MDEV-26971: JSON file interface to wsrep node state.

Integration with status reporter in wsrep-lib.

Status reporter reports changes in wsrep state and logged errors/
warnings to a json file which then can be read and interpreted by
an external monitoring tool.

Rationale: until the server is fully initialized it is unaccessible
by client and the only source of information is an error log which
is not machine-friendly. Since wsrep node can spend a very long time
in initialization phase (state transfer), it may be a very long time
that automatic tools can't easily monitor its liveness and progression.

New variable: wsrep_status_file specifies the output file name.
If not set, no file is created and no reporting is done.

Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

1 files changed, 61 insertions, 0 deletions

diff --git a/sql/wsrep_status.h b/sql/wsrep_status.h
new file mode 100644
index 00000000000..1c99a4cfe88
--- /dev/null
+++ b/sql/wsrep_status.h
@@ -0,0 +1,61 @@
+/* Copyright 2021 Codership Oy <info@codership.com>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#ifndef WSREP_STATUS_H
+#define WSREP_STATUS_H
+
+/* wsrep-lib */
+#include "wsrep/reporter.hpp"
+
+/* implementation */
+#include "wsrep_mutex.h"
+
+class Wsrep_status
+{
+public:
+  static void init_once(const std::string& file_name);
+  static void destroy();
+
+  static void report_state(enum wsrep::server_state::state const state,
+                           float const progress = wsrep::reporter::indefinite)
+  {
+    if (!Wsrep_status::m_instance) return;
+
+    Wsrep_status::m_instance->report_state(state, progress);
+  }
+
+  static void report_log_msg(wsrep::reporter::log_level level,
+                             const char* tag, size_t tag_len,
+                             const char* buf, size_t buf_len,
+                             double const tstamp = wsrep::reporter::undefined);
+//  {
+//    if (!Wsrep_status::m_instance) return;
+//
+//    Wsrep_status::m_instance->report_log_msg(level, msg, tstamp);
+//  }
+
+  static bool is_instance_initialized()
+  {
+      return m_instance;
+  }
+
+private:
+  Wsrep_status(const std::string& file_name);
+
+  static Wsrep_mutex*     m_mutex;
+  static wsrep::reporter* m_instance;
+};
+
+#endif /* WSREP_STATUS_H */