codership/wsrep-lib#100 Support for assign_read_view() wsrep API call

Marshall the call from the `client_state` interface down to provider.

include/wsrep/client_state.hpp

@@ -270,6 +270,25 @@ namespace wsrep
             return transaction_.start_transaction(id);
         }
 
+        /**
+         * Establish read view ID of the transaction.
+         *
+         * This method should be preferably called immediately before any
+         * first read or write operation in the transaction is performed,
+         * Then it can be called with default NULL parameter and will use
+         * the current last committed GTID.
+         * Alternatively it can be called at any time before commit with an
+         * explicit GTID that corresponds to transaction read view.
+         *
+         * @param gtid optional explicit GTID of the transaction read view.
+         */
+        int assign_read_view(const wsrep::gtid* const gtid = NULL)
+        {
+            assert(mode_ == m_local);
+            assert(state_ == s_exec);
+            return transaction_.assign_read_view(gtid);
+        }
+
         /**
          * Append a key into transaction write set.
          */

include/wsrep/provider.hpp

@@ -274,6 +274,8 @@ namespace wsrep
         // Write set replication
         // TODO: Rename to assing_read_view()
         virtual int start_transaction(wsrep::ws_handle&) = 0;
+        virtual enum status assign_read_view(
+            wsrep::ws_handle&, const wsrep::gtid*) = 0;
         virtual int append_key(wsrep::ws_handle&, const wsrep::key&) = 0;
         virtual enum status append_data(
             wsrep::ws_handle&, const wsrep::const_buffer&) = 0;

include/wsrep/transaction.hpp

@@ -138,6 +138,8 @@ namespace wsrep
                                  const wsrep::ws_meta& ws_meta,
                                  bool is_commit);
 
+        int assign_read_view(const wsrep::gtid* gtid);
+
         int append_key(const wsrep::key&);
 
         int append_data(const wsrep::const_buffer&);

src/provider.cpp

@@ -75,7 +75,7 @@ std::string wsrep::provider::capability::str(int caps)
     WSREP_PRINT_CAPABILITY(annotation,           "ANNOTATION");
     WSREP_PRINT_CAPABILITY(preordered,           "PREORDERED");
     WSREP_PRINT_CAPABILITY(streaming,            "STREAMING");
-    WSREP_PRINT_CAPABILITY(snapshot,             "SNAPSHOT");
+    WSREP_PRINT_CAPABILITY(snapshot,             "READ_VIEW");
     WSREP_PRINT_CAPABILITY(nbo,                  "NBO");
 
 #undef WSREP_PRINT_CAPABILITY
@@ -107,7 +107,7 @@ std::string wsrep::flags_to_string(int flags)
     if (flags & provider::flag::prepare)
         oss << "prepare | ";
     if (flags & provider::flag::snapshot)
-        oss << "snapshot | ";
+        oss << "read_view | ";
     if (flags & provider::flag::implicit_deps)
         oss << "implicit_deps | ";
 

src/transaction.cpp

@@ -208,6 +208,19 @@ int wsrep::transaction::prepare_for_ordering(
     return 0;
 }
 
+int wsrep::transaction::assign_read_view(const wsrep::gtid* const gtid)
+{
+    try
+    {
+        return provider().assign_read_view(ws_handle_, gtid);
+    }
+    catch (...)
+    {
+        wsrep::log_error() << "Failed to assign read view";
+        return 1;
+    }
+}
+
 int wsrep::transaction::append_key(const wsrep::key& key)
 {
     try

src/wsrep_provider_v26.cpp

@@ -690,6 +690,25 @@ wsrep::wsrep_provider_v26::run_applier(
     return map_return_value(wsrep_->recv(wsrep_, applier_ctx));
 }
 
+enum wsrep::provider::status
+wsrep::wsrep_provider_v26::assign_read_view(wsrep::ws_handle& ws_handle,
+                                            const wsrep::gtid* gtid)
+{
+    const wsrep_gtid_t* gtid_ptr(NULL);
+    wsrep_gtid_t tmp;
+
+    if (gtid)
+    {
+        ::memcpy(&tmp.uuid, gtid->id().data(), sizeof(tmp.uuid));
+        tmp.seqno = gtid->seqno().get();
+        gtid_ptr = &tmp;
+    }
+
+    mutable_ws_handle mwsh(ws_handle);
+    return map_return_value(wsrep_->assign_read_view(wsrep_, mwsh.native(),
+                                                     gtid_ptr));
+}
+
 int wsrep::wsrep_provider_v26::append_key(wsrep::ws_handle& ws_handle,
                                           const wsrep::key& key)
 {

src/wsrep_provider_v26.hpp

@@ -46,6 +46,8 @@ namespace wsrep
 
         enum wsrep::provider::status run_applier(wsrep::high_priority_service*);
         int start_transaction(wsrep::ws_handle&) { return 0; }
+        enum wsrep::provider::status
+        assign_read_view(wsrep::ws_handle&, const wsrep::gtid*);
         int append_key(wsrep::ws_handle&, const wsrep::key&);
         enum wsrep::provider::status
         append_data(wsrep::ws_handle&, const wsrep::const_buffer&);

test/mock_provider.hpp

@@ -143,6 +143,10 @@ namespace wsrep
             }
         }
 
+        enum wsrep::provider::status
+        assign_read_view(wsrep::ws_handle&, const wsrep::gtid*)
+            WSREP_OVERRIDE
+        { return wsrep::provider::success; }
         int append_key(wsrep::ws_handle&, const wsrep::key&)
             WSREP_OVERRIDE
         { return 0; }

test/transaction_test.cpp

@@ -68,6 +68,9 @@ BOOST_FIXTURE_TEST_CASE_TEMPLATE(transaction_1pc, T,
     BOOST_REQUIRE(tc.id() == wsrep::transaction_id(1));
     BOOST_REQUIRE(tc.state() == wsrep::transaction::s_executing);
 
+    // Establish default read view
+    BOOST_REQUIRE(0 == cc.assign_read_view(NULL));
+
     // Verify that the commit can be succesfully executed in separate command
     BOOST_REQUIRE(cc.after_statement() == 0);
     cc.after_command_before_result();