PG_RECEIVEXLOG(1) PostgreSQL 9.3.2 Documentation PG_RECEIVEXLOG(1)NAMEpg_receivexlog - streams transaction logs from a PostgreSQL cluster
SYNOPSISpg_receivexlog [option...]
DESCRIPTIONpg_receivexlog is used to stream transaction log from a running
PostgreSQL cluster. The transaction log is streamed using the streaming
replication protocol, and is written to a local directory of files.
This directory can be used as the archive location for doing a restore
using point-in-time recovery (see Section 24.3, “Continuous Archiving
and Point-in-Time Recovery (PITR)”, in the documentation).
pg_receivexlog streams the transaction log in real time as it's being
generated on the server, and does not wait for segments to complete
like archive_command does. For this reason, it is not necessary to set
archive_timeout when using pg_receivexlog.
The transaction log is streamed over a regular PostgreSQL connection,
and uses the replication protocol. The connection must be made with a
superuser or a user having REPLICATION permissions (see Section 20.2,
“Role Attributes”, in the documentation), and pg_hba.conf must
explicitly permit the replication connection. The server must also be
configured with max_wal_senders set high enough to leave at least one
session available for the stream.
If the connection is lost, or if it cannot be initially established,
with a non-fatal error, pg_receivexlog will retry the connection
indefinitely, and reestablish streaming as soon as possible. To avoid
this behavior, use the -n parameter.
OPTIONS
The following command-line options control the location and format of
the output.
-D directory, --directory=directory
Directory to write the output to.
This parameter is required.
The following command-line options control the running of the program.
-n, --no-loop
Don't loop on connection errors. Instead, exit right away with an
error.
-v, --verbose
Enables verbose mode.
The following command-line options control the database connection
parameters.
-d connstr, --dbname=connstr
Specifies parameters used to connect to the server, as a connection
string. See Section 31.1.1, “Connection Strings”, in the
documentation for more information.
The option is called --dbname for consistency with other client
applications, but because pg_receivexlog doesn't connect to any
particular database in the cluster, database name in the connection
string will be ignored.
-h host, --host=host
Specifies the host name of the machine on which the server is
running. If the value begins with a slash, it is used as the
directory for the Unix domain socket. The default is taken from the
PGHOST environment variable, if set, else a Unix domain socket
connection is attempted.
-p port, --port=port
Specifies the TCP port or local Unix domain socket file extension
on which the server is listening for connections. Defaults to the
PGPORT environment variable, if set, or a compiled-in default.
-s interval, --status-interval=interval
Specifies the number of seconds between status packets sent back to
the server. This allows for easier monitoring of the progress from
server. A value of zero disables the periodic status updates
completely, although an update will still be sent when requested by
the server, to avoid timeout disconnect. The default value is 10
seconds.
-U username, --username=username
User name to connect as.
-w, --no-password
Never issue a password prompt. If the server requires password
authentication and a password is not available by other means such
as a .pgpass file, the connection attempt will fail. This option
can be useful in batch jobs and scripts where no user is present to
enter a password.
-W, --password
Force pg_receivexlog to prompt for a password before connecting to
a database.
This option is never essential, since pg_receivexlog will
automatically prompt for a password if the server demands password
authentication. However, pg_receivexlog will waste a connection
attempt finding out that the server wants a password. In some cases
it is worth typing -W to avoid the extra connection attempt.
Other options are also available:
-V, --version
Print the pg_receivexlog version and exit.
-?, --help
Show help about pg_receivexlog command line arguments, and exit.
ENVIRONMENT
This utility, like most other PostgreSQL utilities, uses the
environment variables supported by libpq (see Section 31.14,
“Environment Variables”, in the documentation).
NOTES
When using pg_receivexlog instead of archive_command, the server will
continue to recycle transaction log files even if the backups are not
properly archived, since there is no command that fails. This can be
worked around by having an archive_command that fails when the file has
not been properly archived yet, for example:
archive_command = 'sleep 5 && test -f /mnt/server/archivedir/%f'
The initial timeout is necessary because pg_receivexlog works using
asynchronous replication and can therefore be slightly behind the
master.
EXAMPLES
To stream the transaction log from the server at mydbserver and store
it in the local directory /usr/local/pgsql/archive:
$ pg_receivexlog-h mydbserver -D /usr/local/pgsql/archive
SEE ALSOpg_basebackup(1)PostgreSQL 9.3.2 2013 PG_RECEIVEXLOG(1)
