New filter: exitwhen: exit gracefully when an event occurs.

Author: rwmjones

.gitignore

@@ -127,6 +127,7 @@ plugins/*/*.3
 /tests/test-data
 /tests/test-delay
 /tests/test-exit-with-parent
+/tests/test-exitwhen-pipe-closed
 /tests/test-ext2
 /tests/test-file-block
 /tests/test-golang

configure.ac

@@ -104,6 +104,7 @@ filters="\
         delay \
         error \
         exitlast \
+        exitwhen \
 	exportname \
         ext2 \
         extentlist \
@@ -1228,6 +1229,7 @@ AC_CONFIG_FILES([Makefile
                  filters/delay/Makefile
                  filters/error/Makefile
                  filters/exitlast/Makefile
+                 filters/exitwhen/Makefile
                  filters/exportname/Makefile
                  filters/ext2/Makefile
                  filters/extentlist/Makefile

docs/nbdkit-captive.pod

@@ -15,8 +15,9 @@ You can run nbdkit under another process and have nbdkit reliably
 clean up.  There are two techniques depending on whether you want
 nbdkit to start the other process (L</CAPTIVE NBDKIT>), or if you want
 the other process to start nbdkit (L</EXIT WITH PARENT>).  Another way
-is to have nbdkit exit after the last client connection, see
-L<nbdkit-exitlast-filter(1)>.
+is to have nbdkit exit after the last client connection
+(L<nbdkit-exitlast-filter(1)>) or after an event
+(L<nbdkit-exitwhen-filter(1)>).
 
 =head1 CAPTIVE NBDKIT
 
@@ -150,10 +151,14 @@ C<nbdkit --exit-with-parent> only from the main thread (unless you
 actually want nbdkit to exit with the thread, but that may not work
 reliably on all operating systems).
 
+To exit when an unrelated process exits, use
+L<nbdkit-exitwhen-filter(1)> C<exit-when-process-exits> feature.
+
 =head1 SEE ALSO
 
 L<nbdkit(1)>,
 L<nbdkit-exitlast-filter(1)>,
+L<nbdkit-exitwhen-filter(1)>,
 L<prctl(2)> (on Linux),
 L<procctl(2)> (on FreeBSD).
 

docs/nbdkit-service.pod

@@ -145,6 +145,7 @@ L</SOCKET ACTIVATION>.
 L<nbdkit(1)>,
 L<nbdkit-client(1)>,
 L<nbdkit-exitlast-filter(1)>,
+L<nbdkit-exitwhen-filter(1)>,
 L<nbdkit-ip-filter(1)>,
 L<nbdkit-limit-filter(1)>,
 L<systemd(1)>,

filters/exitlast/nbdkit-exitlast-filter.pod

@@ -17,6 +17,8 @@ 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).
 
+To exit when an event occurs, try L<nbdkit-exitwhen-filter(1)>.
+
 =head1 PARAMETERS
 
 There are no parameters specific to nbdkit-exitlast-filter.  Any
@@ -42,6 +44,7 @@ C<nbdkit-exitlast-filter> first appeared in nbdkit 1.20.
 =head1 SEE ALSO
 
 L<nbdkit(1)>,
+L<nbdkit-exitwhen-filter(1)>,
 L<nbdkit-ip-filter(1)>,
 L<nbdkit-limit-filter(1)>,
 L<nbdkit-rate-filter(1)>,

filters/exitwhen/Makefile.am

@@ -0,0 +1,67 @@
+# 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-exitwhen-filter.pod
+
+filter_LTLIBRARIES = nbdkit-exitwhen-filter.la
+
+nbdkit_exitwhen_filter_la_SOURCES = \
+	exitwhen.c \
+	$(top_srcdir)/include/nbdkit-filter.h \
+	$(NULL)
+
+nbdkit_exitwhen_filter_la_CPPFLAGS = \
+	-I$(top_srcdir)/include \
+	-I$(top_srcdir)/common/utils \
+	$(NULL)
+nbdkit_exitwhen_filter_la_CFLAGS = $(WARNINGS_CFLAGS)
+nbdkit_exitwhen_filter_la_LIBADD = \
+	$(top_builddir)/common/utils/libutils.la \
+	$(IMPORT_LIBRARY_ON_WINDOWS) \
+	$(NULL)
+nbdkit_exitwhen_filter_la_LDFLAGS = \
+	-module -avoid-version -shared $(NO_UNDEFINED_ON_WINDOWS) \
+	-Wl,--version-script=$(top_srcdir)/filters/filters.syms \
+	$(NULL)
+
+if HAVE_POD
+
+man_MANS = nbdkit-exitwhen-filter.1
+CLEANFILES += $(man_MANS)
+
+nbdkit-exitwhen-filter.1: nbdkit-exitwhen-filter.pod
+	$(PODWRAPPER) --section=1 --man $@ \
+	    --html $(top_builddir)/html/$@.html \
+	    $<
+
+endif HAVE_POD