Basic Notation
--------------
+OVSDB uses JSON, as defined by RFC 4627, for its schema format and its
+wire protocol format. The JSON implementation in Open vSwitch has the
+following limitations:
+
+ - Null bytes (\u0000) are not allowed in strings.
+
+ - Only UTF-8 encoding is supported. (RFC 4627 also mentions
+ UTF-16BE, UTF-16LE, and UTF-32.)
+
+ - RFC 4627 says that names within a JSON object should be unique.
+ The Open vSwitch JSON parser discards all but the last value
+ for a name that is specified more than once.
+
The descriptions below use the following shorthand notations for JSON
values. Additional notation is presented later.
A JSON object with the following members:
"name": <id> required
- "comment": <string> optional
"tables": {<id>: <table-schema>, ...} required
The "name" identifies the database as a whole. It must be
provided to most JSON-RPC requests to identify the database being
- operated on. The "comment" optionally provides more information
- about the database. The value of "tables" is a JSON object whose
- names are table names and whose values are <table-schema>s.
+ operated on. The value of "tables" is a JSON object whose names
+ are table names and whose values are <table-schema>s.
<table-schema>
A JSON object with the following members:
- "comment": <string> optional
"columns": {<id>: <column-schema>, ...} required
+ "maxRows": <integer> optional
- The "comment" optionally provides information about this table for
- a human reader. The value of "columns" is a JSON object whose
- names are column names and whose values are <column-schema>s.
+ The value of "columns" is a JSON object whose names are column
+ names and whose values are <column-schema>s.
Every table has the following columns whose definitions are not
included in the schema:
the database process is stopped and then started again, each
"_version" also changes to a new random value.
+ If "maxRows" is specified, as a positive integer, it limits the
+ maximum number of rows that may be present in the table. This is
+ a "deferred" constraint, enforced only at transaction commit time
+ (see the "transact" request below). If "maxRows" is not
+ specified, the size of the table is limited only by the resources
+ available to the database server.
+
<column-schema>
A JSON object with the following members:
- "comment": <string> optional
"type": <type> required
"ephemeral": <boolean> optional
+ "mutable": <boolean> optional
- The "comment" optionally provides information about this column
- for a human reader. The "type" specifies the type of data stored
- in this column. If "ephemeral" is specified as true, then this
- column's values are not guaranteed to be durable; they may be lost
- when the database restarts.
+ The "type" specifies the type of data stored in this column. If
+ "ephemeral" is specified as true, then this column's values are
+ not guaranteed to be durable; they may be lost when the database
+ restarts. If "mutable" is specified as false, then this column's
+ values may not be modified after they are initially set with the
+ "insert" operation.
<type>
<atomic-type> or a JSON object with the following members:
"type": <atomic-type> required
+ "enum": <value> optional
"minInteger": <integer> optional, integers only
"maxInteger": <integer> optional, integers only
"minReal": <real> optional, reals only
"maxReal": <real> optional, reals only
- "reMatch": <string> optional, strings only
- "reComment": <string> optional, strings only
"minLength": <integer> optional, strings only
"maxLength": <integer> optional, strings only
"refTable": <id> optional, uuids only
+ "refType": "strong" or "weak" optional, only with "refTable"
An <atomic-type> by itself is equivalent to a JSON object with a
single member "type" whose value is the <atomic-type>.
+ "enum" may be specified as a <value> whose type is a set of one
+ or more values specified for the member "type". If "enum" is
+ specified, then the valid values of the <base-type> are limited to
+ those in the <value>.
+
+ "enum" is mutually exclusive with the following constraints.
+
If "type" is "integer", then "minInteger" or "maxInteger" or both
may also be specified, restricting the valid integer range. If
both are specified, then the maxInteger must be greater than or
specified, then the maxReal must be greater than or equal to
minReal.
- If "type" is "string", then:
+ If "type" is "string", then "minLength" and "maxLength" or both
+ may be specified, restricting the valid length of value strings.
+ If both are specified, then maxLength must be greater than or
+ equal to minLength. String length is measured in characters (not
+ bytes or UTF-16 code units).
- "reMatch" may be a JavaScript (Perl 5-like) regular expression
- that restricts the allowed values. The regular expression
- must match the entire string value, that is, it is treated as
- if it begins with ^ and ends with $, regardless of whether it
- really does.
-
- If "reMatch" is specified, then "reComment" may be a string
- that describes the allowed values, phrased so that it fits
- into a sentence such as "This value must be...".
+ If "type" is "uuid", then "refTable", if present, must be the name
+ of a table within this database. If "refTable" is specified, then
+ "refType" may also be specified. If "refTable" is set, the effect
+ depends on "refType":
- "minLength" and "maxLength" or both may be specified,
- restricting the valid length of value strings. If both are
- specified, then maxLength must be greater than or equal to
- minLength. String length is measured in characters (not bytes
- or UTF-16 code units).
+ - If "refType" is "strong" or if "refType" is omitted, the
+ allowed UUIDs are limited to UUIDs for rows in the named
+ table.
- If "type" is "uuid", then "refTable", if present, must be the name
- of a table within this database. If "refTable" is set, the
- allowed UUIDs are limited to UUIDs for rows in the named table.
+ - If "refType" is "weak", then any UUIDs are allowed, but
+ UUIDs that do not correspond to rows in the named table will
+ be automatically deleted.
"refTable" constraints are "deferred" constraints: they are
enforced only at transaction commit time (see the "transact"
* The JSON-RPC specification for HTTP transport is incomplete.
+We are using TCP port 6632 for the database JSON-RPC connection.
+
The database wire protocol consists of the following JSON-RPC methods:
list_dbs
When the commit was attempted, a column's value referenced the
UUID for a row that did not exist in the table named by the
- column's <base-type> key or value "refTable". (This can be
- caused by inserting a row that references a nonexistent row,
- by deleting a row that is still referenced by another row, by
- specifying the UUID for a row in the wrong table, and other
- ways.)
+ column's <base-type> key or value "refTable" that has a
+ "refType" of "strong". (This can be caused by inserting a row
+ that references a nonexistent row, by deleting a row that is
+ still referenced by another row, by specifying the UUID for a
+ row in the wrong table, and other ways.)
+
+ "error": "constraint violation"
+
+ A column with a <base-type> key or value "refTable" whose
+ "refType" is "weak" became empty due to deletion(s) caused
+ because the rows that it referenced were deleted (or never
+ existed, if the column's row was inserted within the
+ transaction), and this column is not allowed to be empty
+ because its <type> has a "min" of 1.
+
+ "error": "constraint violation"
+
+ The number of rows in a table exceeds the maximum number
+ permitted by the table's "maxRows" value (see <table-schema>).
If "params" contains one or more "wait" operations, then the
transaction may take an arbitrary amount of time to complete. The
"params": [<db-name>, <json-value>, <monitor-requests>] required
"id": <nonnull-json-value> required
-<monitor-requests> is an object that maps from a table name to a
-<monitor-request>.
+<monitor-requests> is an object that maps from a table name to an
+array of <monitor-request> objects. For backward compatibility, a
+single <monitor-request> may be used instead of an array; it is
+treated as a single-element array.
Each <monitor-request> is an object with the following members:
"id": same "id" as request
This JSON-RPC request enables a client to replicate tables or subsets
-of tables within database <db-name>. Each <monitor-request> specifies
-a table to be replicated. The JSON-RPC response to the "monitor"
-includes the initial contents of each table. Afterward, when changes
-to those tables are committed, the changes are automatically sent to
-the client using the "update" monitor notification. This monitoring
-persists until the JSON-RPC session terminates or until the client
-sends a "monitor_cancel" JSON-RPC request.
+of tables within database <db-name>. Each element of
+<monitor-requests> specifies a table to be replicated. The JSON-RPC
+response to the "monitor" includes the initial contents of each table,
+unless disabled (see below). Afterward, when changes to those tables
+are committed, the changes are automatically sent to the client using
+the "update" monitor notification. This monitoring persists until the
+JSON-RPC session terminates or until the client sends a
+"monitor_cancel" JSON-RPC request.
-Each <monitor-request> describes how to monitor a table:
+Each <monitor-request> describes how to monitor columns in a table:
The circumstances in which an "update" notification is sent for a
row within the table are determined by <monitor-select>:
sent whenever when a row in the table is modified.
The "columns" member specifies the columns whose values are
- monitored. If "columns" is omitted, all columns in the table,
- except for "_uuid", are monitored.
+ monitored. It must not contain duplicates. If "columns" is
+ omitted, all columns in the table, except for "_uuid", are
+ monitored.
+
+If there is more than one <monitor-request> in an array of them, then
+each <monitor-request> in the array should specify both "columns" and
+"select", and the "columns" must be non-overlapping sets.
The "result" in the JSON-RPC response to the "monitor" request is a
<table-updates> object (see below) that contains the contents of the
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