схема базы данных сервера (_Server database schema)
Имя (Name)
ovsdb-server - _Server database schema
Every ovsdb-server (version 2.9 or later) always hosts an
instance of this schema, which holds information on the status
and configuration of the server itself. This database is read-
only. This manpage describes the schema for this database.
Резюме таблицы (Table summary)
The following list summarizes the purpose of each of the tables
in the _Server database. Each table is described in more detail
on a later page.
Table Purpose
Database Databases.
Database TABLE
This table describes the databases hosted by the database server,
with one row per database. As its database configuration and
status changes, the server automatically and immediately updates
the table to match.
The OVSDB protocol specified in RFC 7047 does not provide a way
for an OVSDB client to find out about some kinds of configuration
changes, such as about databases added or removed while a client
is connected to the server, or databases changing between
read/write and read-only due to a transition between active and
backup roles. This table provides a solution: clients can monitor
the table's contents to find out about important changes.
Traditionally, ovsdb-server disconnects all of its clients when a
significant configuration change occurs, because this prompts a
well-written client to reassess what is available from the server
when it reconnects. Because this table provides an alternative
and more efficient way to find out about those changes, OVS 2.9
also introduces the set_db_change_aware RPC, documented in
ovsdb-server(7), to allow clients to suppress this disconnection
behavior.
When a database is removed from the server, in addition to
Database table updates, the server sends canceled messages, as
described in RFC 7047 section 4.1.4, in reply to outstanding
transactions for the removed database. The server also cancels
any outstanding monitoring initiated by monitor or monitor_cond
requested on the removed database, sending the monitor_canceled
RPC described in ovsdb-server(7). Only clients that disable
disconnection with set_db_change_aware receive these messages.
Clients can use the _uuid column in this table as a generation
number. The server generates a fresh _uuid every time it adds a
database, so that removing and then re-adding a database to the
server causes its row _uuid to change.
Summary:
name string
model string, one of clustered, relay, or
standalone
schema optional string
connected boolean
Clustered Databases:
leader boolean
cid optional uuid
sid optional uuid
index optional integer
Details:
name: string
The database's name, as specified in its schema.
model: string, one of clustered, relay, or standalone
The storage model: standalone for a standalone or active-
backup database, clustered for a clustered database, relay
for a relay database.
schema: optional string
The database schema, as a JSON string. In the case of a
clustered database, this is empty until it finishes
joining its cluster. In the case of a relay database, this
is empty until it connects to the relay source.
connected: boolean
True if the database is connected to its storage. A
standalone database is always connected. A clustered
database is connected if the server is in contact with a
majority of its cluster. A relay database is connected if
the server is in contact with the relay source, i.e. is
connected to the server it syncs from. An unconnected
database cannot be modified and its data might be
unavailable or stale.
Clustered Databases:
These columns are most interesting and in some cases only
relevant for clustered databases, that is, those where the model
column is clustered.
leader: boolean
True if the database is the leader in its cluster. For a
standalone or active-backup database, this is always true.
For a relay database, this is always false.
cid: optional uuid
The cluster ID for this database, which is the same for
all of the servers that host this particular clustered
database. For a standalone, active-backup or relay
database, this is empty.
sid: optional uuid
The server ID for this database, different for each server
that hosts a particular clustered database. A server that
hosts more than one clustered database will have a
different sid in each one. For a standalone, active-backup
or relay database, this is empty.
index: optional integer
For a clustered database, the index of the log entry
currently exposed to clients. For a given server, this
increases monotonically. When a client switches from one
server to another in a cluster, it can ensure that it
never sees an older snapshot of data by avoiding servers
that have index less than the largest value they have
already observed.
For a standalone, active-backup or relay database, this is
empty.
