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.\" ========================================================================
.\"
.IX Title "nbdkit-delay-filter 1"
.TH nbdkit-delay-filter 1 "2023-01-04" "nbdkit-1.32.5" "NBDKIT"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
nbdkit\-delay\-filter \- nbdkit delay filter
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& nbdkit \-\-filter=delay plugin rdelay=SECS wdelay=SECS [plugin\-args...]
.Ve
.PP
.Vb 1
\& nbdkit \-\-filter=delay plugin rdelay=NNms wdelay=NNms [plugin\-args...]
.Ve
.PP
.Vb 10
\& nbdkit \-\-filter=delay plugin [plugin\-args ...]
\&          delay\-read=(SECS|NNms)
\&          delay\-write=(SECS|NNms)
\&          delay\-zero=(SECS|NNms)
\&          delay\-trim=(SECS|NNms)
\&          delay\-extents=(SECS|NNms)
\&          delay\-cache=(SECS|NNms)
\&          delay\-fast\-zero=BOOL
\&          delay\-open=(SECS|NNms)
\&          delay\-close=(SECS|NNms)
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`nbdkit\-delay\-filter\*(C'\fR is a filter that delays read and write requests
by some seconds or milliseconds.  This is used to simulate a slow or
remote server, or to test certain kinds of race conditions in Linux.
To limit server bandwidth use \fBnbdkit\-rate\-filter\fR\|(1) instead.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Delays reads and writes by 100ms:
.PP
.Vb 1
\& nbdkit \-\-filter=delay file disk.img rdelay=100ms wdelay=100ms
.Ve
.PP
Delay only zero operations by 1 second, nothing else is affected:
.PP
.Vb 1
\& nbdkit \-\-filter=delay file disk.img delay\-zero=1
.Ve
.SH "PARAMETERS"
.IX Header "PARAMETERS"
.IP "\fBrdelay=\fR\s-1SECS\s0" 4
.IX Item "rdelay=SECS"
.PD 0
.IP "\fBrdelay=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "rdelay=NNms"
.IP "\fBdelay\-read=\fR\s-1SECS\s0" 4
.IX Item "delay-read=SECS"
.IP "\fBdelay\-read=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-read=NNms"
.PD
Delay read operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR milliseconds.
.Sp
The two forms \f(CW\*(C`rdelay\*(C'\fR and \f(CW\*(C`delay\-read\*(C'\fR work identically.
.IP "\fBdelay\-write=\fR\s-1SECS\s0" 4
.IX Item "delay-write=SECS"
.PD 0
.IP "\fBdelay\-write=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-write=NNms"
.PD
Delay write operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR milliseconds.
.IP "\fBdelay\-zero=\fR\s-1SECS\s0" 4
.IX Item "delay-zero=SECS"
.PD 0
.IP "\fBdelay\-zero=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-zero=NNms"
.PD
(nbdkit ≥ 1.10)
.Sp
Delay zero operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR milliseconds.  See
also \fBdelay-fast-zero\fR.
.IP "\fBdelay\-trim=\fR\s-1SECS\s0" 4
.IX Item "delay-trim=SECS"
.PD 0
.IP "\fBdelay\-trim=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-trim=NNms"
.PD
(nbdkit ≥ 1.10)
.Sp
Delay trim/discard operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR milliseconds.
.IP "\fBdelay\-extents=\fR\s-1SECS\s0" 4
.IX Item "delay-extents=SECS"
.PD 0
.IP "\fBdelay\-extents=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-extents=NNms"
.PD
(nbdkit ≥ 1.12)
.Sp
Delay block status (extents) operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR
milliseconds.
.IP "\fBdelay\-cache=\fR\s-1SECS\s0" 4
.IX Item "delay-cache=SECS"
.PD 0
.IP "\fBdelay\-cache=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-cache=NNms"
.PD
(nbdkit ≥ 1.14)
.Sp
Delay advisory cache operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR
milliseconds.
.IP "\fBwdelay=\fR\s-1SECS\s0" 4
.IX Item "wdelay=SECS"
.PD 0
.IP "\fBwdelay=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "wdelay=NNms"
.PD
Delay write, zero and trim operations by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR
milliseconds.
.IP "\fBdelay\-fast\-zero=\fR\s-1BOOL\s0" 4
.IX Item "delay-fast-zero=BOOL"
(nbdkit ≥ 1.16)
.Sp
The \s-1NBD\s0 specification documents an extension called fast zero, in
which the client may request that a server should reply with
\&\f(CW\*(C`ENOTSUP\*(C'\fR as soon as possible if the zero operation offers no real
speedup over a corresponding write.  By default, this parameter is
true, and fast zero requests are serviced by the plugin after the same
delay as any other zero request; but setting this parameter to false
instantly fails a fast zero response without waiting for or consulting
the plugin.
.IP "\fBdelay\-open=\fR\s-1SECS\s0" 4
.IX Item "delay-open=SECS"
.PD 0
.IP "\fBdelay\-open=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-open=NNms"
.PD
(nbdkit ≥ 1.28)
.Sp
Delay open (client connection) by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR
milliseconds.
.IP "\fBdelay\-close=\fR\s-1SECS\s0" 4
.IX Item "delay-close=SECS"
.PD 0
.IP "\fBdelay\-close=\fR\s-1NN\s0\fBms\fR" 4
.IX Item "delay-close=NNms"
.PD
(nbdkit ≥ 1.28)
.Sp
Delay close (client disconnection) by \f(CW\*(C`SECS\*(C'\fR seconds or \f(CW\*(C`NN\*(C'\fR
milliseconds.  This can also cause server shutdown to be delayed if
clients are connected at the time.  This only affects clients that
gracefully disconnect (using \f(CW\*(C`NBD_CMD_DISC\*(C'\fR / libnbd function
\&\fBnbd_shutdown\fR\|(3)).  Clients that abruptly disconnect from the server
cannot be delayed.
.SH "FILES"
.IX Header "FILES"
.IP "\fI\f(CI$filterdir\fI/nbdkit\-delay\-filter.so\fR" 4
.IX Item "$filterdir/nbdkit-delay-filter.so"
The filter.
.Sp
Use \f(CW\*(C`nbdkit \-\-dump\-config\*(C'\fR to find the location of \f(CW$filterdir\fR.
.SH "VERSION"
.IX Header "VERSION"
\&\f(CW\*(C`nbdkit\-delay\-filter\*(C'\fR first appeared in nbdkit 1.2, based on earlier
\&\f(CW\*(C`rdelay\*(C'\fR and \f(CW\*(C`wdelay\*(C'\fR options in \fBnbdkit\-file\-plugin\fR\|(1).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-filter\fR\|(3),
\&\fBnbdkit\-pause\-filter\fR\|(1),
\&\fBnbdkit\-rate\-filter\fR\|(1).
.SH "AUTHORS"
.IX Header "AUTHORS"
Richard W.M. Jones
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2018\-2021 Red Hat Inc.
.SH "LICENSE"
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP "\(bu" 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP "\(bu" 4
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.
.IP "\(bu" 4
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.
.PP
\&\s-1THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS\s0 ''\s-1AS IS\s0'' \s-1AND
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\s0 (\s-1INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES\s0; \s-1LOSS OF
USE, DATA, OR PROFITS\s0; \s-1OR BUSINESS INTERRUPTION\s0) \s-1HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT\s0 (\s-1INCLUDING NEGLIGENCE OR OTHERWISE\s0) \s-1ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.\s0