alfred: Externalizing ALFRED_INTERVAL for setting synchronization interval

diff --git a/alfred.h b/alfred.h
index a9906c8..5b7e965 100644
--- a/alfred.h
+++ b/alfred.h
@@ -131,6 +131,7 @@  struct globals {
 	uint16_t changed_data_type_count; /* maximum is 256 */
 
 	struct timespec if_check;
+	struct timespec sync_period;
 
 	struct hashtable_t *data_hash;
 	struct hashtable_t *transaction_hash;
diff --git a/main.c b/main.c
index 9cab705..3aa89fd 100644
--- a/main.c
+++ b/main.c
@@ -59,6 +59,8 @@  static void alfred_usage(void)
 	printf("  -m, --master                        start up the daemon in
master mode, which\n");
 	printf("                                      accepts data from slaves
and syncs it with\n");
 	printf("                                      other masters\n");
+	printf("  -p, --sync-period [period]          set synchronization
period, in seconds\n");
+	printf("                                      fractional seconds are
supported (i.e. 0.2 = 5 Hz)\n");
 	printf("\n");
 	printf("  -u, --unix-path [path]              path to unix socket used
for client-server\n");
 	printf("                                      communication (default:
\""ALFRED_SOCK_PATH_DEFAULT"\")\n");
@@ -156,6 +158,7 @@  out:
 static struct globals *alfred_init(int argc, char *argv[])
 {
 	int opt, opt_ind, i, ret;
+	double sync_period = 0.0;
 	struct globals *globals;
 	struct option long_options[] = {
 		{"set-data",		required_argument,	NULL,	's'},
@@ -170,6 +173,7 @@  static struct globals *alfred_init(int argc, char
*argv[])
 		{"update-command",	required_argument,	NULL,	'c'},
 		{"version",		no_argument,		NULL,	'v'},
 		{"verbose",		no_argument,		NULL,	'd'},
+		{"sync-period",		required_argument,	NULL,	'p'},
 		{NULL,			0,			NULL,	0},
 	};
 
@@ -193,12 +197,14 @@  static struct globals *alfred_init(int argc, char
*argv[])
 	globals->unix_path = ALFRED_SOCK_PATH_DEFAULT;
 	globals->verbose = 0;
 	globals->update_command = NULL;
+	globals->sync_period.tv_sec = ALFRED_INTERVAL;
+	globals->sync_period.tv_nsec = 0;
 	INIT_LIST_HEAD(&globals->changed_data_types);
 	globals->changed_data_type_count = 0;
 
 	time_random_seed();
 
-	while ((opt = getopt_long(argc, argv, "ms:r:hi:b:vV:M:I:u:dc:",
long_options,
+	while ((opt = getopt_long(argc, argv, "ms:r:hi:b:vV:M:I:u:dc:p:",
long_options,
 				  &opt_ind)) != -1) {
 		switch (opt) {
 		case 'r':
@@ -265,6 +271,12 @@  static struct globals *alfred_init(int argc, char
*argv[])
 			printf("%s %s\n", argv[0], SOURCE_VERSION);
 			printf("A.L.F.R.E.D. - Almighty Lightweight Remote Fact Exchange
Daemon\n");
 			return NULL;
+		case 'p':
+			sync_period = strtod(optarg, NULL);
+			globals->sync_period.tv_sec = (int) sync_period;
+			globals->sync_period.tv_nsec = (double)(sync_period -
(int)sync_period) * 1e9;
+			printf(" ** Setting sync interval to: %.9f seconds (%ld.%09ld)\n",
sync_period, globals->sync_period.tv_sec, globals->sync_period.tv_nsec);
+			break;
 		case 'h':
 		default:
 			alfred_usage();
diff --git a/man/alfred.8 b/man/alfred.8
index 49d42bc..df37040 100644
--- a/man/alfred.8
+++ b/man/alfred.8
@@ -118,6 +118,11 @@  overhead).
 \fB\-c\fP, \fB\-\-update-command\fP \fIcommand\fP
 Specify command to execute on data change. It will be called with
data-type list
 as arguments.
+.TP
+\fB\-p\fP, \fB\-\-sync-period\fP \fIperiod\fP
+Specify alfred synchronization period, in seconds. If not specified,
the default
+ALFRED_INTERVAL setting of 10 seconds will be used. Fractional seconds
are 
+supported.
 .
 .SH EXAMPLES
 Start an alfred server listening on bridge br0 (assuming that this
bridge
diff --git a/server.c b/server.c
index 47aee4f..c5df945 100644
--- a/server.c
+++ b/server.c
@@ -372,7 +372,7 @@  int alfred_server(struct globals *globals)
 
 	while (1) {
 		clock_gettime(CLOCK_MONOTONIC, &now);
-		now.tv_sec -= ALFRED_INTERVAL;
+		time_diff(&now, &globals->sync_period, &now);
 		if (!time_diff(&last_check, &now, &tv)) {
 			tv.tv_sec = 0;
 			tv.tv_nsec = 0;
@@ -409,7 +409,7 @@  int alfred_server(struct globals *globals)
 
 		if (globals->opmode == OPMODE_MASTER) {
 			/* we are a master */
-			printf("announce master ...\n");
+			printf("[%ld.%09ld] announce master ...\n", last_check.tv_sec,
last_check.tv_nsec);
 			announce_master(globals);
 			sync_data(globals);