[PATCH 1/3] Use the Xapian::DB_RETRY_LOCK flag when available

[David Bremner <david@tethera.net>]

From: Istvan Marko <notmuch@kismala.com>

Xapian 1.3 has introduced the DB_RETRY_LOCK flag (Xapian bug
275). Detect it in configure and optionally use it. With this flag
commands that need the write lock will wait for their turn instead of
aborting when it's not immediately available.

Amended by db: allow disabling in configure
---
 configure       | 35 +++++++++++++++++++++++++++++++++++
 lib/database.cc |  8 +++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 49fa5b9..ae0a027 100755
--- a/configure
+++ b/configure
@@ -72,6 +72,7 @@ WITH_EMACS=1
 WITH_BASH=1
 WITH_RUBY=1
 WITH_ZSH=1
+WITH_RETRY_LOCK=1
 
 usage ()
 {
@@ -140,6 +141,7 @@ Some features can be disabled (--with-feature=no is equivalent to
 	--without-emacs			Do not install lisp file
 	--without-ruby			Do not install ruby bindings
 	--without-zsh-completion	Do not install zsh completions files
+	--without-retry-lock		Do not use blocking xapian opens, even if available
 
 Additional options are accepted for compatibility with other
 configure-script calling conventions, but don't do anything yet:
@@ -211,6 +213,14 @@ for option; do
 	fi
     elif [ "${option}" = '--without-ruby' ] ; then
 	WITH_RUBY=0
+    elif [ "${option%%=*}" = '--with-retry-lock' ]; then
+	if [ "${option#*=}" = 'no' ]; then
+	    WITH_RETRY_LOCK=0
+	else
+	    WITH_RETRY_LOCK=1
+	fi
+    elif [ "${option}" = '--without-retry-lock' ] ; then
+	WITH_RETRY_LOCK=0
     elif [ "${option%%=*}" = '--with-zsh-completion' ]; then
 	if [ "${option#*=}" = 'no' ]; then
 	    WITH_ZSH=0
@@ -392,6 +402,24 @@ EOF
     rm -f _field_processor.o _field_processor.cc
 
     default_xapian_backend=""
+    # DB_RETRY_LOCK is only supported on Xapian > 1.3.2
+    have_xapian_db_retry_lock=0
+    if [ $WITH_RETRY_LOCK = "1" ]; then
+	printf "Checking for Xapian lock retry support... "
+	cat>_retry.cc<<EOF
+#include <xapian.h>
+int flag = Xapian::DB_RETRY_LOCK;
+EOF
+	if ${CXX} ${CXXFLAGS_for_sh} ${xapian_cxxflags} -c _retry.cc -o _retry.o > /dev/null 2>&1
+	then
+	    have_xapian_db_retry_lock=1
+	    printf "Yes.\n"
+	else
+	    printf "No. (optional)\n"
+	fi
+	rm -f _retry.o _retry.cc
+    fi
+
     printf "Testing default Xapian backend... "
     cat >_default_backend.cc <<EOF
 #include <xapian.h>
@@ -1022,6 +1050,9 @@ HAVE_XAPIAN_COMPACT = ${have_xapian_compact}
 # Whether the Xapian version in use supports field processors
 HAVE_XAPIAN_FIELD_PROCESSOR = ${have_xapian_field_processor}
 
+# Whether the Xapian version in use supports DB_RETRY_LOCK
+HAVE_XAPIAN_DB_RETRY_LOCK = ${have_xapian_db_retry_lock}
+
 # Whether the getpwuid_r function is standards-compliant
 # (if not, then notmuch will #define _POSIX_PTHREAD_SEMANTICS
 # to enable the standards-compliant version -- needed for Solaris)
@@ -1097,6 +1128,7 @@ COMMON_CONFIGURE_CFLAGS = \\
 	-DSTD_ASCTIME=\$(STD_ASCTIME)				\\
 	-DHAVE_XAPIAN_COMPACT=\$(HAVE_XAPIAN_COMPACT)		\\
 	-DHAVE_XAPIAN_FIELD_PROCESSOR=\$(HAVE_XAPIAN_FIELD_PROCESSOR) \\
+	-DHAVE_XAPIAN_DB_RETRY_LOCK=\$(HAVE_XAPIAN_DB_RETRY_LOCK) \\
 	-DUTIL_BYTE_ORDER=\$(UTIL_BYTE_ORDER)
 
 CONFIGURE_CFLAGS = \$(COMMON_CONFIGURE_CFLAGS)
@@ -1117,6 +1149,9 @@ NOTMUCH_HAVE_XAPIAN_COMPACT=${have_xapian_compact}
 # Whether the Xapian version in use supports field processors
 NOTMUCH_HAVE_XAPIAN_FIELD_PROCESSOR=${have_xapian_field_processor}
 
+# Whether the Xapian version in use supports lock retry
+NOTMUCH_HAVE_XAPIAN_DB_RETRY_LOCK=${have_xapian_db_retry_lock}
+
 # Which backend will Xapian use by default?
 NOTMUCH_DEFAULT_XAPIAN_BACKEND=${default_xapian_backend}
 
diff --git a/lib/database.cc b/lib/database.cc
index afafe88..66ee267 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -49,6 +49,12 @@ typedef struct {
 #define STRINGIFY(s) _SUB_STRINGIFY(s)
 #define _SUB_STRINGIFY(s) #s
 
+#if HAVE_XAPIAN_DB_RETRY_LOCK
+#define DB_ACTION (Xapian::DB_CREATE_OR_OPEN | Xapian::DB_RETRY_LOCK)
+#else
+#define DB_ACTION Xapian::DB_CREATE_OR_OPEN
+#endif
+
 /* Here's the current schema for our database (for NOTMUCH_DATABASE_VERSION):
  *
  * We currently have three different types of documents (mail, ghost,
@@ -939,7 +945,7 @@ notmuch_database_open_verbose (const char *path,
 
 	if (mode == NOTMUCH_DATABASE_MODE_READ_WRITE) {
 	    notmuch->xapian_db = new Xapian::WritableDatabase (xapian_path,
-							       Xapian::DB_CREATE_OR_OPEN);
+							       DB_ACTION);
 	} else {
 	    notmuch->xapian_db = new Xapian::Database (xapian_path);
 	}
-- 
2.8.1