[Libguestfs] [PATCH nbdkit 3/4] New filter: exitlast filter to exit on last client connection.

--- docs/nbdkit-service.pod | 1 + filters/exitlast/nbdkit-exitlast-filter.pod | 58 +++++++++++++++ filters/ip/nbdkit-ip-filter.pod | 1 + filters/rate/nbdkit-rate-filter.pod | 1 + configure.ac | 3 + filters/exitlast/Makefile.am | 60 ++++++++++++++++ tests/Makefile.am | 3 + filters/exitlast/exitlast.c | 80 +++++++++++++++++++++ tests/test-exitlast.sh | 66 +++++++++++++++++ TODO | 6 +- 10 files changed, 276 insertions(+), 3 deletions(-) diff --git a/docs/nbdkit-service.pod b/docs/nbdkit-service.pod index 44bc111f..ecc8e94b 100644 --- a/docs/nbdkit-service.pod +++ b/docs/nbdkit-service.pod @@ -143,6 +143,7 @@ L</SOCKET ACTIVATION>. =head1 SEE ALSO L<nbdkit(1)>, +L<nbdkit-exitlast-filter(1)>, L<nbdkit-ip-filter(1)>, L<systemd(1)>, L<systemd.socket(5)>, diff --git a/filters/exitlast/nbdkit-exitlast-filter.pod b/filters/exitlast/nbdkit-exitlast-filter.pod new file mode 100644 index 00000000..e0fbd6ea --- /dev/null +++ b/filters/exitlast/nbdkit-exitlast-filter.pod @@ -0,0 +1,58 @@ +=head1 NAME + +nbdkit-exitlast-filter - exit on last client connection + +=head1 SYNOPSIS + + nbdkit --filter=exitlast PLUGIN + +=head1 DESCRIPTION + +C<nbdkit-exitlast-filter> is an nbdkit filter that causes nbdkit to +exit when there are no more client connections. Note that it doesn't +exit before the first client connection. + +One use for this is in combination with a superserver, to save +resources when nbdkit is not in use (see L<nbdkit-service(1)>). +Another use is to ensure nbdkit exits after the client has finished +(but see also nbdkit-captive(1) for other ways to do this). + +=head1 PARAMETERS + +There are no parameters specific to nbdkit-exitlast-filter. Any +parameters are passed through to and processed by the underlying +plugin in the normal way. + +=head1 FILES + +=over 4 + +=item F<$filterdir/nbdkit-exitlast-filter.so> + +The filter. + +Use C<nbdkit --dump-config> to find the location of C<$filterdir>. + +=back + +=head1 VERSION + +C<nbdkit-exitlast-filter> first appeared in nbdkit 1.20. + +=head1 SEE ALSO + +L<nbdkit(1)>, +L<nbdkit-ip-filter(1)>, +L<nbdkit-rate-filter(1)>, +L<nbdkit-captive(1)>, +L<nbdkit-service(1)>, +L<nbdkit-filter(3)>, +L<nbdkit-plugin(3)>. + +=head1 AUTHORS + +Richard W.M. Jones + +=head1 COPYRIGHT + +Copyright (C) 2020 Red Hat Inc. diff --git a/filters/ip/nbdkit-ip-filter.pod b/filters/ip/nbdkit-ip-filter.pod index b91633c6..1621ebec 100644 --- a/filters/ip/nbdkit-ip-filter.pod +++ b/filters/ip/nbdkit-ip-filter.pod @@ -145,6 +145,7 @@ C<nbdkit-ip-filter> first appeared in nbdkit 1.18. =head1 SEE ALSO L<nbdkit(1)>, +L<nbdkit-exitlast-filter(1)>, L<nbdkit-filter(3)>. =head1 AUTHORS diff --git a/filters/rate/nbdkit-rate-filter.pod b/filters/rate/nbdkit-rate-filter.pod index e8bfa42b..acf7d8b0 100644 --- a/filters/rate/nbdkit-rate-filter.pod +++ b/filters/rate/nbdkit-rate-filter.pod @@ -129,6 +129,7 @@ C<nbdkit-rate-filter> first appeared in nbdkit 1.12. L<nbdkit(1)>, L<nbdkit-blocksize-filter(1)>, L<nbdkit-delay-filter(1)>, +L<nbdkit-exitlast-filter(1)>, L<nbdkit-filter(3)>, L<iptables(8)>, L<tc(8)>. diff --git a/configure.ac b/configure.ac index 0b7d8b7c..0b980238 100644 --- a/configure.ac +++ b/configure.ac @@ -97,6 +97,7 @@ filters="\ cow \ delay \ error \ + exitlast \ ext2 \ extentlist \ fua \ @@ -267,6 +268,7 @@ AC_CHECK_HEADERS([\ alloca.h \ byteswap.h \ endian.h \ + stdatomic.h \ sys/endian.h \ sys/mman.h \ sys/prctl.h \ @@ -1022,6 +1024,7 @@ AC_CONFIG_FILES([Makefile filters/cow/Makefile filters/delay/Makefile filters/error/Makefile + filters/exitlast/Makefile filters/ext2/Makefile filters/extentlist/Makefile filters/fua/Makefile diff --git a/filters/exitlast/Makefile.am b/filters/exitlast/Makefile.am new file mode 100644 index 00000000..690008f1 --- /dev/null +++ b/filters/exitlast/Makefile.am @@ -0,0 +1,60 @@ +# nbdkit +# Copyright (C) 2019-2020 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-exitlast-filter.pod + +filter_LTLIBRARIES = nbdkit-exitlast-filter.la + +nbdkit_exitlast_filter_la_SOURCES = \ + exitlast.c \ + $(top_srcdir)/include/nbdkit-filter.h \ + $(NULL) + +nbdkit_exitlast_filter_la_CPPFLAGS = -I$(top_srcdir)/include +nbdkit_exitlast_filter_la_CFLAGS = $(WARNINGS_CFLAGS) +nbdkit_exitlast_filter_la_LDFLAGS = \ + -module -avoid-version -shared \ + -Wl,--version-script=$(top_srcdir)/filters/filters.syms \ + $(NULL) + +if HAVE_POD + +man_MANS = nbdkit-exitlast-filter.1 +CLEANFILES += $(man_MANS) + +nbdkit-exitlast-filter.1: nbdkit-exitlast-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 eb51757a..2ac8fb31 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -1052,6 +1052,9 @@ TESTS += \ test-error-triggered.sh \ $(NULL) +# exitlast filter test. +TESTS += test-exitlast.sh + # extentlist filter test. TESTS += test-extentlist.sh diff --git a/filters/exitlast/exitlast.c b/filters/exitlast/exitlast.c new file mode 100644 index 00000000..51efda03 --- /dev/null +++ b/filters/exitlast/exitlast.c @@ -0,0 +1,80 @@ +/* nbdkit + * Copyright (C) 2019-2020 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 <nbdkit-filter.h> + +#ifdef HAVE_STDATOMIC_H +#include <stdatomic.h> +#else +/* Some old platforms lack atomic types, but 32 bit ints are usually + * "atomic enough". + */ +#define _Atomic /**/ +#endif + +/* Counts client connections. When this drops to zero we exit. */ +static _Atomic unsigned connections; + +static void * +exitlast_open (nbdkit_next_open *next, nbdkit_backend *nxdata, + int readonly) +{ + if (next (nxdata, readonly) == -1) + return NULL; + + connections++; + + return NBDKIT_HANDLE_NOT_NEEDED; +} + +static void +exitlast_close (void *handle) +{ + if (--connections == 0) { + nbdkit_debug ("exitlast: exiting on last client connection"); + nbdkit_shutdown (); + } +} + +static struct nbdkit_filter filter = { + .name = "exitlast", + .longname = "nbdkit exitlast filter", + .open = exitlast_open, + .close = exitlast_close, +}; + +NBDKIT_REGISTER_FILTER(filter) diff --git a/tests/test-exitlast.sh b/tests/test-exitlast.sh new file mode 100755 index 00000000..d24a177f --- /dev/null +++ b/tests/test-exitlast.sh @@ -0,0 +1,66 @@ +#!/usr/bin/env bash +# nbdkit +# Copyright (C) 2019-2020 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 -x + +requires qemu-img --version + +sock=`mktemp -u` +files="exitlast.pid $sock" +cleanup_fn rm -f $files + +# Start nbdkit with the exitlast filter. +start_nbdkit -P exitlast.pid -U $sock --filter=exitlast memory size=1M + +pid=`cat exitlast.pid` + +# nbdkit should start up even though there are no client connections. +if ! kill -s 0 $pid; then + echo "$0: nbdkit exited before first connection" + exit 1 +fi + +# Connect with a client. +qemu-img info "nbd:unix:$sock" || exit 1 + +# Now nbdkit should exit. Wait for it to do so. +for i in {1..60}; do + if ! kill -s 0 $pid; then + break + fi + sleep 1 +done +if kill -s 0 $pid; then + echo "$0: nbdkit did not exit after last client connection" + exit 1 +fi diff --git a/TODO b/TODO index 21cbfe5b..cd2e47a5 100644 --- a/TODO +++ b/TODO @@ -10,9 +10,6 @@ General ideas for improvements sizes and threads, as that should make it easier to identify systematic issues. -* Exit on last connection (the default behaviour of qemu-nbd unless - you use -t). - * Limit number of incoming connections (like qemu-nbd -e). * For parallel plugins, only create threads on demand from parallel @@ -173,6 +170,9 @@ Suggestions for filters MBs of extra data) https://github.com/facebook/zstd/issues/395#issuecomment-535875379 +* nbdkit-exitlast-filter could probably use a configurable timeout so + that it hangs around in case another connection comes along quickly. + nbdkit-rate-filter: * allow other kinds of traffic shaping such as VBR -- 2.25.0