Move backend_syncfreq code down into back-ldbm. Creates new configuration

for LDBM backends called "dbsync", which takes minimum of one argument up
to 3 args which are sync frequency, # of delays, and delay periods.  See
man page update for "dbsync" configuration for more details.

doc/man/man5/slapd.conf.5

@@ -640,11 +640,41 @@ method, this option is ignored without comment.  The default is 100000 bytes.
 .B dbnolocking
 Specify that no database locking should be performed.  
 Enabling this option may improve performance at the expense of data security.
+.TP
 .B dbnosync
 Specify that on-disk database contents should not be immediately
 synchronized with in memory changes.  Enabling this option may improve
 performance at the expense of data security.
 .TP
+.B dbsync <frequency> <maxdelays> <delayinterval>
+Flush dirty database buffers to disk every
+.B <seconds>
+seconds.  Implies
+.B dbnosync
+(ie. indvidual updates are no longer written to disk).  It attempts to avoid
+syncs during periods of peak activity by waiting
+.B <delayinterval>
+seconds if the server is busy, repeating this delay up to
+.B <maxdelays>
+times before proceeding.  
+It is an attempt to provide higher write performance with some amount of data
+security.  Note that it may still be possible to get an inconsistent 
+database if the underlying engine fills its cache and writes out individual
+pages and slapd crashes or is killed before the next sync.
+.B <maxdelays>
+and
+.B <delayinterval>
+are optional and default to
+.B 12
+and
+.B 5
+respectively, giving a total elapsed delay of 60 seconds before a sync
+will occur.
+.B <maxdelays>
+may be zero, and
+.B <delayinterval>
+must be 1 or greater.
+.TP
 .B directory <directory>
 Specify the directory where the LDBM files containing this database and
 associated indexes live.  A separate directory must be specified for

servers/slapd/back-ldbm/back-ldbm.h

@@ -119,6 +119,11 @@ struct ldbminfo {
 	ldap_pvt_thread_cond_t		li_dbcache_cv;
 	DB_ENV			*li_dbenv;
 	int			li_envdirok;
+	int			li_dbsyncfreq;
+	int			li_dbsyncwaitn;
+	int			li_dbsyncwaitinterval;
+	ldap_pvt_thread_t	li_dbsynctid;
+	int			li_dbshutdown;
 };
 
 LDAP_END_DECL

servers/slapd/back-ldbm/close.c

@@ -17,6 +17,12 @@
 int
 ldbm_back_db_close( Backend *be )
 {
+	struct ldbminfo *li = (struct ldbminfo *) be->be_private;
+	if ( li->li_dbsyncfreq > 0 )
+	{
+		li->li_dbshutdown++;
+		ldap_pvt_thread_join( li->li_dbsynctid, (void *) NULL );
+	}
 #ifdef NEW_LOGGING
 	LDAP_LOG(( "backend", LDAP_LEVEL_CRIT,
 		   "ldbm_back_db_close: ldbm backend syncing\n" ));

servers/slapd/back-ldbm/config.c

@@ -101,6 +101,58 @@ ldbm_back_db_config(
 	{
 		li->li_dbwritesync = 0;
 
+	/* run sync thread */
+	} else if ( strcasecmp( argv[0], "dbsync" ) == 0 ) {
+#ifndef NO_THREADS
+		int i;
+		if ( argc < 2 ) {
+			Debug( LDAP_DEBUG_ANY,
+    "%s: line %d: missing frquency value in \"dbsync <frequency> [<wait-times> [wait-interval]]\" line\n",
+			    fname, lineno, 0 );
+			return 1;
+		}
+
+		i = atoi( argv[1] );
+
+		if( i < 0 ) {
+			Debug( LDAP_DEBUG_ANY,
+    "%s: line %d: frquency value (%d) invalid \"dbsync <frequency> [<wait-times> [wait-interval]]\" line\n",
+			    fname, lineno, i );
+			return 1;
+		}
+
+		li->li_dbsyncfreq = i;
+		li->li_dbwritesync = 0;
+
+		if ( argc > 2 ) {
+			i = atoi( argv[2] );
+			if ( i < 0 ) {
+				Debug( LDAP_DEBUG_ANY,
+	    "%s: line %d: frquency value (%d) invalid \"dbsync <frequency> [<wait-times> [wait-interval]]\" line\n",
+				    fname, lineno, i );
+				return 1;
+			}
+			li ->li_dbsyncwaitn = i;
+		}
+
+		if ( argc > 3 ) {
+			i = atoi( argv[3] );
+			if ( i <= 0 ) {
+				Debug( LDAP_DEBUG_ANY,
+	    "%s: line %d: frquency value (%d) invalid \"dbsync <frequency> [<wait-times> [wait-interval]]\" line\n",
+				    fname, lineno, i );
+				return 1;
+			}
+			li ->li_dbsyncwaitinterval = i;
+		}
+
+#else
+		Debug( LDAP_DEBUG_ANY,
+    "\"dbsync\" policies not supported in non-threaded environments\n");
+		return 1;
+#endif
+
+
 	/* anything else */
 	} else {
 		fprintf( stderr,

servers/slapd/back-ldbm/dbcache.c

@@ -376,3 +376,35 @@ ldbm_cache_delete(
 
 	return( rc );
 }
+
+void *
+ldbm_cache_sync_daemon(
+	void *be_ptr
+)
+{
+	Backend *be = (Backend *)be_ptr;
+	struct ldbminfo	*li = (struct ldbminfo *) be->be_private;
+
+	Debug( LDAP_DEBUG_ANY, "synchronizer starting for %s\n", li->li_directory, 0, 0 );
+  
+	while (!li->li_dbshutdown) {
+		int i = li->li_dbsyncwaitn;
+
+		sleep( li->li_dbsyncfreq );
+
+		while (i && ldap_pvt_thread_pool_backload(&connection_pool) != 0) {
+			Debug( LDAP_DEBUG_ANY, "delay syncing %s\n", li->li_directory, 0, 0 );
+			sleep(li->li_dbsyncwaitinterval);
+			i--;
+		}
+
+		if (!li->li_dbshutdown) {
+			Debug( LDAP_DEBUG_ANY, "syncing %s\n", li->li_directory, 0, 0 );
+			ldbm_cache_sync( be );
+		}
+	}
+
+  	Debug( LDAP_DEBUG_ANY, "synchronizer stopping\n", 0, 0, 0 );
+  
+	return NULL;
+}

servers/slapd/back-ldbm/init.c

@@ -159,6 +159,18 @@ ldbm_back_db_init(
 	/* envdirok is turned on by ldbm_initialize_env if DB3 */
 	li->li_envdirok = 0;
 
+	/* syncfreq is 0 if disabled, or # seconds */
+	li->li_dbsyncfreq = 0;
+
+	/* wait up to dbsyncwaitn times if server is busy */
+	li->li_dbsyncwaitn = 12;
+
+	/* delay interval */
+	li->li_dbsyncwaitinterval = 5;
+
+	/* flag to notify ldbm_cache_sync_daemon to shut down */
+	li->li_dbshutdown = 0;
+
 	/* initialize various mutex locks & condition variables */
 	ldap_pvt_thread_mutex_init( &li->li_root_mutex );
 	ldap_pvt_thread_mutex_init( &li->li_add_mutex );
@@ -180,6 +192,22 @@ ldbm_back_db_open(
 	struct ldbminfo *li = (struct ldbminfo *) be->be_private;
 	li->li_dbenv = ldbm_initialize_env( li->li_directory,
 		li->li_dbcachesize, &li->li_envdirok );
+
+	/* sync thread */
+	if ( li->li_dbsyncfreq > 0 )
+	{
+		int rc;
+		rc = ldap_pvt_thread_create( &li->li_dbsynctid,
+			0, ldbm_cache_sync_daemon, (void*)be );
+
+		if ( rc != 0 )
+		{
+			Debug(	LDAP_DEBUG_ANY,
+				"sync ldap_pvt_thread_create failed (%d)\n", rc, 0, 0 );
+			return 1;
+		}
+	}
+
 	return 0;
 }
 

servers/slapd/back-ldbm/proto-back-ldbm.h

@@ -70,6 +70,7 @@ void ldbm_cache_sync LDAP_P(( Backend *be ));
 Datum ldbm_cache_fetch LDAP_P(( DBCache *db, Datum key ));
 int ldbm_cache_store LDAP_P(( DBCache *db, Datum key, Datum data, int flags ));
 int ldbm_cache_delete LDAP_P(( DBCache *db, Datum key ));
+void *ldbm_cache_sync_daemon LDAP_P(( void *));
 
 /*
  * dn2id.c