NAME

nbdkit-delay-filter - 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).

AUTHORS

Richard W.M. Jones

COPYRIGHT

LICENSE

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

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

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