroup() |
+-------------^------------+
|
|
|
+----------+---------+
| |
+------+-------+ +------+-------+
| LXC | | Docker |
+--------------+ +--------------+
| (inherinted) | | (inherinted) |
+------+-------+ +------+-------+
| |
+---------+---------+
|
| constructs
|
+---------v---------+
| Container |
+-------------------+
| __getattr__(a) |
| __setattr__(a, v) |
+-------------------+
Sequentional diagram that illustrates the creation of a single container.
Legend:
e = engine [Docker|LXC]
.. = kwargs (variable number of keyword argument)
+-------+ +------------------+ +-----------------+
| RF KW | | ContainerManager | | ContainerEngine |
+---+---+ +--------+---------+ +--------+--------+
| | |
| 1: new ContainerManager(e) | |
+-+---------------------------->+-+ |
|-| |-| 2: new ContainerEngine |
|-| |-+----------------------->+-+
|-| |-| |-|
|-| +-+ +-+
|-| | |
|-| 3: construct_container(..) | |
|-+---------------------------->+-+ |
|-| |-| 4: init() |
|-| |-+----------------------->+-+
|-| |-| |-| 5: new +-------------+
|-| |-| |-+-------->| Container A |
|-| |-| |-| +-------------+
|-| |-|<-----------------------+-|
|-| +-+ +-+
|-| | |
|-| 6: acquire_all_containers() | |
|-+---------------------------->+-+ |
|-| |-| 7: acquire() |
|-| |-+----------------------->+-+
|-| |-| |-|
|-| |-| |-+--+
|-| |-| |-| | 8: is_container_present()
|-| |-| True/False |-|<-+
|-| |-| |-|
|-| |-| |-|
+---------------------------------------------------------------------------------------------+
| |-| ALT [isRunning & force] |-| |-|--+ |
| |-| |-| |-| | 8a: destroy() |
| |-| |-| |-<--+ |
+---------------------------------------------------------------------------------------------+
|-| |-| |-|
|-| +-+ +-+
|-| | |
|-| 9: create_all_containers() | |
|-+---------------------------->+-+ |
|-| |-| 10: create() |
|-| |-+----------------------->+-+
|-| |-| |-+--+
|-| |-| |-| | 11: wait('RUNNING')
|-| |-| |-<--+
|-| +-+ +-+
|-| | |
+---------------------------------------------------------------------------------------------+
| |-| ALT | | |
| |-| (install_vpp, configure_vpp) | | |
| |-| | | |
+---------------------------------------------------------------------------------------------+
|-| | |
|-| 12: destroy_all_containers() | |
|-+---------------------------->+-+ |
|-| |-| 13: destroy() |
|-| |-+----------------------->+-+
|-| |-| |-|
|-| +-+ +-+
|-| | |
+++ | |
| | |
+ + +
Container Data Structure¶
Container is represented in Python L1 library as a separate Class with instance
variables and no methods except overriden __getattr__ and __setattr__.
Instance variables are assigned to container dynamically during the
construct_container(**kwargs) call and are passed down from the RF keyword.
Usage example:
| Construct VNF containers on all DUTs
| | [Arguments] | ${technology} | ${image} | ${cpu_count}=${1} | ${count}=${1}
| | ...
| | ${group}= | Set Variable | VNF
| | ${skip_cpus}= | Evaluate | ${vpp_cpus}+${system_cpus}
| | Import Library | resources.libraries.python.ContainerUtils.ContainerManager
| | ... | engine=${container_engine} | WITH NAME | ${group}
| | ${duts}= | Get Matches | ${nodes} | DUT*
| | :FOR | ${dut} | IN | @{duts}
| | | ${env}= | Create List | DEBIAN_FRONTEND=noninteractive
| | | ${mnt}= | Create List | /tmp:/mnt/host | /dev:/dev
| | | ${cpu_node}= | Get interfaces numa node | ${nodes['${dut}']}
| | | ... | ${dut1_if1} | ${dut1_if2}
| | | Run Keyword | ${group}.Construct containers
| | | ... | name=${dut}_${group} | node=${nodes['${dut}']} | mnt=${mnt}
| | | ... | image=${container_image} | cpu_count=${container_cpus}
| | | ... | cpu_skip=${skip_cpus} | cpuset_mems=${cpu_node}
| | | ... | cpu_shared=${False} | env=${env} | count=${container_count}
| | | ... | install_dkms=${container_install_dkms}
| | Append To List | ${container_groups} | ${group}
Mandatory parameters to create standalone container are: node, name,
image [imagevar], cpu_count, cpu_skip, cpuset_mems,
cpu_shared.
There is no parameters check functionality. Passing required arguments is in coder responsibility. All the above parameters are required to calculate the correct cpu placement. See documentation for the full reference.
Kubernetes¶
Kubernetes is implemented as separate library KubernetesUtils.py,
with a class with the same name. This utility provides an API for L2
Robot Keywords to control kubectl installed on each of DUTs. One
time initialization script, resources/libraries/bash/k8s_setup.sh
does reset/init kubectl, applies Calico v2.6.3 and initializes the
csit namespace. CSIT namespace is required to not to interfere with
existing setups and it further simplifies apply/get/delete
Pod/ConfigMap operations on SUTs.
Kubernetes utility is based on YAML templates to avoid crafting the huge
YAML configuration files, what would lower the readability of code and
requires complicated algorithms. The templates can be found in
resources/templates/kubernetes and can be leveraged in the future
for other separate tasks.
Two types of YAML templates are defined:
- Static - do not change between deployments, that is infrastructure containers like Kafka, Calico, ETCD.
- Dynamic - per test suite/case topology YAML files e.g. SFC_controller, VNF, VSWITCH.
Making own python wrapper library of kubectl instead of using the
official Python package allows to control and deploy environment over
the SSH library without the need of using isolated driver running on
each of DUTs.
Ligato¶
Ligato integration does require to compile the vpp-agent tool and build the
bundled Docker image. Compilation of vpp-agent depends on specific VPP. In
ligato/vpp-agent repository there are well prepared scripts for building the
Docker image. Building docker image is possible via series of commands:
git clone https://github.com/ligato/vpp-agent
cd vpp_agent/docker/dev_vpp_agent
sudo docker build -t dev_vpp_agent --build-arg AGENT_COMMIT=<agent commit id>\
--build-arg VPP_COMMIT=<vpp commit id> --no-cache .
sudo ./shrink.sh
cd ../prod_vpp_agent
sudo ./build.sh
sudo ./shrink.sh
CSIT requires Docker image to include the desired VPP version (per patch testing, nightly testing, on demand testing).
The entire build process of building dev_vpp_agent image heavily depends
on internet connectivity and also takes a significant amount of time (~1-1.5h
based on internet bandwidth and allocated resources). The optimal solution would
be to build the image on jenkins slave, transfer the Docker image to DUTs and
execute separate suite of tests.
To adress the amount of time required to build dev_vpp_agent image, we can
pull existing specific version of `dev_vpp_agent` and exctract the
`vpp-agent` from it.
We created separate sets of Jenkins jobs, that will be executing following:
- Clone latest CSIT and Ligato repositaries.
- Pull specific version of
dev_vpp_agentimage from Dockerhub. - Extract VPP API (from
.debpackage) and copy intodev_vpp_agentimage - Rebuild vpp-agent and extract outside image.
- Build
prod_vpp_imageDocker image fromdev_vpp_agentimage. - Transfer
prod_vpp_agentimage to DUTs. - Execute subset of performance tests designed for Ligato testing.
+-----------------------------------------------+
| ubuntu:16.04 <-----| Base image on Dockerhub
+------------------------^----------------------+
|
|
+------------------------+----------------------+
| ligato/dev_vpp_agent <------| Pull this image from
+------------------------^----------------------+ | Dockerhub ligato/dev_vpp_agent:<version>
|
| Rebuild and extract agent.tar.gz from dev_vpp_agent
+------------------------+----------------------+
| prod_vpp_agent <------| Build by passing own
+-----------------------------------------------+ | vpp.tar.gz (from nexus
| or built by JJB) and
| agent.tar.gz extracted
| from ligato/dev_vpp_agent
Approximate size of vnf-agent docker images:
REPOSITORY TAG IMAGE ID CREATED SIZE
dev-vpp-agent latest 78c53bd57e2 6 weeks ago 9.79GB
prod_vpp_agent latest f68af5afe601 5 weeks ago 443MB
In CSIT we need to create separate performance suite under
tests/kubernetes/perf which contains modified Suite setup in comparison
to standard perf tests. This is due to reason that VPP will act as vswitch in
Docker image and not as standalone installed service.
Tested Topologies¶
Listed CSIT container networking test topologies are defined with DUT containerized VPP switch forwarding packets between NF containers. Each NF container runs their own instance of VPP in L2XC configuration.
Following container networking topologies are tested in CSIT-1904.2:
- LXC topologies:
- eth-l2xcbase-eth-2memif-1lxc.
- eth-l2bdbasemaclrn-eth-2memif-1lxc.
- Docker topologies:
- eth-l2xcbase-eth-2memif-1docker.
- eth-l2xcbase-eth-1memif-1docker
- Kubernetes/Ligato topologies:
- eth-1drcl2bdbasemaclrn-eth-2memif-1drcl2xc-1paral
- eth-1drcl2bdbasemaclrn-eth-2memif-2drcl2xc-1horiz
- eth-1drcl2bdbasemaclrn-eth-2memif-4drcl2xc-1horiz
- eth-1drcl2bdbasemaclrn-eth-4memif-2drcl2xc-1chain
- eth-1drcl2bdbasemaclrn-eth-8memif-4drcl2xc-1chain
- eth-1drcl2xcbase-eth-2memif-1drcl2xc-1paral
- eth-1drcl2xcbase-eth-2memif-2drcl2xc-1horiz
- eth-1drcl2xcbase-eth-2memif-4drcl2xc-1horiz
- eth-1drcl2xcbase-eth-4memif-2drcl2xc-1chain
- eth-1drcl2xcbase-eth-8memif-4drcl2xc-1chain
References¶
| [lxc] | Linux Containers |
| [lxcnamespace] | Resource management: Linux kernel Namespaces and cgroups. |
| [stgraber] | (1, 2) LXC 1.0: Blog post series. |
| [lxcsecurity] | (1, 2) Linux Containers Security. |
| [capabilities] | Linux manual - capabilities - overview of Linux capabilities. |
| [cgroup1] | Linux kernel documentation: cgroups. |
| [cgroup2] | Linux kernel documentation: Control Group v2. |
| [selinux] | SELinux Project Wiki. |
| [lxcsecfeatures] | LXC 1.0: Security features. |
| [lxcsource] | Linux Containers source. |
| [apparmor] | Ubuntu AppArmor. |
| [seccomp] | SECure COMPuting with filters. |
| [docker] | Docker. |
| [k8sdoc] | Kubernetes documentation. |
| [ligato] | Ligato. |
| [govpp] | FD.io goVPP project. |
| [vppagent] | Ligato vpp-agent. |
| [imagevar] | Image parameter is required in initial commit version. There is plan to implement container build class to build Docker/LXC image. |