ovsdb/ovsdb-server.1.in

   1 .\" -*- nroff -*-
   2 .de IQ
   3 .  br
   4 .  ns
   5 .  IP "\\$1"
   6 ..
   7 .TH ovsdb\-server 1 "@VERSION@" "Open vSwitch" "Open vSwitch Manual"
   8 .\" This program's name:
   9 .ds PN ovsdb\-server
  10 .
  11 .SH NAME
  12 ovsdb\-server \- Open vSwitch database server
  13 .
  14 .SH SYNOPSIS
  15 \fBovsdb\-server\fR
  16 [\fIdatabase\fR]\&...
  17 [\fB\-\-remote=\fIremote\fR]\&...
  18 [\fB\-\-run=\fIcommand\fR]
  19 .so lib/daemon-syn.man
  20 .so lib/service-syn.man
  21 .so lib/vlog-syn.man
  22 .so ovsdb/replication-syn.man
  23 .so lib/ssl-syn.man
  24 .so lib/ssl-bootstrap-syn.man
  25 .so lib/ssl-peer-ca-cert-syn.man
  26 .so lib/ssl-connect-syn.man
  27 .so lib/unixctl-syn.man
  28 .so lib/common-syn.man
  29 .
  30 .SH DESCRIPTION
  31 The \fBovsdb\-server\fR program provides RPC interfaces to one or more
  32 Open vSwitch databases (OVSDBs).  It supports JSON-RPC client
  33 connections over active or passive TCP/IP or Unix domain sockets.
  34 .PP
  35 Each OVSDB file may be specified on the command line as \fIdatabase\fR.
  36 If none is specified, the default is \fB@DBDIR@/conf.db\fR.  The database
  37 files must already have been created and initialized using, for
  38 example, \fBovsdb\-tool create\fR.
  39 .
  40 .SH "ACTIVE and BACKUP"
  41 \fBovsdb\-server\fR runs either as a backup server, or as an active server.
  42 When  \fBovsdb\-server\fR is running as a backup server, all transactions that
  43 can modify the database content, including the lock commands are rejected.
  44 Active server, on the other hand, accepts all ovsdb server transactions.
  45 When \fBovsdb\-server\fR role changes, all existing client connection are
  46 reset, requiring clients to reconnect to the server.
  47 .PP
  48 By default, \fBovsdb\-server\fR runs as an active server, except when the
  49 \fB\-\-sync\-from=\fIserver\fR command line option is specified and without
  50 the \fB\-\-no\-sync option\fR.  During runtime, \fBovsdb\-server\fR role can be switch by using appctl commands.
  51 .PP
  52 \fBovsdb-server/connect\-active\-ovsdb\-server\fR switches
  53 \fBovsdb\-server\fR into a backup server, Conversely,
  54 \fBovsdb-server/disconnect\-active\-ovsdb\-server\fR switches server into
  55 an active one.
  56 .
  57 .SH OPTIONS
  58 .
  59 .IP "\fB\-\-remote=\fIremote\fR"
  60 Adds \fIremote\fR as a connection method used by \fBovsdb\-server\fR.
  61 \fIremote\fR must take one of the following forms:
  62 .
  63 .RS
  64 .so ovsdb/remote-passive.man
  65 .so ovsdb/remote-active.man
  66 .
  67 .IP "\fBdb:\fIdb\fB,\fItable\fB,\fIcolumn\fR"
  68 Reads additional connection methods from \fIcolumn\fR in all of the
  69 rows in \fItable\fR within \fIdb\fR.  As the contents of \fIcolumn\fR changes,
  70 \fBovsdb\-server\fR also adds and drops connection methods accordingly.
  71 .IP
  72 If \fIcolumn\fR's type is string or set of strings, then the
  73 connection methods are taken directly from the column.  The connection
  74 methods in the column must have one of the forms described above.
  75 .IP
  76 If \fIcolumn\fR's type is UUID or set of UUIDs and references a table,
  77 then each UUID is looked up in the referenced table to obtain a row.
  78 The following columns in the row, if present and of the correct type,
  79 configure a connection method.  Any additional columns are ignored.
  80 .RS
  81 .IP "\fBtarget\fR (string)"
  82 Connection method, in one of the forms described above.  This column
  83 is mandatory: if it is missing or empty then no connection method can
  84 be configured.
  85 .IP "\fBmax_backoff\fR (integer)"
  86 Maximum number of milliseconds to wait between connection attempts.
  87 .IP "\fBinactivity_probe\fR (integer)"
  88 Maximum number of milliseconds of idle time on connection to
  89 client before sending an inactivity probe message.
  90 .IP "\fBread_only\fR (boolean)"
  91 If true, only read-only transactions are allowed on this connection.
  92 .RE
  93 .IP
  94 It is an error for \fIcolumn\fR to have another type.
  95 .RE
  96 .
  97 .IP
  98 To connect or listen on multiple connection methods, use multiple
  99 \fB\-\-remote\fR options.
 100 .
 101 .IP "\fB\-\-run=\fIcommand\fR]"
 102 Ordinarily \fBovsdb\-server\fR runs forever, or until it is told to
 103 exit (see \fBRUNTIME MANAGEMENT COMMANDS\fR below).  With this option,
 104 \fBovsdb\-server\fR instead starts a shell subprocess running
 105 \fIcommand\fR.  When the subprocess terminates, \fBovsdb\-server\fR
 106 also exits gracefully.  If the subprocess exits normally with exit
 107 code 0, then \fBovsdb\-server\fR exits with exit code 0 also;
 108 otherwise, it exits with exit code 1.
 109 .IP
 110 This option can be useful where a database server is needed only to
 111 run a single command, e.g.:
 112 .B "ovsdb\-server \-\-remote=punix:socket \-\-run='ovsdb\-client dump unix:socket Open_vSwitch'"
 113 .IP
 114 This option is not supported on Windows platform.
 115 .SS "Daemon Options"
 116 .ds DD \
 117 \fBovsdb\-server\fR detaches only after it starts listening on all \
 118 configured remotes.
 119 .so lib/daemon.man
 120 .SS "Service Options"
 121 .so lib/service.man
 122 .SS "Logging Options"
 123 .so lib/vlog.man
 124 .SS "Syncing Options"
 125 .so ovsdb/replication.man
 126 .SS "Public Key Infrastructure Options"
 127 The options described below for configuring the SSL public key
 128 infrastructure accept a special syntax for obtaining their
 129 configuration from the database.  If any of these options is given
 130 \fBdb:\fIdb\fB,\fItable\fB,\fIcolumn\fR as its argument, then the
 131 actual file name is read from the specified \fIcolumn\fR in \fItable\fR
 132 within the \fIdb\fR database.  The \fIcolumn\fR must have type
 133 string or set of strings.  The first nonempty string in the table is taken
 134 as the file name.  (This means that ordinarily there should be at most
 135 one row in \fItable\fR.)
 136 .so lib/ssl.man
 137 .so lib/ssl-bootstrap.man
 138 .so lib/ssl-peer-ca-cert.man
 139 .SS "SSL Connection Options"
 140 .so lib/ssl-connect.man
 141 .SS "Other Options"
 142 .so lib/unixctl.man
 143 .so lib/common.man
 144 .SH "RUNTIME MANAGEMENT COMMANDS"
 145 \fBovs\-appctl\fR(8) can send commands to a running
 146 \fBovsdb\-server\fR process.  The currently supported commands are
 147 described below.
 148 .SS "OVSDB\-SERVER COMMANDS"
 149 These commands are specific to \fBovsdb\-server\fR.
 150 .IP "\fBexit\fR"
 151 Causes \fBovsdb\-server\fR to gracefully terminate.
 152 .IP "\fBovsdb\-server/compact\fR [\fIdb\fR]\&..."
 153 Compacts each database \fIdb\fR in-place.  If no \fIdb\fR is
 154 specified, compacts every database in-place.  A database is also
 155 compacted automatically when a transaction is logged if it is over 4
 156 times as large as its previous compacted size (and at least 10 MB),
 157 but not before 100 commits have been added or 10 minutes have elapsed
 158 since the last compaction.
 159 .
 160 .IP "\fBovsdb\-server/reconnect\fR"
 161 Makes \fBovsdb\-server\fR drop all of the JSON\-RPC
 162 connections to database clients and reconnect.
 163 .IP
 164 This command might be useful for debugging issues with database
 165 clients.
 166 .
 167 .IP "\fBovsdb\-server/add\-remote \fIremote\fR"
 168 Adds a remote, as if \fB\-\-remote=\fIremote\fR had been specified on
 169 the \fBovsdb\-server\fR command line.  (If \fIremote\fR is already a
 170 remote, this command succeeds without changing the configuration.)
 171 .
 172 .IP "\fBovsdb\-server/remove\-remote \fIremote\fR"
 173 Removes the specified \fIremote\fR from the configuration, failing
 174 with an error if \fIremote\fR is not configured as a remote.  This
 175 command only works with remotes that were named on \fB\-\-remote\fR or
 176 \fBovsdb\-server/add\-remote\fR, that is, it will not remove remotes
 177 added indirectly because they were read from the database by
 178 configuring a \fBdb:\fIdb\fB,\fItable\fB,\fIcolumn\fR remote.
 179 (You can remove a database source with \fBovsdb\-server/remove\-remote
 180 \fBdb:\fIdb\fB,\fItable\fB,\fIcolumn\fR, but not individual
 181 remotes found indirectly through the database.)
 182 .
 183 .IP "\fBovsdb\-server/list\-remotes"
 184 Outputs a list of the currently configured remotes named on
 185 \fB\-\-remote\fR or \fBovsdb\-server/add\-remote\fR, that is, it does
 186 not list remotes added indirectly because they were read from the
 187 database by configuring a
 188 \fBdb:\fIdb\fB,\fItable\fB,\fIcolumn\fR remote.
 189 .
 190 .IP "\fBovsdb\-server/add\-db \fIdatabase\fR"
 191 Adds the \fIdatabase\fR to the running \fBovsdb\-server\fR.  The database
 192 file must already have been created and initialized using, for example,
 193 \fBovsdb\-tool create\fR.
 194 .
 195 .IP "\fBovsdb\-server/remove\-db \fIdatabase\fR"
 196 Removes \fIdatabase\fR from the running \fBovsdb\-server\fR.  \fIdatabase\fR
 197 must be a database name as listed by \fBovsdb-server/list\-dbs\fR.
 198 .IP
 199 If a remote has been configured that points to the specified
 200 \fIdatabase\fR (e.g. \fB\-\-remote=db:\fIdatabase\fB,\fR... on the
 201 command line), then it will be disabled until another database with
 202 the same name is added again (with \fBovsdb\-server/add\-db\fR).
 203 .IP
 204 Any public key infrastructure options specified through this database
 205 (e.g. \fB\-\-private\-key=db:\fIdatabase,\fR... on the command line)
 206 will be disabled until another database with the same name is added
 207 again (with \fBovsdb\-server/add\-db\fR).
 208 .
 209 .IP "\fBovsdb\-server/list\-dbs"
 210 Outputs a list of the currently configured databases added either through
 211 the command line or through the \fBovsdb\-server/add\-db\fR command.
 212 .
 213 .IP "\fBovsdb\-server/set\-active\-ovsdb\-server \fIserver"
 214 Sets  the active \fIserver\fR from which \fBovsdb\-server\fR connects through
 215 \fBovsdb\-server/connect\-active\-ovsdb\-server\fR.
 216 .
 217 .IP "\fBovsdb\-server/get\-active\-ovsdb\-server"
 218 Gets the active server from which \fBovsdb\-server\fR is currently synchronizing
 219 its databases.
 220 .
 221 .IP "\fBovsdb\-server/connect\-active\-ovsdb\-server"
 222 Causes \fBovsdb\-server\fR to synchronize its databases with the server
 223 specified by \fBovsdb\-server/set\-active\-ovsdb\-server\fR.
 224 .
 225 .IP "\fBovsdb\-server/disconnect\-active\-ovsdb\-server"
 226 Causes \fBovsdb\-server\fR to  stop  synchronizing  its  databases with a active server.
 227 .
 228 .IP "\fBovsdb\-server/set\-sync\-exclude\-tables \fIdb\fB:\fItable\fR[\fB,\fIdb\fB:\fItable\fR]..."
 229 Sets the \fItable\fR whitin \fIdb\fR that will be excluded from synchronization.
 230 .
 231 .IP "\fBovsdb\-server/get\-sync\-exclude\-tables"
 232 Gets  the  tables  that are currently excluded from synchronization.
 233 .
 234 .IP "\fBovsdb\-server/sync\-status"
 235 Prints a summary of replication run time information. The \fBstate\fR
 236 information is always provided, indicating whether the server is running
 237 in the \fIactive\fR or the \fIbackup\fR mode.
 238 When running in backup mode, replication connection status, which
 239 can be either \fIconnecting\fR, \fIreplicating\fR or \fIerror\fR, are shown.
 240 When the connection is in \fIreplicating\fR state, further output shows
 241 the list of databases currently replicating, and the tables that are
 242 excluded.
 243 .
 244 .so lib/vlog-unixctl.man
 245 .so lib/memory-unixctl.man
 246 .so lib/coverage-unixctl.man
 247 .SH "SPECIFICATIONS"
 248 .
 249 .PP
 250 \fBovsdb\-server\fR implements the Open vSwitch Database (OVSDB)
 251 protocol specified in RFC 7047, with the following clarifications:
 252 .
 253 .IP "3.1. JSON Usage"
 254 RFC 4627 says that names within a JSON object should be unique.
 255 The Open vSwitch JSON parser discards all but the last value
 256 for a name that is specified more than once.
 257 .
 258 .IP
 259 The definition of <error> allows for implementation extensions.
 260 Currently \fBovsdb\-server\fR uses the following additional "error"
 261 strings which might change in later releases):
 262 .
 263 .RS
 264 .IP "\fBsyntax error\fR or \fBunknown column\fR"
 265 The request could not be parsed as an OVSDB request.  An additional
 266 "syntax" member, whose value is a string that contains JSON, may
 267 narrow down the particular syntax that could not be parsed.
 268 .IP "\fBinternal error\fR"
 269 The request triggered a bug in \fBovsdb\-server\fR.
 270 .IP "\fBovsdb error\fR"
 271 A map or set contains a duplicate key.
 272 .RE
 273 .
 274 .IP "3.2. Schema Format"
 275 RFC 7047 requires the "version" field in <database-schema>.  Current
 276 versions of \fBovsdb\-server\fR allow it to be omitted (future
 277 versions are likely to require it).
 278 .IP
 279 RFC 7047 allows columns that contain weak references to be immutable.
 280 This raises the issue of the behavior of the weak reference when the
 281 rows that it references are deleted.  Since version 2.6,
 282 \fBovsdb\-server\fR forces columns that contain weak references to be
 283 mutable.
 284 .
 285 .IP "4. Wire Protocol"
 286 The original OVSDB specifications included the following reason,
 287 omitted from RFC 7047, to operate JSON-RPC directly over a stream
 288 instead of over HTTP:
 289 .
 290 .RS
 291 .IP \(bu
 292 JSON-RPC is a peer-to-peer protocol, but HTTP is a client-server
 293 protocol, which is a poor match.  Thus, JSON-RPC over HTTP requires
 294 the client to periodically poll the server to receive server requests.
 295 .IP \(bu
 296 HTTP is more complicated than stream connections and doesn't provide
 297 any corresponding advantage.
 298 .IP \(bu
 299 The JSON-RPC specification for HTTP transport is incomplete.
 300 .RE
 301 .
 302 .IP "4.1.5. Monitor"
 303 For backward compatibility, \fBovsdb\-server\fR currently permits a
 304 single <monitor-request> to be used instead of an array; it is treated
 305 as a single-element array.  Future versions of \fBovsdb\-server\fR
 306 might remove this compatibility feature.
 307 .IP
 308 Because the <json-value> parameter is used to match subsequent update
 309 notifications (see below) to the request, it must be unique among all
 310 active monitors.  \fBovsdb\-server\fR rejects attempt to create two
 311 monitors with the same identifier.
 312 .
 313 .IP "4.1.12. Monitor_cond"
 314 A new monitor method added in Open vSwitch version 2.6. The monitor_cond
 315 request enables a client to replicate subsets of tables within an OVSDB
 316 database by requesting notifications of changes to rows matching one of
 317 the conditions specified in "where" by receiving the specified contents
 318 of these rows when table updates occur. Monitor_cond also allows a more
 319 efficient update notifications by receiving table-updates2 notifications
 320 (described below).
 321 .
 322 .IP
 323 The monitor method described in Section 4.1.5 also applies to monitor_cond,
 324 with the following exceptions:
 325 .
 326 .RS
 327 .IP \(bu
 328 RPC request method becomes "monitor_cond".
 329 .IP \(bu
 330 Reply result follows <table-updates2>, described in Section 4.1.14.
 331 .IP \(bu
 332 Subsequent changes are sent to the client using the "update2" monitor
 333 notification, described in Section 4.1.14
 334 .IP \(bu
 335 Update notifications are being sent only for rows matching [<condition>*].
 336 .RE
 337 .
 338 .IP
 339 The request object has the following members:
 340 .
 341 .PP
 342 .RS
 343 .nf
 344 "method": "monitor_cond"
 345 "params": [<db-name>, <json-value>, <monitor-cond-requests>]
 346 "id": <nonnull-json-value>
 347 .fi
 348 .RE
 349 .
 350 .IP
 351 The <json-value> parameter is used to match subsequent update notifications
 352 (see below) to this request. The <monitor-cond-requests> object maps the name
 353 of the table to an array of <monitor-cond-request>.
 354 .
 355 .IP
 356 Each <monitor-cond-request> is an object with the following members:
 357 .
 358 .PP
 359 .RS
 360 .nf
 361 "columns": [<column>*]            optional
 362 "where": [<condition>*]           optional
 363 "select": <monitor-select>        optional
 364 .fi
 365 .RE
 366 .
 367 .IP
 368 The "columns", if present, define the columns within the table to be monitored
 369 that match conditions. If not present all columns are being monitored.
 370 .
 371 .IP
 372 The "where" if present is a JSON array of <condition> and boolean values. If not
 373 present or condition is an empty array, implicit True will be considered and
 374 updates on all rows will be sent.
 375 .
 376 .IP
 377 <monitor-select> is an object with the following members:
 378 .
 379 .PP
 380 .RS
 381 .nf
 382 "initial": <boolean>              optional
 383 "insert": <boolean>               optional
 384 "delete": <boolean>               optional
 385 "modify": <boolean>               optional
 386 .fi
 387 .RE
 388 .
 389 .IP
 390 The contents of this object specify how the columns or table are to be
 391 monitored as explained in more detail below.
 392 .
 393 .IP
 394 The response object has the following members:
 395 .
 396 .PP
 397 .RS
 398 .nf
 399 "result": <table-updates2>
 400 "error": null
 401 "id": same "id" as request
 402 .fi
 403 .RE
 404 .
 405 .IP
 406 The <table-updates2> object is described in detail in Section 4.1.14. It
 407 contains the contents of the tables for which "initial" rows are selected.
 408 If no tables initial contents are requested, then "result" is an empty object.
 409 .
 410 .IP
 411 Subsequently, when changes to a specified table that match one of the conditions
 412 in monitor-cond-request are committed, the changes are automatically sent to the
 413 client using the "update2" monitor notification (see Section 4.1.14). This
 414 monitoring persists until the JSON-RPC session terminates or until the client
 415 sends a "monitor_cancel" JSON-RPC request.
 416 .
 417 .IP
 418 Each <monitor-cond-request> specifies one or more conditions and the manner in
 419 which the rows that match the conditions are to be monitored. The circumstances in
 420 which an "update" notification is sent for a row within the table are determined by
 421 <monitor-select>:
 422 .
 423 .RS
 424 .IP \(bu
 425 If "initial" is omitted or true, every row in the original table that matches one of
 426 the conditions is sent as part of the response to the "monitor_cond" request.
 427 .IP \(bu
 428 If "insert" is omitted or true, "update" notifications are sent for rows newly
 429 inserted into the table that match conditions or for rows modified in the table
 430 so that their old version does not match the condition and new version does.
 431 .IP \(bu
 432 If "delete" is omitted or true, "update" notifications are sent for rows deleted
 433 from the table that match conditions or for rows modified in the table so that
 434 their old version does match the conditions and new version does not.
 435 .IP \(bu
 436 If "modify" is omitted or true, "update" notifications are sent whenever a row in
 437 the table that matches conditions in both old and new version is modified.
 438 .RE
 439 .
 440 .IP
 441 Both monitor and monitor_cond sessions can exist concurrently. However,
 442 monitor and monitor_cond shares the same <json-value> parameter space; it
 443 must be unique among all monitor and monitor_cond sessions.
 444 .
 445 .IP "4.1.13. Monitor_cond_change"
 446 The "monitor_cond_change" request enables a client to change an existing
 447 "monitor_cond" replication of the database by specifying a new condition
 448 and columns for each replicated table. Currently changing the columns set
 449 is not supported.
 450 .
 451 .IP
 452 The request object has the following members:
 453 .
 454 .IP
 455 .RS
 456 .nf
 457 "method": "monitor_cond_change"
 458 "params": [<json-value>, <json-value>, <monitor-cond-update-requests>]
 459 "id": <nonnull-json-value>
 460 .fi
 461 .RE
 462 .
 463 .IP
 464 The <json-value> parameter should have a value of an existing conditional
 465 monitoring session from this client. The second <json-value> in params array
 466 is the requested value for this session. This value is valid only after
 467 "monitor_cond_change" is committed. A user can use these values to distinguish
 468 between update messages before conditions update and after. The
 469 <monitor-cond-update-requests> object maps the name of the table to an array of
 470 <monitor-cond-update-request>.
 471 .
 472 .IP
 473 Each <monitor-cond-update-request> is an object with the following members:
 474 .
 475 .IP
 476 .RS
 477 .nf
 478 "columns": [<column>*]         optional
 479 "where": [<condition>*]        optional
 480 .fi
 481 .RE
 482 .
 483 .IP
 484 The "columns" specify a new array of columns to be monitored
 485 (Currently unsupported).
 486 .
 487 .IP
 488 The "where" specify a new array of conditions to be applied to this monitoring
 489 session.
 490 .
 491 .IP
 492 The response object has the following members:
 493 .
 494 .IP
 495 .RS
 496 .nf
 497 "result": null
 498 "error": null
 499 "id": same "id" as request
 500 .fi
 501 .RE
 502 .IP
 503 Subsequent <table-updates2> notifications are described in detail in Section
 504 4.1.14 in the RFC. If insert contents are requested by original monitor_cond
 505 request, <table-updates2> will contain rows that match the new condition and
 506 do not match the old condition.
 507 If deleted contents are requested by origin monitor request, <table-updates2>
 508 will contain any matched rows by old condition and not matched by the new
 509 condition.
 510 .
 511 .IP
 512 Changes according to the new conditions are automatically sent to the client
 513 using the "update2" monitor notification. An update, if any, as a result of a
 514 condition change, will be sent to the client before the reply to the
 515 "monitor_cond_change" request.
 516 .
 517 .IP "4.1.14. Update2 notification"
 518 The "update2" notification is sent by the server to the client to report
 519 changes in tables that are being monitored following a "monitor_cond" request
 520 as described above. The notification has the following members:
 521 .
 522 .RS
 523 .nf
 524 "method": "update2"
 525 "params": [<json-value>, <table-updates2>]
 526 "id": null
 527 .fi
 528 .RE
 529 .
 530 .IP
 531 The <json-value> in "params" is the same as the value passed as the
 532 <json-value>  in "params" for the corresponding "monitor" request.
 533 <table-updates2> is an object that maps from a table name to a <table-update2>.
 534 A <table-update2> is an object that maps from row's UUID to a <row-update2>
 535 object. A <row-update2> is an object with one of the following members:
 536 .
 537 .RS
 538 .IP "\(dqinitial\(dq: <row>"
 539 present for "initial" updates
 540 .IP "\(dqinsert\(dq: <row>"
 541 present for "insert" updates
 542 .IP "\(dqdelete\(dq: <row>"
 543 present for "delete" updates
 544 .IP "\(dqmodify\(dq: <row>"
 545 present for "modify" updates
 546 .RE
 547 .
 548 .IP
 549 The format of <row> is described in Section 5.1.
 550 .
 551 .IP
 552 <row> is always a null object for a "delete" update. In "initial" and
 553 "insert" updates, <row> omits columns whose values equal the default
 554 value of the column type.
 555 .
 556 .IP
 557 For a "modify" update, <row> contains only the columns that are modified.
 558 <row> stores the difference between the old and new value for those columns,
 559 as described below.
 560 .
 561 .IP
 562 For columns with single value, the difference is the value of the new
 563 column.
 564 .
 565 .IP
 566 The difference between two sets are all elements that only belong
 567 to one of the sets.
 568 .
 569 .IP
 570 The difference between two maps are all key-value pairs whose keys
 571 appears in only one of the maps, plus the key-value pairs whose keys
 572 appear in both maps but with different values.  For the latter
 573 elements, <row> includes the value from the new column.
 574 .
 575 .IP
 576 Initial views of rows are not presented in update2 notifications,
 577 but in the response object to the monitor_cond request. The formatting
 578 of the <table-updates2> object, however, is the same in either case.
 579 .
 580 .IP "5.1. Notation"
 581 For <condition>, RFC 7047 only allows the use of \fB!=\fR, \fB==\fR,
 582 \fBincludes\fR, and \fBexcludes\fR operators with set types.  Open
 583 vSwitch 2.4 and later extend <condition> to allow the use of \fB<\fR,
 584 \fB<=\fR, \fB>=\fR, and \fB>\fR operators with columns with type ``set
 585 of 0 or 1 integer'' and ``set of 0 or 1 real''.  These conditions
 586 evaluate to false when the column is empty, and otherwise as described
 587 in RFC 7047 for integer and real types.
 588 .
 589 .IP
 590 <condition> is specified in Section 5.1 in the RFC with the following change:
 591 A condition can be either a 3-element JSON array as described in the RFC or a
 592 boolean value. In case of an empty array an implicit true boolean value will be
 593 considered.
 594 .
 595 .SH "BUGS"
 596 .
 597 In Open vSwitch before version 2.4, when \fBovsdb\-server\fR sent
 598 JSON-RPC error responses to some requests, it incorrectly formulated
 599 them with the \fBresult\fR and \fBerror\fR swapped, so that the
 600 response appeared to indicate success (with a nonsensical result)
 601 rather than an error.  The requests that suffered from this problem
 602 were:
 603 .
 604 .IP \fBtransact\fR
 605 .IQ \fBget_schema\fR
 606 Only if the request names a nonexistent database.
 607 .IP \fBmonitor\fR
 608 .IQ \fBlock\fR
 609 .IQ \fBunlock\fR
 610 In all error cases.
 611 .
 612 .PP
 613 Of these cases, the only error that a well-written application is
 614 likely to encounter in practice is \fBmonitor\fR of tables or columns
 615 that do not exist, in an situation where the application has been
 616 upgraded but the old database schema is still temporarily in use.  To
 617 handle this situation gracefully, we recommend that clients should
 618 treat a \fBmonitor\fR response with a \fBresult\fR that contains an
 619 \fBerror\fR key-value pair as an error (assuming that the database
 620 being monitored does not contain a table named \fBerror\fR).
 621 .
 622 .SH "SEE ALSO"
 623 .
 624 .BR ovsdb\-tool (1).