Fix connection name in Multiserver configs in YAML-tests (#3301)

While testing in YAML framework, I realized that a multiserver config
like `MultiServer (4.0.575.0 then Embedded)` is actually connecting to
4.0.575.0 external server and JDBC in-process !current_version (instead
of Embedded). This PR fixes this naming so as to avoid ambiguity.

Also, `MultiServerConnection`s, while alternating their connections,
logs operations like `Sending operation createStatement to connection 0`
meaning, it is sending the current request to first (default, index 0)
connection which is not super clear when debugging issues related to
compatibility. This PR changes that log to explicitly specify the
connection name.

Author: g31pranjal

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/SimpleYamlConnection.java

@@ -41,10 +41,17 @@ public class SimpleYamlConnection implements YamlConnection {
     private final RelationalConnection underlying;
     @Nonnull
     private final List<SemanticVersion> versions;
+    @Nonnull
+    private final String connectionLabel;
 
     public SimpleYamlConnection(@Nonnull Connection connection, @Nonnull SemanticVersion version) throws SQLException {
+        this(connection, version, version.toString());
+    }
+
+    public SimpleYamlConnection(@Nonnull Connection connection, @Nonnull SemanticVersion version, @Nonnull String connectionLabel) throws SQLException {
         underlying = connection.unwrap(RelationalConnection.class);
         this.versions = List.of(version);
+        this.connectionLabel = connectionLabel;
     }
 
     @Override
@@ -94,4 +101,9 @@ public List<SemanticVersion> getVersions() {
     public SemanticVersion getInitialVersion() {
         return versions.get(0);
     }
+
+    @Override
+    public String toString() {
+        return connectionLabel;
+    }
 }

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/configs/JDBCMultiServerConfig.java

@@ -64,9 +64,9 @@ public YamlConnectionFactory createConnectionFactory() {
     @Override
     public String toString() {
         if (initialConnection == 0) {
-            return "MultiServer (Embedded then " + externalServer.getVersion() + ")";
+            return "MultiServer (" + super.toString() + " then " + externalServer.getVersion() + ")";
         } else {
-            return "MultiServer (" + externalServer.getVersion() + " then Embedded)";
+            return "MultiServer (" + externalServer.getVersion() + " then " + super.toString() + ")";
         }
     }
 }

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/connectionfactory/EmbeddedYamlConnectionFactory.java

@@ -34,7 +34,7 @@
 public class EmbeddedYamlConnectionFactory implements YamlConnectionFactory {
     @Override
     public YamlConnection getNewConnection(@Nonnull URI connectPath) throws SQLException {
-        return new SimpleYamlConnection(DriverManager.getConnection(connectPath.toString()), SemanticVersion.current());
+        return new SimpleYamlConnection(DriverManager.getConnection(connectPath.toString()), SemanticVersion.current(), "Embedded");
     }
 
     @Override

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/connectionfactory/JDBCInProcessYamlConnectionFactory.java

@@ -49,7 +49,7 @@ public YamlConnection getNewConnection(@Nonnull URI connectPath) throws SQLExcep
         URI connectPathPlusServerName = JDBCURI.addQueryParameter(connectPath, JDBCURI.INPROCESS_URI_QUERY_SERVERNAME_KEY, server.getServerName());
         String uriStr = connectPathPlusServerName.toString().replaceFirst("embed:", "relational://");
         LOG.info("Rewrote {} as {}", connectPath, uriStr);
-        return new SimpleYamlConnection(DriverManager.getConnection(uriStr), SemanticVersion.current());
+        return new SimpleYamlConnection(DriverManager.getConnection(uriStr), SemanticVersion.current(), "JDBC In-Process");
     }
 
     @Override

yaml-tests/src/main/java/com/apple/foundationdb/relational/yamltests/connectionfactory/MultiServerConnectionFactory.java

@@ -227,7 +227,7 @@ private YamlConnection getCurrentConnection(boolean advance, String op) {
             if (connectionSelectionPolicy == ConnectionSelectionPolicy.ALTERNATE) {
                 YamlConnection result = underlyingConnections.get(currentConnectionSelector);
                 if (logger.isInfoEnabled()) {
-                    logger.info("Sending operation {} to connection {}", op, currentConnectionSelector);
+                    logger.info("Sending operation {} to connection: {}", op, result.toString());
                 }
                 if (advance) {
                     currentConnectionSelector = (currentConnectionSelector + 1) % underlyingConnections.size();