MDEV-26851 : Add interface to monitor connections in Galera

CONTRIBUTORS.txt

@@ -22,6 +22,7 @@ Authors from Codership Oy:
  * Alexey Yurchenko <alexey.yurchenko@galeracluster.com>, Codership Oy
  * Mario Karuza <mario.karuza@galeracluster.com>, Codership Oy
  * Daniele Sciascia <daniele.sciascia@galeracluster.com>, Codership Oy
+ * Jan Lindström <jan.lindstrom@galeracluster.com>, Codership Oy
  [Codership employees, add name and email/username above this line, but leave this line intact]
 
 Other contributors:

include/wsrep/connection_monitor_service.hpp

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2024-2026 Codership Oy <info@codership.com>
+ *
+ * This file is part of wsrep-lib.
+ *
+ * Wsrep-lib 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, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Wsrep-lib 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 wsrep-lib.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+/** @file connection_monitor_service.hpp
+ *
+ * Service interface for interacting with DBMS provided
+ * connection monitor callback.
+ */
+
+#ifndef WSREP_CONNECTION_MONITOR_SERVICE_HPP
+#define WSREP_CONNECTION_MONITOR_SERVICE_HPP
+
+#include "compiler.hpp"
+#include "wsrep/buffer.hpp"
+#include "v26/wsrep_connection_monitor_service.h"
+
+namespace wsrep
+{
+    class connection_monitor_service
+    {
+    public:
+
+        virtual ~connection_monitor_service() { }
+
+        /**
+         * Connection monitor connect callback.
+         */
+        virtual bool connection_monitor_connect_cb(
+                                                   wsrep_connection_key_t id,
+                                                   const wsrep::const_buffer& scheme,
+                                                   const wsrep::const_buffer& local_addr,
+                                                   const wsrep::const_buffer& remote_addr
+                                                  ) WSREP_NOEXCEPT = 0;
+        /**
+         * Connection monitor disconnect callback.
+         */
+        virtual bool connection_monitor_disconnect_cb(wsrep_connection_key_t id
+                                                     ) WSREP_NOEXCEPT=0;
+
+        /**
+         * Connection monitor SSL/TLS info callback.
+         */
+        virtual bool connection_monitor_ssl_info_cb(wsrep_connection_key_t id,
+                                                    const wsrep::const_buffer& ciper,
+                                                    const wsrep::const_buffer& subject,
+                                                    const wsrep::const_buffer& issuer,
+                                                    const wsrep::const_buffer& version
+                                                   ) WSREP_NOEXCEPT = 0;
+    };
+}
+
+#endif // WSREP_CONNECTION_MONITOR_SERVICE_HPP

include/wsrep/provider.hpp

@@ -47,6 +47,7 @@ namespace wsrep
     class tls_service;
     class allowlist_service;
     class event_service;
+    class connection_monitor_service;
 
     class stid
     {
@@ -450,6 +451,7 @@ namespace wsrep
             wsrep::tls_service* tls_service;
             wsrep::allowlist_service* allowlist_service;
             wsrep::event_service* event_service;
+            wsrep::connection_monitor_service* connection_monitor_service;
 
             // some GCC and clang versions don't support C++11 default
             // initializers fully, so we need to use explicit constructors
@@ -461,17 +463,20 @@ namespace wsrep
                 , tls_service()
                 , allowlist_service()
                 , event_service()
+                , connection_monitor_service()
             {
             }
 
             services(wsrep::thread_service* thr,
                      wsrep::tls_service*    tls,
                      wsrep::allowlist_service* all,
-                     wsrep::event_service*  event)
+                     wsrep::event_service*  event,
+                     wsrep::connection_monitor_service* con)
                 : thread_service(thr)
                 , tls_service(tls)
                 , allowlist_service(all)
                 , event_service(event)
+                , connection_monitor_service(con)
             {
             }
         };

src/CMakeLists.txt

@@ -6,6 +6,7 @@ add_library(wsrep-lib
   allowlist_service_v1.cpp
   client_state.cpp
   config_service_v1.cpp
+  connection_monitor_service_v1.cpp
   event_service_v1.cpp
   exception.cpp
   gtid.cpp

src/connection_monitor_service_v1.cpp

@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2024-2025 Codership Oy <info@codership.com>
+ *
+ * This file is part of wsrep-lib.
+ *
+ * Wsrep-lib 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, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Wsrep-lib 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 wsrep-lib.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "connection_monitor_service_v1.hpp"
+#include "service_helpers.hpp"
+
+#include "wsrep/buffer.hpp"
+#include "v26/wsrep_connection_monitor_service.h"
+#include "wsrep/connection_monitor_service.hpp"
+
+#include <cassert>
+#include <dlfcn.h>
+#include <cerrno>
+
+namespace wsrep_connection_monitor_service_v1
+{
+    // Pointer to connection monitor service implementation provided by
+    // the application.
+    static wsrep::connection_monitor_service* connection_monitor_service_impl{ 0 };
+    static std::atomic<size_t> use_count;
+
+    //
+    // connection monitor service callbacks
+    //
+
+    void connection_monitor_connect_cb(
+        wsrep_connection_monitor_context_t*,
+        wsrep_connection_key_t id,
+        const wsrep_buf_t* scheme,
+        const wsrep_buf_t* local_address,
+        const wsrep_buf_t* remote_address
+    )
+    {
+        assert(connection_monitor_service_impl);
+        wsrep::const_buffer scheme_value(scheme->ptr, scheme->len);
+        wsrep::const_buffer remote_addr(remote_address->ptr, remote_address->len);
+        wsrep::const_buffer local_addr(local_address->ptr, local_address->len);
+        connection_monitor_service_impl->connection_monitor_connect_cb(
+                                                               id,
+                                                               scheme_value,
+                                                               local_addr,
+                                                               remote_addr);
+    }
+
+    void connection_monitor_disconnect_cb(
+        wsrep_connection_monitor_context_t*,
+        wsrep_connection_key_t id
+    )
+    {
+        assert(connection_monitor_service_impl);
+        connection_monitor_service_impl->connection_monitor_disconnect_cb(id);
+    }
+
+  void connection_monitor_ssl_info_cb(
+        wsrep_connection_monitor_context_t*,
+        wsrep_connection_key_t id,
+        const wsrep_buf_t* cipher,
+        const wsrep_buf_t* certificate_subject,
+        const wsrep_buf_t* certificate_issuer,
+        const wsrep_buf_t* version)
+    {
+        assert(connection_monitor_service_impl);
+        wsrep::const_buffer ssl_cipher(cipher->ptr, cipher->len);
+        wsrep::const_buffer cert_sub(certificate_subject->ptr, certificate_subject->len);
+        wsrep::const_buffer cert_iss(certificate_issuer->ptr, certificate_issuer->len);
+        wsrep::const_buffer vers(version->ptr, version->len);
+        connection_monitor_service_impl->connection_monitor_ssl_info_cb(
+            id, ssl_cipher, cert_sub, cert_iss, vers);
+    }
+
+    static wsrep_connection_monitor_service_v1_t connection_monitor_service_callbacks
+        = { connection_monitor_connect_cb,
+            connection_monitor_disconnect_cb,
+	    connection_monitor_ssl_info_cb,
+            0 };
+}
+
+int wsrep::connection_monitor_service_v1_probe(void* dlh)
+{
+    typedef int (*init_fn)(wsrep_connection_monitor_service_v1_t*);
+    typedef void (*deinit_fn)();
+    if (wsrep_impl::service_probe<init_fn>(
+            dlh, WSREP_CONNECTION_MONITOR_SERVICE_INIT_FUNC_V1, "connection monitor service v1") ||
+        wsrep_impl::service_probe<deinit_fn>(
+            dlh, WSREP_CONNECTION_MONITOR_SERVICE_DEINIT_FUNC_V1, "connection monitor service v1"))
+    {
+        wsrep::log_warning() << "Provider does not support connection monitor service v1";
+        return 1;
+    }
+
+    return 0;
+}
+
+int wsrep::connection_monitor_service_v1_init(void* dlh,
+                                              wsrep::connection_monitor_service* connection_service)
+{
+    if (not (dlh && connection_service)) return EINVAL;
+    typedef int (*init_fn)(wsrep_connection_monitor_service_v1_t*);
+    wsrep_connection_monitor_service_v1::connection_monitor_service_impl = connection_service;
+    int ret(0);
+    if ((ret = wsrep_impl::service_init<init_fn>(
+             dlh, WSREP_CONNECTION_MONITOR_SERVICE_INIT_FUNC_V1,
+             &wsrep_connection_monitor_service_v1::connection_monitor_service_callbacks,
+             "connection monitor service v1")))
+    {
+        wsrep_connection_monitor_service_v1::connection_monitor_service_impl = 0;
+    }
+    else
+    {
+        ++wsrep_connection_monitor_service_v1::use_count;
+    }
+    return ret;
+}
+
+void wsrep::connection_monitor_service_v1_deinit(void* dlh)
+{
+    typedef int (*deinit_fn)();
+    wsrep_impl::service_deinit<deinit_fn>(
+        dlh, WSREP_CONNECTION_MONITOR_SERVICE_DEINIT_FUNC_V1, "connection monitor service v1");
+    assert(wsrep_connection_monitor_service_v1::use_count > 0);
+    --wsrep_connection_monitor_service_v1::use_count;
+    if (wsrep_connection_monitor_service_v1::use_count == 0)
+    {
+        wsrep_connection_monitor_service_v1::connection_monitor_service_impl = 0;
+    }
+}

src/connection_monitor_service_v1.hpp

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2024-2025 Codership Oy <info@codership.com>
+ *
+ * This file is part of wsrep-lib.
+ *
+ * Wsrep-lib 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, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Wsrep-lib 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 wsrep-lib.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef WSREP_CONNECTION_MONITOR_SERVICE_V1_HPP
+#define WSREP_CONNECTION_MONITOR_SERVICE_V1_HPP
+
+namespace wsrep
+{
+    class connection_monitor_service;
+    /**
+     * Probe connection_monitor_service_v1 support in loaded library.
+     *
+     * @param dlh Handle returned by dlopen().
+     *
+     * @return Zero on success, non-zero system error code on failure.
+     */
+    int connection_monitor_service_v1_probe(void *dlh);
+
+    /**
+     * Initialize the connection_monitor service.
+     *
+     * @param dlh Handle returned by dlopen().
+     * @param connection_monitor_service Pointer to
+     *            wsrep::connection_monitor_service implementation.
+     *
+     * @return Zero on success, non-zero system error code on failure.
+     */
+    int connection_monitor_service_v1_init(void* dlh,
+            wsrep::connection_monitor_service* connection_monitor_service);
+
+    /**
+     * Deinitialize the connection monitor service.
+     *
+     * @params dlh Handler returned by dlopen().
+     */
+    void connection_monitor_service_v1_deinit(void* dlh);
+
+}
+
+#endif // WSREP_CONNECTION_MONITOR_SERVICE_V1_HPP

src/wsrep_provider_v26.cpp

@@ -28,6 +28,7 @@
 #include "wsrep/thread_service.hpp"
 #include "wsrep/tls_service.hpp"
 #include "wsrep/allowlist_service.hpp"
+#include "wsrep/connection_monitor_service.hpp"
 
 #include "service_helpers.hpp"
 #include "thread_service_v1.hpp"
@@ -36,6 +37,7 @@
 #include "event_service_v1.hpp"
 #include "v26/wsrep_api.h"
 #include "v26/wsrep_node_isolation.h"
+#include "connection_monitor_service_v1.hpp"
 
 #include <dlfcn.h>
 #include <cassert>
@@ -674,6 +676,22 @@ namespace
     }
 
     wsrep_node_isolation_mode_set_fn_v1 node_isolation_mode_set;
+
+    static int init_connection_monitor_service(void* dlh,
+                                      wsrep::connection_monitor_service* connection_monitor_service)
+    {
+        assert(connection_monitor_service);
+        if (not wsrep::connection_monitor_service_v1_probe(dlh))
+        {
+            return wsrep::connection_monitor_service_v1_init(dlh, connection_monitor_service);
+        }
+        return 1;
+    }
+
+    static void deinit_connection_monitor_service(void* dlh)
+    {
+        wsrep::connection_monitor_service_v1_deinit(dlh);
+    }
 }
 
 
@@ -721,6 +739,15 @@ void wsrep::wsrep_provider_v26::init_services(
     node_isolation_mode_set
         = wsrep_impl::resolve_function<wsrep_node_isolation_mode_set_fn_v1>(
             wsrep_->dlh, WSREP_NODE_ISOLATION_MODE_SET_V1);
+
+    if (services.connection_monitor_service)
+    {
+        if (init_connection_monitor_service(wsrep_->dlh, services.connection_monitor_service))
+        {
+            throw wsrep::runtime_error("Failed to initialize connection monitor service");
+        }
+        services_enabled_.connection_monitor_service = services.connection_monitor_service;
+    }
 }
 
 void wsrep::wsrep_provider_v26::deinit_services()
@@ -734,6 +761,8 @@ void wsrep::wsrep_provider_v26::deinit_services()
     if (services_enabled_.allowlist_service)
         deinit_allowlist_service(wsrep_->dlh);
     node_isolation_mode_set = nullptr;
+    if (services_enabled_.connection_monitor_service)
+        deinit_connection_monitor_service(wsrep_->dlh);
 }
 
 wsrep::wsrep_provider_v26::wsrep_provider_v26(