Updates to Neo4j server to introduce core-edge

* Adds CORE and EDGE modes
* Adds endpoints to the HTTP API to distinguish
  leader/follower

enterprise/server-enterprise/src/main/java/org/neo4j/server/enterprise/EnterpriseNeoServer.java

@@ -25,6 +25,8 @@
 import java.util.List;
 import java.util.regex.Pattern;
 
+import org.neo4j.coreedge.server.core.CoreGraphDatabase;
+import org.neo4j.coreedge.server.edge.EdgeGraphDatabase;
 import org.neo4j.graphdb.EnterpriseGraphDatabase;
 import org.neo4j.helpers.collection.Iterables;
 import org.neo4j.kernel.GraphDatabaseAPI;
@@ -39,21 +41,43 @@
 import org.neo4j.server.modules.ServerModule;
 import org.neo4j.server.rest.management.AdvertisableService;
 import org.neo4j.server.web.ServerInternalSettings;
-import org.neo4j.server.webadmin.rest.MasterInfoServerModule;
+import org.neo4j.server.webadmin.rest.DatabaseRoleInfoServerModule;
 import org.neo4j.server.webadmin.rest.MasterInfoService;
 
 import static java.util.Arrays.asList;
+
 import static org.neo4j.helpers.collection.Iterables.mix;
 import static org.neo4j.server.database.LifecycleManagingDatabase.lifecycleManagingDatabase;
 
 public class EnterpriseNeoServer extends AdvancedNeoServer
 {
-    public static final String HA = "HA";
+    public enum Mode
+    {
+        SINGLE,
+        HA,
+        CORE,
+        EDGE;
+
+        public static Mode fromString( String value )
+        {
+            try
+            {
+                return Mode.valueOf( value );
+            }
+            catch ( IllegalArgumentException ex )
+            {
+                return SINGLE;
+            }
+        }
+
+    }
+
     private static final GraphFactory HA_FACTORY = new GraphFactory()
     {
         @Override
         public GraphDatabaseAPI newGraphDatabase( Config config, Dependencies dependencies )
         {
+
             File storeDir = config.get( ServerInternalSettings.legacy_db_location );
             return new HighlyAvailableGraphDatabase( storeDir, config.getParams(), dependencies );
         }
@@ -68,23 +92,55 @@ public GraphDatabaseAPI newGraphDatabase( Config config, Dependencies dependenci
         }
     };
 
+    private static final GraphFactory CORE_FACTORY = new GraphFactory()
+    {
+        @Override
+        public GraphDatabaseAPI newGraphDatabase( Config config, Dependencies dependencies )
+        {
+            File storeDir = config.get( ServerInternalSettings.legacy_db_location );
+            return new CoreGraphDatabase( storeDir, config.getParams(), dependencies );
+        }
+    };
+
+    private static final GraphFactory EDGE_FACTORY = new GraphFactory()
+    {
+        @Override
+        public GraphDatabaseAPI newGraphDatabase( Config config, Dependencies dependencies )
+        {
+            File storeDir = config.get( ServerInternalSettings.legacy_db_location );
+            return new EdgeGraphDatabase( storeDir, config.getParams(), dependencies );
+        }
+    };
+
     public EnterpriseNeoServer( Config config, Dependencies dependencies, LogProvider logProvider )
     {
         super( config, createDbFactory( config ), dependencies, logProvider );
     }
 
     protected static Database.Factory createDbFactory( Config config )
     {
-        String mode = config.get( EnterpriseServerSettings.mode ).toUpperCase();
-        return lifecycleManagingDatabase( mode.equals( HA ) ? HA_FACTORY : ENTERPRISE_FACTORY );
+        final Mode mode = Mode.fromString( config.get( EnterpriseServerSettings.mode ).toUpperCase() );
+
+        switch ( mode )
+        {
+        case HA:
+            return lifecycleManagingDatabase( HA_FACTORY );
+        case CORE:
+            return lifecycleManagingDatabase( CORE_FACTORY );
+        case EDGE:
+            return lifecycleManagingDatabase( EDGE_FACTORY );
+        default: // Anything else gives community, including Mode.SINGLE
+            return lifecycleManagingDatabase( ENTERPRISE_FACTORY );
+        }
     }
 
+
     @SuppressWarnings( "unchecked" )
     @Override
     protected Iterable<ServerModule> createServerModules()
     {
         return mix(
-                asList( (ServerModule) new MasterInfoServerModule( webServer, getConfig(),
+                asList( (ServerModule) new DatabaseRoleInfoServerModule( webServer, getConfig(),
                         logProvider ) ), super.createServerModules() );
     }
 

enterprise/server-enterprise/src/main/java/org/neo4j/server/webadmin/rest/CoreDatabaseAvailabilityDiscoveryRepresentation.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2002-2015 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.server.webadmin.rest;
+
+import org.neo4j.server.rest.repr.MappingRepresentation;
+import org.neo4j.server.rest.repr.MappingSerializer;
+
+public class CoreDatabaseAvailabilityDiscoveryRepresentation extends MappingRepresentation
+{
+    private static final String WRITABLE_KEY = "writable";
+    private static final String DISCOVERY_REPRESENTATION_TYPE = "discovery";
+
+    private final String basePath;
+    private final String isWritableUri;
+
+    public CoreDatabaseAvailabilityDiscoveryRepresentation( String basePath, String isWritableUri )
+    {
+        super( DISCOVERY_REPRESENTATION_TYPE );
+        this.basePath = basePath;
+        this.isWritableUri = isWritableUri;
+    }
+
+    @Override
+    protected void serialize( MappingSerializer serializer )
+    {
+        serializer.putUri( WRITABLE_KEY, basePath + isWritableUri );
+    }
+}

enterprise/server-enterprise/src/main/java/org/neo4j/server/webadmin/rest/CoreDatabaseAvailabilityService.java

@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2002-2015 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.server.webadmin.rest;
+
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.Response;
+
+import org.neo4j.coreedge.server.core.CoreGraphDatabase;
+import org.neo4j.coreedge.raft.roles.Role;
+import org.neo4j.graphdb.GraphDatabaseService;
+import org.neo4j.server.rest.management.AdvertisableService;
+import org.neo4j.server.rest.repr.BadInputException;
+import org.neo4j.server.rest.repr.OutputFormat;
+
+import static javax.ws.rs.core.MediaType.TEXT_PLAIN_TYPE;
+import static javax.ws.rs.core.Response.Status.FORBIDDEN;
+import static javax.ws.rs.core.Response.Status.NOT_FOUND;
+import static javax.ws.rs.core.Response.Status.OK;
+import static javax.ws.rs.core.Response.status;
+
+@Path(CoreDatabaseAvailabilityService.BASE_PATH)
+public class CoreDatabaseAvailabilityService implements AdvertisableService
+{
+    public static final String BASE_PATH = "server/core";
+    public static final String IS_WRITABLE_PATH = "/writable";
+    public static final String IS_AVAILABLE_PATH = "/available";
+
+    private final OutputFormat output;
+    private final CoreGraphDatabase coreDatabase;
+
+    public CoreDatabaseAvailabilityService( @Context OutputFormat output, @Context GraphDatabaseService db )
+    {
+        this.output = output;
+        if ( db instanceof CoreGraphDatabase )
+        {
+            this.coreDatabase = (CoreGraphDatabase) db;
+        }
+        else
+        {
+            this.coreDatabase = null;
+        }
+    }
+
+    @GET
+    public Response discover() throws BadInputException
+    {
+        if ( coreDatabase == null )
+        {
+            return status( FORBIDDEN ).build();
+        }
+
+        String isSlaveUri = IS_WRITABLE_PATH;
+
+        return output.ok( new CoreDatabaseAvailabilityDiscoveryRepresentation( BASE_PATH, isSlaveUri ) );
+    }
+
+    @GET
+    @Path(IS_WRITABLE_PATH)
+    public Response isWritable() throws BadInputException
+    {
+        if ( coreDatabase == null )
+        {
+            return status( FORBIDDEN ).build();
+        }
+
+        if ( coreDatabase.getRole() == Role.LEADER )
+        {
+            return positiveResponse();
+        }
+
+        return negativeResponse();
+    }
+
+    @GET
+    @Path( IS_AVAILABLE_PATH )
+    public Response isAvailable()
+    {
+        if ( coreDatabase == null )
+        {
+            return status( FORBIDDEN ).build();
+        }
+
+        return positiveResponse();
+    }
+
+    private Response negativeResponse()
+    {
+        return plainTextResponse( NOT_FOUND, "false" );
+    }
+
+    private Response positiveResponse()
+    {
+        return plainTextResponse( OK, "true" );
+    }
+
+    private Response plainTextResponse( Response.Status status, String entityBody )
+    {
+        return status( status ).type( TEXT_PLAIN_TYPE ).entity( entityBody ).build();
+    }
+
+    @Override
+    public String getName()
+    {
+        return "core";
+    }
+
+    @Override
+    public String getServerPath()
+    {
+        return BASE_PATH;
+    }
+}

enterprise/server-enterprise/src/main/java/org/neo4j/server/webadmin/rest/MasterInfoServerModule.java → enterprise/server-enterprise/src/main/java/org/neo4j/server/webadmin/rest/DatabaseRoleInfoServerModule.java

@@ -31,13 +31,13 @@
 
 import static java.util.Arrays.asList;
 
-public class MasterInfoServerModule implements ServerModule
+public class DatabaseRoleInfoServerModule implements ServerModule
 {
     private final WebServer server;
     private final Config config;
     private final Log log;
 
-    public MasterInfoServerModule( WebServer server, Config config, LogProvider logProvider )
+    public DatabaseRoleInfoServerModule( WebServer server, Config config, LogProvider logProvider )
     {
         this.server = server;
         this.config = config;
@@ -62,7 +62,7 @@ public void stop()
 
     private List<String> getClassNames()
     {
-        return asList( MasterInfoService.class.getName() );
+        return asList( MasterInfoService.class.getName(), CoreDatabaseAvailabilityService.class.getName() );
     }
 
     private URI managementApiUri()