diff --git a/dbsim/db_server_service.cpp b/dbsim/db_server_service.cpp
index ea800a8..a5e2070 100644
--- a/dbsim/db_server_service.cpp
+++ b/dbsim/db_server_service.cpp
@@ -48,6 +48,11 @@ void db::server_service::background_rollback(wsrep::client_state&)
 {
 }
 
+void db::server_service::log_message(enum wsrep::log::level level,
+                                     const char* message)
+{
+    wsrep::log(level, server_.server_state().name().c_str()) << message;
+}
 void db::server_service::log_dummy_write_set(
     wsrep::client_state&, const wsrep::ws_meta& meta)
 {
diff --git a/dbsim/db_server_service.hpp b/dbsim/db_server_service.hpp
index 3deee8b..4764e30 100644
--- a/dbsim/db_server_service.hpp
+++ b/dbsim/db_server_service.hpp
@@ -22,6 +22,7 @@ namespace db
         int start_sst(const std::string&, const wsrep::gtid&, bool) override;
         std::string sst_request() override;
         void background_rollback(wsrep::client_state&) override;
+        void log_message(enum wsrep::log::level, const char* message);
         void log_dummy_write_set(wsrep::client_state&, const wsrep::ws_meta&)
             override;
         void log_view(wsrep::client_state&, const wsrep::view&) override;
diff --git a/dbsim/db_simulator.cpp b/dbsim/db_simulator.cpp
index 31bb094..f98ad2c 100644
--- a/dbsim/db_simulator.cpp
+++ b/dbsim/db_simulator.cpp
@@ -74,10 +74,10 @@ std::string db::simulator::stats() const
 
 void db::simulator::start()
 {
-    wsrep::log() << "Provider: " << params_.wsrep_provider;
+    wsrep::log_info() << "Provider: " << params_.wsrep_provider;
 
     std::string cluster_address(build_cluster_address());
-    wsrep::log() << "Cluster address: " << cluster_address;
+    wsrep::log_info() << "Cluster address: " << cluster_address;
     for (size_t i(0); i < params_.n_servers; ++i)
     {
         std::ostringstream name_os;
@@ -121,7 +121,7 @@ void db::simulator::start()
     }
 
     // Start client threads
-    wsrep::log() << "####################### Starting client load";
+    wsrep::log_info() << "####################### Starting client load";
     clients_start_ = std::chrono::steady_clock::now();
     size_t index(0);
     for (auto& i : servers_)
@@ -142,9 +142,9 @@ void db::simulator::stop()
         server.stop_clients();
     }
     clients_stop_ = std::chrono::steady_clock::now();
-    wsrep::log() << "######## Stats ############";
-    wsrep::log()  << stats();
-    wsrep::log() << "######## Stats ############";
+    wsrep::log_info() << "######## Stats ############";
+    wsrep::log_info()  << stats();
+    wsrep::log_info() << "######## Stats ############";
     if (params_.fast_exit)
     {
         exit(0);
@@ -158,7 +158,7 @@ void db::simulator::stop()
         for_each(status.begin(), status.end(),
                  [](const wsrep::provider::status_variable& sv)
                  {
-                     wsrep::log() << sv.name() << " = " << sv.value();
+                     wsrep::log_info() << sv.name() << " = " << sv.value();
                  });
         server.server_state().disconnect();
         server.server_state().wait_until_state(
diff --git a/include/wsrep/exception.hpp b/include/wsrep/exception.hpp
index 9fc4fdf..6d43505 100644
--- a/include/wsrep/exception.hpp
+++ b/include/wsrep/exception.hpp
@@ -10,13 +10,18 @@
 
 namespace wsrep
 {
+    extern bool abort_on_exception;
+
     class runtime_error : public std::runtime_error
     {
     public:
         runtime_error(const std::string& msg)
             : std::runtime_error(msg)
         {
-            // ::abort();
+            if (abort_on_exception)
+            {
+                ::abort();
+            }
         }
     };
 
diff --git a/include/wsrep/logger.hpp b/include/wsrep/logger.hpp
index f968559..35288de 100644
--- a/include/wsrep/logger.hpp
+++ b/include/wsrep/logger.hpp
@@ -16,14 +16,33 @@ namespace wsrep
     class log
     {
     public:
-        log(const std::string& prefix = "INFO")
-            : prefix_(prefix)
+        enum level
+        {
+            debug,
+            info,
+            warning,
+            error
+        };
+        static const char* to_c_string(enum level level)
+        {
+            switch (level)
+            {
+            case debug:   return "debug";
+            case info:    return "info";
+            case warning: return "warning";
+            case error:   return "error";
+            };
+            return "unknown";
+        }
+        log(enum wsrep::log::level level, const char* prefix = "")
+            : level_(level)
+            , prefix_(prefix)
             , oss_()
         { }
         ~log()
         {
             wsrep::unique_lock<wsrep::mutex> lock(mutex_);
-            os_ << prefix_ << ": " << oss_.str() << "\n";
+            os_ << prefix_ << ": " << oss_.str() << std::endl;
         }
         template <typename T>
         std::ostream& operator<<(const T& val)
@@ -31,7 +50,10 @@ namespace wsrep
             return (oss_ << val);
         }
     private:
-        const std::string prefix_;
+        log(const log&);
+        log& operator=(const log&);
+        enum level level_;
+        const char* prefix_;
         std::ostringstream oss_;
         static wsrep::mutex& mutex_;
         static std::ostream& os_;
@@ -41,28 +63,28 @@ namespace wsrep
     {
     public:
         log_error()
-            : log("ERROR") { }
+            : log(error) { }
     };
 
     class log_warning : public log
     {
     public:
         log_warning()
-            : log("WARNING") { }
+            : log(warning) { }
     };
 
     class log_info : public log
     {
     public:
         log_info()
-            : log("INFO") { }
+            : log(info) { }
     };
 
     class log_debug : public log
     {
     public:
         log_debug()
-            : log("DEBUG") { }
+            : log(debug) { }
     };
 }
 
diff --git a/include/wsrep/server_service.hpp b/include/wsrep/server_service.hpp
index 2dd5a61..5f2119e 100644
--- a/include/wsrep/server_service.hpp
+++ b/include/wsrep/server_service.hpp
@@ -13,6 +13,8 @@
 #ifndef WSREP_SERVER_SERVICE_HPP
 #define WSREP_SERVER_SERVICE_HPP
 
+#include "logger.hpp"
+
 #include <string>
 
 namespace wsrep
@@ -53,6 +55,14 @@ namespace wsrep
          */
         virtual void background_rollback(wsrep::client_state&) = 0;
 
+        /**
+         * Log message
+         *
+         * @param level   Requested logging level
+         * @param message Message
+         */
+        virtual void log_message(enum wsrep::log::level level,
+                                 const char* message) = 0;
         /**
          * Log a dummy write set. A dummy write set is usually either
          * a remotely generated write set which failed certification in
diff --git a/include/wsrep/server_state.hpp b/include/wsrep/server_state.hpp
index ab41334..da646f5 100644
--- a/include/wsrep/server_state.hpp
+++ b/include/wsrep/server_state.hpp
@@ -73,7 +73,6 @@
 #include "id.hpp"
 #include "transaction_id.hpp"
 #include "provider.hpp"
-// #include "gtid.hpp"
 
 #include <vector>
 #include <string>
@@ -312,6 +311,26 @@ namespace wsrep
          */
         enum wsrep::provider::status causal_read(int timeout) const;
 
+        /**
+         * Prepares server state for SST.
+         *
+         * @return String containing a SST request
+         */
+        std::string prepare_for_sst();
+
+        /**
+         * Start a state snapshot transfer.
+         *
+         * @param sst_requets SST request string
+         * @param gtid Current GTID
+         * @param bypass Bypass flag
+         *
+         * @return Zero in case of success, non-zero otherwise
+         */
+        int start_sst(const std::string& sst_request,
+                      const wsrep::gtid& gtid,
+                      bool bypass);
+
         /**
          *
          */
@@ -353,7 +372,11 @@ namespace wsrep
                      const wsrep::ws_meta& ws_meta,
                      const wsrep::const_buffer& data);
 
-        enum state state() const { return state_; }
+        enum state state() const
+        {
+            wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+            return state_;
+        }
         /**
          * Set server wide wsrep debug logging level.
          *
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 531932c..5357a25 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -4,6 +4,7 @@
 
 add_library(wsrep-lib
   client_state.cpp
+  exception.cpp
   gtid.cpp
   id.cpp
   logger.cpp
diff --git a/src/exception.cpp b/src/exception.cpp
new file mode 100644
index 0000000..e7ae9f8
--- /dev/null
+++ b/src/exception.cpp
@@ -0,0 +1,7 @@
+//
+// Copyright (C) 2018 Codership Oy <info@codership.com>
+//
+
+#include "wsrep/exception.hpp"
+
+bool wsrep::abort_on_exception(false);
diff --git a/src/server_state.cpp b/src/server_state.cpp
index d1c2726..a9c6dbf 100644
--- a/src/server_state.cpp
+++ b/src/server_state.cpp
@@ -55,13 +55,50 @@ wsrep::server_state::~server_state()
     delete provider_;
 }
 
+std::string wsrep::server_state::prepare_for_sst()
+{
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    state(lock, s_joiner);
+    return server_service_.sst_request();
+}
+
+int wsrep::server_state::start_sst(const std::string& sst_request,
+                                   const wsrep::gtid& gtid,
+                                   bool bypass)
+{
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    state(lock, s_donor);
+    int ret(0);
+    lock.unlock();
+    if (server_service_.start_sst(sst_request, gtid, bypass))
+    {
+        lock.lock();
+        wsrep::log_warning() << "SST start failed";
+        state(lock, s_synced);
+        ret = 1;
+    }
+    return ret;
+}
+
 void wsrep::server_state::sst_sent(const wsrep::gtid& gtid, int error)
 {
-    provider_->sst_sent(gtid, error);
+    if (provider_->sst_sent(gtid, error))
+    {
+        server_service_.log_message(wsrep::log::warning,
+                                    "SST sent returned an error");
+    }
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    state(lock, s_joined);
 }
+
 void wsrep::server_state::sst_received(const wsrep::gtid& gtid, int error)
 {
-    provider_->sst_received(gtid, error);
+    if (provider_->sst_received(gtid, error))
+    {
+        throw wsrep::runtime_error("SST received failed");
+    }
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    state(lock, s_joined);
 }
 
 void wsrep::server_state::wait_until_state(
@@ -114,14 +151,14 @@ wsrep::server_state::causal_read(int timeout) const
 
 void wsrep::server_state::on_connect()
 {
-    wsrep::log() << "Server " << name_ << " connected to cluster";
+    wsrep::log_info() << "Server " << name_ << " connected to cluster";
     wsrep::unique_lock<wsrep::mutex> lock(mutex_);
     state(lock, s_connected);
 }
 
 void wsrep::server_state::on_view(const wsrep::view& view)
 {
-    wsrep::log() << "================================================\nView:\n"
+    wsrep::log_info() << "================================================\nView:\n"
                  << "id: " << view.state_id() << "\n"
                  << "status: " << view.status() << "\n"
                  << "own_index: " << view.own_index() << "\n"
@@ -131,10 +168,10 @@ void wsrep::server_state::on_view(const wsrep::view& view)
     for (std::vector<wsrep::view::member>::const_iterator i(members.begin());
          i != members.end(); ++i)
     {
-        wsrep::log() << "id: " << i->id() << " "
-                     << "name: " << i->name();
+        wsrep::log_info() << "id: " << i->id() << " "
+                          << "name: " << i->name();
     }
-    wsrep::log() << "=================================================";
+    wsrep::log_info() << "=================================================";
     wsrep::unique_lock<wsrep::mutex> lock(mutex_);
     if (view.final())
     {
@@ -144,12 +181,23 @@ void wsrep::server_state::on_view(const wsrep::view& view)
 
 void wsrep::server_state::on_sync()
 {
-    wsrep::log() << "Server " << name_ << " synced with group";
+    wsrep::log_info() << "Server " << name_ << " synced with group";
     wsrep::unique_lock<wsrep::mutex> lock(mutex_);
-    if (state_ != s_synced)
+    /* Follow the path joiner -> joined -> synced to notify possible
+       waiters. */
+    switch (state_)
     {
+    case s_connected:
+        state(lock, s_joiner);
+    case s_joiner:
+        state(lock, s_joined);
+    case s_joined:
         state(lock, s_synced);
-    }
+        break;
+    default:
+        /* State */
+        state(lock, s_synced);
+    };
 }
 
 int wsrep::server_state::on_apply(
@@ -363,8 +411,8 @@ void wsrep::server_state::state(
             {  0,   1,   0,    1,    0,   0,   0,   0,   0}, /* dis */
             {  0,   0,   1,    0,    0,   0,   0,   0,   0}, /* ing */
             {  0,   0,   0,    1,    0,   1,   0,   0,   0}, /* ized */
-            {  0,   0,   0,    0,    1,   0,   0,   1,   0}, /* cted */
-            {  0,   0,   0,    0,    0,   1,   0,   1,   0}, /* jer */
+            {  0,   0,   0,    0,    1,   0,   0,   0,   0}, /* cted */
+            {  0,   0,   0,    0,    0,   1,   0,   0,   0}, /* jer */
             {  0,   0,   0,    0,    0,   0,   0,   1,   1}, /* jed */
             {  0,   0,   0,    0,    0,   1,   0,   0,   1}, /* dor */
             {  0,   0,   0,    0,    0,   1,   1,   0,   1}, /* sed */
@@ -373,8 +421,8 @@ void wsrep::server_state::state(
 
     if (allowed[state_][state])
     {
-        wsrep::log() << "server " << name_ << " state change: "
-                     << state_ << " -> " << state;
+        wsrep::log_info() << "server " << name_ << " state change: "
+                          << state_ << " -> " << state;
         state_ = state;
         cond_.notify_all();
         while (state_waiters_[state_])
diff --git a/src/wsrep_provider_v26.cpp b/src/wsrep_provider_v26.cpp
index 808b582..3eb5342 100644
--- a/src/wsrep_provider_v26.cpp
+++ b/src/wsrep_provider_v26.cpp
@@ -8,6 +8,7 @@
 #include "wsrep/client_state.hpp"
 #include "wsrep/view.hpp"
 #include "wsrep/exception.hpp"
+#include "wsrep/logger.hpp"
 
 #include <wsrep_api.h>
 
@@ -306,10 +307,10 @@ namespace
     }
 
     wsrep_cb_status_t view_cb(void* app_ctx,
-                                     void* recv_ctx __attribute__((unused)),
-                                     const wsrep_view_info_t* view_info,
-                                     const char*,
-                                     size_t)
+                              void* recv_ctx __attribute__((unused)),
+                              const wsrep_view_info_t* view_info,
+                              const char*,
+                              size_t)
     {
         assert(app_ctx);
         assert(view_info);
@@ -337,7 +338,7 @@ namespace
 
         try
         {
-            std::string req(server_state.server_service().sst_request());
+            std::string req(server_state.prepare_for_sst());
             *sst_req = ::strdup(req.c_str());
             *sst_req_len = strlen(req.c_str());
             return WSREP_CB_SUCCESS;
@@ -417,7 +418,7 @@ namespace
             wsrep::gtid gtid(wsrep::id(req_gtid->uuid.data,
                                        sizeof(req_gtid->uuid.data)),
                              wsrep::seqno(req_gtid->seqno));
-            if (server_state.server_service().start_sst(req, gtid, bypass))
+            if (server_state.start_sst(req, gtid, bypass))
             {
                 return WSREP_CB_FAILURE;
             }
@@ -428,6 +429,27 @@ namespace
             return WSREP_CB_FAILURE;
         }
     }
+
+    void logger_cb(wsrep_log_level_t level, const char* msg)
+    {
+        switch (level)
+        {
+        case WSREP_LOG_FATAL:
+        case WSREP_LOG_ERROR:
+            wsrep::log_error() << "wsrep-lib: " << msg;
+            break;
+        case WSREP_LOG_WARN:
+            wsrep::log_warning() << "wsrep-lib: " <<msg;
+            break;
+        case WSREP_LOG_INFO:
+            wsrep::log_info() << "wsrep-lib: " << msg;
+            break;
+        case WSREP_LOG_DEBUG:
+            wsrep::log_debug() << "wsrep-lib: " << msg;
+            break;
+        }
+    }
+
 }
 
 wsrep::wsrep_provider_v26::wsrep_provider_v26(
@@ -448,7 +470,7 @@ wsrep::wsrep_provider_v26::wsrep_provider_v26(
     init_args.proto_ver = 1;
     init_args.state_id = 0;
     init_args.state = 0;
-    init_args.logger_cb = 0;
+    init_args.logger_cb = &logger_cb;
     init_args.connected_cb = &connected_cb;
     init_args.view_cb = &view_cb;
     init_args.sst_request_cb = &sst_request_cb;
diff --git a/test/mock_server_state.hpp b/test/mock_server_state.hpp
index 6943153..1aa7e05 100644
--- a/test/mock_server_state.hpp
+++ b/test/mock_server_state.hpp
@@ -52,7 +52,10 @@ namespace wsrep
         {
             delete client_state;
         }
-
+        void log_message(enum wsrep::log::level level, const char* message)
+        {
+            wsrep::log(level, name().c_str()) << message;
+        }
         void log_dummy_write_set(wsrep::client_state&,
                                  const wsrep::ws_meta&)
             WSREP_OVERRIDE