Ganeti automatic instance allocation
====================================
-Documents Ganeti version 2.1
+Documents Ganeti version 2.5
.. contents::
cluster, indexed by instance name; the contents are similar to the
instance definitions for the allocate mode, with the addition of:
- admin_up
+ admin_state
if this instance is set to run (but not the actual status of the
instance)
In all cases, it includes:
type
- the request type; this can be either ``allocate``, ``relocate`` or
- ``multi-evacuate``; the ``allocate`` request is used when a new
- instance needs to be placed on the cluster, while the ``relocate``
- request is used when an existing instance needs to be moved within
- the cluster; the ``multi-evacuate`` protocol requests that the
- script computes the optimal relocate solution for all secondary
- instances of the given nodes
+ the request type; this can be either ``allocate``, ``relocate``,
+ ``change-group`` or ``node-evacuate``. The
+ ``allocate`` request is used when a new instance needs to be placed
+ on the cluster. The ``relocate`` request is used when an existing
+ instance needs to be moved within its node group.
+
+ The ``multi-evacuate`` protocol used to request that the script
+ computes the optimal relocate solution for all secondary instances
+ of the given nodes. It is now deprecated and needs only be
+ implemented if backwards compatibility with Ganeti 2.4 and lower is
+ needed.
+
+ The ``change-group`` request is used to relocate multiple instances
+ across multiple node groups. ``node-evacuate`` evacuates instances
+ off their node(s). These are described in a separate :ref:`design
+ document <multi-reloc-detailed-design>`.
For both allocate and relocate mode, the following extra keys are needed
in the ``request`` dictionary:
name
the name of the instance; if the request is a realocation, then this
name will be found in the list of instances (see below), otherwise
- is the FQDN of the new instance
+ is the FQDN of the new instance; type *string*
required_nodes
how many nodes should the algorithm return; while this information
can be deduced from the instace's disk template, it's better if
this computation is left to Ganeti as then allocator scripts are
- less sensitive to changes to the disk templates
+ less sensitive to changes to the disk templates; type *integer*
disk_space_total
the total disk space that will be used by this instance on the
(new) nodes; again, this information can be computed from the list
of instance disks and its template type, but Ganeti is better
- suited to compute it
+ suited to compute it; type *integer*
+
+.. pyassert::
+
+ constants.DISK_ACCESS_SET == set([constants.DISK_RDONLY,
+ constants.DISK_RDWR])
Allocation needs, in addition:
instance (in the order they are exported to the hypervisor):
mode
- either ``r`` or ``w`` denoting if the disk is read-only or
+ either :pyeval:`constants.DISK_RDONLY` or
+ :pyeval:`constants.DISK_RDWR` denoting if the disk is read-only or
writable
size
relocate_from
a list of nodes to move the instance away from (note that with
Ganeti 2.0, this list will always contain a single node, the
- current secondary of the instance)
+ current secondary of the instance); type *list of strings*
+
+As for ``node-evacuate``, it needs the following request arguments:
+
+ instances
+ a list of instance names to evacuate; type *list of strings*
-In the case of multi-evacuate, there's one single request argument (in
-addition to ``type``):
+ evac_mode
+ specify which instances to evacuate; one of ``primary-only``,
+ ``secondary-only``, ``all``, type *string*
- evac_nodes
- the names of the nodes to be evacuated
+``change-group`` needs the following request arguments:
+
+ instances
+ a list of instance names whose group to change; type
+ *list of strings*
+
+ target_groups
+ must either be the empty list, or contain a list of group UUIDs that
+ should be considered for relocating instances to; type
+ *list of strings*
Response message
~~~~~~~~~~~~~~~~
entry in the input message, otherwise Ganeti will consider the result
as failed
- for multi-evacuation mode, this is a list of lists; each element of
- the list is a list of instance name and the new secondary node
+ for the ``node-evacuate`` and ``change-group`` modes, this is a
+ dictionary containing, among other information, a list of lists of
+ serialized opcodes; see the :ref:`design document
+ <multi-reloc-result>` for a detailed description
.. note:: Current Ganeti version accepts either ``result`` or ``nodes``
as a backwards-compatibility measure (older versions only supported
}
}
-Input message, node evacuation::
-
- {
- "version": 2,
- ...
- "request": {
- "type": "multi-evacuate",
- "evac_nodes": [
- "node2"
- ],
- }
- }
-
Response messages
~~~~~~~~~~~~~~~~~
Reference implementation
~~~~~~~~~~~~~~~~~~~~~~~~
-Ganeti's default iallocator is "hail" which is part of the separate
-ganeti-htools project. In order to see its source code please clone
-``git://git.ganeti.org/htools.git``. Note that htools is implemented
-using the Haskell programming language.
+Ganeti's default iallocator is "hail" which is available when "htools"
+components have been enabled at build time (see :doc:`install-quick` for
+more details).
.. vim: set textwidth=72 :
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