#1042 Update database schema automatically

This patch adds database schema management capabilities to ogServer:

- ogServer now tracks the version of its database schema, if no version
is detected, creates a 'version' table with a single row starting at 0.
- ogServer can upgrade its database schema to a newer version if
detected. (ogServer ships required SQL commands to do so)

If ogServer is unable to upgrade the schema at startup (if needed be) it
*will not* start.

Defines schema update v1 which upgrades database engine tables of
ogServer database (usually named 'ogAdmBD') from myISAM to innoDB.

3 files changed, 164 insertions, 0 deletions

diff --git a/src/dbi.h b/src/dbi.h
index 1daaeb8..798fecd 100644
--- a/src/dbi.h
+++ b/src/dbi.h
@@ -93,4 +93,6 @@ int og_dbi_get_computer_info(struct og_dbi *dbi, struct og_computer *computer,
 			     struct in_addr addr);
 int og_dbi_add_image(struct og_dbi *dbi, const struct og_image *image);
 
+int og_dbi_schema_update(void);
+
 #endif
diff --git a/src/main.c b/src/main.c
index 36b2fe0..ea04a2b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -87,6 +87,9 @@ int main(int argc, char *argv[])
 	ev_io_init(&ev_io_agent_rest, og_server_accept_cb, socket_agent_rest, EV_READ);
 	ev_io_start(og_loop, &ev_io_agent_rest);
 
+	if (og_dbi_schema_update() < 0)
+		exit(EXIT_FAILURE);
+
 	if (og_dbi_schedule_get() < 0) {
 		syslog(LOG_ERR, "Cannot connect to database\n");
 		exit(EXIT_FAILURE);
diff --git a/src/schema.c b/src/schema.c
new file mode 100644
index 0000000..f7b705b
--- /dev/null
+++ b/src/schema.c
@@ -0,0 +1,159 @@
+/*
+ * Copyright (C) 2021 Soleta Networks <info@soleta.eu>
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU Affero General Public License as published by the
+ * Free Software Foundation, version 3.
+ */
+
+#include <syslog.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <string.h>
+#include "dbi.h"
+#include "cfg.h"
+#include <syslog.h>
+#include <string.h>
+#include <stdio.h>
+
+struct og_server_cfg ogconfig;
+
+static int og_dbi_create_version(struct og_dbi *dbi)
+{
+	const char *msglog;
+	dbi_result result;
+
+	result = dbi_conn_queryf(dbi->conn, "CREATE TABLE `version` "
+					    "(`version` smallint unsigned NOT NULL) "
+					    "ENGINE='MyISAM' COLLATE 'utf8_general_ci'");
+	if (!result) {
+		dbi_conn_error(dbi->conn, &msglog);
+		syslog(LOG_INFO, "Could not create schema version table (%s:%d) %s\n",
+		       __func__, __LINE__, msglog);
+		return -1;
+	}
+	dbi_result_free(result);
+
+	result = dbi_conn_queryf(dbi->conn, "INSERT INTO `version` (`version`) VALUES ('0')");
+	if (!result) {
+		dbi_conn_error(dbi->conn, &msglog);
+		syslog(LOG_INFO, "Could not insert into schema version table (%s:%d) %s\n",
+		       __func__, __LINE__, msglog);
+		return -1;
+	}
+	dbi_result_free(result);
+
+	return 0;
+}
+static int og_dbi_schema_version(struct og_dbi *dbi)
+{
+	const char *msglog;
+	dbi_result result;
+	uint32_t version;
+
+	result = dbi_conn_queryf(dbi->conn, "SELECT * from version");
+	if (!result) {
+		dbi_conn_error(dbi->conn, &msglog);
+		syslog(LOG_INFO, "no version table found (%s:%d) %s\n",
+		       __func__, __LINE__, msglog);
+		return -1;
+	}
+
+	if (!dbi_result_last_row(result)) {
+		dbi_conn_error(dbi->conn, &msglog);
+		syslog(LOG_ERR, "cannot get last row from version table (%s:%d) %s\n",
+		       __func__, __LINE__, msglog);
+		return -1;
+	}
+
+	version = dbi_result_get_uint(result, "version");
+
+	dbi_result_free(result);
+
+	return version;
+}
+static int og_dbi_schema_v1(struct og_dbi *dbi)
+{
+	const char *msglog, *command;
+	dbi_result result, result_alter;
+
+	result = dbi_conn_queryf(dbi->conn, "SELECT concat('alter table `',TABLE_SCHEMA,'`.`',TABLE_NAME,'` engine=innodb;')"
+					    "AS cmd FROM information_schema.TABLES WHERE TABLE_SCHEMA='%s'",
+					    ogconfig.db.name);
+
+	while (dbi_result_next_row(result)) {
+		command = dbi_result_get_string(result, "cmd");
+
+		syslog(LOG_DEBUG, "Upgrading to innoDB: %s\n", command);
+		result_alter = dbi_conn_query(dbi->conn, command);
+		if (!result_alter) {
+			dbi_conn_error(dbi->conn, &msglog);
+			syslog(LOG_INFO, "Error when upgrading engine to innoDB (%s:%d) %s\n",
+			       __func__, __LINE__, msglog);
+			return -1;
+		}
+		dbi_result_free(result_alter);
+	}
+	dbi_result_free(result);
+
+	result = dbi_conn_query(dbi->conn, "UPDATE version SET version = 1");
+	if (!result) {
+		dbi_conn_error(dbi->conn, &msglog);
+		syslog(LOG_INFO, "Could not update version row (%s:%d) %s\n",
+		       __func__, __LINE__, msglog);
+		return -1;
+	}
+	dbi_result_free(result);
+
+	return 0;
+}
+
+static struct og_schema_version {
+	int	version;
+	int	(*update)(struct og_dbi *dbi);
+} schema_version[] = {
+	{	.version = 1,	.update = og_dbi_schema_v1	},
+	{	0,		NULL				},
+};
+
+int og_dbi_schema_update(void)
+{
+	int version, i, err;
+	struct og_dbi *dbi;
+	const char *msglog;
+
+	dbi = og_dbi_open(&ogconfig.db);
+	if (!dbi) {
+		dbi_conn_error(dbi->conn, &msglog);
+		syslog(LOG_ERR, "failed to query database (%s:%d) %s\n",
+		       __func__, __LINE__, msglog);
+		return -1;
+	}
+
+	version = og_dbi_schema_version(dbi);
+
+	if (version < 0) {
+		syslog(LOG_INFO, "creating table version in schema\n");
+		og_dbi_create_version(dbi);
+	} else {
+		syslog(LOG_INFO, "database schema version %d\n", version);
+	}
+
+	for (i = 0; schema_version[i].version; i++) {
+		if (version >= schema_version[i].version)
+			continue;
+
+		syslog(LOG_INFO, "upgrading to schema version %d\n", schema_version[i].version);
+
+		err = schema_version[i].update(dbi);
+		if (err < 0) {
+			syslog(LOG_ERR, "failed to update schema!\n");
+			og_dbi_close(dbi);
+			return -1;
+		}
+	}
+
+	og_dbi_close(dbi);
+
+	return 0;
+}