mirror of
https://github.com/ceph/ceph
synced 2024-12-26 13:33:57 +00:00
200 lines
7.0 KiB
ReStructuredText
200 lines
7.0 KiB
ReStructuredText
===================
|
|
Monitor bootstrap
|
|
===================
|
|
|
|
Terminology:
|
|
|
|
* ``cluster``: a set of monitors
|
|
* ``quorum``: an active set of monitors consisting of a majority of the cluster
|
|
|
|
In order to initialize a new monitor, it must always be fed:
|
|
|
|
#. a logical name
|
|
#. secret keys
|
|
#. a cluster fsid (uuid)
|
|
|
|
In addition, a monitor needs to know two things:
|
|
|
|
#. what address to bind to
|
|
#. who its peers are (if any)
|
|
|
|
There are a range of ways to do both.
|
|
|
|
Logical id
|
|
==========
|
|
|
|
The logical id should be unique across the cluster. It will be
|
|
appended to ``mon.`` to logically describe the monitor in the Ceph
|
|
cluster. For example, if the logical id is ``foo``, the monitor's
|
|
name will be ``mon.foo``.
|
|
|
|
For most users, there is no more than one monitor per host, which
|
|
makes the short hostname logical choice.
|
|
|
|
Secret keys
|
|
===========
|
|
|
|
The ``mon.`` secret key is stored a ``keyring`` file in the ``mon data`` directory. It can be generated
|
|
with a command like::
|
|
|
|
ceph-authtool --create-keyring /path/to/keyring --gen-key -n mon.
|
|
|
|
When creating a new monitor cluster, the keyring should also contain a ``client.admin`` key that can be used
|
|
to administer the system::
|
|
|
|
ceph-authtool /path/to/keyring --gen-key -n client.admin --cap mon 'allow *' --cap osd 'allow *' --cap mds 'allow'
|
|
|
|
The resulting keyring is fed to ``ceph-mon --mkfs`` with the ``--keyring <keyring>`` command-line argument.
|
|
|
|
Cluster fsid
|
|
============
|
|
|
|
The cluster fsid is a normal uuid, like that generated by the ``uuidgen`` command. It
|
|
can be provided to the monitor in two ways:
|
|
|
|
#. via the ``--fsid <uuid>`` command-line argument (or config file option)
|
|
#. via a monmap provided to the new monitor via the ``--monmap <path>`` command-line argument.
|
|
|
|
Monitor address
|
|
===============
|
|
|
|
The monitor address can be provided in several ways.
|
|
|
|
#. via the ``--public-addr <ip[:port]>`` command-line option (or config file option)
|
|
#. via the ``--public-network <cidr>`` command-line option (or config file option)
|
|
#. via the monmap provided via ``--monmap <path>``, if it includes a monitor with our name
|
|
#. via the bootstrap monmap (provided via ``--inject-monmap <path>`` or generated from ``--mon-host <list>``) if it includes a monitor with no name (``noname-<something>``) and an address configured on the local host.
|
|
|
|
Peers
|
|
=====
|
|
|
|
The monitor peers are provided in several ways:
|
|
|
|
#. via the initial monmap, provided via ``--monmap <filename>``
|
|
#. via the bootstrap monmap generated from ``--mon-host <list>``
|
|
#. via the bootstrap monmap generated from ``[mon.*]`` sections with ``mon addr`` in the config file
|
|
#. dynamically via the admin socket
|
|
|
|
However, these methods are not completely interchangeable because of
|
|
the complexity of creating a new monitor cluster without danger of
|
|
races.
|
|
|
|
Cluster creation
|
|
================
|
|
|
|
There are three basic approaches to creating a cluster:
|
|
|
|
#. Create a new cluster by specifying the monitor names and addresses ahead of time.
|
|
#. Create a new cluster by specifying the monitor names ahead of time, and dynamically setting the addresses as ``ceph-mon`` daemons configure themselves.
|
|
#. Create a new cluster by specifying the monitor addresses ahead of time.
|
|
|
|
|
|
Names and addresses
|
|
-------------------
|
|
|
|
Generate a monmap using ``monmaptool`` with the names and addresses of the initial
|
|
monitors. The generated monmap will also include a cluster fsid. Feed that monmap
|
|
to each monitor daemon::
|
|
|
|
ceph-mon --mkfs -i <name> --monmap <initial_monmap> --keyring <initial_keyring>
|
|
|
|
When the daemons start, they will know exactly who they and their peers are.
|
|
|
|
|
|
Addresses only
|
|
--------------
|
|
|
|
The initial monitor addresses can be specified with the ``mon host`` configuration value,
|
|
either via a config file or the command-line argument. This method has the advantage that
|
|
a single global config file for the cluster can have a line like::
|
|
|
|
mon host = a.foo.com, b.foo.com, c.foo.com
|
|
|
|
and will also serve to inform any ceph clients or daemons who the monitors are.
|
|
|
|
The ``ceph-mon`` daemons will need to be fed the initial keyring and cluster fsid to
|
|
initialize themselves:
|
|
|
|
ceph-mon --mkfs -i <name> --fsid <uuid> --keyring <initial_keyring>
|
|
|
|
When the daemons first start up, they will share their names with each other and form a
|
|
new cluster.
|
|
|
|
Names only
|
|
----------
|
|
|
|
In dynamic "cloud" environments, the cluster creator may not (yet)
|
|
know what the addresses of the monitors are going to be. Instead,
|
|
they may want machines to configure and start themselves in parallel
|
|
and, as they come up, form a new cluster on their own. The problem is
|
|
that the monitor cluster relies on strict majorities to keep itself
|
|
consistent, and in order to "create" a new cluster, it needs to know
|
|
what the *initial* set of monitors will be.
|
|
|
|
This can be done with the ``mon initial members`` config option, which
|
|
should list the ids of the initial monitors that are allowed to create
|
|
the cluster::
|
|
|
|
mon initial members = foo, bar, baz
|
|
|
|
The monitors can then be initialized by providing the other pieces of
|
|
information (they keyring, cluster fsid, and a way of determining
|
|
their own address). For example::
|
|
|
|
ceph-mon --mkfs -i <name> --mon-initial-hosts 'foo,bar,baz' --keyring <initial_keyring> --public-addr <ip>
|
|
|
|
When these daemons are started, they will know their own address, but
|
|
not their peers. They can learn those addresses via the admin socket::
|
|
|
|
ceph daemon mon.<id> add_bootstrap_peer_hint <peer ip>
|
|
|
|
Once they learn enough of their peers from the initial member set,
|
|
they will be able to create the cluster.
|
|
|
|
|
|
Cluster expansion
|
|
=================
|
|
|
|
Cluster expansion is slightly less demanding than creation, because
|
|
the creation of the initial quorum is not an issue and there is no
|
|
worry about creating separately independent clusters.
|
|
|
|
New nodes can be forced to join an existing cluster in two ways:
|
|
|
|
#. by providing no initial monitor peers addresses, and feeding them dynamically.
|
|
#. by specifying the ``mon initial members`` config option to prevent the new nodes from forming a new, independent cluster, and feeding some existing monitors via any available method.
|
|
|
|
Initially peerless expansion
|
|
----------------------------
|
|
|
|
Create a new monitor and give it no peer addresses other than its own. For
|
|
example::
|
|
|
|
ceph-mon --mkfs -i <myid> --fsid <fsid> --keyring <mon secret key> --public-addr <ip>
|
|
|
|
Once the daemon starts, you can give it one or more peer addresses to join with::
|
|
|
|
ceph daemon mon.<id> add_bootstrap_peer_hint <peer ip>
|
|
|
|
This monitor will never participate in cluster creation; it can only join an existing
|
|
cluster.
|
|
|
|
Expanding with initial members
|
|
------------------------------
|
|
|
|
You can feed the new monitor some peer addresses initially and avoid badness by also
|
|
setting ``mon initial members``. For example::
|
|
|
|
ceph-mon --mkfs -i <myid> --fsid <fsid> --keyring <mon secret key> --public-addr <ip> --mon-host foo,bar,baz
|
|
|
|
When the daemon is started, ``mon initial members`` must be set via the command line or config file::
|
|
|
|
ceph-mon -i <myid> --mon-initial-members foo,bar,baz
|
|
|
|
to prevent any risk of split-brain.
|
|
|
|
|
|
|
|
|
|
|