1nbdkit-noparallel-filter(1)         NBDKIT         nbdkit-noparallel-filter(1)
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NAME

6       nbdkit-noparallel-filter - nbdkit noparallel filter
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SYNOPSIS

9        nbdkit --filter=noparallel plugin [serialize=MODE] [plugin-args...]
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DESCRIPTION

12       "nbdkit-noparallel-filter" is a filter that intentionally disables
13       parallelism in handling requests from clients. It is mainly useful for
14       evaluating timing differences between various levels of parallelism. It
15       can also be used as a way to work around any bugs in a plugin's claimed
16       level of parallel support, without recompiling the plugin, or to ease
17       efforts when connecting with a client that can batch up several
18       requests but is not prepared to handle out-of-order replies.
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PARAMETERS

21       serialize=requests
22       serialize=all-requests
23       serialize=connections
24           Optional, controls how much serialization the filter will enforce.
25           Mode requests (default) prevents a single client from having more
26           than one in-flight request, but does not prevent parallel requests
27           from a second connection (if the plugin supports that). Mode all-
28           requests is stricter, enforcing that at most one request
29           (regardless of connection) will be active, but does not prevent
30           parallel connections (if the plugin supports that). Mode
31           connections is strictest, where there can be at most one client at
32           a time, and where the server will no longer advertise
33           "NBD_FLAG_MULTI_CONN" to clients.
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EXAMPLES

36       Serve the file disk.img, but disallow out-of-order transaction
37       completion to a given client:
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39        nbdkit --filter=noparallel file disk.img
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41       Serve the file disk.img, but allowing only one client at a time:
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43        nbdkit --filter=noparallel file serialize=connections disk.img
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FILES

46       $filterdir/nbdkit-noparallel-filter.so
47           The filter.
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49           Use "nbdkit --dump-config" to find the location of $filterdir.
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VERSION

52       "nbdkit-noparallel-filter" first appeared in nbdkit 1.14.
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SEE ALSO

55       nbdkit(1), nbdkit-file-plugin(1), nbdkit-filter(3),
56       nbdkit-fua-filter(1), nbdkit-nocache-filter(1),
57       nbdkit-noextents-filter(1), nbdkit-nozero-filter(1).
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AUTHORS

60       Eric Blake
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63       Copyright (C) 2018-2019 Red Hat Inc.
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LICENSE

66       Redistribution and use in source and binary forms, with or without
67       modification, are permitted provided that the following conditions are
68       met:
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70       ·   Redistributions of source code must retain the above copyright
71           notice, this list of conditions and the following disclaimer.
72
73       ·   Redistributions in binary form must reproduce the above copyright
74           notice, this list of conditions and the following disclaimer in the
75           documentation and/or other materials provided with the
76           distribution.
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78       ·   Neither the name of Red Hat nor the names of its contributors may
79           be used to endorse or promote products derived from this software
80           without specific prior written permission.
81
82       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
83       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
84       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
85       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
86       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
87       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
88       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
89       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
90       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
91       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
92       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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96nbdkit-1.16.1                     2019-12-03       nbdkit-noparallel-filter(1)
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