nbdkit-delay-filter - Man Page

nbdkit delay filter

Synopsis

 nbdkit --filter=delay plugin rdelay=SECS wdelay=SECS [plugin-args...]

 nbdkit --filter=delay plugin rdelay=NNms wdelay=NNms [plugin-args...]

 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

Description

nbdkit-delay-filter 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 nbdkit-rate-filter(1) instead.

Examples

Delays reads and writes by 100ms:

 nbdkit --filter=delay file disk.img rdelay=100ms wdelay=100ms

Delay only zero operations by 1 second, nothing else is affected:

 nbdkit --filter=delay file disk.img delay-zero=1

Parameters

rdelay=SECS
rdelay=NNms
delay-read=SECS
delay-read=NNms

Delay read operations by SECS seconds or NN milliseconds.

The two forms rdelay and delay-read work identically.

delay-write=SECS
delay-write=NNms

Delay write operations by SECS seconds or NN milliseconds.

delay-zero=SECS
delay-zero=NNms

Delay zero operations by SECS seconds or NN milliseconds.  See also delay-fast-zero.

delay-trim=SECS
delay-trim=NNms

Delay trim/discard operations by SECS seconds or NN milliseconds.

delay-extents=SECS
delay-extents=NNms

Delay block status (extents) operations by SECS seconds or NN milliseconds.

delay-cache=SECS
delay-cache=NNms

Delay advisory cache operations by SECS seconds or NN milliseconds.

wdelay=SECS
wdelay=NNms

Delay write, zero and trim operations by SECS seconds or NN milliseconds.

delay-fast-zero=BOOL

The NBD specification documents an extension called fast zero, in which the client may request that a server should reply with ENOTSUP 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.

Files

$filterdir/nbdkit-delay-filter.so

The filter.

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

Version

nbdkit-delay-filter first appeared in nbdkit 1.2, based on earlier rdelay and wdelay options in nbdkit-file-plugin(1).

See Also

nbdkit(1), nbdkit-filter(3), nbdkit-rate-filter(1).

Authors

Richard W.M. Jones

License

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

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.

Referenced By

nbdkit(1), nbdkit-file-plugin(1), nbdkit-filter(3), nbdkit-rate-filter(1), nbdkit-release-notes-1.10(1), nbdkit-release-notes-1.14(1).

2020-06-29 nbdkit-1.21.13