Re: [Libguestfs] [PATCH nbdkit] New filter: request-request

Similar to nbdkit-retry-filter, but this only retries single failing requests rather than reopening the whole plugin. This is intended to be used with the curl filter to solve: https://bugzilla.redhat.com/show_bug.cgi?id=2013000 --- docs/nbdkit-captive.pod | 3 +- .../nbdkit-retry-request-filter.pod | 67 +++++ filters/retry/nbdkit-retry-filter.pod | 7 +- plugins/curl/nbdkit-curl-plugin.pod | 1 + configure.ac | 2 + filters/retry-request/Makefile.am | 68 ++++++ filters/retry-request/retry-request.c | 229 ++++++++++++++++++ 7 files changed, 375 insertions(+), 2 deletions(-) diff --git a/docs/nbdkit-captive.pod b/docs/nbdkit-captive.pod index d340b8ae0..eafe36d8b 100644 --- a/docs/nbdkit-captive.pod +++ b/docs/nbdkit-captive.pod @@ -118,7 +118,8 @@ help performance: --run 'qemu-img convert $nbd disk.img' If the source suffers from temporary network failures -L<nbdkit-retry-filter(1)> may help. +L<nbdkit-retry-filter(1)> or L<nbdkit-retry-request-filter(1)> may +help. To overwrite a file inside an uncompressed tar file (the file being overwritten must be the same size), use L<nbdkit-tar-filter(1)> like diff --git a/filters/retry-request/nbdkit-retry-request-filter.pod b/filters/retry-request/nbdkit-retry-request-filter.pod new file mode 100644 index 000000000..1216cf83b --- /dev/null +++ b/filters/retry-request/nbdkit-retry-request-filter.pod @@ -0,0 +1,67 @@ +=head1 NAME + +nbdkit-retry-request-filter - retry single requests on error + +=head1 SYNOPSIS + + nbdkit --filter=retry-request PLUGIN [retry-request-retries=N] + +=head1 DESCRIPTION + +C<nbdkit-retry-request-filter> is a filter for nbdkit that +transparently retries single requests if they fail. This is useful +for plugins that are not completely reliable or have random behaviour. +For example L<nbdkit-curl-plugin(1)> might behave this way if pointed +at a load balancer which sometimes redirects to web server that are +not responsive. + +An alternative filter with different trade-offs is +L<nbdkit-retry-filter(1)>. That filter is more heavyweight because it +always reopens the whole plugin connection on failure. + +=head1 PARAMETERS + +=over 4 + +=item B<retry-request-retries=>N + +The number of times any single request will be retried before we give +up and fail the operation. The default is 2. + +=item B<retry-request-delay=>N + +The number of seconds to wait before retrying. The default is 2 +seconds. + +=back + +=head1 FILES + +=over 4 + +=item F<$filterdir/nbdkit-retry-request-filter.so> + +The filter. + +Use C<nbdkit --dump-config> to find the location of C<$filterdir>. + +=back + +=head1 VERSION + +C<nbdkit-retry-filter> first appeared in nbdkit 1.30. + +=head1 SEE ALSO + +L<nbdkit(1)>, +L<nbdkit-filter(3)>, +L<nbdkit-readahead-filter(1)>, +L<nbdkit-retry-filter(1)>. + +=head1 AUTHORS + +Richard W.M. Jones + +=head1 COPYRIGHT + +Copyright (C) 2019-2021 Red Hat Inc. diff --git a/filters/retry/nbdkit-retry-filter.pod b/filters/retry/nbdkit-retry-filter.pod index fee4b7e64..babd82bbd 100644 --- a/filters/retry/nbdkit-retry-filter.pod +++ b/filters/retry/nbdkit-retry-filter.pod @@ -16,6 +16,10 @@ make long-running copy operations reliable in the presence of temporary network failures, without requiring any changes to the plugin or the NBD client. +An alternative and more fine-grained filter is +L<nbdkit-retry-request-filter(1)> which will retry only single +requests that fail. + Several optional parameters are available to control: =over 4 @@ -113,7 +117,8 @@ C<nbdkit-retry-filter> first appeared in nbdkit 1.16. L<nbdkit(1)>, L<nbdkit-filter(3)>, -L<nbdkit-readahead-filter(1)>. +L<nbdkit-readahead-filter(1)>, +L<nbdkit-retry-request-filter(1)>. =head1 AUTHORS diff --git a/plugins/curl/nbdkit-curl-plugin.pod b/plugins/curl/nbdkit-curl-plugin.pod index c7acf6225..07f71b389 100644 --- a/plugins/curl/nbdkit-curl-plugin.pod +++ b/plugins/curl/nbdkit-curl-plugin.pod @@ -503,6 +503,7 @@ L<nbdkit-extentlist-filter(1)>, L<nbdkit-file-plugin(1)>, L<nbdkit-readahead-filter(1)>, L<nbdkit-retry-filter(1)>, +L<nbdkit-retry-request-filter(1)>, L<nbdkit-ssh-plugin(1)>, L<nbdkit-torrent-plugin(1)>, L<nbdkit-plugin(3)>, diff --git a/configure.ac b/configure.ac index fd15e2960..3fd8a397e 100644 --- a/configure.ac +++ b/configure.ac @@ -139,6 +139,7 @@ filters="\ rate \ readahead \ retry \ + retry-request \ stats \ swab \ tar \ @@ -1342,6 +1343,7 @@ AC_CONFIG_FILES([Makefile filters/rate/Makefile filters/readahead/Makefile filters/retry/Makefile + filters/retry-request/Makefile filters/stats/Makefile filters/swab/Makefile filters/tar/Makefile diff --git a/filters/retry-request/Makefile.am b/filters/retry-request/Makefile.am new file mode 100644 index 000000000..95fdafdcd --- /dev/null +++ b/filters/retry-request/Makefile.am @@ -0,0 +1,68 @@ +# nbdkit +# Copyright (C) 2019-2021 Red Hat Inc. +# +# 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 +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +include $(top_srcdir)/common-rules.mk + +EXTRA_DIST = nbdkit-retry-request-filter.pod + +filter_LTLIBRARIES = nbdkit-retry-request-filter.la + +nbdkit_retry_request_filter_la_SOURCES = \ + retry-request.c \ + $(top_srcdir)/include/nbdkit-filter.h \ + $(NULL) + +nbdkit_retry_request_filter_la_CPPFLAGS = \ + -I$(top_srcdir)/include \ + -I$(top_srcdir)/common/include \ + -I$(top_srcdir)/common/utils \ + $(NULL) +nbdkit_retry_request_filter_la_CFLAGS = $(WARNINGS_CFLAGS) +nbdkit_retry_request_filter_la_LDFLAGS = \ + -module -avoid-version -shared $(NO_UNDEFINED_ON_WINDOWS) \ + -Wl,--version-script=$(top_srcdir)/filters/filters.syms \ + $(NULL) +nbdkit_retry_request_filter_la_LIBADD = \ + $(top_builddir)/common/utils/libutils.la \ + $(IMPORT_LIBRARY_ON_WINDOWS) \ + $(NULL) + +if HAVE_POD + +man_MANS = nbdkit-retry-request-filter.1 +CLEANFILES += $(man_MANS) + +nbdkit-retry-request-filter.1: nbdkit-retry-request-filter.pod + $(PODWRAPPER) --section=1 --man $@ \ + --html $(top_builddir)/html/$@.html \ + $< + +endif HAVE_POD diff --git a/filters/retry-request/retry-request.c b/filters/retry-request/retry-request.c new file mode 100644 index 000000000..d0a8b67bc --- /dev/null +++ b/filters/retry-request/retry-request.c @@ -0,0 +1,229 @@ +/* nbdkit + * Copyright (C) 2019-2021 Red Hat Inc. + * + * 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 + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <stdbool.h> +#include <inttypes.h> +#include <string.h> +#include <sys/time.h> + +#include <nbdkit-filter.h> + +#include "cleanup.h" +#include "windows-compat.h" + +static unsigned retries = 2; /* 0 = filter is disabled */ +static unsigned delay = 2; + +static int +retry_request_thread_model (void) +{ + return NBDKIT_THREAD_MODEL_PARALLEL; +} + +static int +retry_request_config (nbdkit_next_config *next, nbdkit_backend *nxdata, + const char *key, const char *value) +{ + if (strcmp (key, "retry-request-retries") == 0) { + if (nbdkit_parse_unsigned ("retry-request-retries", value, &retries) == -1) + return -1; + return 0; + } + else if (strcmp (key, "retry-request-delay") == 0) { + if (nbdkit_parse_unsigned ("retry-request-delay", value, &delay) == -1) + return -1; + if (delay == 0) { + nbdkit_error ("retry-request-delay cannot be 0"); + return -1; + } + return 0; + } + + return next (nxdata, key, value); +} + +#define retry_request_config_help \ + "retry-request-retries=<N> Number of retries (default: 2).\n" \ + "retry-request-delay=<N> Seconds to wait before retry (default: 2).\n" + +/* This macro encapsulates the logic of retrying. */ +#define RETRY(code) \ + do { \ + unsigned i; \

+ r = -1; \ + for (i = 0; r == -1 && i <= retries; ++i) { \ + if (i > 0) { \ + nbdkit_debug ("retry %d: waiting %d seconds before retrying", \ + i, delay); \

+ if (nbdkit_nanosleep (delay, 0) == -1) { \ + if (*err == 0) *err = errno; \

+ return -1; \ + } \ + } \ + code; \

+ } \ + } while (0) + +/* XXX This doesn't attempt to retry the initial open call. Should it? + * Argument against: You probably want the initial open to fail + * quickly. Argument for: curl's open call makes a request (to fetch + * the size) so retrying could be useful. + */ + +static int +retry_request_pread (nbdkit_next *next, + void *handle, void *buf, uint32_t count, uint64_t offset, + uint32_t flags, int *err) +{ + int r; + + RETRY (r = next->pread (next, buf, count, offset, flags, err)); + return r; +} + +static int +retry_request_pwrite (nbdkit_next *next, + void *handle, + const void *buf, uint32_t count, uint64_t offset, + uint32_t flags, int *err) +{ + int r; + + RETRY (r = next->pwrite (next, buf, count, offset, flags, err)); + return r; +} + +static int +retry_request_trim (nbdkit_next *next, + void *handle, + uint32_t count, uint64_t offset, uint32_t flags, + int *err) +{ + int r; + + RETRY (r = next->trim (next, count, offset, flags, err)); + return r; +} + +static int +retry_request_flush (nbdkit_next *next, + void *handle, uint32_t flags, + int *err) +{ + int r; + + RETRY (r = next->flush (next, flags, err)); + return r; +} + +static int +retry_request_zero (nbdkit_next *next, + void *handle, + uint32_t count, uint64_t offset, uint32_t flags, + int *err) +{ + int r; + + RETRY (r = next->zero (next, count, offset, flags, err)); + return r; +} + +static int +retry_request_extents (nbdkit_next *next, + void *handle, + uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents *extents, int *err) +{ + CLEANUP_EXTENTS_FREE struct nbdkit_extents *extents2 = NULL; + int r; + + RETRY ( + /* Each retry must begin with extents reset to the right beginning. */ + nbdkit_extents_free (extents2); + extents2 = nbdkit_extents_new (offset, next->get_size (next)); + if (extents2 == NULL) { + *err = errno; + return -1; /* Not worth a retry after ENOMEM. */ + } + r = next->extents (next, count, offset, flags, extents2, err); + );

+ + if (r == 0) { + size_t i; + + /* Transfer the successful extents back to the caller. */ + for (i = 0; i < nbdkit_extents_count (extents2); ++i) { + struct nbdkit_extent e = nbdkit_get_extent (extents2, i); + + if (nbdkit_add_extent (extents, e.offset, e.length, e.type) == -1) { + *err = errno; + return -1; + } + } + } + + return r; +} + +static int +retry_request_cache (nbdkit_next *next, + void *handle, + uint32_t count, uint64_t offset, uint32_t flags, + int *err) +{ + int r; + + RETRY (r = next->cache (next, count, offset, flags, err)); + return r; +} + +static struct nbdkit_filter filter = {

+ .name = "retry-request", + .longname = "nbdkit retry request filter", + .thread_model = retry_request_thread_model, + .config = retry_request_config, + .config_help = retry_request_config_help, + .pread = retry_request_pread, + .pwrite = retry_request_pwrite, + .trim = retry_request_trim, + .flush = retry_request_flush, + .zero = retry_request_zero, + .extents = retry_request_extents, + .cache = retry_request_cache, +}; + +NBDKIT_REGISTER_FILTER(filter)