xenial (1) pg_receivexlog.1.gz

NAME

       pg_receivexlog - stream transaction logs from a PostgreSQL server

SYNOPSIS

       pg_receivexlog [option...]

DESCRIPTION

       pg_receivexlog is used to stream the 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.

       Unlike the WAL receiver of a PostgreSQL standby server, pg_receivexlog by default flushes WAL data only
       when a WAL file is closed. The option --synchronous must be specified to flush WAL data in real time.

       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 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

       -D directory
       --directory=directory
           Directory to write the output to.

           This parameter is required.

       --if-not-exists
           Do not error out when --create-slot is specified and a slot with the specified name already exists.

       -n
       --no-loop
           Don't loop on connection errors. Instead, exit right away with an error.

       -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.

       -S slotname
       --slot=slotname
           Require pg_receivexlog to use an existing replication slot (see Section 25.2.6, “Replication Slots”,
           in the documentation). When this option is used, pg_receivexlog will report a flush position to the
           server, indicating when each segment has been synchronized to disk so that the server can remove that
           segment if it is not otherwise needed.

           When the replication client of pg_receivexlog is configured on the server as a synchronous standby,
           then using a replication slot will report the flush position to the server, but only when a WAL file
           is closed. Therefore, that configuration will cause transactions on the primary to wait for a long
           time and effectively not work satisfactorily. The option --synchronous (see below) must be specified
           in addition to make this work correctly.

       --synchronous
           Flush the WAL data to disk immediately after it has been received. Also send a status packet back to
           the server immediately after flushing, regardless of --status-interval.

           This option should be specified if the replication client of pg_receivexlog is configured on the
           server as a synchronous standby, to ensure that timely feedback is sent to the server.

       -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.

       -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.

       pg_receivexlog can perform one of the two following actions in order to control physical replication
       slots:

       --create-slot
           Create a new physical replication slot with the name specified in --slot, then exit.

       --drop-slot
           Drop the replication slot with the name specified in --slot, then exit.

       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 as the main WAL backup method, it is strongly
       recommended to use replication slots. Otherwise, the server is free to recycle or remove transaction log
       files before they are backed up, because it does not have any information, either from archive_command or
       the replication slots, about how far the WAL stream has been archived. Note, however, that a replication
       slot will fill up the server's disk space if the receiver does not keep up with fetching the WAL data.

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 ALSO

       pg_basebackup(1)