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

6       nbdkit-log-filter - nbdkit log filter
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SYNOPSIS

9        nbdkit --filter=log plugin logfile=FILE [logappend=BOOL] [plugin-args...]
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DESCRIPTION

12       "nbdkit-log-filter" is a filter that logs all transactions.  When used
13       as the first filter, it can show the original client requests; as a
14       later filter, it can show how earlier filters have modified the
15       original request.  The log results are placed in a user-specified file;
16       for more details on the log format, see FILES.  Note that using "nbdkit
17       -v -f" produces much more verbose logging details to stderr about every
18       aspect of nbdkit operation, although this requires running nbdkit in
19       the foreground; while the log filter is designed to work even when
20       nbdkit is run as a daemon.
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PARAMETERS

23       The nbdkit-log-filter requires a single parameter "logfile" which
24       specifies the path of the file to use for logging.  If the file already
25       exists, it will be truncated unless the "logappend" parameter was
26       specified with a value that can be parsed as a boolean true.
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EXAMPLES

29       Serve the file disk.img, and log each client transaction in the file
30       disk.log:
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32        nbdkit --filter=log file disk.img logfile=disk.log
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34       Repeat the task, but with the cow (copy-on-write) filter to perform
35       local caching of data served from the original plugin:
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37        nbdkit --filter=cow --filter=log file disk.img logfile=disk.log2
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39       After running a client that performs the same operations under each of
40       the two servers, you can compare disk.log and disk.log2 to see the
41       impact of the caching.
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FILES

44       "logfile=FILE" parameter
45           This filter writes to the file specified by the "logfile=FILE"
46           parameter.  All lines include a timestamp, a connection counter,
47           then details about the command.  The following actions are logged:
48           Connect, Read, Write, Zero, Trim, Extents, Cache, Flush, and
49           Disconnect.  Except for Connect and Disconnect, an event is logged
50           across two lines for call and return value, to allow tracking
51           duration and tracing any parallel execution, using id for
52           correlation (incremented per action on the connection).
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54           An example logging session of a client that performs a single
55           successful read is:
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57            2018-01-27 20:38:22.959984 connection=1 Connect size=0x400 write=1 flush=1 rotational=0 trim=0 zero=1 fua=1 extents=1 cache=0 fast_zero=0
58            2018-01-27 20:38:23.001720 connection=1 Read id=1 offset=0x0 count=0x100 ...
59            2018-01-27 20:38:23.001995 connection=1 ...Read id=1 return=0 (Success)
60            2018-01-27 20:38:23.044259 connection=1 Disconnect transactions=1
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62       $filterdir/nbdkit-log-filter.so
63           The filter.
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65           Use "nbdkit --dump-config" to find the location of $filterdir.
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VERSION

68       "nbdkit-log-filter" first appeared in nbdkit 1.2.
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SEE ALSO

71       nbdkit(1), nbdkit-file-plugin(1), nbdkit-cow-filter(1),
72       nbdkit-filter(3), nbdkit-stats-filter(1).
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AUTHORS

75       Eric Blake
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78       Copyright (C) 2018 Red Hat Inc.
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LICENSE

81       Redistribution and use in source and binary forms, with or without
82       modification, are permitted provided that the following conditions are
83       met:
84
85       ·   Redistributions of source code must retain the above copyright
86           notice, this list of conditions and the following disclaimer.
87
88       ·   Redistributions in binary form must reproduce the above copyright
89           notice, this list of conditions and the following disclaimer in the
90           documentation and/or other materials provided with the
91           distribution.
92
93       ·   Neither the name of Red Hat nor the names of its contributors may
94           be used to endorse or promote products derived from this software
95           without specific prior written permission.
96
97       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
98       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
99       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
100       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
101       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
102       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
103       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
104       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
105       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
106       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
107       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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111nbdkit-1.16.1                     2019-12-03              nbdkit-log-filter(1)
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