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