pidfile support

Makefile

@@ -10,13 +10,15 @@ CONFIG_DIR = /usr/local/etc
 PLUGIN_DIR = /usr/local/lib/sammler
 DATA_DIR = /var/lib/sammler
 LOG_DIR = /var/log
+PID_DIR = /var/run
 WWW_DIR = /var/www
 WWW_CONFIG = $(WWW_DIR)/sammler_graph.conf
 WWW_OWNER = www-data
 
 # ############################
 
-SRC := sammler.c configfile.c event.c helper.c logging.c network.c plugins.c probe.c sockaddr.c
+SRC := configfile.c event.c helper.c logging.c network.c pidfile.c plugins.c probe.c
+SRC += sammler.c sockaddr.c
 CFLAGS := -O2 -Wall -MMD -fno-stack-protector -I.
 LDFLAGS := -ldl -rdynamic
 
@@ -67,6 +69,7 @@ install: all
 	install -D -m 755 -s $(TARGET) $(DESTDIR)$(BINARY_DIR)/$(TARGET)
 	install -D -m 644 sammler.conf $(DESTDIR)$(CONFIG_DIR)/sammler.conf
 	sed -i -e "s:^logfile .*$$:logfile $(LOG_DIR)/sammler.log:" \
+		-e "s:^pidfile .*$$:pidfile $(PID_DIR)/sammler.pid:" \
 		-e "s:^rrd_dir .*$$:rrd_dir $(DATA_DIR):" \
 		-e "s:^plugin_dir .*$$:plugin_dir $(PLUGIN_DIR):" \
 		$(DESTDIR)$(CONFIG_DIR)/sammler.conf

pidfile.c

@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <signal.h>
+
+#include "logging.h"
+
+int pidfile_create(const char *filename)
+{
+	int fd = open(filename, O_CREAT | O_EXCL | O_RDWR, 0644);
+	if (fd < 0)
+		return -1;
+
+	char buf[8];
+	int len = snprintf(buf, sizeof(buf), "%d", getpid());
+	write(fd, buf, len);
+
+	close(fd);
+	return 0;
+}
+
+int pidfile_remove(const char *filename)
+{
+	return unlink(filename);
+}
+
+pid_t pidfile_check(const char *filename, int remove_stale)
+{
+	int fd = open(filename, O_RDWR);
+	if (fd < 0) {
+		if (errno == ENOENT) {
+			errno = 0;
+			return 0;
+		}
+		return -1;
+	}
+
+	char buf[9];
+	int len = read(fd, buf, sizeof(buf) -1);
+	buf[len] = '\0';
+
+	char *tmp;
+	pid_t pid = strtol(buf, &tmp, 10);
+	if (len == 0 || tmp == buf)
+		pid = -1;
+
+	/* just return the pid */
+	if (!remove_stale)
+		return pid;
+
+	/* invalid pid, remove stale file */
+	if (pid == -1) {
+		pidfile_remove(filename);
+		return 0;
+	}
+
+	/* check if pid is still running */
+	if (kill(pid, 0) == 0 || errno != ESRCH) {
+		errno = 0;
+		return pid;
+	}
+
+	errno = 0;
+	pidfile_remove(filename);
+	return 0;
+}

pidfile.h

@@ -0,0 +1,11 @@
+#ifndef _PIDFILE_H_
+#define _PIDFILE_H_
+
+#include <sys/types.h>
+
+int pidfile_create(const char *filename);
+int pidfile_remove(const char *filename);
+
+pid_t pidfile_check(const char *filename, int remove_stale);
+
+#endif // _PIDFILE_H_

sammler.c

@@ -32,11 +32,13 @@
 #include "logging.h"
 #include "network.h"
 #include "rrdtool.h"
+#include "pidfile.h"
 #include "plugins.h"
 #include "probe.h"
 
 #define DEFAULT_CONFIG "sammler.conf"
 #define DEFAULT_LOGFILE "sammler.log"
+#define DEFAULT_PIDFILE "sammler.pid"
 
 static struct option opts[] = {
 	{"config",	1, 0, 'c'},
@@ -88,12 +90,26 @@ int main(int argc, char *argv[])
 	/* check logfile */
 	const char *logfile = config_get_string("global", "logfile", DEFAULT_LOGFILE);
 	if (logfile != NULL && debug == 0) {
+		/* check pidfile */
+		const char *pidfile = config_get_string("global", "pidfile", DEFAULT_PIDFILE);
+		if (pidfile_check(pidfile, 1) != 0) {
+			log_print(LOG_ERROR, "sammler already running");
+			exit(1);
+		}
+
 		/* start logging */
-		if (log_init(logfile))
+		const char *logfile = config_get_string("global", "logfile", DEFAULT_LOGFILE);
+		if (log_init(logfile) < 0)
 			exit(1);
 
 		/* zum daemon mutieren */
 		daemon(-1, 0);
+
+		/* create pidfile */
+		if (pidfile_create(pidfile) < 0) {
+			log_print(LOG_ERROR, "failed to create pidfile %s", pidfile);
+			exit(1);
+		}
 	}
 
 	log_print(LOG_EVERYTIME, "sammler (pid:%d)", getpid());

sammler.conf

@@ -6,6 +6,7 @@
 forward_only false
 
 logfile sammler.log
+pidfile sammler.pid
 
 rrd_dir rrd