diff --git a/dbsim/db_high_priority_service.cpp b/dbsim/db_high_priority_service.cpp
index f260f52..e3788ab 100644
--- a/dbsim/db_high_priority_service.cpp
+++ b/dbsim/db_high_priority_service.cpp
@@ -20,6 +20,11 @@ int db::high_priority_service::start_transaction(
     return client_.client_state().start_transaction(ws_handle, ws_meta);
 }
 
+const wsrep::transaction& db::high_priority_service::transaction() const
+{
+    return client_.client_state().transaction();
+}
+
 void db::high_priority_service::adopt_transaction(const wsrep::transaction&)
 {
     throw wsrep::not_implemented_error();
diff --git a/dbsim/db_high_priority_service.hpp b/dbsim/db_high_priority_service.hpp
index f0479ad..aeaca90 100644
--- a/dbsim/db_high_priority_service.hpp
+++ b/dbsim/db_high_priority_service.hpp
@@ -17,6 +17,7 @@ namespace db
         high_priority_service(db::server& server, db::client& client);
         int start_transaction(const wsrep::ws_handle&,
                               const wsrep::ws_meta&) override;
+        const wsrep::transaction& transaction() const override;
         void adopt_transaction(const wsrep::transaction&) override;
         int apply_write_set(const wsrep::ws_meta&,
                             const wsrep::const_buffer&) override;
diff --git a/include/wsrep/client_state.hpp b/include/wsrep/client_state.hpp
index dcac518..fccb5ea 100644
--- a/include/wsrep/client_state.hpp
+++ b/include/wsrep/client_state.hpp
@@ -434,11 +434,17 @@ namespace wsrep
             return transaction_.start_replaying(ws_meta);
         }
 
+        /**
+         * Adopt a streaming transaction state. This is must be
+         * called from high_priority_service::adopt_transaction()
+         * during streaming transaction rollback. The call will
+         * set up enough context for handling the rollback
+         * fragment.
+         */
         void adopt_transaction(const wsrep::transaction& transaction)
         {
             assert(mode_ == m_high_priority);
-            transaction_.start_transaction(transaction.id());
-            transaction_.streaming_context() = transaction.streaming_context();
+            transaction_.adopt(transaction);
         }
 
         /** @name Non-transactional operations */
diff --git a/include/wsrep/high_priority_service.hpp b/include/wsrep/high_priority_service.hpp
index e8d04c8..12fc49c 100644
--- a/include/wsrep/high_priority_service.hpp
+++ b/include/wsrep/high_priority_service.hpp
@@ -36,6 +36,12 @@ namespace wsrep
         virtual int start_transaction(const wsrep::ws_handle&,
                                       const wsrep::ws_meta&) = 0;
 
+        /**
+         * Return transaction object associated to high priority
+         * service state.
+         */
+        virtual const wsrep::transaction& transaction() const = 0;
+
         /**
          * Adopt a transaction.
          */
@@ -83,8 +89,18 @@ namespace wsrep
 
         /**
          * Commit a transaction.
+         * An implementation must call
+         * wsrep::client_state::prepare_for_ordering() to set
+         * the ws_handle and ws_meta before the commit if the
+         * commit process will go through client state commit
+         * processing. Otherwise the implementation must release
+         * commit order explicitly via provider.
+         *
+         * @param ws_handle Write set handle
+         * @param ws_meta Write set meta
          */
-        virtual int commit(const wsrep::ws_handle&, const wsrep::ws_meta&) = 0;
+        virtual int commit(const wsrep::ws_handle& ws_handle,
+                           const wsrep::ws_meta& ws_meta) = 0;
         /**
          * Roll back a transaction
          */
diff --git a/include/wsrep/key.hpp b/include/wsrep/key.hpp
index 152732b..a367db2 100644
--- a/include/wsrep/key.hpp
+++ b/include/wsrep/key.hpp
@@ -8,6 +8,8 @@
 #include "exception.hpp"
 #include "buffer.hpp"
 
+#include <iosfwd>
+
 namespace wsrep
 {
     class key
@@ -60,6 +62,7 @@ namespace wsrep
 
     typedef std::vector<wsrep::key> key_array;
 
+    std::ostream& operator<<(std::ostream&, const wsrep::key&);
 }
 
 #endif // WSREP_KEY_HPP
diff --git a/include/wsrep/provider.hpp b/include/wsrep/provider.hpp
index 68392c6..2e546f8 100644
--- a/include/wsrep/provider.hpp
+++ b/include/wsrep/provider.hpp
@@ -262,7 +262,7 @@ namespace wsrep
         virtual enum status bf_abort(wsrep::seqno bf_seqno,
                                      wsrep::transaction_id victim_trx,
                                      wsrep::seqno& victim_seqno) = 0;
-        virtual int rollback(wsrep::transaction_id) = 0;
+        virtual enum status rollback(wsrep::transaction_id) = 0;
         virtual enum status commit_order_enter(const wsrep::ws_handle&,
                                                const wsrep::ws_meta&) = 0;
         virtual int commit_order_leave(const wsrep::ws_handle&,
diff --git a/include/wsrep/transaction.hpp b/include/wsrep/transaction.hpp
index 3a36e16..1732ed2 100644
--- a/include/wsrep/transaction.hpp
+++ b/include/wsrep/transaction.hpp
@@ -88,6 +88,7 @@ namespace wsrep
         int start_transaction(const wsrep::ws_handle& ws_handle,
                               const wsrep::ws_meta& ws_meta);
 
+        void adopt(const transaction& transaction);
         void fragment_applied(wsrep::seqno seqno);
 
         int prepare_for_ordering(const wsrep::ws_handle& ws_handle,
@@ -155,6 +156,7 @@ namespace wsrep
         void clear_fragments();
         void cleanup();
         void debug_log_state(const char*) const;
+        void debug_log_key_append(const wsrep::key& key);
 
         wsrep::server_service& server_service_;
         wsrep::client_service& client_service_;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5357a25..ad1cba1 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -7,6 +7,7 @@ add_library(wsrep-lib
   exception.cpp
   gtid.cpp
   id.cpp
+  key.cpp
   logger.cpp
   provider.cpp
   seqno.cpp
diff --git a/src/client_state.cpp b/src/client_state.cpp
index e051a6a..1f32fac 100644
--- a/src/client_state.cpp
+++ b/src/client_state.cpp
@@ -36,6 +36,7 @@ void wsrep::client_state::close()
     if (transaction_.active())
     {
         client_service_.bf_rollback();
+        transaction_.after_statement();
     }
     debug_log_state("close: leave");
 }
@@ -421,7 +422,19 @@ void wsrep::client_state::state(
     wsrep::unique_lock<wsrep::mutex>& lock WSREP_UNUSED,
     enum wsrep::client_state::state state)
 {
-    assert(wsrep::this_thread::get_id() == owning_thread_id_);
+    // For locally processing client states (local, toi, rsu)
+    // changing the state is allowed only from the owning thread.
+    // In high priority mode the processing thread however may
+    // change and we check only that store_globals() has been
+    // called by the current thread to gain ownership.
+    //
+    // Note that this check assumes that there is always a single
+    // thread per local client connection. This may not always
+    // hold and the sanity check mechanism may need to be revised.
+    assert((mode_ != m_high_priority &&
+            wsrep::this_thread::get_id() == owning_thread_id_) ||
+           (mode_ == m_high_priority &&
+            wsrep::this_thread::get_id() == current_thread_id_));
     assert(lock.owns_lock());
     static const char allowed[state_max_][state_max_] =
         {
diff --git a/src/key.cpp b/src/key.cpp
new file mode 100644
index 0000000..281805c
--- /dev/null
+++ b/src/key.cpp
@@ -0,0 +1,36 @@
+//
+// Copyright (C) 2018 Codership Oy <info@codership.com>
+//
+
+#include "wsrep/key.hpp"
+#include <ostream>
+#include <iomanip>
+
+namespace
+{
+    void print_key_part(std::ostream& os, const void* ptr, size_t len)
+    {
+        std::ios::fmtflags flags_save(os.flags());
+        os << len << ": ";
+        for (size_t i(0); i < len; ++i)
+        {
+            os << std::hex
+               << std::setfill('0')
+               << std::setw(2)
+               << static_cast<int>(
+                   *(reinterpret_cast<const unsigned char*>(ptr) + i)) << " ";
+        }
+        os.flags(flags_save);
+    }
+}
+
+std::ostream& wsrep::operator<<(std::ostream& os, const wsrep::key& key)
+{
+    os << "type: " << key.type();
+    for (size_t i(0); i < key.size(); ++i)
+    {
+        os << "\n    ";
+        print_key_part(os, key.key_parts()[i].data(), key.key_parts()[i].size());
+    }
+    return os;
+}
diff --git a/src/server_state.cpp b/src/server_state.cpp
index fd01627..87792cc 100644
--- a/src/server_state.cpp
+++ b/src/server_state.cpp
@@ -28,6 +28,79 @@ namespace
         return (bootstrap || cluster_address == "gcomm://");
     }
 
+    int apply_fragment(wsrep::server_state& server_state,
+                       wsrep::high_priority_service& high_priority_service,
+                       wsrep::high_priority_service& streaming_applier,
+                       const wsrep::ws_handle& ws_handle,
+                       const wsrep::ws_meta& ws_meta,
+                       const wsrep::const_buffer& data)
+    {
+        int ret;
+        {
+            wsrep::high_priority_switch sw(high_priority_service,
+                                           streaming_applier);
+            ret = streaming_applier.apply_write_set(ws_meta, data);
+            streaming_applier.after_apply();
+        }
+        ret = ret || high_priority_service.append_fragment_and_commit(
+            ws_handle, ws_meta, data);
+        high_priority_service.after_apply();
+        return ret;
+    }
+
+
+    int commit_fragment(wsrep::server_state& server_state,
+                        wsrep::high_priority_service& high_priority_service,
+                        wsrep::high_priority_service* streaming_applier,
+                        const wsrep::ws_handle& ws_handle,
+                        const wsrep::ws_meta& ws_meta,
+                        const wsrep::const_buffer& data)
+    {
+        int ret;
+        // Make high priority switch to go out of scope
+        // before the streaming applier is released.
+        {
+            wsrep::high_priority_switch sw(
+                high_priority_service, *streaming_applier);
+            streaming_applier->remove_fragments(ws_meta);
+            ret = streaming_applier->commit(ws_handle, ws_meta);
+            streaming_applier->after_apply();
+        }
+        server_state.stop_streaming_applier(
+            ws_meta.server_id(), ws_meta.transaction_id());
+        server_state.server_service().release_high_priority_service(
+            streaming_applier);
+        return ret;
+    }
+
+    int rollback_fragment(wsrep::server_state& server_state,
+                          wsrep::high_priority_service& high_priority_service,
+                          wsrep::high_priority_service* streaming_applier,
+                          const wsrep::ws_handle& ws_handle,
+                          const wsrep::ws_meta& ws_meta,
+                          const wsrep::const_buffer& data)
+    {
+        int ret= 0;
+        // Adopts transaction state and starts a transaction for
+        // high priority service
+        high_priority_service.adopt_transaction(
+            streaming_applier->transaction());
+        {
+            wsrep::high_priority_switch ws(
+                high_priority_service, *streaming_applier);
+            streaming_applier->rollback();
+            streaming_applier->after_apply();
+        }
+        server_state.stop_streaming_applier(
+            ws_meta.server_id(), ws_meta.transaction_id());
+        server_state.server_service().release_high_priority_service(
+            streaming_applier);
+
+        high_priority_service.remove_fragments(ws_meta);
+        high_priority_service.commit(ws_handle, ws_meta);
+        return ret;
+    }
+
     int apply_write_set(wsrep::server_state& server_state,
                         wsrep::high_priority_service& high_priority_service,
                         const wsrep::ws_handle& ws_handle,
@@ -36,6 +109,14 @@ namespace
     {
         int ret(0);
         if (wsrep::starts_transaction(ws_meta.flags()) &&
+                 wsrep::commits_transaction(ws_meta.flags()) &&
+                 wsrep::rolls_back_transaction(ws_meta.flags()))
+        {
+            // Non streaming rollback (certification failed)
+            ret = high_priority_service.log_dummy_write_set(
+                ws_handle, ws_meta);
+        }
+        else if (wsrep::starts_transaction(ws_meta.flags()) &&
             wsrep::commits_transaction(ws_meta.flags()))
         {
             if (high_priority_service.start_transaction(ws_handle, ws_meta))
@@ -66,13 +147,12 @@ namespace
             server_state.start_streaming_applier(
                 ws_meta.server_id(), ws_meta.transaction_id(), sa);
             sa->start_transaction(ws_handle, ws_meta);
-            {
-                wsrep::high_priority_switch sw(high_priority_service, *sa);
-                sa->apply_write_set(ws_meta, data);
-                sa->after_apply();
-            }
-            high_priority_service.append_fragment_and_commit(ws_handle, ws_meta, data);
-            high_priority_service.after_apply();
+            ret = apply_fragment(server_state,
+                                 high_priority_service,
+                                 *sa,
+                                 ws_handle,
+                                 ws_meta,
+                                 data);
         }
         else if (ws_meta.flags() == 0)
         {
@@ -92,17 +172,13 @@ namespace
             }
             else
             {
-                wsrep::high_priority_switch sw(high_priority_service, *sa);
-                ret = sa->apply_write_set(ws_meta, data);
-                sa->after_apply();
+                ret = apply_fragment(server_state,
+                                     high_priority_service,
+                                     *sa,
+                                     ws_handle,
+                                     ws_meta,
+                                     data);
             }
-            ret = ret || high_priority_service.append_fragment_and_commit(
-                ws_handle, ws_meta, data);
-            if (ret)
-            {
-                high_priority_service.rollback();
-            }
-            high_priority_service.after_apply();
         }
         else if (wsrep::commits_transaction(ws_meta.flags()))
         {
@@ -130,24 +206,48 @@ namespace
                 }
                 else
                 {
-                    // Make high priority switch to go out of scope
-                    // before the streaming applier is released.
-                    {
-                        wsrep::high_priority_switch sw(
-                            high_priority_service, *sa);
-                        sa->remove_fragments(ws_meta);
-                        ret = sa->commit(ws_handle, ws_meta);
-                        sa->after_apply();
-                    }
-                    server_state.stop_streaming_applier(
-                        ws_meta.server_id(), ws_meta.transaction_id());
-                    server_state.server_service().release_high_priority_service(sa);
+                    // Commit fragment consumes sa
+                    ret = commit_fragment(server_state,
+                                          high_priority_service,
+                                          sa,
+                                          ws_handle,
+                                          ws_meta,
+                                          data);
                 }
             }
         }
+        else if (wsrep::rolls_back_transaction(ws_meta.flags()))
+        {
+            wsrep::high_priority_service* sa(
+                server_state.find_streaming_applier(
+                    ws_meta.server_id(), ws_meta.transaction_id()));
+            if (sa == 0)
+            {
+                // It is possible that rapid group membership changes
+                // may cause streaming transaction be rolled back before
+                // commit fragment comes in. Although this is a valid
+                // situation, log a warning if a sac cannot be found as
+                // it may be an indication of  a bug too.
+                wsrep::log_warning()
+                    << "Could not find applier context for "
+                    << ws_meta.server_id()
+                    << ": " << ws_meta.transaction_id();
+                ret = high_priority_service.log_dummy_write_set(
+                    ws_handle, ws_meta);
+            }
+            else
+            {
+                // Rollback fragment consumes sa
+                ret = rollback_fragment(server_state,
+                                        high_priority_service,
+                                        sa,
+                                        ws_handle,
+                                        ws_meta,
+                                        data);
+            }
+        }
         else
         {
-            // SR fragment applying not implemented yet
             assert(0);
         }
         return ret;
@@ -633,13 +733,6 @@ int wsrep::server_state::on_apply(
     const wsrep::ws_meta& ws_meta,
     const wsrep::const_buffer& data)
 {
-    if (rolls_back_transaction(ws_meta.flags()))
-    {
-        provider().commit_order_enter(ws_handle, ws_meta);
-        // todo: server_service_.log_dummy_write_set();
-        provider().commit_order_leave(ws_handle, ws_meta);
-        return 0;
-    }
     if (is_toi(ws_meta.flags()))
     {
         return apply_toi(provider(), high_priority_service,
diff --git a/src/transaction.cpp b/src/transaction.cpp
index b801e18..073a1e7 100644
--- a/src/transaction.cpp
+++ b/src/transaction.cpp
@@ -111,11 +111,12 @@ int wsrep::transaction::start_transaction(
 {
     debug_log_state("start_transaction enter");
     assert(active() == false);
+    assert(flags() == 0);
     id_ = id;
     state_ = s_executing;
     state_hist_.clear();
     ws_handle_ = wsrep::ws_handle(id);
-    flags_ |= wsrep::provider::flag::start_transaction;
+    flags(wsrep::provider::flag::start_transaction);
     switch (client_state_.mode())
     {
     case wsrep::client_state::m_high_priority:
@@ -140,12 +141,14 @@ int wsrep::transaction::start_transaction(
     {
         // assert(ws_meta.flags());
         assert(active() == false);
+        assert(flags() == 0);
         id_ = ws_meta.transaction_id();
         assert(client_state_.mode() == wsrep::client_state::m_high_priority);
         state_ = s_executing;
         state_hist_.clear();
         ws_handle_ = ws_handle;
         ws_meta_ = ws_meta;
+        flags(wsrep::provider::flag::start_transaction);
         certified_ = true;
     }
     else
@@ -156,6 +159,16 @@ int wsrep::transaction::start_transaction(
     return 0;
 }
 
+void wsrep::transaction::adopt(const wsrep::transaction& transaction)
+{
+    debug_log_state("adopt enter");
+    assert(transaction.is_streaming());
+    start_transaction(transaction.id());
+    flags_  = transaction.flags();
+    streaming_context_ = transaction.streaming_context();
+    debug_log_state("adopt leave");
+}
+
 void wsrep::transaction::fragment_applied(wsrep::seqno seqno)
 {
     assert(active());
@@ -195,6 +208,7 @@ int wsrep::transaction::append_key(const wsrep::key& key)
     /** @todo Collect table level keys for SR commit */
     try
     {
+        debug_log_key_append(key);
         sr_keys_.insert(key);
         return provider().append_key(ws_handle_, key);
     }
@@ -493,49 +507,62 @@ int wsrep::transaction::before_rollback()
     debug_log_state("before_rollback_enter");
     assert(state() == s_executing ||
            state() == s_must_abort ||
-           state() == s_aborting || // Background rollbacker
+           // Background rollbacker or rollback initiated from SE
+           state() == s_aborting ||
            state() == s_cert_failed ||
            state() == s_must_replay);
 
-    switch (state())
+    switch (client_state_.mode())
     {
-    case s_executing:
-        // Voluntary rollback
-        if (is_streaming())
-        {
-            streaming_rollback();
-        }
-        state(lock, s_aborting);
-        break;
-    case s_must_abort:
-        if (certified())
-        {
-            state(lock, s_must_replay);
-        }
-        else
+    case wsrep::client_state::m_local:
+        switch (state())
         {
+        case s_executing:
+            // Voluntary rollback
             if (is_streaming())
             {
                 streaming_rollback();
             }
             state(lock, s_aborting);
+            break;
+        case s_must_abort:
+            if (certified())
+            {
+                state(lock, s_must_replay);
+            }
+            else
+            {
+                if (is_streaming())
+                {
+                    streaming_rollback();
+                }
+                state(lock, s_aborting);
+            }
+            break;
+        case s_cert_failed:
+            if (is_streaming())
+            {
+                streaming_rollback();
+            }
+            state(lock, s_aborting);
+            break;
+        case s_aborting:
+            if (is_streaming())
+            {
+                provider().rollback(id_.get());
+            }
+            break;
+        case s_must_replay:
+            break;
+        default:
+            assert(0);
+            break;
         }
         break;
-    case s_cert_failed:
-        if (is_streaming())
-        {
-            streaming_rollback();
-        }
+    case wsrep::client_state::m_high_priority:
+        assert(state_ == s_executing);
         state(lock, s_aborting);
         break;
-    case s_aborting:
-        if (is_streaming())
-        {
-            provider().rollback(id_.get());
-        }
-        break;
-    case s_must_replay:
-        break;
     default:
         assert(0);
         break;
@@ -551,6 +578,11 @@ int wsrep::transaction::after_rollback()
     assert(state() == s_aborting ||
            state() == s_must_replay);
 
+    if (is_streaming())
+    {
+        clear_fragments();
+    }
+
     if (state() == s_aborting)
     {
         state(lock, s_aborted);
@@ -709,6 +741,16 @@ void wsrep::transaction::after_applying()
     {
         cleanup();
     }
+    else
+    {
+        // State remains executing, so this is a streaming applier.
+        // Reset the meta data to avoid releasing commit order
+        // critical section above if the next fragment is rollback
+        // fragment. Rollback fragment ordering will be handled by
+        // another instance while removing the fragments from
+        // storage.
+        ws_meta_ = wsrep::ws_meta();
+    }
     debug_log_state("after_applying leave");
 }
 
@@ -804,6 +846,13 @@ void wsrep::transaction::state(
                     << " -> " << to_string(next_state);
     }
     assert(lock.owns_lock());
+    // BF aborter is allowed to change the state to must abort and
+    // further to aborting and aborted if the background rollbacker
+    // is launched.
+    assert(client_state_.owning_thread_id_ == wsrep::this_thread::get_id() ||
+           next_state == s_must_abort ||
+           next_state == s_aborting ||
+           next_state == s_aborted);
     static const char allowed[n_states][n_states] =
         { /*  ex pr ce co oc ct cf ma ab ad mr re */
             { 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0}, /* ex */
@@ -898,7 +947,7 @@ int wsrep::transaction::certify_fragment(
         if (storage_service.append_fragment(
                 server_id,
                 id(),
-                flags_,
+                flags(),
                 wsrep::const_buffer(data.data(), data.size())))
         {
             lock.lock();
@@ -911,7 +960,7 @@ int wsrep::transaction::certify_fragment(
         enum wsrep::provider::status
             cert_ret(provider().certify(client_state_.id().get(),
                                         ws_handle_,
-                                        flags_,
+                                        flags(),
                                         sr_ws_meta));
         switch (cert_ret)
         {
@@ -933,8 +982,12 @@ int wsrep::transaction::certify_fragment(
             ret = 1;
             break;
         }
-        provider().release(ws_handle_);
     }
+    // Note: This does not release the handle in the provider
+    // since streaming is still on. However it is needed to
+    // make provider internal state to transition for the
+    // next fragment.
+    provider().release(ws_handle_);
     lock.lock();
     if (ret)
     {
@@ -943,7 +996,7 @@ int wsrep::transaction::certify_fragment(
     else
     {
         state(lock, s_executing);
-        flags_ &= ~wsrep::provider::flag::start_transaction;
+        flags(flags() & ~wsrep::provider::flag::start_transaction);
     }
     return ret;
 }
@@ -1139,7 +1192,13 @@ int wsrep::transaction::append_sr_keys_for_commit()
 
 void wsrep::transaction::streaming_rollback()
 {
+    debug_log_state("streaming_rollback enter");
     assert(streaming_context_.rolled_back() == false);
+    // Create a high priority applier which will handle the
+    // rollback fragment or clean up on configuration change.
+    // Adopt transaction will copy fragment set and appropriate
+    // meta data. Mark current transaction streaming context
+    // rolled back.
     wsrep::high_priority_service* sa(
         server_service_.streaming_applier_service(
             client_state_.client_service()));
@@ -1147,8 +1206,14 @@ void wsrep::transaction::streaming_rollback()
         client_state_.server_state().id(), id(), sa);
     sa->adopt_transaction(*this);
     streaming_context_.cleanup();
-    // Replicate rollback fragment
-    provider().rollback(id_.get());
+    streaming_context_.rolled_back(id_);
+    enum wsrep::provider::status ret;
+    if ((ret = provider().rollback(id_.get())))
+    {
+        wsrep::log_warning() << "Failed to replicate rollback fragment for "
+                             << id_.get() << ": " << ret;
+    }
+    debug_log_state("streaming_rollback leave");
 }
 
 void wsrep::transaction::clear_fragments()
@@ -1174,8 +1239,10 @@ void wsrep::transaction::cleanup()
     bf_abort_provider_status_ = wsrep::provider::success;
     bf_abort_client_state_ = 0;
     ws_meta_ = wsrep::ws_meta();
+    flags_ = 0;
     certified_ = false;
     pa_unsafe_ = false;
+    streaming_context_.cleanup();
     client_service_.cleanup_transaction();
     debug_log_state("cleanup_leave");
 }
@@ -1185,11 +1252,30 @@ void wsrep::transaction::debug_log_state(
 {
     WSREP_TC_LOG_DEBUG(
         1, context
-        << "(" << client_state_.id().get()
-        << "," << int64_t(id_.get())
-        << "," << ws_meta_.seqno().get()
-        << "," << wsrep::to_string(state_)
-        << "," << wsrep::to_string(bf_abort_state_)
-        << "," << wsrep::to_string(client_state_.current_error())
-        << ")");
+        << "\n    server: " << client_state_.server_state().id()
+        << ", client: " << client_state_.id().get()
+        << ", state: " << wsrep::to_c_string(client_state_.state())
+        << ", mode: " << wsrep::to_c_string(client_state_.mode())
+        << "\n    trx_id: " << int64_t(id_.get())
+        << ", seqno: " << ws_meta_.seqno().get()
+        << ", flags: " << flags()
+        << "\n"
+        << "    state: " << wsrep::to_c_string(state_)
+        << ", bfa_state: " << wsrep::to_c_string(bf_abort_state_)
+        << ", error: " << wsrep::to_c_string(client_state_.current_error())
+        << "\n"
+        << "    is_sr: " << is_streaming()
+        << ", frags: " << streaming_context_.fragments_certified()
+        << ", bytes: " << streaming_context_.bytes_certified()
+        << ", sr_rb: " << streaming_context_.rolled_back()
+        << "\n    own: " << (client_state_.owning_thread_id_ == wsrep::this_thread::get_id())
+        << "");
+}
+
+void wsrep::transaction::debug_log_key_append(const wsrep::key& key)
+{
+    WSREP_TC_LOG_DEBUG(2, "key_append"
+                       << "trx_id: "
+                       << int64_t(id().get())
+                       << " append key: " << key);
 }
diff --git a/src/wsrep_provider_v26.cpp b/src/wsrep_provider_v26.cpp
index f592f17..6963606 100644
--- a/src/wsrep_provider_v26.cpp
+++ b/src/wsrep_provider_v26.cpp
@@ -631,6 +631,12 @@ wsrep::wsrep_provider_v26::bf_abort(
     return map_return_value(ret);
 }
 
+enum wsrep::provider::status
+wsrep::wsrep_provider_v26::rollback(wsrep::transaction_id id)
+{
+    return map_return_value(wsrep_->rollback(wsrep_, id.get(), 0));
+}
+
 enum wsrep::provider::status
 wsrep::wsrep_provider_v26::commit_order_enter(
     const wsrep::ws_handle& ws_handle,
diff --git a/src/wsrep_provider_v26.hpp b/src/wsrep_provider_v26.hpp
index 6794c55..903b751 100644
--- a/src/wsrep_provider_v26.hpp
+++ b/src/wsrep_provider_v26.hpp
@@ -42,7 +42,7 @@ namespace wsrep
         bf_abort(wsrep::seqno,
                  wsrep::transaction_id,
                  wsrep::seqno&);
-        int rollback(const wsrep::transaction_id) { ::abort(); return 0; }
+        enum wsrep::provider::status rollback(const wsrep::transaction_id);
         enum wsrep::provider::status
         commit_order_enter(const wsrep::ws_handle&,
                            const wsrep::ws_meta&);
diff --git a/test/mock_high_priority_service.cpp b/test/mock_high_priority_service.cpp
index ffcce0d..483e037 100644
--- a/test/mock_high_priority_service.cpp
+++ b/test/mock_high_priority_service.cpp
@@ -35,11 +35,12 @@ int wsrep::mock_high_priority_service::apply_write_set(
     return (fail_next_applying_ ? 1 : 0);
 }
 
-int wsrep::mock_high_priority_service::commit(const wsrep::ws_handle&,
-                                              const wsrep::ws_meta&)
+int wsrep::mock_high_priority_service::commit(
+    const wsrep::ws_handle& ws_handle,
+    const wsrep::ws_meta& ws_meta)
 {
-
     int ret(0);
+    client_state_->prepare_for_ordering(ws_handle, ws_meta, true);
     if (client_state_->client_service().do_2pc())
     {
         ret = client_state_->before_prepare() ||
diff --git a/test/mock_high_priority_service.hpp b/test/mock_high_priority_service.hpp
index e0d2887..fc7ad15 100644
--- a/test/mock_high_priority_service.hpp
+++ b/test/mock_high_priority_service.hpp
@@ -31,6 +31,8 @@ namespace wsrep
         int start_transaction(const wsrep::ws_handle&, const wsrep::ws_meta&)
             WSREP_OVERRIDE;
 
+        const wsrep::transaction& transaction() const
+        { return client_state_->transaction(); }
         void adopt_transaction(const wsrep::transaction&) WSREP_OVERRIDE;
         int apply_write_set(const wsrep::ws_meta&,
                             const wsrep::const_buffer&) WSREP_OVERRIDE;
diff --git a/test/mock_provider.hpp b/test/mock_provider.hpp
index 576d0c2..18ea0ca 100644
--- a/test/mock_provider.hpp
+++ b/test/mock_provider.hpp
@@ -131,11 +131,11 @@ namespace wsrep
         enum wsrep::provider::status
         append_data(wsrep::ws_handle&, const wsrep::const_buffer&)
         { return wsrep::provider::success; }
-        int rollback(const wsrep::transaction_id)
+        enum wsrep::provider::status rollback(const wsrep::transaction_id)
         {
             ++fragments_;
             ++rollback_fragments_;
-            return 0;
+            return wsrep::provider::success;
         }
         enum wsrep::provider::status
         commit_order_enter(const wsrep::ws_handle& ws_handle,