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nbdkit-log-filter(1)		    NBDKIT		  nbdkit-log-filter(1)

NAME
       nbdkit-log-filter - nbdkit log filter

SYNOPSIS
	nbdkit --filter=log plugin logfile=FILE	[logappend=BOOL] [plugin-args...]

DESCRIPTION
       "nbdkit-log-filter" is a	filter that logs all transactions.  When used
       as the first filter, it can show	the original client requests; as a
       later filter, it	can show how earlier filters have modified the
       original	request.  The log results are placed in	a user-specified file;
       for more	details	on the log format, see FILES.  Note that using "nbdkit
       -v -f" produces much more verbose logging details to stderr about every
       aspect of nbdkit	operation, although this requires running nbdkit in
       the foreground; while the log filter is designed	to work	even when
       nbdkit is run as	a daemon.

PARAMETERS
       logfile=FILE
	   The file where the log is written.  This parameter is required.

       logappend=true
       logappend=false
	   (nbdkit aY 1.8)

	   When	set to "false" (the default), if the file already exists it
	   will	be truncated.  When set	to "true", the filter appends to the
	   existing file.

EXAMPLES
       Serve the file disk.img,	and log	each client transaction	in the file
       disk.log:

	nbdkit --filter=log file disk.img logfile=disk.log

       Repeat the task,	but with the cow (copy-on-write) filter	to perform
       local caching of	data served from the original plugin:

	nbdkit --filter=cow --filter=log file disk.img logfile=disk.log2

       After running a client that performs the	same operations	under each of
       the two servers,	you can	compare	disk.log and disk.log2 to see the
       impact of the caching.

FILES
       "logfile=FILE" parameter
	   This	filter writes to the file specified by the "logfile=FILE"
	   parameter.  All lines include a timestamp, a	connection counter,
	   then	details	about the command.  The	following actions are logged:
	   Connect, Read, Write, Zero, Trim, Extents, Cache, Flush, and
	   Disconnect.	Except for Connect and Disconnect, an event is logged
	   across two lines for	call and return	value, to allow	tracking
	   duration and	tracing	any parallel execution,	using id for
	   correlation (incremented per	action on the connection).

	   An example logging session of a client that performs	a single
	   successful read is:

	    2018-01-27 20:38:22.959984 connection=1 Connect size=0x400 write=1 flush=1 rotational=0 trim=0 zero=1 fua=1	extents=1 cache=0 fast_zero=0
	    2018-01-27 20:38:23.001720 connection=1 Read id=1 offset=0x0 count=0x100 ...
	    2018-01-27 20:38:23.001995 connection=1 ...Read id=1 return=0 (Success)
	    2018-01-27 20:38:23.044259 connection=1 Disconnect transactions=1

       $filterdir/nbdkit-log-filter.so
	   The filter.

	   Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION
       "nbdkit-log-filter" first appeared in nbdkit 1.2.

SEE ALSO
       nbdkit(1), nbdkit-file-plugin(1), nbdkit-cow-filter(1),
       nbdkit-filter(3), nbdkit-stats-filter(1).

AUTHORS
       Eric Blake

COPYRIGHT
       Copyright (C) 2018 Red Hat Inc.

LICENSE
       Redistribution and use in source	and binary forms, with or without
       modification, are permitted provided that the following conditions are
       met:

       o   Redistributions of source code must retain the above	copyright
	   notice, this	list of	conditions and the following disclaimer.

       o   Redistributions in binary form must reproduce the above copyright
	   notice, this	list of	conditions and the following disclaimer	in the
	   documentation and/or	other materials	provided with the
	   distribution.

       o   Neither the name of Red Hat nor the names of	its contributors may
	   be used to endorse or promote products derived from this software
	   without specific prior written permission.

       THIS SOFTWARE IS	PROVIDED BY RED	HAT AND	CONTRIBUTORS ''AS IS'' AND ANY
       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
       LIABLE FOR ANY DIRECT, INDIRECT,	INCIDENTAL, SPECIAL, EXEMPLARY,	OR
       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
       SUBSTITUTE GOODS	OR SERVICES; LOSS OF USE, DATA,	OR PROFITS; OR
       BUSINESS	INTERRUPTION) HOWEVER CAUSED AND ON ANY	THEORY OF LIABILITY,
       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
       OTHERWISE) ARISING IN ANY WAY OUT OF THE	USE OF THIS SOFTWARE, EVEN IF
       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

nbdkit-1.20.4			  2021-09-21		  nbdkit-log-filter(1)

NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | EXAMPLES | FILES | VERSION | SEE ALSO | AUTHORS | COPYRIGHT | LICENSE

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