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.

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