1OVSDB-SERVER(7)                  Open vSwitch                  OVSDB-SERVER(7)
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NAME

6       ovsdb-server - Open vSwitch Database Server Protocol
7

DESCRIPTION

9       ovsdb-server  implements  the  Open  vSwitch  Database (OVSDB) protocol
10       specified in RFC 7047.  This document provides clarifications  for  how
11       ovsdb-server  implements the protocol and describes the extensions that
12       it provides beyond RFC 7047.  Numbers in section headings refer to cor‐
13       responding sections in RFC 7047.
14
15   3.1 JSON Usage
16       RFC  4627  says  that names within a JSON object should be unique.  The
17       Open vSwitch JSON parser discards all but the last  value  for  a  name
18       that is specified more than once.
19
20       The  definition  of <error> allows for implementation extensions.  Cur‐
21       rently ovsdb-server uses the following additional error strings  (which
22       might change in later releases):
23
24       syntax error or unknown column
25              The  request  could not be parsed as an OVSDB request.  An addi‐
26              tional syntax member, whose value  is  a  string  that  contains
27              JSON,  may  narrow  down the particular syntax that could not be
28              parsed.
29
30       internal error
31              The request triggered a bug in ovsdb-server.
32
33       ovsdb error
34              A map or set contains a duplicate key.
35
36       permission error
37              The request was denied by the role-based access  control  exten‐
38              sion, introduced in version 2.8.
39
40   3.2 Schema Format
41       RFC 7047 requires the version field in <database-schema>.  Current ver‐
42       sions of ovsdb-server allow it  to  be  omitted  (future  versions  are
43       likely to require it).
44
45       RFC  7047  allows columns that contain weak references to be immutable.
46       This raises the issue of the behavior of the weak  reference  when  the
47       rows  that  it references are deleted.  Since version 2.6, ovsdb-server
48       forces columns that contain weak references to be mutable.
49
50       Since version 2.8, the table name RBAC_Role is used internally  by  the
51       role-based  access  control extension to ovsdb-server and should not be
52       used for purposes other than defining mappings of role names  to  table
53       access  permissions.  This table has one row per role name and the fol‐
54       lowing columns:
55
56       name   The role name.
57
58       permissions
59              A map of table name to a reference to a row in a  separate  per‐
60              mission table.
61
62       The  separate RBAC permission table has one row per access control con‐
63       figuration and the following columns:
64
65       name   The name of the table to which the row applies.
66
67       authorization
68              The set of column names and column:key pairs to be compared with
69              the  client ID in order to determine the authorization status of
70              the requested operation.
71
72       insert_delete
73              A boolean value, true if authorized insertions and deletions are
74              allowed, false if no insertions or deletions are allowed.
75
76       update The  set  of  columns  and column:key pairs for which authorized
77              update and mutate operations should be permitted.
78
79   4 Wire Protocol
80       The original OVSDB specifications included the following reasons, omit‐
81       ted  from  RFC 7047, to operate JSON-RPC directly over a stream instead
82       of over HTTP:
83
84       · JSON-RPC is a peer-to-peer protocol, but HTTP is a client-server pro‐
85         tocol,  which is a poor match.  Thus, JSON-RPC over HTTP requires the
86         client to periodically poll the server to receive server requests.
87
88       · HTTP is more complicated than stream connections and doesn’t  provide
89         any corresponding advantage.
90
91       · The JSON-RPC specification for HTTP transport is incomplete.
92
93   4.1.3 Transact
94       Since  version 2.8, role-based access controls can be applied to opera‐
95       tions within a transaction that would modify the contents of the  data‐
96       base  (these  operations include row insert, row delete, column update,
97       and column mutate). Role-based access controls  are  applied  when  the
98       database  schema  contains a table with the name RBAC_Role and the con‐
99       nection on which the transaction request was received has an associated
100       role  name  (from the role column in the remote connection table). When
101       role-based access controls are enabled, transactions that are otherwise
102       well-formed may be rejected depending on the client’s role, ID, and the
103       contents of the RBAC_Role table and associated permissions table.
104
105   4.1.5 Monitor
106       For backward compatibility, ovsdb-server  currently  permits  a  single
107       <monitor-request>  to  be  used instead of an array; it is treated as a
108       single-element array.  Future versions  of  ovsdb-server  might  remove
109       this compatibility feature.
110
111       Because  the  <json-value> parameter is used to match subsequent update
112       notifications (see below) to the request, it must be unique  among  all
113       active  monitors.   ovsdb-server rejects attempt to create two monitors
114       with the same identifier.
115
116       When a given client sends a transact request that changes a table  that
117       the same client is monitoring, ovsdb-server always sends the update (or
118       update2 or update3) for these changes before it sends the reply to  the
119       transact  request.   Thus,  when a client receives a transact reply, it
120       can know immediately what changes (if any) the transaction  made.   (If
121       ovsdb-server  might  use  the other order, then a client that wishes to
122       act on based on the results of its own transactions would not know when
123       this was guaranteed to have taken place.)
124
125   4.1.7 Monitor Cancellation
126       When  a database monitored by a session is removed, and database change
127       awareness is enabled for the session (see Section 4.1.16), the database
128       server  spontaneously cancels all monitors (including conditional moni‐
129       tors described in Section 4.1.12) for the removed database.   For  each
130       canceled monitor, it issues a notification in the following form:
131
132          "method": "monitor_canceled"
133          "params": [<json-value>]
134          "id": null
135
136   4.1.12 Monitor_cond
137       A  new  monitor  method  added  in Open vSwitch version 2.6.  The moni‐
138       tor_cond request enables a client to replicate subsets of tables within
139       an OVSDB database by requesting notifications of changes to rows match‐
140       ing one of the conditions specified in where by receiving the specified
141       contents  of  these  rows  when table updates occur.  monitor_cond also
142       allows  a  more  efficient  update  notifications  by  receiving   <ta‐
143       ble-updates2> notifications (described below).
144
145       The  monitor  method  described  in Section 4.1.5 also applies to moni‐
146       tor_cond, with the following exceptions:
147
148       · RPC request method becomes monitor_cond.
149
150       · Reply result follows <table-updates2>, described in Section 4.1.14.
151
152       · Subsequent changes are sent to the client using the  update2  monitor
153         notification, described in Section 4.1.14
154
155       · Update  notifications  are being sent only for rows matching [<condi‐
156         tion>*].
157
158       The request object has the following members:
159
160          "method": "monitor_cond"
161          "params": [<db-name>, <json-value>, <monitor-cond-requests>]
162          "id": <nonnull-json-value>
163
164       The <json-value> parameter is used to match subsequent update notifica‐
165       tions  (see below) to this request.  The <monitor-cond-requests> object
166       maps the name of the table to an array of <monitor-cond-request>.
167
168       Each <monitor-cond-request> is an object with the following members:
169
170          "columns": [<column>*]            optional
171          "where": [<condition>*]           optional
172          "select": <monitor-select>        optional
173
174       The columns, if present, define the columns within the table to be mon‐
175       itored  that  match  conditions.  If not present, all columns are moni‐
176       tored.
177
178       The where, if present, is a JSON array of <condition> and boolean  val‐
179       ues.  If not present or condition is an empty array, implicit True will
180       be considered and updates on all rows will be sent.
181
182       <monitor-select> is an object with the following members:
183
184          "initial": <boolean>              optional
185          "insert": <boolean>               optional
186          "delete": <boolean>               optional
187          "modify": <boolean>               optional
188
189       The contents of this object specify how the columns or table are to  be
190       monitored as explained in more detail below.
191
192       The response object has the following members:
193
194          "result": <table-updates2>
195          "error": null
196          "id": same "id" as request
197
198       The  <table-updates2>  object is described in detail in Section 4.1.14.
199       It contains the contents of the  tables  for  which  initial  rows  are
200       selected.   If no tables initial contents are requested, then result is
201       an empty object.
202
203       Subsequently, when changes to a specified table that match one  of  the
204       conditions  in  <monitor-cond-request>  are  committed, the changes are
205       automatically sent to the client using the update2 monitor notification
206       (see Section 4.1.14).  This monitoring persists until the JSON-RPC ses‐
207       sion terminates or until the client  sends  a  monitor_cancel  JSON-RPC
208       request.
209
210       Each  <monitor-cond-request>  specifies  one or more conditions and the
211       manner in which the rows that match the conditions are to be monitored.
212       The  circumstances  in  which  an update notification is sent for a row
213       within the table are determined by <monitor-select>:
214
215       · If initial is omitted or true, every row in the original  table  that
216         matches  one of the conditions is sent as part of the response to the
217         monitor_cond request.
218
219       · If insert is omitted or true, update notifications are sent for  rows
220         newly inserted into the table that match conditions or for rows modi‐
221         fied in the table so that their old version does not match the condi‐
222         tion and new version does.
223
224       · If  delete is omitted or true, update notifications are sent for rows
225         deleted from the table that match conditions or for rows modified  in
226         the table so that their old version does match the conditions and new
227         version does not.
228
229       · If modify is omitted or true, update notifications are sent  whenever
230         a  row  in the table that matches conditions in both old and new ver‐
231         sion is modified.
232
233       Both monitor and monitor_cond sessions can exist concurrently. However,
234       monitor  and monitor_cond shares the same <json-value> parameter space;
235       it must be unique among all monitor and monitor_cond sessions.
236
237   4.1.13 Monitor_cond_change
238       The monitor_cond_change request enables a client to change an  existing
239       monitor_cond  replication of the database by specifying a new condition
240       and columns for each replicated table.  Currently changing the  columns
241       set is not supported.
242
243       The request object has the following members:
244
245          "method": "monitor_cond_change"
246          "params": [<json-value>, <json-value>, <monitor-cond-update-requests>]
247          "id": <nonnull-json-value>
248
249       The  <json-value>  parameter  should have a value of an existing condi‐
250       tional monitoring session from this client. The second <json-value>  in
251       params  array  is  the  requested value for this session. This value is
252       valid only after monitor_cond_change is committed. A user can use these
253       values  to distinguish between update messages before conditions update
254       and after. The <monitor-cond-update-requests> object maps the  name  of
255       the  table  to  an  array  of <monitor-cond-update-request>.  Monitored
256       tables not included in <monitor-cond-update-requests> retain their cur‐
257       rent conditions.
258
259       Each <monitor-cond-update-request> is an object with the following mem‐
260       bers:
261
262          "columns": [<column>*]         optional
263          "where": [<condition>*]        optional
264
265       The columns specify a new array of columns to  be  monitored,  although
266       this feature is not yet supported.
267
268       The where specify a new array of conditions to be applied to this moni‐
269       toring session.
270
271       The response object has the following members:
272
273          "result": null
274          "error": null
275          "id": same "id" as request
276
277       Subsequent <table-updates2> notifications are described  in  detail  in
278       Section  4.1.14 in the RFC.  If insert contents are requested by origi‐
279       nal monitor_cond request, <table-updates2> will contain rows that match
280       the  new condition and do not match the old condition.  If deleted con‐
281       tents are requested by origin monitor  request,  <table-updates2>  will
282       contain  any  matched  rows by old condition and not matched by the new
283       condition.
284
285       Changes according to the new conditions are automatically sent  to  the
286       client using the update2 monitor notification.  An update, if any, as a
287       result of a condition change, will be sent to  the  client  before  the
288       reply to the monitor_cond_change request.
289
290   4.1.14 Update2 notification
291       The  update2 notification is sent by the server to the client to report
292       changes in tables that are being  monitored  following  a  monitor_cond
293       request as described above. The notification has the following members:
294
295          "method": "update2"
296          "params": [<json-value>, <table-updates2>]
297          "id": null
298
299       The  <json-value>  in  params  is  the  same as the value passed as the
300       <json-value> in params for the  corresponding  monitor  request.   <ta‐
301       ble-updates2>  is  an  object  that  maps  from  a table name to a <ta‐
302       ble-update2>.  A <table-update2> is an object that maps from row’s UUID
303       to a <row-update2> object. A <row-update2> is an object with one of the
304       following members:
305
306       "initial": <row>
307              present for initial updates
308
309       "insert": <row>
310              present for insert updates
311
312       "delete": <row>
313              present for delete updates
314
315       "modify": <row>"
316              present for modify updates
317
318       The format of <row> is described in Section 5.1.
319
320       <row> is always a null object for a  delete  update.   In  initial  and
321       insert  updates,  <row>  omits  columns  whose values equal the default
322       value of the column type.
323
324       For a modify update, <row> contains only the columns that are modified.
325       <row>  stores  the  difference  between the old and new value for those
326       columns, as described below.
327
328       For columns with single value, the difference is the value of  the  new
329       column.
330
331       The  difference  between  two sets are all elements that only belong to
332       one of the sets.
333
334       The difference between two maps are  all  key-value  pairs  whose  keys
335       appears  in  only  one of the maps, plus the key-value pairs whose keys
336       appear in both maps but with different values.   For  the  latter  ele‐
337       ments, <row> includes the value from the new column.
338
339       Initial  views  of rows are not presented in update2 notifications, but
340       in the response object to the monitor_cond request.  The formatting  of
341       the <table-updates2> object, however, is the same in either case.
342
343   4.1.15 Monitor_cond_since
344       A  new  monitor  method  added in Open vSwitch version 2.12.  The moni‐
345       tor_cond_since request enables a client to request  changes  that  hap‐
346       pened after a specific transaction id. A client can use this feature to
347       request only latest changes after a server connection reset instead  of
348       re-transfer all data from the server again.
349
350       The  monitor_cond  method  described  in Section 4.1.12 also applies to
351       monitor_cond_since, with the following exceptions:
352
353       · RPC request method becomes monitor_cond_since.
354
355       · Reply result includes extra parameters.
356
357       · Subsequent changes are sent to the client using the  update3  monitor
358         notification, described in Section 4.1.16
359
360       The request object has the following members:
361
362          "method": "monitor_cond_since"
363          "params": [<db-name>, <json-value>, <monitor-cond-requests>, <last-txn-id>]
364          "id": <nonnull-json-value>
365
366       The  <last-txn-id>  parameter is the transaction id that identifies the
367       latest data the client already has, and  it  requests  server  to  send
368       changes AFTER this transaction (exclusive).
369
370       All other parameters are the same as monitor_cond method.
371
372       The response object has the following members:
373
374          "result": [<found>, <last-txn-id>, <table-updates2>]
375          "error": null
376          "id": same "id" as request
377
378       The  <found>  is  a  boolean  value  that  tells  if  the <last-txn-id>
379       requested by client is found in server’s history or not. If  true,  the
380       changes  after  that version up to current is sent. Otherwise, all data
381       is sent.
382
383       The <last-txn-id> is the transaction  id  that  identifies  the  latest
384       transaction  included  in  the  changes  in  <table-updates2>  of  this
385       response, so that client can keep tracking.   If  there  is  no  change
386       involved  in  this response, it is the same as the <last-txn-id> in the
387       request if <found> is true, or zero uuid if <found> is false.   If  the
388       server does not support transaction uuid, it will be zero uuid as well.
389
390       All other parameters are the same as in response object of monitor_cond
391       method.
392
393       Like in monitor_cond, subsequent changes that match conditions in <mon‐
394       itor-cond-request>  are  automatically  sent  to  the client, but using
395       update3 monitor notification (see Section 4.1.16), instead of update2.
396
397   4.1.16 Update3 notification
398       The update3 notification is sent by the server to the client to  report
399       changes   in   tables  that  are  being  monitored  following  a  moni‐
400       tor_cond_since request as described above.  The  notification  has  the
401       following members:
402
403          "method": "update3"
404          "params": [<json-value>, <last-txn-id>, <table-updates2>]
405          "id": null
406
407       The  <last-txn-id>  is  the same as described in the response object of
408       monitor_cond_since.
409
410       All other parameters are the same as in  update2  monitor  notification
411       (see Section 4.1.14).
412
413   4.1.17 Get Server ID
414       A  new  RPC method added in Open vSwitch version 2.7.  The request con‐
415       tains the following members:
416
417          "method": "get_server_id"
418          "params": null
419          "id": <nonnull-json-value>
420
421       The response object contains the following members:
422
423          "result": "<server_id>"
424          "error": null
425          "id": same "id" as request
426
427       <server_id> is JSON string that contains a UUID that  uniquely  identi‐
428       fies  the running OVSDB server process.  A fresh UUID is generated when
429       the process restarts.
430
431   4.1.18 Database Change Awareness
432       RFC 7047 does not provide a way for a client to  find  out  about  some
433       kinds  of  configuration  changes,  such  as  about  databases added or
434       removed while a client is connected to the server, or databases  chang‐
435       ing between read/write and read-only due to a transition between active
436       and backup roles.  Traditionally, ovsdb-server disconnects all  of  its
437       clients  when  this happens, because this prompts a well-written client
438       to reassess what is available from the server when it reconnects.
439
440       OVS 2.9 provides a way for clients to keep  track  of  these  kinds  of
441       changes,  by  monitoring  the  Database  table  in the _Server database
442       introduced in this  release  (see  ovsdb-server(5)  for  details).   By
443       itself,  this  does  not  suppress ovsdb-server disconnection behavior,
444       because a client might monitor this database without understanding  its
445       special semantics.  Instead, ovsdb-server provides a special request:
446
447          "method": "set_db_change_aware"
448          "params": [<boolean>]
449          "id": <nonnull-json-value>
450
451       If  the  boolean  in  the  request  is  true, it suppresses the connec‐
452       tion-closing behavior for the current connection,  and  false  restores
453       the default behavior.  The reply is always the same:
454
455          "result": {}
456          "error": null
457          "id": same "id" as request
458
459   4.1.19 Schema Conversion
460       Open vSwitch 2.9 adds a new JSON-RPC request to convert an online data‐
461       base from one schema to another.  The request  contains  the  following
462       members:
463
464          "method": "convert"
465          "params": [<db-name>, <database-schema>]
466          "id": <nonnull-json-value>
467
468       Upon  receipt,  the server converts database <db-name> to schema <data‐
469       base-schema>.  The schema’s name must be <db-name>.  The conversion  is
470       atomic,  consistent,  isolated,  and durable.  The data in the database
471       must be valid when interpreted under <database-schema>, with  only  one
472       exception:  data  for  tables  and columns that do not exist in the new
473       schema are ignored.  Columns that exist in <database-schema> but not in
474       the  database are set to their default values.  All of the new schema’s
475       constraints apply in full.
476
477       If the conversion is successful, the server notifies clients  that  use
478       the  set_db_change_aware RPC introduced in Open vSwitch 2.9 and cancels
479       their outstanding transactions and monitors.   The  server  disconnects
480       other  clients, enabling them to notice the change when they reconnect.
481       The server sends the following reply:
482
483          "result": {}
484          "error": null
485          "id": same "id" as request
486
487       If the conversion fails, then the server sends an error  reply  in  the
488       following form:
489
490          "result": null
491          "error": [<error>]
492          "id": same "id" as request
493
494   5.1 Notation
495       For  <condition>, RFC 7047 only allows the use of !=, ==, includes, and
496       excludes operators with set types.  Open vSwitch 2.4 and  later  extend
497       <condition>  to allow the use of <, <=, >=, and > operators with a col‐
498       umn with type “set of 0 or 1 integer” and an integer argument, and with
499       “set of 0 or 1 real” and a real argument.  These conditions evaluate to
500       false when the column is empty, and otherwise as described in RFC  7047
501       for integer and real types.
502
503       <condition>  is  specified in Section 5.1 in the RFC with the following
504       change: A condition can be either a 3-element JSON array  as  described
505       in  the  RFC  or a boolean value. In case of an empty array an implicit
506       true boolean value will be considered.
507
508   5.2.6 Wait, 5.2.7 Commit, 5.2.9 Comment
509       RFC 7047 says that the wait, commit, and  comment  operations  have  no
510       corresponding  result object.  This is not true.  Instead, when such an
511       operation is successful, it yields a result object with no members.
512

AUTHOR

514       The Open vSwitch Development Community
515
517       2019, The Open vSwitch Development Community
518
519
520
521
5222.12                             Sep 10, 2019                  OVSDB-SERVER(7)
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