pg_receivexlog1Applicationpg_receivexlogstreams transaction logs from a PostgreSQL clusterpg_receivexlogpg_receivexlogoption
Description
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
).
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 does.
For this reason, it is not necessary to set
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
), and pg_hba.conf
must explicitly permit the replication connection. The server must also be
configured with 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.
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.
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.
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.
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.
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
Other options are also available:
Print the pg_receivexlog version and exit.
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 ).
Notes
When using pg_receivexlog instead of
, 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 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/archiveSee Also