From b2eb1ef329680f0faff37550954748fec4616001 Mon Sep 17 00:00:00 2001
From: Sergey Poznyakoff <gray@gnu.org.ua>
Date: Sun, 22 May 2011 19:05:39 +0300
Subject: Optionally check if there is a running instance already

* src/config.c (nssync_kw) <pidfile>: New statement.
* src/nssync.c (pidfile): New global.
(create_pidfile, remove_pidfile, check_pidfile): New
functions.
(main): Call check_pidfile.
* src/nssync.h (pidfile): New extern.
---
 src/config.c |  6 +++++
 src/nssync.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/nssync.h |  1 +
 3 files changed, 79 insertions(+)

diff --git a/src/config.c b/src/config.c
index ff9c9e4..a2d92b1 100644
--- a/src/config.c
+++ b/src/config.c
@@ -119,6 +119,12 @@ static struct grecs_keyword nssync_kw[] = {
 	{ "slave-status-file",
 	  NULL, "Check slave status and save it in the given file",
 	  grecs_type_string, &slave_status_file },
+
+	{ "pidfile",
+	  "file",
+	  "At startup, check if <file> already exists and is "
+	  "owned by an existing process.  Exit if so.",
+	  grecs_type_string, &pidfile },
 	
 	{ "tempdir",
 	  NULL, "Name for the temporary directory (must exist)",
diff --git a/src/nssync.c b/src/nssync.c
index 3d90c40..9f8fb9d 100644
--- a/src/nssync.c
+++ b/src/nssync.c
@@ -24,6 +24,7 @@ int preprocess_only;
 int debug_level;
 char *config_file = SYSCONFDIR "/nssync.conf";
 char *slave_status_file;
+char *pidfile;
 int force;
 char *tempdir;
 char *reload_command = "/usr/sbin/rndc reload";
@@ -234,7 +235,76 @@ check_slave_status()
 	free(sql_file);
 	free(sql_off);
 }
+
+void
+create_pidfile()
+{
+	FILE *fp;
+
+	if (!pidfile)
+		return;
+	
+	fp = fopen(pidfile, "w");
+	if (!fp) {
+		error(_("cannot create pidfile `%s': %s"),
+		      pidfile, strerror(errno));
+		exit(EX_TEMPFAIL);
+	}
+	fprintf(fp, "%lu", (unsigned long) getpid());
+	fclose(fp);
+}
+
+void
+remove_pidfile()
+{
+	if (pidfile && unlink(pidfile))
+		error(_("cannot unlink pidfile `%s': %s"),
+		      pidfile, strerror(errno));
+}
+
+/* Check whether pidfile NAME exists and if so, whether its PID is still
+   active. Exit if it is. */
+void
+check_pidfile()
+{
+	unsigned long pid;
+	FILE *fp;
+
+	if (!pidfile)
+		return;
+	
+	fp = fopen(pidfile, "r");
+	
+	if (!fp) {
+		if (errno == ENOENT)
+			return;
+		error(_("cannot open pidfile `%s': %s"),
+		      pidfile, strerror(errno));
+		exit(EX_TEMPFAIL);
+	}
+	if (fscanf(fp, "%lu", &pid) != 1) {
+		error(_("cannot get pid from pidfile `%s'"), pidfile);
+	} else {
+		if (kill(pid, 0) == 0) {
+			error(_("%s appears to run with pid %lu. "
+				"If it does not, remove `%s' and retry."),
+			      program_name, pid, pidfile);
+			exit(EX_TEMPFAIL);
+		}
+	}
 		
+	fclose(fp);
+	if (unlink(pidfile)) {
+		error(_("cannot unlink pidfile `%s': %s"),
+		      pidfile, strerror(errno));
+		exit(EX_NOPERM);
+	}
+
+	create_pidfile();
+	atexit(remove_pidfile);
+}
+
+
 
 int
 main(int argc, char **argv)
@@ -249,6 +319,8 @@ main(int argc, char **argv)
 	config_parse();
 	sql_connect();
 
+	check_pidfile();
+	
 	if (slave_status_file)
 		check_slave_status();
 	
diff --git a/src/nssync.h b/src/nssync.h
index 52c317a..d083e7f 100644
--- a/src/nssync.h
+++ b/src/nssync.h
@@ -33,6 +33,7 @@ extern int preprocess_only;
 extern int debug_level;
 extern char *config_file;
 extern char *slave_status_file;
+extern char *pidfile;
 extern char *tempdir;
 extern char *compare_command;
 extern char *reload_command;
-- 
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