.. contents:: :depth: 4
-Detailed design
-===============
-
As for 2.1 we divide the 2.2 design into three areas:
- core changes, which affect the master daemon/job queue/locking or
all/most logical units
- logical unit/feature changes
-- external interface changes (eg. command line, os api, hooks, ...)
+- external interface changes (e.g. command line, OS API, hooks, ...)
+
Core changes
-------------
+============
Master Daemon Scaling improvements
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+----------------------------------
Current state and shortcomings
-++++++++++++++++++++++++++++++
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Currently the Ganeti master daemon is based on four sets of threads:
scalability issues:
Core daemon connection handling
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
++++++++++++++++++++++++++++++++
Since the 16 client worker threads handle one connection each, it's very
easy to exhaust them, by just connecting to masterd 16 times and not
informed that everything is proceeding, and doesn't need to time out.
Wait for job change
-^^^^^^^^^^^^^^^^^^^
++++++++++++++++++++
The REQ_WAIT_FOR_JOB_CHANGE luxi operation makes the relevant client
thread block on its job for a relative long time. This is another easy
contention (see below).
Job Queue lock
-^^^^^^^^^^^^^^
+++++++++++++++
The job queue lock is quite heavily contended, and certain easily
reproducible workloads show that's it's very easy to put masterd in
remote rpcs to complete (starting, finishing, and submitting jobs)
Proposed changes
-++++++++++++++++
+~~~~~~~~~~~~~~~~
In order to be able to interact with the master daemon even when it's
under heavy load, and to make it simpler to add core functionality
understand, debug, and scale.
Connection handling
-^^^^^^^^^^^^^^^^^^^
++++++++++++++++++++
We'll move the main thread of ganeti-masterd to asyncore, so that it can
share the mainloop code with all other Ganeti daemons. Then all luxi
thread on the socket.
Wait for job change
-^^^^^^^^^^^^^^^^^^^
++++++++++++++++++++
The REQ_WAIT_FOR_JOB_CHANGE luxi request is changed to be
subscription-based, so that the executing thread doesn't have to be
them at a maximum rate (lower priority).
Job Queue lock
-^^^^^^^^^^^^^^
+++++++++++++++
In order to decrease the job queue lock contention, we will change the
code paths in the following ways, initially:
Remote procedure call timeouts
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+------------------------------
Current state and shortcomings
-++++++++++++++++++++++++++++++
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The current RPC protocol used by Ganeti is based on HTTP. Every request
consists of an HTTP PUT request (e.g. ``PUT /hooks_runner HTTP/1.0``)
unresponsive node daemon cases.
Proposed changes
-++++++++++++++++
+~~~~~~~~~~~~~~~~
RPC glossary
-^^^^^^^^^^^^
+++++++++++++
Function call ID
Unique identifier returned by ``ganeti-noded`` after invoking a
Process started by ``ganeti-noded`` to call actual (backend) function.
Protocol
-^^^^^^^^
+++++++++
Initially we chose HTTP as our RPC protocol because there were existing
libraries, which, unfortunately, turned out to miss important features
would be an implicit ping-mechanism.
Request handling
-^^^^^^^^^^^^^^^^
+++++++++++++++++
To support the protocol changes described above, the way the node daemon
handles request will have to change. Instead of forking and handling
Inter-cluster instance moves
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+----------------------------
Current state and shortcomings
-++++++++++++++++++++++++++++++
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
With the current design of Ganeti, moving whole instances between
different clusters involves a lot of manual work. There are several ways
this process in Ganeti 2.2.
Proposed changes
-++++++++++++++++
+~~~~~~~~~~~~~~~~
Authorization, Authentication and Security
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+++++++++++++++++++++++++++++++++++++++++++
Until now, each Ganeti cluster was a self-contained entity and wouldn't
talk to other Ganeti clusters. Nodes within clusters only had to trust
certificate while providing a client certificate to the server.
Copying data
-^^^^^^^^^^^^
+++++++++++++
To simplify the implementation, we decided to operate at a block-device
level only, allowing us to easily support non-DRBD instance moves.
directly, where it'll be written to the new block device directly again.
Workflow
-^^^^^^^^
+++++++++
#. Third party tells source cluster to shut down instance, asks for the
instance specification and for the public part of an encryption key
#. Source cluster removes the instance if requested
Instance move in pseudo code
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+++++++++++++++++++++++++++++
.. highlight:: python
.. highlight:: text
Miscellaneous notes
-^^^^^^^^^^^^^^^^^^^
++++++++++++++++++++
- A very similar system could also be used for instance exports within
the same cluster. Currently OpenSSH is being used, but could be
Privilege separation
-~~~~~~~~~~~~~~~~~~~~
+--------------------
Current state and shortcomings
-++++++++++++++++++++++++++++++
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
All Ganeti daemons are run under the user root. This is not ideal from a
security perspective as for possible exploitation of any daemon the user
is in the same group.
Implementation
-++++++++++++++
+~~~~~~~~~~~~~~
For Ganeti 2.2 the implementation will be focused on a the RAPI daemon
only. This involves changes to ``daemons.py`` so it's possible to drop
Feature changes
----------------
+===============
KVM Security
-~~~~~~~~~~~~
+------------
Current state and shortcomings
-++++++++++++++++++++++++++++++
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Currently all kvm processes run as root. Taking ownership of the
hypervisor process, from inside a virtual machine, would mean a full
option of subverting other basic services on the cluster (eg: ssh).
Proposed changes
-++++++++++++++++
+~~~~~~~~~~~~~~~~
We would like to decrease the surface of attack available if an
hypervisor is compromised. We can do so adding different features to
subvert the node.
Dropping privileges in kvm to a single user (easy)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+++++++++++++++++++++++++++++++++++++++++++++++++++
By passing the ``-runas`` option to kvm, we can make it drop privileges.
The user can be chosen by an hypervisor parameter, so that each instance
- read unprotected data on the node filesystem
Running kvm in a chroot (slightly harder)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
++++++++++++++++++++++++++++++++++++++++++
By passing the ``-chroot`` option to kvm, we can restrict the kvm
process in its own (possibly empty) root directory. We need to set this
Running kvm with a pool of users (slightly harder)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+++++++++++++++++++++++++++++++++++++++++++++++++++
If rather than passing a single user as an hypervisor parameter, we have
a pool of useable ones, we can dynamically choose a free one to use and
can still be combined with the chroot benefits.
Running iptables rules to limit network interaction (easy)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
These don't need to be handled by Ganeti, but we can ship examples. If
the users used to run VMs would be blocked from sending some or all
Running kvm inside a container (even harder)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+++++++++++++++++++++++++++++++++++++++++++++
Recent linux kernels support different process namespaces through
control groups. PIDs, users, filesystems and even network interfaces can
just rely on iptables.
Implementation plan
-+++++++++++++++++++
+~~~~~~~~~~~~~~~~~~~
We will first implement dropping privileges for kvm processes as a
single user, and most probably backport it to 2.1. Then we'll ship
External interface changes
---------------------------
+==========================
OS API
-~~~~~~
+------
The OS variants implementation in Ganeti 2.1 didn't prove to be useful
enough to alleviate the need to hack around the Ganeti API in order to
OS version
-++++++++++
+~~~~~~~~~~
A new ``os_version`` file will be supported by Ganeti. This file is not
required, but if existing, its contents will be checked for consistency
intra-cluster migration.
Parameters
-++++++++++
+~~~~~~~~~~
The interface between Ganeti and the OS scripts will be based on
environment variables, and as such the parameters and their values will
need to be valid in this context.
Names
-^^^^^
++++++
The parameter names will be declared in a new file, ``parameters.list``,
together with a one-line documentation (whitespace-separated). Example::
parameters which differ in case only.
Values
-^^^^^^
+++++++
The values of the parameters are, from Ganeti's point of view,
completely freeform. If a given parameter has, from the OS' point of
Environment variables
-+++++++++++++++++++++
+^^^^^^^^^^^^^^^^^^^^^
The parameters will be exposed in the environment upper-case and
prefixed with the string ``OSP_``. For example, a parameter declared in
projects / ganeti-local / commitdiff