3 nbdkit-error-filter - inject errors for testing clients
7 nbdkit --filter=error PLUGIN
8 [error=EPERM|EIO|ENOMEM|EINVAL|ENOSPC|ESHUTDOWN]
10 [error-file=/tmp/inject]
11 [error-pread=...] [error-pread-rate=...] [error-pread-file=...]
12 [error-pwrite=...] [error-pwrite-rate=...] [error-pwrite-file=...]
13 [error-trim=...] [error-trim-rate=...] [error-trim-file=...]
14 [error-zero=...] [error-zero-rate=...] [error-zero-file=...]
15 [error-extents=...] [error-extents-rate=...] [error-extents-file=...]
16 [error-cache=...] [error-cache-rate=...] [error-cache-file=...]
20 C<nbdkit-error-filter> is an nbdkit filter that injects random errors
21 into replies from the server. This is used for testing that NBD
22 clients can handle errors.
24 All parameters are optional, but you should usually specify one of the
25 C<error-rate> or C<error-*-rate> parameters,
26 B<otherwise this filter will do nothing>.
30 Inject a low rate of errors randomly into the connection:
32 nbdkit --filter=error file disk.img error-rate=1%
34 Reading, trimming, cache and extents (block status) requests will be
35 successful, but all writes and zeroing will return "No space left on
38 nbdkit --filter=error file disk.img \
40 error-pwrite-rate=100% \
43 To make all connections fail hard 60 seconds after the server is
47 nbdkit --filter=error file disk.img \
49 error-file=/tmp/inject
50 sleep 60; touch /tmp/inject
56 =item B<error=EPERM|EIO|ENOMEM|EINVAL|ENOSPC|ESHUTDOWN>
58 When a random error is injected, you can select which one from the
59 range of possible NBD errors (the NBD protocol only supports a limited
60 range of error codes).
62 This parameter is optional and the default is C<EIO>
63 ("Input/output error").
65 =item B<error-rate=>NB<%>
67 =item B<error-rate=>0..1
69 The rate of injected errors per NBD request. This can be expressed as
70 either a percentage between C<0%> and C<100%> or as a probability
71 between C<0> and C<1>. If C<0%> or C<0> is used then no errors are
72 ever injected, and if C<100%> or C<1> is used then all requests return
75 This parameter is optional and the default is C<0%>.
76 B<Unless you set this, the filter will do nothing.>
78 =item B<error-file=>FILENAME
80 Errors will only be injected when F<FILENAME> exists. (Note you must
81 also specify the C<error-rate>).
83 You can use this for fine-grained control over when to inject errors,
84 for example if you want to trigger an error at an exact moment during
85 a test, arrange for this file to be created at the appropriate time.
86 Or conversely to test error recovery in a client, create the file
87 initially, and then delete it to check the client can recover.
89 This parameter is optional.
91 =item B<error-pread>, B<error-pread-rate>, B<error-pread-file>.
93 Same as C<error>, C<error-rate> and C<error-file> but only apply the
94 settings to NBD pread requests.
96 =item B<error-pwrite>, B<error-pwrite-rate>, B<error-pwrite-file>.
98 Same as C<error>, C<error-rate> and C<error-file> but only apply the
99 settings to NBD pwrite requests.
101 =item B<error-trim>, B<error-trim-rate>, B<error-trim-file>.
103 Same as C<error>, C<error-rate> and C<error-file> but only apply the
104 settings to NBD trim requests.
106 =item B<error-zero>, B<error-zero-rate>, B<error-zero-file>.
108 Same as C<error>, C<error-rate> and C<error-file> but only apply the
109 settings to NBD zero requests.
111 =item B<error-extents>, B<error-extents-rate>, B<error-extents-file>.
115 Same as C<error>, C<error-rate> and C<error-file> but only apply the
116 settings to NBD block status requests to read extents.
118 =item B<error-cache>, B<error-cache-rate>, B<error-cache-file>.
122 Same as C<error>, C<error-rate> and C<error-file> but only apply the
123 settings to NBD cache requests.
129 =head2 Peculiar debug output
131 If you are looking at the debugging output (using C<nbdkit -f -v>)
132 references to the name of this filter show up as C<"error-inject:">,
133 and such lines indicate that the filter is not altering output, for
136 nbdkit: file.9: debug: error-inject: pread count=1024 offset=0 flags=0x0
138 Conversely, references to the string C<"error:"> occur when the
139 L<nbdkit_error(3)> API was used, including when this filter injects an
142 nbdkit: file.4: error: injecting ENOSPC error into pwrite
148 =item F<$filterdir/nbdkit-error-filter.so>
152 Use C<nbdkit --dump-config> to find the location of C<$filterdir>.
158 C<nbdkit-error-filter> first appeared in nbdkit 1.6.
163 L<nbdkit-file-plugin(1)>,
164 L<nbdkit-full-plugin(1)>,
165 L<nbdkit-retry-filter(1)>,
166 L<nbdkit-retry-request-filter(1)>,