speed up tinkerpop test

how to:
1.speed up rocksdb backend by truncating tables
2.don't need to clear if the database is empty
3.don't need to clear variables if it's empty
4.don't need to commit hbase each len-prefix for delete index-label

potential problems:
1.mysql may block if create task vertex-label when truncating table
2.rocksdb may miss CF if create task vertex-label when truncating table
3.hbase may block if truncate hbase with version<2.0

improve #14

Change-Id: I4b2393aea8b0fc63c1886e984a576a1f5808b25c

hugegraph-api/src/main/java/com/baidu/hugegraph/api/GraphsAPI.java

@@ -36,13 +36,10 @@
 import javax.ws.rs.core.Context;
 import javax.ws.rs.core.SecurityContext;
 
-import org.apache.tinkerpop.gremlin.structure.Edge;
-import org.apache.tinkerpop.gremlin.structure.Vertex;
 import org.slf4j.Logger;
 
 import com.baidu.hugegraph.HugeGraph;
 import com.baidu.hugegraph.core.GraphManager;
-import com.baidu.hugegraph.schema.SchemaManager;
 import com.baidu.hugegraph.server.RestServer;
 import com.baidu.hugegraph.util.Log;
 import com.codahale.metrics.annotation.Timed;
@@ -127,27 +124,7 @@ public void clear(@Context GraphManager manager,
             throw new IllegalArgumentException(String.format(
                       "Please take the message: %s", CONFIRM_CLEAR));
         }
-
-        // Clear vertex and edge
-        commit(g, () -> {
-            g.traversal().E().toStream().forEach(Edge::remove);
-            g.traversal().V().toStream().forEach(Vertex::remove);
-        });
-
-        // Schema operation will auto commit
-        SchemaManager schema = g.schema();
-        schema.getIndexLabels().forEach(elem -> {
-            schema.indexLabel(elem.name()).remove();
-        });
-        schema.getEdgeLabels().forEach(elem -> {
-            schema.edgeLabel(elem.name()).remove();
-        });
-        schema.getVertexLabels().forEach(elem -> {
-            schema.vertexLabel(elem.name()).remove();
-        });
-        schema.getPropertyKeys().forEach(elem -> {
-            schema.propertyKey(elem.name()).remove();
-        });
+        g.truncateBackend();
     }
 
     @PUT

hugegraph-api/src/main/java/com/baidu/hugegraph/auth/HugeGraphAuthProxy.java

@@ -168,6 +168,11 @@ public void clearBackend() {
         this.hugegraph.clearBackend();
     }
 
+    public void truncateBackend() {
+        this.verifyPermission(ROLE_ADMIN);
+        this.hugegraph.truncateBackend();
+    }
+
     public void restoring(boolean restoring) {
         this.verifyPermission(ROLE_ADMIN);
         this.hugegraph.restoring(restoring);

hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraSessionPool.java

@@ -222,6 +222,10 @@ public void open() {
             this.session = cluster().connect(keyspace());
         }
 
+        public boolean opened() {
+            return this.session != null;
+        }
+
         @Override
         public boolean closed() {
             if (this.session == null) {

hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraStore.java

@@ -19,8 +19,11 @@
 
 package com.baidu.hugegraph.backend.store.cassandra;
 
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -242,12 +245,25 @@ public BackendFeatures features() {
     @Override
     public void init() {
         this.checkClusterConnected();
-        this.initKeyspace();
 
+        if (this.sessions.session().opened()) {
+            // Session has ever been opened.
+            LOG.warn("Session has ever been opened(exist keyspace '{}' before)",
+                     this.keyspace);
+        } else {
+            // Create keyspace if need
+            if (!this.existsKeyspace()) {
+                this.initKeyspace();
+            }
+            // Open session explicitly to get the exception when it fails
+            this.sessions.session().open();
+        }
+
+        // Create tables
         this.checkSessionConnected();
         this.initTables();
 
-        LOG.info("Store initialized: {}", this.store);
+        LOG.debug("Store initialized: {}", this.store);
     }
 
     @Override
@@ -260,7 +276,15 @@ public void clear() {
             this.clearKeyspace();
         }
 
-        LOG.info("Store cleared: {}", this.store);
+        LOG.debug("Store cleared: {}", this.store);
+    }
+
+    @Override
+    public void truncate() {
+        this.checkSessionConnected();
+
+        this.truncateTables();
+        LOG.debug("Store truncated: {}", this.store);
     }
 
     @Override
@@ -358,7 +382,8 @@ protected void initKeyspace() {
         replication.putIfAbsent("replication_factor", factor);
 
         Statement stmt = SchemaBuilder.createKeyspace(this.keyspace)
-                         .ifNotExists().with().replication(replication);
+                                      .ifNotExists().with()
+                                      .replication(replication);
 
         // Create keyspace with non-keyspace-session
         LOG.debug("Create keyspace: {}", stmt);
@@ -370,7 +395,6 @@ protected void initKeyspace() {
                 session.close();
             }
         }
-        this.sessions.session().open();
     }
 
     protected void clearKeyspace() {
@@ -394,18 +418,29 @@ protected boolean existsKeyspace() {
 
     protected void initTables() {
         CassandraSessionPool.Session session = this.sessions.session();
-        for (CassandraTable table : this.tables.values()) {
+        for (CassandraTable table : this.tables()) {
             table.init(session);
         }
     }
 
     protected void clearTables() {
         CassandraSessionPool.Session session = this.sessions.session();
-        for (CassandraTable table : this.tables.values()) {
+        for (CassandraTable table : this.tables()) {
             table.clear(session);
         }
     }
 
+    protected void truncateTables() {
+        CassandraSessionPool.Session session = this.sessions.session();
+        for (CassandraTable table : this.tables()) {
+            table.truncate(session);
+        }
+    }
+
+    protected Collection<CassandraTable> tables() {
+        return this.tables.values();
+    }
+
     protected final CassandraTable table(HugeType type) {
         assert type != null;
         CassandraTable table = this.tables.get(type);
@@ -464,19 +499,10 @@ public CassandraSchemaStore(BackendStoreProvider provider,
         }
 
         @Override
-        protected void initTables() {
-            super.initTables();
-
-            CassandraSessionPool.Session session = super.sessions.session();
-            this.counters.init(session);
-        }
-
-        @Override
-        protected void clearTables() {
-            super.clearTables();
-
-            CassandraSessionPool.Session session = super.sessions.session();
-            this.counters.clear(session);
+        protected Collection<CassandraTable> tables() {
+            List<CassandraTable> tables = new ArrayList<>(super.tables());
+            tables.add(this.counters);
+            return tables;
         }
 
         @Override

hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java

@@ -570,4 +570,9 @@ protected void createIndex(CassandraSessionPool.Session session,
     public void clear(CassandraSessionPool.Session session) {
         this.dropTable(session);
     }
+
+    public void truncate(CassandraSessionPool.Session session) {
+        LOG.debug("Truncate table: {}", this.table());
+        session.execute(QueryBuilder.truncate(this.table()));
+    }
 }

hugegraph-core/src/main/java/com/baidu/hugegraph/HugeGraph.java

@@ -23,6 +23,7 @@
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
+import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.apache.tinkerpop.gremlin.process.computer.GraphComputer;
@@ -96,8 +97,8 @@ public class HugeGraph implements Graph {
     }
 
     private final String name;
-    private boolean closed;
-    private boolean restoring;
+    private volatile boolean closed;
+    private volatile boolean restoring;
 
     private final HugeConfig configuration;
 
@@ -187,7 +188,7 @@ public void initBackend() {
         this.loadGraphStore().open(this.configuration);
         try {
             this.storeProvider.init();
-            new BackendStoreInfo(this).init();
+            this.initBackendStoreInfo();
         } finally {
             this.loadGraphStore().close();
             this.loadSystemStore().close();
@@ -196,6 +197,8 @@ public void initBackend() {
     }
 
     public void clearBackend() {
+        this.waitUntilAllTasksCompleted();
+
         this.loadSchemaStore().open(this.configuration);
         this.loadSystemStore().open(this.configuration);
         this.loadGraphStore().open(this.configuration);
@@ -208,7 +211,28 @@ public void clearBackend() {
         }
     }
 
+    public void truncateBackend() {
+        this.waitUntilAllTasksCompleted();
+
+        this.storeProvider.truncate();
+        this.initBackendStoreInfo();
+    }
+
+    private void waitUntilAllTasksCompleted() {
+        Long timeout = this.configuration.get(CoreOptions.TASK_WAIT_TIMEOUT);
+        try {
+            this.taskScheduler().waitUntilAllTasksCompleted(timeout);
+        } catch (TimeoutException e) {
+            throw new HugeException("Failed to wait all tasks to complete", e);
+        }
+    }
+
+    private void initBackendStoreInfo() {
+        new BackendStoreInfo(this).init();
+    }
+
     private SchemaTransaction openSchemaTransaction() throws HugeException {
+        this.checkGraphNotClosed();
         try {
             return new CachedSchemaTransaction(this, this.loadSchemaStore());
         } catch (BackendException e) {
@@ -219,6 +243,7 @@ private SchemaTransaction openSchemaTransaction() throws HugeException {
     }
 
     private GraphTransaction openGraphTransaction() throws HugeException {
+        this.checkGraphNotClosed();
         try {
             return new CachedGraphTransaction(this, this.loadGraphStore());
         } catch (BackendException e) {
@@ -235,12 +260,16 @@ private BackendStoreProvider loadStoreProvider() {
         return BackendProviderFactory.open(backend, this.name);
     }
 
-    private BackendStore loadSchemaStore() {
+    private void checkGraphNotClosed() {
+        E.checkState(!this.closed, "Graph '%s' has been closed", this);
+    }
+
+    public BackendStore loadSchemaStore() {
         String name = this.configuration.get(CoreOptions.STORE_SCHEMA);
         return this.storeProvider.loadSchemaStore(name);
     }
 
-    private BackendStore loadGraphStore() {
+    public BackendStore loadGraphStore() {
         String graph = this.configuration.get(CoreOptions.STORE_GRAPH);
         return this.storeProvider.loadGraphStore(graph);
     }
@@ -251,6 +280,7 @@ public BackendStore loadSystemStore() {
     }
 
     public SchemaTransaction schemaTransaction() {
+        this.checkGraphNotClosed();
         /*
          * NOTE: each schema operation will be auto committed,
          * Don't need to open tinkerpop tx by readWrite() and commit manually.
@@ -259,6 +289,7 @@ public SchemaTransaction schemaTransaction() {
     }
 
     public GraphTransaction graphTransaction() {
+        this.checkGraphNotClosed();
         /*
          * NOTE: graph operations must be committed manually,
          * Maybe users need to auto open tinkerpop tx by readWrite().

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/LocalCounter.java

@@ -46,4 +46,8 @@ public Id nextId(HugeType type) {
         }
         return IdGenerator.of(counter.incrementAndGet());
     }
+
+    public void reset() {
+        this.counters.clear();
+    }
 }

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/CachedBackendStore.java

@@ -81,6 +81,11 @@ public void clear() {
         this.store.clear();
     }
 
+    @Override
+    public void truncate() {
+        this.store.truncate();
+    }
+
     @Override
     public void beginTx() {
         this.store.beginTx();