* Moved causal reads/gtid wait into server state interface

* Changed undefined seqno to be defined as -1

src/server_state.cpp

@@ -77,6 +77,41 @@ void wsrep::server_state::wait_until_state(
     cond_.notify_all();
 }
 
+void wsrep::server_state::last_committed_gtid(const wsrep::gtid& gtid)
+{
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    assert(last_committed_gtid_.is_undefined() ||
+           last_committed_gtid_.seqno() + 1 == gtid.seqno());
+    last_committed_gtid_ = gtid;
+    cond_.notify_all();
+}
+
+wsrep::gtid wsrep::server_state::last_committed_gtid() const
+{
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    return last_committed_gtid_;
+}
+
+int wsrep::server_state::wait_for_gtid(const wsrep::gtid& gtid) const
+{
+    wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+    if (gtid.id() != last_committed_gtid_.id())
+    {
+        return 1;
+    }
+    while (last_committed_gtid_.seqno() < gtid.seqno())
+    {
+        cond_.wait(lock);
+    }
+    return 0;
+}
+
+enum wsrep::provider::status
+wsrep::server_state::causal_read(int timeout) const
+{
+    return provider_->causal_read(timeout);
+}
+
 void wsrep::server_state::on_connect()
 {
     wsrep::log() << "Server " << name_ << " connected to cluster";

src/transaction.cpp

@@ -89,7 +89,7 @@ int wsrep::transaction::start_replaying(const wsrep::ws_meta& ws_meta)
     assert(active());
     assert(client_state_.mode() == wsrep::client_state::m_high_priority);
     assert(state() == s_replaying);
-    assert(ws_meta_.seqno().nil() == false);
+    assert(ws_meta_.seqno().is_undefined() == false);
     certified_ = true;
     return 0;
 }

src/wsrep_provider_v26.cpp

@@ -69,12 +69,12 @@ namespace
 
     static inline wsrep_seqno_t seqno_to_native(wsrep::seqno seqno)
     {
-        return (seqno.nil() ? WSREP_SEQNO_UNDEFINED : seqno.get());
+        return seqno.get();
     }
 
     static inline wsrep::seqno seqno_from_native(wsrep_seqno_t seqno)
     {
-        return wsrep::seqno(seqno == WSREP_SEQNO_UNDEFINED ? 0 : seqno);
+        return wsrep::seqno(seqno);
     }
     template <typename F, typename T>
     inline uint32_t map_one(const int flags, const F from,
@@ -520,9 +520,9 @@ int wsrep::wsrep_provider_v26::resync()
     return (wsrep_->resync(wsrep_) != WSREP_OK);
 }
 
-int wsrep::wsrep_provider_v26::pause()
+wsrep::seqno wsrep::wsrep_provider_v26::pause()
 {
-    return (wsrep_->pause(wsrep_) != WSREP_OK);
+    return wsrep::seqno(wsrep_->pause(wsrep_));
 }
 
 int wsrep::wsrep_provider_v26::resume()
@@ -633,6 +633,12 @@ wsrep::wsrep_provider_v26::replay(const wsrep::ws_handle& ws_handle,
         wsrep_->replay_trx(wsrep_, mwsh.native(), applier_ctx));
 }
 
+enum wsrep::provider::status
+wsrep::wsrep_provider_v26::causal_read(int timeout) const
+{
+    return map_return_value(wsrep_->sync_wait(wsrep_, 0, timeout, 0));
+}
+
 int wsrep::wsrep_provider_v26::sst_sent(const wsrep::gtid& gtid, int err)
 {
     wsrep_gtid_t wsrep_gtid;

src/wsrep_provider_v26.hpp

@@ -25,7 +25,7 @@ namespace wsrep
 
         int desync();
         int resync();
-        int pause();
+        wsrep::seqno pause();
         int resume();
 
         enum wsrep::provider::status run_applier(void*);
@@ -49,6 +49,9 @@ namespace wsrep
                                const wsrep::ws_meta&);
         int release(wsrep::ws_handle&);
         enum wsrep::provider::status replay(const wsrep::ws_handle&, void*);
+
+        enum wsrep::provider::status causal_read(int) const;
+
         int sst_sent(const wsrep::gtid&,int);
         int sst_received(const wsrep::gtid& gtid, int);