diff --git a/dbsim/db_client.cpp b/dbsim/db_client.cpp
index 2a66100..944fd16 100644
--- a/dbsim/db_client.cpp
+++ b/dbsim/db_client.cpp
@@ -5,6 +5,8 @@
 #include "db_client.hpp"
 #include "db_server.hpp"
 
+#include "wsrep/logger.hpp"
+
 db::client::client(db::server& server,
                    wsrep::client_id client_id,
                    enum wsrep::client_state::mode mode,
diff --git a/dbsim/db_server.cpp b/dbsim/db_server.cpp
index 3901580..430ea72 100644
--- a/dbsim/db_server.cpp
+++ b/dbsim/db_server.cpp
@@ -6,6 +6,8 @@
 #include "db_client.hpp"
 #include "db_simulator.hpp"
 
+#include "wsrep/logger.hpp"
+
 db::server::server(simulator& simulator,
                    const std::string& name,
                    const std::string& server_id,
@@ -32,7 +34,7 @@ void db::server::applier_thread()
                                   &applier.client_state()));
     enum wsrep::provider::status ret(
         server_state_.provider().run_applier(cc));
-    wsrep::log() << "Applier thread exited with error code " << ret;
+    wsrep::log_info() << "Applier thread exited with error code " << ret;
 }
 
 void db::server::start_applier()
diff --git a/dbsim/db_server_state.cpp b/dbsim/db_server_state.cpp
index 74ea3ba..79a8fd2 100644
--- a/dbsim/db_server_state.cpp
+++ b/dbsim/db_server_state.cpp
@@ -5,6 +5,8 @@
 #include "db_server_state.hpp"
 #include "db_server.hpp"
 
+#include "wsrep/logger.hpp"
+
 wsrep::client_state* db::server_state::local_client_state()
 {
     return server_.local_client_state();
diff --git a/dbsim/db_simulator.cpp b/dbsim/db_simulator.cpp
index 48a1302..31bb094 100644
--- a/dbsim/db_simulator.cpp
+++ b/dbsim/db_simulator.cpp
@@ -3,6 +3,9 @@
 //
 
 #include "db_simulator.hpp"
+
+#include "wsrep/logger.hpp"
+
 #include <boost/filesystem.hpp>
 #include <sstream>
 
diff --git a/include/wsrep/client_state.hpp b/include/wsrep/client_state.hpp
index a689240..a059607 100644
--- a/include/wsrep/client_state.hpp
+++ b/include/wsrep/client_state.hpp
@@ -18,7 +18,6 @@
 #include "lock.hpp"
 #include "buffer.hpp"
 #include "thread.hpp"
-#include "logger.hpp"
 
 namespace wsrep
 {
@@ -117,12 +116,16 @@ namespace wsrep
         /**
          * Return true if the transaction commit requires
          * two-phase commit.
+         *
+         * @todo deprecate
          */
         bool do_2pc() const
         {
             return client_service_.do_2pc();
         }
 
+        /** @name Client command handling */
+        /** @{ */
         /**
          * This mehod should be called before the processing of command
          * received from DBMS client starts.
@@ -165,7 +168,10 @@ namespace wsrep
          * idle.
          */
         void after_command_after_result();
+        /** @} */
 
+        /** @name Statement level operations */
+        /** @{ */
         /**
          * Before statement execution operations.
          *
@@ -199,10 +205,10 @@ namespace wsrep
          * * Do rollback if requested
          */
         enum after_statement_result after_statement();
+        /** @} */
 
-        //
-        // Replicating interface
-        //
+        /** @name Replication interface */
+        /** @{ */
         /**
          * Start a new transaction with a transaction id.
          *
@@ -240,10 +246,10 @@ namespace wsrep
         {
             return client_service_.prepare_data_for_replication(*this, tc);
         }
+        /** @} */
 
-        //
-        // Streaming interface
-        //
+        /** @name Streaming replication interface */
+        /** @{ */
         /**
          * This method should be called after every row operation.
          */
@@ -270,22 +276,7 @@ namespace wsrep
         int enable_streaming(
             enum wsrep::streaming_context::fragment_unit
             fragment_unit,
-            size_t fragment_size)
-        {
-            assert(mode_ == m_replicating);
-            if (transaction_.active() &&
-                transaction_.streaming_context_.fragment_unit() !=
-                fragment_unit)
-            {
-                wsrep::log_error()
-                    << "Changing fragment unit for active transaction "
-                    << "not allowed";
-                return 1;
-            }
-            transaction_.streaming_context_.enable(
-                fragment_unit, fragment_size);
-            return 0;
-        }
+            size_t fragment_size);
 
         /** @todo deprecate */
         size_t bytes_generated() const
@@ -321,11 +312,10 @@ namespace wsrep
         {
             client_service_.remove_fragments(transaction_);
         }
+        /** @} */
 
-        //
-        // Applying interface
-        //
-
+        /** @name Applying interface */
+        /** @{ */
         int start_transaction(const wsrep::ws_handle& wsh,
                               const wsrep::ws_meta& meta)
         {
@@ -346,11 +336,10 @@ namespace wsrep
                 *this,
                 transaction_.ws_handle(), transaction_.ws_meta());
         }
+        /** @} */
 
-        //
-        // Commit ordering
-        //
-
+        /** @name Commit ordering interface */
+        /** @{ */
         int before_prepare()
         {
             wsrep::unique_lock<wsrep::mutex> lock(mutex_);
@@ -382,10 +371,10 @@ namespace wsrep
             assert(state_ == s_exec || mode_ == m_local);
             return transaction_.after_commit();
         }
+        /** @} */
 
-        //
-        // Rollback
-        //
+        /** @name Rollback interface */
+        /** @{ */
         int rollback()
         {
             return client_service_.rollback(*this);
@@ -402,6 +391,7 @@ namespace wsrep
             assert(state_ == s_idle || state_ == s_exec || state_ == s_result);
             return transaction_.after_rollback();
         }
+        /** @} */
 
         //
         // BF aborting
@@ -481,6 +471,33 @@ namespace wsrep
          */
         int wait_for_gtid(const wsrep::gtid&) const;
 
+        //
+        //
+        //
+
+        /** @name Non-transactional operations */
+        /** @{*/
+
+        /**
+         * Enter total order isolation critical section.
+         */
+        int enter_toi();
+
+        /**
+         * Leave total order isolation critical section.
+         */
+        void leave_toi();
+
+        /**
+         * Begin non-blocking operation.
+         */
+        int begin_nbo();
+
+        /**
+         * End non-blocking operation
+         */
+        void end_nbo();
+        /** @} */
         //
         // Debug interface
         //
diff --git a/include/wsrep/provider.hpp b/include/wsrep/provider.hpp
index 090a602..050976a 100644
--- a/include/wsrep/provider.hpp
+++ b/include/wsrep/provider.hpp
@@ -16,8 +16,6 @@
 
 #include <string>
 #include <vector>
-#include <ostream>
-#include <sstream>
 
 namespace wsrep
 {
@@ -267,26 +265,7 @@ namespace wsrep
         wsrep::server_state& server_state_;
     };
 
-    static inline std::string flags_to_string(int flags)
-    {
-        std::ostringstream oss;
-        if (flags & provider::flag::start_transaction)
-            oss << "start_transaction | ";
-        if (flags & provider::flag::commit)
-            oss << "commit | ";
-        if (flags & provider::flag::rollback)
-            oss << "rollback | ";
-        if (flags & provider::flag::isolation)
-            oss << "isolation | ";
-        if (flags & provider::flag::pa_unsafe)
-            oss << "pa_unsafe | ";
-        if (flags & provider::flag::snapshot)
-            oss << "snapshot | ";
-
-        std::string ret(oss.str());
-        if (ret.size() > 3) ret.erase(ret.size() - 3);
-        return ret;
-    }
+    std::string flags_to_string(int flags);
 
     static inline bool starts_transaction(int flags)
     {
diff --git a/include/wsrep/seqno.hpp b/include/wsrep/seqno.hpp
index 878133e..24bdd28 100644
--- a/include/wsrep/seqno.hpp
+++ b/include/wsrep/seqno.hpp
@@ -7,7 +7,7 @@
 
 #include "exception.hpp"
 
-#include <ostream>
+#include <iosfwd>
 
 namespace wsrep
 {
@@ -65,10 +65,7 @@ namespace wsrep
         long long seqno_;
     };
 
-    static inline std::ostream& operator<<(std::ostream& os, wsrep::seqno seqno)
-    {
-        return (os << seqno.get());
-    }
+    std::ostream& operator<<(std::ostream& os, wsrep::seqno seqno);
 }
 
 #endif // WSREP_SEQNO_HPP
diff --git a/include/wsrep/transaction.hpp b/include/wsrep/transaction.hpp
index bfc00db..756b147 100644
--- a/include/wsrep/transaction.hpp
+++ b/include/wsrep/transaction.hpp
@@ -2,6 +2,7 @@
 // Copyright (C) 2018 Codership Oy <info@codership.com>
 //
 
+/** @file transaction.hpp */
 #ifndef WSREP_TRANSACTION_CONTEXT_HPP
 #define WSREP_TRANSACTION_CONTEXT_HPP
 
diff --git a/include/wsrep/transaction_id.hpp b/include/wsrep/transaction_id.hpp
index 1ef4488..9bbf19d 100644
--- a/include/wsrep/transaction_id.hpp
+++ b/include/wsrep/transaction_id.hpp
@@ -5,7 +5,7 @@
 #ifndef WSREP_TRANSACTION_ID_HPP
 #define WSREP_TRANSACTION_ID_HPP
 
-#include <ostream>
+#include <iosfwd>
 
 namespace wsrep
 {
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 9b1cd10..e42ad46 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -7,6 +7,7 @@ add_library(wsrep-lib
   id.cpp
   logger.cpp
   provider.cpp
+  seqno.cpp
   server_state.cpp
   transaction.cpp
   wsrep_provider_v26.cpp)
diff --git a/src/client_state.cpp b/src/client_state.cpp
index 7fad9e4..31e1d58 100644
--- a/src/client_state.cpp
+++ b/src/client_state.cpp
@@ -185,6 +185,26 @@ wsrep::client_state::after_statement()
     return asr_success;
 }
 
+int wsrep::client_state::enable_streaming(
+    enum wsrep::streaming_context::fragment_unit
+    fragment_unit,
+    size_t fragment_size)
+{
+    assert(mode_ == m_replicating);
+    if (transaction_.active() &&
+        transaction_.streaming_context_.fragment_unit() !=
+        fragment_unit)
+    {
+        wsrep::log_error()
+            << "Changing fragment unit for active transaction "
+            << "not allowed";
+        return 1;
+    }
+    transaction_.streaming_context_.enable(
+        fragment_unit, fragment_size);
+    return 0;
+}
+
 // Private
 
 void wsrep::client_state::debug_log_state(const char* context) const
diff --git a/src/provider.cpp b/src/provider.cpp
index ea951fd..0cf3eeb 100644
--- a/src/provider.cpp
+++ b/src/provider.cpp
@@ -33,3 +33,24 @@ wsrep::provider* wsrep::provider::make_provider(
     }
     return 0;
 }
+
+std::string wsrep::flags_to_string(int flags)
+{
+    std::ostringstream oss;
+    if (flags & provider::flag::start_transaction)
+        oss << "start_transaction | ";
+    if (flags & provider::flag::commit)
+        oss << "commit | ";
+    if (flags & provider::flag::rollback)
+        oss << "rollback | ";
+    if (flags & provider::flag::isolation)
+        oss << "isolation | ";
+    if (flags & provider::flag::pa_unsafe)
+        oss << "pa_unsafe | ";
+    if (flags & provider::flag::snapshot)
+        oss << "snapshot | ";
+
+    std::string ret(oss.str());
+    if (ret.size() > 3) ret.erase(ret.size() - 3);
+    return ret;
+}
diff --git a/src/seqno.cpp b/src/seqno.cpp
new file mode 100644
index 0000000..a3d1b2d
--- /dev/null
+++ b/src/seqno.cpp
@@ -0,0 +1,11 @@
+//
+// Copyright (C) 2018 Codership Oy <info@codership.com>
+//
+
+#include "wsrep/seqno.hpp"
+#include <ostream>
+
+std::ostream& wsrep::operator<<(std::ostream& os, wsrep::seqno seqno)
+{
+    return (os << seqno.get());
+}