nbdkit-openonce-filter - open the underlying plugin once
nbdkit --filter=openonce PLUGINnbdkit-openonce-filter is a filter for nbdkit(1) that opens the underlying plugin once (per export). This can be used if the plugin is slow to open/connect (such as nbdkit-ssh-plugin(1) or nbdkit-vddk-plugin(1)).
Some disadvantages are:
Multiple NBD clients may be sharing one connection to the plugin which might cause performance issues.
The plugin stays open until nbdkit shuts down.
This defeats multi-conn. If nbdkit advertises multi-conn, NBD clients may make multiple connections but will end up connecting to the same underlying plugin instance. (See also nbdkit-multi-conn-filter(1)).
There are no parameters specific to nbdkit-openonce-filter. Any parameters are passed through to and processed by the underlying plugin in the normal way.
The filter.
Use nbdkit --dump-config to find the location of $filterdir.
nbdkit-openonce-filter first appeared in nbdkit 1.44.
nbdkit(1), nbdkit-cache-filter(1), nbdkit-multi-conn-filter(1), nbdkit-retry-filter(1), nbdkit-curl-plugin(1), nbdkit-ssh-plugin(1), nbdkit-vddk-plugin(1), nbdkit-filter(3).
Richard W.M. Jones
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