ovsdb: Replication usability improvements

Based on feedbacks from initial HA manager integration, added the
'--active' command line option and appctl command
"ovsdb-server/sync-status. See man page updates for details.

Added the RPL_S_INIT state in the state machine. This state is
not strictly necessary for the replication state machine, but is
introduced to make sure the state is update immediately when
the state machine is reset, via replication_init(). Without it
ovsdb/sync-status may display "replicating" or crash, if the command
is issued between after replication_init() is called, but before
the state variable is updated from replication_run().

Added a test to simulate the integration of HA manager with OVSDB
server using replication.

Other documentation and API improvements.

Tested-by: Numan Siddique <nusiddiq@redhat.com>
Signed-off-by: Andy Zhou <azhou@ovn.org>
Acked-by: Ben Pfaff <blp@ovn.org>

Documentation/OVSDB-replication.md

@@ -144,7 +144,7 @@ commands are the following.
     between the active server and frees the memory used for the replication
     configuration.
 
--   ovsdb-server/set-sync-excluded-tables {db:table,...}: sets the tables list
+-   ovsdb-server/set-sync-exclude-tables {db:table,...}: sets the tables list
     that will be excluded from being replicated.
 
 -   ovsdb-server/get-sync-excluded-tables: gets the tables list that is

ovsdb/jsonrpc-server.c

@@ -343,6 +343,12 @@ ovsdb_jsonrpc_server_reconnect(struct ovsdb_jsonrpc_server *svr, bool read_only)
     }
 }
 
+bool
+ovsdb_jsonrpc_server_is_read_only(struct ovsdb_jsonrpc_server *svr)
+{
+    return svr->read_only;
+}
+
 void
 ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *svr)
 {

ovsdb/jsonrpc-server.h

@@ -65,6 +65,7 @@ void ovsdb_jsonrpc_server_reconnect(struct ovsdb_jsonrpc_server *, bool read_onl
 
 void ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *);
 void ovsdb_jsonrpc_server_wait(struct ovsdb_jsonrpc_server *);
+bool ovsdb_jsonrpc_server_is_read_only(struct ovsdb_jsonrpc_server *);
 
 void ovsdb_jsonrpc_server_get_memory_usage(const struct ovsdb_jsonrpc_server *,
                                            struct simap *usage);

ovsdb/ovsdb-server.1.in

@@ -36,7 +36,7 @@ If none is specified, the default is \fB@DBDIR@/conf.db\fR.  The database
 files must already have been created and initialized using, for
 example, \fBovsdb\-tool create\fR.
 .
-.SH "ACTIVE and BACKUP "
+.SH "ACTIVE and BACKUP"
 \fBovsdb\-server\fR runs either as a backup server, or as an active server.
 When  \fBovsdb\-server\fR is running as a backup server, all transactions that
 can modify the database content, including the lock commands are rejected.
@@ -45,12 +45,12 @@ When \fBovsdb\-server\fR role changes, all existing client connection are
 reset, requiring clients to reconnect to the server.
 .PP
 By default, \fBovsdb\-server\fR runs as an active server, except when the
-\fB\-\-sync\-from=\fIserver\fR command line option is specified.  During
-runtime, \fBovsdb\-server\fR role can be switch by using appctl commands.
+\fB\-\-sync\-from=\fIserver\fR command line option is specified and without
+the \fB\-\-no\-sync option\fR.  During runtime, \fBovsdb\-server\fR role can be switch by using appctl commands.
 .PP
 \fBovsdb-server/connect\-active\-ovsdb\-server\fR switches
-\fBovsdb\-server\fR role into a backup server, Conversely,
-\fBovsdb-server/disconnect\-active\-ovsdb\-server\fR changes server into
+\fBovsdb\-server\fR into a backup server, Conversely,
+\fBovsdb-server/disconnect\-active\-ovsdb\-server\fR switches server into
 an active one.
 .
 .SH OPTIONS
@@ -220,12 +220,22 @@ specified by \fBovsdb\-server/set\-active\-ovsdb\-server\fR.
 .IP "\fBovsdb\-server/disconnect\-active\-ovsdb\-server"
 Causes \fBovsdb\-server\fR to  stop  synchronizing  its  databases with a active server.
 .
-.IP "\fBovsdb\-server/set\-sync\-excluded\-tables \fIdb\fB:\fItable\fR[\fB,\fIdb\fB:\fItable\fR]..."
+.IP "\fBovsdb\-server/set\-sync\-exclude\-tables \fIdb\fB:\fItable\fR[\fB,\fIdb\fB:\fItable\fR]..."
 Sets the \fItable\fR whitin \fIdb\fR that will be excluded from synchronization.
 .
-.IP "\fBovsdb\-server/get\-sync\-excluded\-tables"
+.IP "\fBovsdb\-server/get\-sync\-exclude\-tables"
 Gets  the  tables  that are currently excluded from synchronization.
 .
+.IP "\fBovsdb\-server/sync\-status"
+Prints a summary of replication run time information. The \fBstate\fR
+information is always provided, indicating whether the server is running
+in the \fIactive\fR or the \fIbackup\fR mode.
+When running in backup mode, replication connection status, which
+can be either \fIconnecting\fR, \fIreplicating\fR or \fIerror\fR, are shown.
+When the connection is in \fIreplicating\fR state, further output shows
+the list of databases currently replicating, and the tables that are
+excluded.
+.
 .so lib/vlog-unixctl.man
 .so lib/memory-unixctl.man
 .so lib/coverage-unixctl.man