wiki:ReferenceGuide

Version 4 (modified by Ted Faber, 7 years ago) (diff)

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Reference Guide

This document describes the details of the commands and data structures that make up the containers system. The User Guide /Tutotial? provides useful context about the workflows and goals of the system that inform these technical details.

containerize.py

The containerize.py command creates a DETER experiment made up of containers. The containerize.py program is available from /share/containers/containerize.py on users.isi.deterlab.net. A sample invocation is:

$ /share/containers/containerize.py MyProject MyExperiment ~/mytopology.tcl

It will create a new experiment in MyProject called MyExperiment containing the experiment topology in mytopology.tcl. All the topology creation commands supported by DETER are supported by the conatainerization system, but emulab/DETER program agents are not. Emulab/DETER start commands are supported.

Containers will create an experiment in a group if the project parameter is of the form project/group. To start an experiment in the testing group of the DETER project, the first parameter is specified as DETER/testing.

Either an ns2 file or a topdl description is supported. Ns2 descriptions must end with .tcl or .ns. Other files are assumed to be topdl descriptions.

By default, containerize.py program will partition the topology into openvz containers, packed 10 containers per physical computer. If the topology is already partitioned - at least one element has a conatiners::partition atttribute - containerize.py will not partition it. The --force-partition flag causes containerize.py to partition the experiment regardless of the presence of containers:partition attributes.

If container types have been assigned to nodes using the containers:node_type attribute, containerize.py will respect them. Valid container types for the containers:node_type attribute or the --default-container parameter are:

Parameter Container
embedded_pnode Physical Node
qemu Qemu VM
openvz Openvz Container
process ViewOS process

The containerize.py command takes several parameters that can change its behavior:

--default-container=kind
Containerize nodes without a container type into kind. If no nodes have been assigned containers, this puts all them into kind containers.
--force-partition
Partition the experiment whether or not it has been paritioned already
--packing=int
Attempt to put int containers into each physical node. The default --packing is 10.
--config=filename
Read configuration variables from filename the configuration values are discussed below.
--pnode-types=type1[,type2...]
Override the site configuration and request nodes of type1 (or type2 etc.) as host nodes.
--end-node-shaping
Attempt to do end node traffic shaping even in containers connected by VDE switches. This works with qemu nodes, but not process nodes. Topologies that include both openvz nodes and qemu nodes that shape traffic should use this.
--vde-switch-shaping
Do traffic shaping in VDE switches. Probably the default, but that is controlled in the site configuration.
--openvz-diskspace
Set the default openvz disk space size. The suffixes G and M stand for gigabytes and megabytes.
--openvz-template
Set the default openvz template. Templates are described in the users guide.
--image
Construct a visualization of the virtual topology and leave it in the experiment directories (default)
--no-image
Do not construct a visualization of the virtual topology and leave it in the experiment directories
--debug
Print additional diagnostics and leave failed DETER experiments on the testbed
--keep-tmp
Do not remove temporary files - for debugging only

This invocation:

$ ./containerize.py --packing 25 --default-container=qemu --force-partition DeterTest faber-packem ~/experiment.xml

takes the topology in ~/experiment.xml (which must be topdl), packs it into 25 qemu containers per physical node, and creates an experiment called DeterTest/faber-packem that can be swapped in. If experiment.xml were already partitioned, it will be re-partitioned. If some nodes in that topology were assigned to openvz nodes already, those nodes will be still be in openvz containers.

The result of a successful containerize.py run is a DETER experiment that can be swapped in.

More detailed examples are available in the tutorial

Site Configuration File

The site configuration file is an attribute value pair file parsed by a python ConfigParser that sets overall container parameters. Many of these have legacy internal names.

The default site configuration is in /share/containers/site.conf on users.isi.deterlab.net.

Acceptable values (and their DETER defaults) are:

backend_server
The IRC server used as a backend coordination service for grandstand. Will be replaced by MAGI. Default: boss.isi.deterlab.net:6667
grandstand_port
Port that third party applications can contact grandstand on. Will be replaced by MAGI. Default: 4919
maverick_url
Default image used by qemu containers. Default: http://scratch/benito/pangolinbz.img.bz2
url_base
Base URL of the DETER web interface on which users can see experiments. Default: http://www.isi.deterlab.net/
qemu_host_hw
Hardware used by containers. Default: pc2133,bpc2133,MicroCloud
xmlrpc_server
Host and port from which to request experiment creation. Default: boss.isi.deterlab.net:3069
qemu_host_os
OSID to request for qemu container nodess. Default: Ubuntu1204-64-STD
exec_root
Root of the directory tree holding containers software and libraries. Developers often change this. Default: /share/containers
openvz_host_os
OSID to request for openvz nodes. Default CentOS6-64-openvz
openvz_guest_url
Location to load the openvz template from. Default: %(exec_root)s/images/ubuntu-10.04-x86.tar.gz
switch_shaping
True if switched containers (see below) should do traffic shaping in the VDE switch that connects them. Default: true
switched_containers
A list of the containers that are networked with VDE switches. Default: qemu,process
openvz_template_dir
The directory that stores openvz template files. Default: %(exec_root)s/images/ (that is the images directory in the exec_root directory defined in the site config file.

Container Notes

Different container types have some quirks. This section lists limitations of each container.

Openvz

Openvz containers use a custom OS image to support their virtualization. They cannot share physical resources with other containers. A physical node holding openvz containers holds only openvz containers. They are interconnected with one another through bridges and kernel virtual networking rather than through VDE switches (as qemu and process containers are)). As a result, openvz containers provide network delays using per-container endpoint traffic shaping. This means that they cannot correctly interconnect with traffic sphped qemu nodes.

Interconnections: VDE switches and local networking

The various containers are interconnected using either local kernel virtual networking or VDE switches. Kernel networking is lower overhead because it does not require process context switching, but VDE switches are a more general solution.

Network behavior changes - loss, delay, rate limits - are introduced into a network of containers using one of two mechanisms: inserting elements into a VDE switch topology or end node traffic shaping. Inserting elements into the VDE switch topology allows the system to modify the behavior for all packets passing through it. Generally this means all packets to or from a host, as the container system inserts these elements in the path between the node and the switch.

This figure shows 3 containers sharing a virtual LAN on a VED switch with no traffic shaping:

Openvz containers are interconnected through kernel networking directly to support their high efficiency, and because talking to another container implies leaving the physical machine. They induce network delays through end node traffic shaping.

Qemu nodes can support either end node tra

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