MDEV-32363 Add interface to set node isolation mode in provider

src/service_helpers.hpp

@@ -100,7 +100,29 @@ namespace wsrep_impl
                 << service_name;
         }
     }
-}
+
+    template <typename Fn> Fn resolve_function(void* dlh, const char* symbol)
+    {
+        union
+        {
+            Fn fun;
+            void* obj;
+        } alias;
+        (void)dlerror();
+        alias.obj = dlsym(dlh, symbol);
+        if (alias.obj)
+        {
+            wsrep::log_info() << "Resolved symbol '" << symbol << "'";
+            return alias.fun;
+        }
+        else
+        {
+            wsrep::log_info()
+                << "Symbol '" << symbol << "' not found from provider";
+            return nullptr;
+        }
+    }
+} // namespace wsrep_impl
 
 #endif // WSREP_SERVICE_HELPERS_HPP
 

src/wsrep_provider_v26.cpp

@@ -29,12 +29,13 @@
 #include "wsrep/tls_service.hpp"
 #include "wsrep/allowlist_service.hpp"
 
+#include "service_helpers.hpp"
 #include "thread_service_v1.hpp"
 #include "tls_service_v1.hpp"
 #include "allowlist_service_v1.hpp"
 #include "event_service_v1.hpp"
 #include "v26/wsrep_api.h"
-
+#include "v26/wsrep_node_isolation.h"
 
 #include <dlfcn.h>
 #include <cassert>
@@ -671,6 +672,8 @@ namespace
     {
         wsrep::event_service_v1_deinit(dlh);
     }
+
+    wsrep_node_isolation_mode_set_fn_v1 node_isolation_mode_set;
 }
 
 
@@ -714,6 +717,10 @@ void wsrep::wsrep_provider_v26::init_services(
             services_enabled_.event_service = services.event_service;
         }
     }
+
+    node_isolation_mode_set
+        = wsrep_impl::resolve_function<wsrep_node_isolation_mode_set_fn_v1>(
+            wsrep_->dlh, WSREP_NODE_ISOLATION_MODE_SET_V1);
 }
 
 void wsrep::wsrep_provider_v26::deinit_services()
@@ -726,6 +733,7 @@ void wsrep::wsrep_provider_v26::deinit_services()
         deinit_thread_service(wsrep_->dlh);
     if (services_enabled_.allowlist_service)
         deinit_allowlist_service(wsrep_->dlh);
+    node_isolation_mode_set = nullptr;
 }
 
 wsrep::wsrep_provider_v26::wsrep_provider_v26(
@@ -1162,6 +1170,40 @@ wsrep::wsrep_provider_v26::options(const std::string& opts)
     return map_return_value(wsrep_->options_set(wsrep_, opts.c_str()));
 }
 
+/*
+ * Set node isolation mode in the provider. This function may be called from
+ * signal handler, so make sure that only 'safe' system calls and library
+ * functions are used. See
+ * https://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html
+ */
+enum wsrep::provider::status
+wsrep::wsrep_provider_v26::set_node_isolation(node_isolation mode)
+{
+    if (not node_isolation_mode_set)
+    {
+        return error_not_implemented;
+    }
+
+    enum wsrep_node_isolation_mode ws_mode = WSREP_NODE_ISOLATION_NOT_ISOLATED;
+    switch (mode)
+    {
+    case node_isolation::not_isolated:
+        ws_mode = WSREP_NODE_ISOLATION_NOT_ISOLATED;
+        break;
+    case node_isolation::isolated:
+        ws_mode = WSREP_NODE_ISOLATION_ISOLATED;
+        break;
+    case node_isolation::force_disconnect:
+        ws_mode = WSREP_NODE_ISOLATION_FORCE_DISCONNECT;
+        break;
+    }
+    if ((*node_isolation_mode_set)(ws_mode) != WSREP_NODE_ISOLATION_SUCCESS)
+    {
+        return error_warning;
+    }
+    return success;
+}
+
 std::string wsrep::wsrep_provider_v26::name() const
 {
     return (wsrep_->provider_name ? wsrep_->provider_name : "unknown");

src/wsrep_provider_v26.hpp

@@ -100,6 +100,7 @@ namespace wsrep
         void reset_status() WSREP_OVERRIDE;
         std::string options() const WSREP_OVERRIDE;
         enum wsrep::provider::status options(const std::string&) WSREP_OVERRIDE;
+        enum status set_node_isolation(enum node_isolation mode) WSREP_OVERRIDE;
         std::string name() const WSREP_OVERRIDE;
         std::string version() const WSREP_OVERRIDE;
         std::string vendor() const WSREP_OVERRIDE;