containers development plans (July 20 version)

Serge E. Hallyn serge at hallyn.com
Fri Jul 20 10:36:15 PDT 2007


(If you missed earlier parts of this thread, you can catch earlier parts of
this thread starting at
https://lists.linux-foundation.org/pipermail/containers/2007-July/005860.html)

======================  Section 0  ======================
=Status of this document
======================  Section 0  ======================

I've added a 'use cases' section.  That is where we attempt to
explain to people not familiar with containers work why it is
worth integrating upstream.

Srivatsa Vaddagiri is independently gathering additional information
on specific task container subsystems.  That will eventually be
incorporated into the final version of this roadmap.

======================  Section 1  ======================
=Introduction
======================  Section 1  ======================

We are trying to create a roadmap for the next year of
'container' development, to be reported to the upcoming kernel
summit.  Containers here is a bit of an ambiguous term, so we are
taking it to mean all of:

	1. namespaces
                kernel resource namespaces to support resource isolation
                and virtualization for virtual servers and application
                checkpoint/restart.
	2. task containers framework
                the task containers (or, as Paul Jackson suggests, resource
                containers) framework by Paul Menage which especially
                provides a framework for subsystems which perform resource
                accounting and limits.
	3. checkpoint/restart

======================  Section 2  ======================
=Detailed development plans
======================  Section 2  ======================

A (still under construction) list of features we expect to be worked on
next year looks like this:

        1. completion of ongoing namespaces
                pid namespace
                        push merged patchset upstream
                        kthread cleanup
                                especially nfs
                                autofs
                        af_unix credentials (stores pid_t?)
                net namespace
                ro bind mounts
        2. continuation with new namespaces
                devpts, console, and ttydrivers
                user
                time
                namespace management tools
                namespace entering  (using one of:)
                        bind_ns()
                        ns container subsystem
                        (vs refuse this functionality)
                multiple /sys mounts
                        break /sys into smaller chunks?
                        shadow dirs vs namespaces
                multiple proc mounts
                        likely need to extend on the work done for pid namespaces
                        i.e. other /proc files will need some care
				virtualization of statistics for 'top', etc
        3. any additional work needed for virtual servers?
                i.e. in-kernel keyring usage for cross-usernamespace permissions, etc
                        nfs and rpc updates needed?
                        general security fixes
                                per-container capabilities?
                        device access controls
                                e.g. root in container should not have access to /dev/sda by default)
                        filesystems access controls

        4. task containers functionality
                base features
                        virtualized continerfs mounts
                                to support vserver mgmnt of sub-containers
                        locking cleanup
                        control file API simplification
                        control file prefixing with subsystem name
		userpace RBCE to provide controls for
			users
			groups
			pgrp
			executable
                specific containers
                        split cpusets into
                                cpuset
                                memset
                        network
                                connect/bind/accept controller using iptables
                        network flow id control
                        userspace per-container OOM handler
			per-container swap
			per-container disk I/O scheduling

        5. checkpoint/restart
                memory c/r
                        (there are a few designs and prototypes)
                        (though this may be ironed out by then)
                        per-container swapfile?
                overall checkpoint strategy  (one of:)
                        in-kernel
                        userspace-driven
                        hybrid
                overall restart strategy
                use freezer API
                use suspend-to-disk?
                sysvipc
                        "set identifier" syscall
		pid namespace
                        clone_with_pid()


======================  Section 3  ======================
=Use cases
======================  Section 3  ======================

	1, Namespaces:

	The most commonly listed uses for namespaces are virtual
	servers and checkpoint restart.  Other uses are debugging
	(running tests in not-quite-virtual-servers) and resource
	isolation, such as the use of mounts namespaces to simulate
	multi-level directories for LSPP.

	2. Task Containers:

	(Vatsa to fill in)

	3. Checkpoint/restart

	load balancing:
	applications can be migrated from high-load systems to ones
	with a lower load.  Long-running applications can be checkpointed
	(or migrated) to start a short-running high-load job, then
	restarted.

	kernel upgrades:
	A long-running application - or whole virtual server - can
	be migrated or checkpointed so that the system can be
	rebooted, and the application can continue to run


======================  Section 4  ======================
=Involved parties
======================  Section 4  ======================

In the list of stakeholders, I try to guess based on past comments and
contributions what *general* area they are most likely to contribute in.
I may try to narrow those down later, but am just trying to get something
out the door right now before my next computer breaks.

Stakeholders:
        Eric Biederman
                everything
        google
                task containers
        ibm (serge, dave, cedric, daniel)
                namespaces
		checkpoint/restart
	bull (benjamin, pierre)
                namespaces
		checkpoint/restart
        ibm (balbir, vatsa)
		task containers
        kerlabs
                checkpoint/restart
        openvz
                everything
        NEC Japan (Masahiko Takahashi)
                checkpoint/restart
        Linux-VServer
                namespaces+containers
        zap project
                checkpoint/restart
        planetlab
                everything
        hp
                (i must have lost an email - what are they
		interested in working on?)
        XtreemOS
                checkpoint/restart
	Fujitsu/VA Linux Japan
		resource control

Is anyone else still missing from the list?

thanks,
-serge


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