Re: [Libguestfs] [PATCH nbdkit v2 1/2] New filter: nbdkit-retry-request-filter

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 | 74 +++++ filters/retry/nbdkit-retry-filter.pod | 7 +- plugins/curl/nbdkit-curl-plugin.pod | 1 + configure.ac | 2 + filters/retry-request/Makefile.am | 68 +++++ tests/Makefile.am | 8 + filters/retry-request/retry-request.c | 278 ++++++++++++++++++ tests/test-retry-request.sh | 94 ++++++ 9 files changed, 533 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 $nbd disk.img' If the source suffers from temporary network failures -L<nbdkit-retry-filter(1)> may help. +L<nbdkit-retry-filter(1)> or L<nbdkit-retry-request-filter(1)> may +help. To overwrite a file inside an uncompressed tar file (the file being overwritten must be the same size), use L<nbdkit-tar-filter(1)> like diff --git a/filters/retry-request/nbdkit-retry-request-filter.pod b/filters/retry-request/nbdkit-retry-request-filter.pod new file mode 100644 index 000000000..fbb467ca9 --- /dev/null +++ b/filters/retry-request/nbdkit-retry-request-filter.pod @@ -0,0 +1,74 @@ +=head1 NAME + +nbdkit-retry-request-filter - retry single requests on error + +=head1 SYNOPSIS + + nbdkit --filter=retry-request PLUGIN + [retry-request-retries=N] [retry-request-delay=N] + [retry-request-open=false] + +=head1 DESCRIPTION + +C<nbdkit-retry-request-filter> is a filter for nbdkit that +transparently retries single requests if they fail. This is useful +for plugins that are not completely reliable or have random behaviour. +For example L<nbdkit-curl-plugin(1)> might behave this way if pointed +at a load balancer which sometimes redirects to web server that is not +responsive. + +An alternative filter with different trade-offs is +L<nbdkit-retry-filter(1)>. That filter is more heavyweight because it +always reopens the whole plugin connection on failure. + +=head1 PARAMETERS + +=over 4 + +=item B<retry-request-retries=>N + +The number of times any single request will be retried before we give +up and fail the operation. The default is 2. + +=item B<retry-request-delay=>N + +The number of seconds to wait before retrying. The default is 2 +seconds. + +=item B<retry-request-open=false> + +If set to false, do not retry opening the plugin. The default is to +treat plugin open in the same way as other requests. + +=back + +=head1 FILES + +=over 4 + +=item F<$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/tests/Makefile.am b/tests/Makefile.am index 2fb39cf09..9a1485a6c 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -1693,6 +1693,14 @@ EXTRA_DIST += \ test-retry-zero-flags.sh \ $(NULL) +# retry-request filter test. +TESTS += \ + test-retry-request.sh \ + $(NULL) +EXTRA_DIST += \ + test-retry-request.sh \ + $(NULL) + # swab filter test. TESTS += \ test-swab-8.sh \ diff --git a/filters/retry-request/retry-request.c b/filters/retry-request/retry-request.c new file mode 100644 index 000000000..ac7eb017f --- /dev/null +++ b/filters/retry-request/retry-request.c @@ -0,0 +1,278 @@ +/* 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 bool retry_open_call = true; + +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) +{ + int r; + + if (strcmp (key, "retry-request-retries") == 0) { + if (nbdkit_parse_unsigned ("retry-request-retries", value, &retries) == -1) + return -1; + if (retries > 1000) { + nbdkit_error ("retry-request-retries: value too large"); + 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; + } + else if (strcmp (key, "retry-request-open") == 0) { + r = nbdkit_parse_bool (value); + if (r == -1) + return -1; + retry_open_call = r; + 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" \ + "retry-request-open=false Do not retry opening the plugin (default: true).\n" + +/* These macros encapsulate the logic of retrying. The code between + * RETRY_START...RETRY_END must set r to 0 or -1 on success or + * failure. + */ +#define RETRY_START \ + { \ + unsigned i; \ + \ + r = -1; \ + for (i = 0; r == -1 && i <= retries; ++i) { \ + if (i > 0) { \ + nbdkit_debug ("retry %u: waiting %u seconds before retrying", \ + i, delay); \ + if (nbdkit_nanosleep (delay, 0) == -1) { \ + if (*err == 0) \ + *err = errno; \ + break; \ + } \ + } \ + do +#define RETRY_END \ + while (0); \ + } \ + } + +static void * +retry_request_open (nbdkit_next_open *next, nbdkit_context *nxdata, + int readonly, const char *exportname, int is_tls) +{ + int r; + + if (retry_open_call) { + int *err = &errno; /* used by the RETRY* macros */

+ + RETRY_START + r = next (nxdata, readonly, exportname); + RETRY_END; + } + else { + r = next (nxdata, readonly, exportname); + } + + return r == 0 ? NBDKIT_HANDLE_NOT_NEEDED : NULL; +} + +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_START + r = next->pread (next, buf, count, offset, flags, err); + RETRY_END; + 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_START + r = next->pwrite (next, buf, count, offset, flags, err); + RETRY_END; + 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_START + r = next->trim (next, count, offset, flags, err); + RETRY_END; + return r; +} + +static int +retry_request_flush (nbdkit_next *next, + void *handle, uint32_t flags, + int *err) +{ + int r; + + RETRY_START + r = next->flush (next, flags, err); + RETRY_END; + 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_START + r = next->zero (next, count, offset, flags, err); + RETRY_END; + 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_START { + /* 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); + } RETRY_END; + + 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_START + r = next->cache (next, count, offset, flags, err); + RETRY_END; + 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, + .open = retry_request_open, + .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) diff --git a/tests/test-retry-request.sh b/tests/test-retry-request.sh new file mode 100755 index 000000000..96c6a1c15 --- /dev/null +++ b/tests/test-retry-request.sh @@ -0,0 +1,94 @@ +#!/usr/bin/env bash +# nbdkit +# Copyright (C) 2018-2021 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. + +source ./functions.sh +set -e +set -x + +requires_plugin sh +requires nbdcopy --version +requires dd iflag=count_bytes </dev/null + +files="retry-request.img retry-request-count" +rm -f $files +cleanup_fn rm -f $files + +touch retry-request-count +start_t=$SECONDS + +# Create a custom plugin which will test retrying requests. +nbdkit -v -U - \ + sh - \ + --filter=retry-request retry-request-retries=3 retry-request-delay=1 \ + --run 'nbdcopy --synchronous "$uri" retry-request.img' <<'EOF' +#!/usr/bin/env bash +case "$1" in + get_size) echo 512 ;; + pread) + # Fail 3 times then succeed. + read i < retry-request-count + ((i++)) + echo $i > retry-request-count + if [ $i -le 3 ]; then + echo "EIO pread failed" >&2 + exit 1 + else + dd if=/dev/zero count=$3 iflag=count_bytes + fi + ;; + + *) exit 2 ;; +esac +EOF + +# In this test we should see 3 failures: +# pread FAILS +# retry and wait 1 second +# pread FAILS +# retry and wait 1 second +# pread FAILS +# retry and wait 1 second +# pread succeeds + +# The minimum time for the test should be 3 seconds. +end_t=$SECONDS +if [ $((end_t - start_t)) -lt 3 ]; then + echo "$0: test ran too quickly" + exit 1 +fi + +# Check retry-request-count = 4 (because we write #retries+1 to the file) +read retry_count < retry-request-count +if [ $retry_count -ne 4 ]; then + echo "$0: retry-request-count ($retry_count) != 4" + exit 1 +fi