pg_receivewal — stream write-ahead logs from a PostgreSQL server
pg_receivewal [option...]
pg_receivewal is used to stream the write-ahead log from a running PostgreSQL cluster. The write-ahead 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 25.3).
pg_receivewal streams the write-ahead 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_receivewal.
   Unlike the WAL receiver of a PostgreSQL standby server, pg_receivewal
   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. Since pg_receivewal does not
   apply WAL, you should not allow it to become a synchronous standby when
   synchronous_commit equals
   remote_apply. If it does, it will appear to be a
   standby that never catches up, and will cause transaction commits to
   block. To avoid this, you should either configure an appropriate value
   for synchronous_standby_names, or specify
   application_name for
   pg_receivewal that does not match it, or
   change the value of synchronous_commit to
   something other than remote_apply.
  
   The write-ahead 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 21.2), 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_receivewal will
   retry the connection indefinitely, and reestablish streaming as soon
   as possible. To avoid this behavior, use the -n
   parameter.
  
-D directory--directory=directoryDirectory 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-loopDon't loop on connection errors. Instead, exit right away with an error.
-s interval--status-interval=intervalSpecifies 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=slotnameRequire pg_receivewal to use an existing replication slot (see Section 26.2.6). When this option is used, pg_receivewal 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_receivewal 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_receivewal is configured on the server as a synchronous standby, to ensure that timely feedback is sent to the server.
-v--verboseEnables verbose mode.
-Z level--compress=level        Enables gzip compression of write-ahead logs, and specifies the
        compression level (0 through 9, 0 being no compression and 9 being best
        compression).  The suffix .gz will
        automatically be added to all filenames.
       
The following command-line options control the database connection parameters.
-d connstr--dbname=connstrSpecifies parameters used to connect to the server, as a connection string. See Section 33.1.1 for more information.
        The option is called --dbname for consistency with other
        client applications, but because pg_receivewal
        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=usernameUser 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--passwordForce pg_receivewal to prompt for a password before connecting to a database.
        This option is never essential, since
        pg_receivewal will automatically prompt
        for a password if the server demands password authentication.
        However, pg_receivewal 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_receivewal 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--versionPrint the pg_receivewal version and exit.
-?--helpShow help about pg_receivewal command line arguments, and exit.
This utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section 33.14).
When using pg_receivewal 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 write-ahead 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.
   To stream the write-ahead log from the server at
   mydbserver and store it in the local directory
   /usr/local/pgsql/archive:
$pg_receivewal -h mydbserver -D /usr/local/pgsql/archive