db: store data in memory during database downtime

This patch is adding a mechanism to store query in a backlog build
in memory. This allow to store events during downtime in memory and
realize the effective insertion when the database comes back.
A memory cap is used to avoid any memory flooding.

1 files changed, 29 insertions, 5 deletions

diff --git a/include/ulogd/db.h b/include/ulogd/db.h
index 1c910ff..a533902 100644
--- a/include/ulogd/db.h
+++ b/include/ulogd/db.h
@@ -20,6 +20,12 @@ struct db_driver {
 			const char *stmt, unsigned int len);
 };
 
+struct db_stmt {
+	char *stmt;
+	int len;
+	struct llist_head list;
+};
+
 struct db_instance {
 	char *stmt; /* buffer for our insert statement */
 	char *stmt_val; /* pointer to the beginning of the "VALUES" part */
@@ -28,9 +34,15 @@ struct db_instance {
 	time_t reconnect;
 	int (*interp)(struct ulogd_pluginstance *upi);
 	struct db_driver *driver;
+	unsigned int backlog_memcap;
+	unsigned int backlog_memusage;
+	unsigned int backlog_oneshot;
+	unsigned char backlog_full;
+	struct llist_head backlog;
 };
 #define TIME_ERR		((time_t)-1)	/* Be paranoid */
 #define RECONNECT_DEFAULT	2
+#define MAX_ONESHOT_REQUEST	10
 
 #define DB_CES							\
 		{						\
@@ -51,13 +63,25 @@ struct db_instance {
 			.key = "procedure",			\
 			.type = CONFIG_TYPE_STRING,		\
 			.options = CONFIG_OPT_MANDATORY,	\
+		},						\
+		{						\
+			.key = "backlog_memcap",		\
+			.type = CONFIG_TYPE_INT,		\
+			.u.value = 0,				\
+		},						\
+		{						\
+			.key = "backlog_oneshot_requests",	\
+			.type = CONFIG_TYPE_INT,		\
+			.u.value = MAX_ONESHOT_REQUEST,		\
 		}
 
-#define DB_CE_NUM	4
-#define table_ce(x)	(x->ces[0])
-#define reconnect_ce(x)	(x->ces[1])
-#define timeout_ce(x)	(x->ces[2])
-#define procedure_ce(x)	(x->ces[3])
+#define DB_CE_NUM		6
+#define table_ce(x)		(x->ces[0])
+#define reconnect_ce(x)		(x->ces[1])
+#define timeout_ce(x)		(x->ces[2])
+#define procedure_ce(x)		(x->ces[3])
+#define backlog_memcap_ce(x)	(x->ces[4])
+#define backlog_oneshot_ce(x)	(x->ces[5])
 
 void ulogd_db_signal(struct ulogd_pluginstance *upi, int signal);
 int ulogd_db_start(struct ulogd_pluginstance *upi);