PG_RECEIVEXLOG(1) PostgreSQL 9.2.7 Documentation PG_RECEIVEXLOG(1)
pg_receivexlog - streams transaction logs from a PostgreSQL cluster
pg_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.
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.
Don't loop on connection errors. Instead, exit right away with an error.
Enables verbose mode.
The following command-line options control the database connection parameters.
-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
is required if replication timeout is configured on the server, and allows for easier
monitoring. A value of zero disables the status updates completely. The default value
is 10 seconds.
-U username, --username=username
User name to connect as.
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.
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:
Print the pg_receivexlog version and exit.
Show help about pg_receivexlog command line arguments, and exit.
This utility, like most other PostgreSQL utilities, uses the environment variables
supported by libpq (see Section 31.14, "Environment Variables", in the documentation).
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.
To stream the transaction log from the server at mydbserver and store it in the local
$ pg_receivexlog -h mydbserver -D /usr/local/pgsql/archive
PostgreSQL 9.2.7 2014-02-17 PG_RECEIVEXLOG(1)