dns_cache: Support periodically saving cache files

src/dns_server.c

@@ -44,6 +44,7 @@
 #include <openssl/ssl.h>
 #include <openssl/x509.h>
 #include <pthread.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -52,6 +53,7 @@
 #include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <sys/types.h>
+#include <sys/wait.h>
 
 #define DNS_MAX_EVENTS 256
 #define IPV6_READY_CHECK_TIME 180
@@ -322,6 +324,9 @@ struct dns_server {
 	int event_fd;
 	struct list_head conn_list;
 
+	pid_t cache_save_pid;
+	time_t cache_save_time;
+
 	/* dns request list */
 	pthread_mutex_t request_list_lock;
 	struct list_head request_list;
@@ -350,6 +355,7 @@ static int _dns_server_reply_all_pending_list(struct dns_request *request, struc
 static void *_dns_server_get_dns_rule(struct dns_request *request, enum domain_rule rule);
 static const char *_dns_server_get_request_groupname(struct dns_request *request);
 static int _dns_server_tcp_socket_send(struct dns_server_conn_tcp_client *tcp_client, void *data, int data_len);
+static int _dns_server_cache_save(int check_lock);
 
 int dns_is_ipv6_ready(void)
 {
@@ -6252,6 +6258,66 @@ static void _dns_server_check_need_exit(void)
 #define _dns_server_check_need_exit()
 #endif
 
+static void _dns_server_save_cache_to_file(void)
+{
+	time_t now;
+	int check_time = dns_conf_cache_checkpoint_time;
+
+	if (dns_conf_cache_persist == 0 || dns_conf_cachesize <= 0 || dns_conf_cache_checkpoint_time <= 0) {
+		return;
+	}
+
+	time(&now);
+	if (server.cache_save_pid > 0) {
+		int ret = waitpid(server.cache_save_pid, NULL, WNOHANG);
+		if (ret == server.cache_save_pid) {
+			server.cache_save_pid = 0;
+		} else if (ret < 0) {
+			tlog(TLOG_ERROR, "waitpid failed, errno %d, error info '%s'", errno, strerror(errno));
+			server.cache_save_pid = 0;
+		} else {
+			if (now - 30 > server.cache_save_time) {
+				kill(server.cache_save_pid, SIGKILL);
+			}
+			return;
+		}
+	}
+
+	if (check_time < 120) {
+		check_time = 120;
+	}
+
+	if (now - check_time < server.cache_save_time) {
+		return;
+	}
+
+	/* server is busy, skip*/
+	pthread_mutex_lock(&server.request_list_lock);
+	if (list_empty(&server.request_list) != 0) {
+		pthread_mutex_unlock(&server.request_list_lock);
+		return;
+	}
+	pthread_mutex_unlock(&server.request_list_lock);
+
+	server.cache_save_time = now;
+
+	int pid = fork();
+	if (pid == 0) {
+		/* child process */
+		for (int i = 3; i < 1024; i++) {
+			close(i);
+		}
+
+		_dns_server_cache_save(1);
+		_exit(0);
+	} else if (pid < 0) {
+		tlog(TLOG_DEBUG, "fork failed, errno %d, error info '%s'", errno, strerror(errno));
+		return;
+	}
+
+	server.cache_save_pid = pid;
+}
+
 static void _dns_server_period_run_second(void)
 {
 	static unsigned int sec = 0;
@@ -6305,6 +6371,8 @@ static void _dns_server_period_run_second(void)
 			tlog(TLOG_INFO, "Update host file data");
 		}
 	}
+
+	_dns_server_save_cache_to_file();
 }
 
 static void _dns_server_period_run(unsigned int msec)
@@ -6902,7 +6970,7 @@ static int _dns_server_cache_init(void)
 	return 0;
 }
 
-static int _dns_server_cache_save(void)
+static int _dns_server_cache_save(int check_lock)
 {
 	char *dns_cache_file = SMARTDNS_CACHE_FILE;
 	if (dns_conf_cache_file[0] != 0) {
@@ -6916,7 +6984,7 @@ static int _dns_server_cache_save(void)
 		return 0;
 	}
 
-	if (dns_cache_save(dns_cache_file) != 0) {
+	if (dns_cache_save(dns_cache_file, check_lock) != 0) {
 		tlog(TLOG_WARN, "save cache failed.");
 		return -1;
 	}
@@ -6974,6 +7042,7 @@ int dns_server_init(void)
 	memset(&server, 0, sizeof(server));
 	pthread_attr_init(&attr);
 	INIT_LIST_HEAD(&server.conn_list);
+	time(&server.cache_save_time);
 
 	epollfd = epoll_create1(EPOLL_CLOEXEC);
 	if (epollfd < 0) {
@@ -7034,8 +7103,14 @@ void dns_server_exit(void)
 		close(server.event_fd);
 		server.event_fd = -1;
 	}
+
+	if (server.cache_save_pid > 0) {
+		kill(server.cache_save_pid, SIGKILL);
+		server.cache_save_pid = 0;
+	}
+
 	_dns_server_close_socket();
-	_dns_server_cache_save();
+	_dns_server_cache_save(0);
 	_dns_server_request_remove_all();
 	pthread_mutex_destroy(&server.request_list_lock);
 	dns_cache_destroy();