mirror of https://github.com/ceph/ceph
333 lines
9.0 KiB
ReStructuredText
333 lines
9.0 KiB
ReStructuredText
|
|
|
|
.. _orchestrator-modules:
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
ceph-mgr orchestrator modules
|
|
=============================
|
|
|
|
.. warning::
|
|
|
|
This is developer documentation, describing Ceph internals that
|
|
are only relevant to people writing ceph-mgr orchestrator modules.
|
|
|
|
In this context, *orchestrator* refers to some external service that
|
|
provides the ability to discover devices and create Ceph services. This
|
|
includes external projects such as Rook.
|
|
|
|
An *orchestrator module* is a ceph-mgr module (:ref:`mgr-module-dev`)
|
|
which implements common management operations using a particular
|
|
orchestrator.
|
|
|
|
Orchestrator modules subclass the ``Orchestrator`` class: this class is
|
|
an interface, it only provides method definitions to be implemented
|
|
by subclasses. The purpose of defining this common interface
|
|
for different orchestrators is to enable common UI code, such as
|
|
the dashboard, to work with various different backends.
|
|
|
|
|
|
.. graphviz::
|
|
|
|
digraph G {
|
|
subgraph cluster_1 {
|
|
volumes [label="mgr/volumes"]
|
|
rook [label="mgr/rook"]
|
|
dashboard [label="mgr/dashboard"]
|
|
orchestrator_cli [label="mgr/orchestrator"]
|
|
orchestrator [label="Orchestrator Interface"]
|
|
cephadm [label="mgr/cephadm"]
|
|
|
|
label = "ceph-mgr";
|
|
}
|
|
|
|
volumes -> orchestrator
|
|
dashboard -> orchestrator
|
|
orchestrator_cli -> orchestrator
|
|
orchestrator -> rook -> rook_io
|
|
orchestrator -> cephadm
|
|
|
|
|
|
rook_io [label="Rook"]
|
|
|
|
rankdir="TB";
|
|
}
|
|
|
|
Behind all the abstraction, the purpose of orchestrator modules is simple:
|
|
enable Ceph to do things like discover available hardware, create and
|
|
destroy OSDs, and run MDS and RGW services.
|
|
|
|
A tutorial is not included here: for full and concrete examples, see
|
|
the existing implemented orchestrator modules in the Ceph source tree.
|
|
|
|
Glossary
|
|
--------
|
|
|
|
Stateful service
|
|
a daemon that uses local storage, such as OSD or mon.
|
|
|
|
Stateless service
|
|
a daemon that doesn't use any local storage, such
|
|
as an MDS, RGW, nfs-ganesha, iSCSI gateway.
|
|
|
|
Label
|
|
arbitrary string tags that may be applied by administrators
|
|
to hosts. Typically administrators use labels to indicate
|
|
which hosts should run which kinds of service. Labels are
|
|
advisory (from human input) and do not guarantee that hosts
|
|
have particular physical capabilities.
|
|
|
|
Drive group
|
|
collection of block devices with common/shared OSD
|
|
formatting (typically one or more SSDs acting as
|
|
journals/dbs for a group of HDDs).
|
|
|
|
Placement
|
|
choice of which host is used to run a service.
|
|
|
|
Key Concepts
|
|
------------
|
|
|
|
The underlying orchestrator remains the source of truth for information
|
|
about whether a service is running, what is running where, which
|
|
hosts are available, etc. Orchestrator modules should avoid taking
|
|
any internal copies of this information, and read it directly from
|
|
the orchestrator backend as much as possible.
|
|
|
|
Bootstrapping hosts and adding them to the underlying orchestration
|
|
system is outside the scope of Ceph's orchestrator interface. Ceph
|
|
can only work on hosts when the orchestrator is already aware of them.
|
|
|
|
Where possible, placement of stateless services should be left up to the
|
|
orchestrator.
|
|
|
|
Completions and batching
|
|
------------------------
|
|
|
|
All methods that read or modify the state of the system can potentially
|
|
be long running. Therefore the module needs to schedule those operations.
|
|
|
|
Each orchestrator module implements its own underlying mechanisms
|
|
for completions. This might involve running the underlying operations
|
|
in threads, or batching the operations up before later executing
|
|
in one go in the background. If implementing such a batching pattern, the
|
|
module would do no work on any operation until it appeared in a list
|
|
of completions passed into *process*.
|
|
|
|
Error Handling
|
|
--------------
|
|
|
|
The main goal of error handling within orchestrator modules is to provide debug information to
|
|
assist users when dealing with deployment errors.
|
|
|
|
.. autoclass:: OrchestratorError
|
|
.. autoclass:: NoOrchestrator
|
|
.. autoclass:: OrchestratorValidationError
|
|
|
|
|
|
In detail, orchestrators need to explicitly deal with different kinds of errors:
|
|
|
|
1. No orchestrator configured
|
|
|
|
See :class:`NoOrchestrator`.
|
|
|
|
2. An orchestrator doesn't implement a specific method.
|
|
|
|
For example, an Orchestrator doesn't support ``add_host``.
|
|
|
|
In this case, a ``NotImplementedError`` is raised.
|
|
|
|
3. Missing features within implemented methods.
|
|
|
|
E.g. optional parameters to a command that are not supported by the
|
|
backend (e.g. the hosts field in :func:`Orchestrator.apply_mons` command with the rook backend).
|
|
|
|
See :class:`OrchestratorValidationError`.
|
|
|
|
4. Input validation errors
|
|
|
|
The ``orchestrator`` module and other calling modules are supposed to
|
|
provide meaningful error messages.
|
|
|
|
See :class:`OrchestratorValidationError`.
|
|
|
|
5. Errors when actually executing commands
|
|
|
|
The resulting Completion should contain an error string that assists in understanding the
|
|
problem. In addition, :func:`Completion.is_errored` is set to ``True``
|
|
|
|
6. Invalid configuration in the orchestrator modules
|
|
|
|
This can be tackled similar to 5.
|
|
|
|
|
|
All other errors are unexpected orchestrator issues and thus should raise an exception that are then
|
|
logged into the mgr log file. If there is a completion object at that point,
|
|
:func:`Completion.result` may contain an error message.
|
|
|
|
|
|
Excluded functionality
|
|
----------------------
|
|
|
|
- Ceph's orchestrator interface is not a general purpose framework for
|
|
managing linux servers -- it is deliberately constrained to manage
|
|
the Ceph cluster's services only.
|
|
- Multipathed storage is not handled (multipathing is unnecessary for
|
|
Ceph clusters). Each drive is assumed to be visible only on
|
|
a single host.
|
|
|
|
Host management
|
|
---------------
|
|
|
|
.. automethod:: Orchestrator.add_host
|
|
.. automethod:: Orchestrator.remove_host
|
|
.. automethod:: Orchestrator.get_hosts
|
|
.. automethod:: Orchestrator.update_host_addr
|
|
.. automethod:: Orchestrator.add_host_label
|
|
.. automethod:: Orchestrator.remove_host_label
|
|
|
|
.. autoclass:: HostSpec
|
|
|
|
Devices
|
|
-------
|
|
|
|
.. automethod:: Orchestrator.get_inventory
|
|
.. autoclass:: InventoryFilter
|
|
|
|
.. py:currentmodule:: ceph.deployment.inventory
|
|
|
|
.. autoclass:: Devices
|
|
:members:
|
|
|
|
.. autoclass:: Device
|
|
:members:
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
Placement
|
|
---------
|
|
|
|
A :ref:`orchestrator-cli-placement-spec` defines the placement of
|
|
daemons of a specific service.
|
|
|
|
In general, stateless services do not require any specific placement
|
|
rules as they can run anywhere that sufficient system resources
|
|
are available. However, some orchestrators may not include the
|
|
functionality to choose a location in this way. Optionally, you can
|
|
specify a location when creating a stateless service.
|
|
|
|
|
|
.. py:currentmodule:: ceph.deployment.service_spec
|
|
|
|
.. autoclass:: PlacementSpec
|
|
:members:
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
|
|
Services
|
|
--------
|
|
|
|
.. autoclass:: ServiceDescription
|
|
|
|
.. py:currentmodule:: ceph.deployment.service_spec
|
|
|
|
.. autoclass:: ServiceSpec
|
|
:members:
|
|
:private-members:
|
|
:noindex:
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
.. automethod:: Orchestrator.describe_service
|
|
|
|
.. automethod:: Orchestrator.service_action
|
|
.. automethod:: Orchestrator.remove_service
|
|
|
|
|
|
Daemons
|
|
-------
|
|
|
|
.. automethod:: Orchestrator.list_daemons
|
|
.. automethod:: Orchestrator.remove_daemons
|
|
.. automethod:: Orchestrator.daemon_action
|
|
|
|
.. autoclass:: DaemonDescription
|
|
.. autoclass:: DaemonDescriptionStatus
|
|
|
|
OSD management
|
|
--------------
|
|
|
|
.. automethod:: Orchestrator.create_osds
|
|
|
|
.. automethod:: Orchestrator.blink_device_light
|
|
.. autoclass:: DeviceLightLoc
|
|
|
|
.. _orchestrator-osd-replace:
|
|
|
|
OSD Replacement
|
|
^^^^^^^^^^^^^^^
|
|
|
|
See :ref:`rados-replacing-an-osd` for the underlying process.
|
|
|
|
Replacing OSDs is fundamentally a two-staged process, as users need to
|
|
physically replace drives. The orchestrator therefore exposes this two-staged process.
|
|
|
|
Phase one is a call to :meth:`Orchestrator.remove_daemons` with ``destroy=True`` in order to mark
|
|
the OSD as destroyed.
|
|
|
|
|
|
Phase two is a call to :meth:`Orchestrator.create_osds` with a Drive Group with
|
|
|
|
.. py:currentmodule:: ceph.deployment.drive_group
|
|
|
|
:attr:`DriveGroupSpec.osd_id_claims` set to the destroyed OSD ids.
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
Services
|
|
--------
|
|
|
|
.. automethod:: Orchestrator.add_daemon
|
|
.. automethod:: Orchestrator.apply_mon
|
|
.. automethod:: Orchestrator.apply_mgr
|
|
.. automethod:: Orchestrator.apply_mds
|
|
.. automethod:: Orchestrator.apply_rbd_mirror
|
|
|
|
.. py:currentmodule:: ceph.deployment.service_spec
|
|
|
|
.. autoclass:: RGWSpec
|
|
:noindex:
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
.. automethod:: Orchestrator.apply_rgw
|
|
|
|
.. py:currentmodule:: ceph.deployment.service_spec
|
|
|
|
.. autoclass:: NFSServiceSpec
|
|
|
|
.. py:currentmodule:: orchestrator
|
|
|
|
.. automethod:: Orchestrator.apply_nfs
|
|
|
|
Upgrades
|
|
--------
|
|
|
|
.. automethod:: Orchestrator.upgrade_available
|
|
.. automethod:: Orchestrator.upgrade_start
|
|
.. automethod:: Orchestrator.upgrade_status
|
|
.. autoclass:: UpgradeStatusSpec
|
|
|
|
Utility
|
|
-------
|
|
|
|
.. automethod:: Orchestrator.available
|
|
.. automethod:: Orchestrator.get_feature_set
|
|
|
|
Client Modules
|
|
--------------
|
|
|
|
.. autoclass:: OrchestratorClientMixin
|
|
:members:
|