NAME

       nbdkit-noparallel-filter - nbdkit noparallel filter

SYNOPSIS

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

DESCRIPTION

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

PARAMETERS

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

EXAMPLES

       Serve the file disk.img, but disallow out-of-order transaction completion to a given client:

        nbdkit --filter=noparallel file disk.img

       Serve the file disk.img, but allowing only one client at a time:

        nbdkit --filter=noparallel file serialize=connections disk.img

FILES

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

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

VERSION

       "nbdkit-noparallel-filter" first appeared in nbdkit 1.14.

SEE ALSO

       nbdkit(1), nbdkit-file-plugin(1), nbdkit-filter(3), nbdkit-fua-filter(1), nbdkit-nocache-filter(1),
       nbdkit-noextents-filter(1), nbdkit-nozero-filter(1).

AUTHORS

       Eric Blake

COPYRIGHT

       Copyright (C) 2018-2019 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:

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

       •   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.

       •   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
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