Create a rotating log function that changes hourly with an exclusive lock while writing

src/libckpool.c

@@ -840,6 +840,43 @@ json_t *json_object_dup(json_t *val, const char *entry)
 	return json_copy(json_object_get(val, entry));
 }
 
+/* Creates a logfile entry which changes filename hourly with exclusive access */
+bool rotating_log(const char *path, const char *msg)
+{
+	mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+	char *filename;
+	struct tm *tm;
+	time_t now;
+	FILE *fp;
+	int fd;
+
+	now = time(NULL);
+	tm = localtime(&now);
+	ASPRINTF(&filename, "%s%04d%02d%02d%02d.log", path, tm->tm_year + 1900, tm->tm_mon + 1,
+		 tm->tm_mday, tm->tm_hour);
+	fd = open(filename, O_CREAT|O_RDWR, mode);
+	if (unlikely(fd == -1)) {
+		LOGERR("Failed to open %s in rotating_log!", filename);
+		return false;
+	}
+	fp = fdopen(fd, "a");
+	if (unlikely(!fp)) {
+		close(fd);
+		LOGERR("Failed to fopen %s in rotating_log!", filename);
+		return false;
+	}
+	if (unlikely(flock(fd, LOCK_EX))) {
+		fclose(fp);
+		close(fd);
+		LOGERR("Failed to flock %s in rotating_log!", filename);
+		return false;
+	}
+	fprintf(fp, "%s\n", msg);
+	fclose(fp);
+	close(fd);
+
+	return true;
+}
 
 /* Align a size_t to 4 byte boundaries for fussy arches */
 void align_len(size_t *len)

src/libckpool.h

@@ -397,6 +397,8 @@ const char *__json_array_string(json_t *val, unsigned int entry);
 char *json_array_string(json_t *val, unsigned int entry);
 json_t *json_object_dup(json_t *val, const char *entry);
 
+bool rotating_log(const char *path, const char *msg);
+
 void align_len(size_t *len);
 void realloc_strcat(char **ptr, const char *s);
 void trail_slash(char **buf);