apache · chenhao7253886 · Sep 4, 2017 · Sep 4, 2017 · Sep 4, 2017
diff --git a/docs/help/Contents/Administration/admin_stmt.md b/docs/help/Contents/Administration/admin_stmt.md
@@ -1,10 +1,12 @@
 # ALTER SYSTEM
 ## description
 
-    该语句用于操作一个集群内的节点。（仅管理员使用！）
+    该语句用于操作一个系统内的节点。（仅管理员使用！）
     语法：
         1) 增加节点
             ALTER SYSTEM ADD BACKEND "host:heartbeat_port"[,"host:heartbeat_port"...];
+        2) 增加空闲节点
+            ALTER SYSTEM ADD FREE BACKEND "host:heartbeat_port"[,"host:heartbeat_port"...];
         2) 删除节点
             ALTER SYSTEM DROP BACKEND "host:heartbeat_port"[,"host:heartbeat_port"...];
         3) 节点下线
@@ -27,18 +29,21 @@
 
     1. 增加一个节点
         ALTER SYSTEM ADD BACKEND "host:port";
+
+    2. 增加一个空闲节点
+        ALTER SYSTEM ADD FREE BACKEND "host:port";
 
-    2. 删除两个节点
+    3. 删除两个节点
         ALTER SYSTEM DROP BACKEND "host1:port", "host2:port";
 
-    3. 下线两个节点
+    4. 下线两个节点
         ALTER SYSTEM DECOMMISSION BACKEND "host1:port", "host2:port";
 
-    4. 增加两个Hdfs Broker
+    5. 增加两个Hdfs Broker
         ALTER SYSTEM ADD BROKER hdfs "host1:port", "host2:port";
 
 ## keyword
-    ALTER,SYSTEM,BACKEND,BROKER
+    ALTER,SYSTEM,BACKEND,BROKER,FREE
 
 # CANCEL ALTER SYSTEM
 ## description

diff --git a/docs/help/Contents/Data Manipulation/manipulation_stmt.md b/docs/help/Contents/Data Manipulation/manipulation_stmt.md
@@ -762,3 +762,12 @@
 
 ## keyword
     SHOW, RESTORE
+
+# SHOW BACKENDS
+## description
+    该语句用于查看cluster内的节点
+    语法：
+        SHOW BACKENDS
+
+## keyword
+    SHOW, BACKENDS
diff --git a/fe/src/com/baidu/palo/alter/SystemHandler.java b/fe/src/com/baidu/palo/alter/SystemHandler.java
@@ -145,7 +145,7 @@ public synchronized void process(List<AlterClause> alterClauses, String clusterN
 
         if (alterClause instanceof AddBackendClause) {
             AddBackendClause addBackendClause = (AddBackendClause) alterClause;
-            Catalog.getCurrentSystemInfo().addBackends(addBackendClause.getHostPortPairs());
+            Catalog.getCurrentSystemInfo().addBackends(addBackendClause.getHostPortPairs(), addBackendClause.isFree());
         } else if (alterClause instanceof DropBackendClause) {
             DropBackendClause dropBackendClause = (DropBackendClause) alterClause;
             if (!dropBackendClause.isForce()) {

diff --git a/fe/src/com/baidu/palo/analysis/AddBackendClause.java b/fe/src/com/baidu/palo/analysis/AddBackendClause.java
@@ -19,8 +19,12 @@
 
 public class AddBackendClause extends BackendClause {
 
-    public AddBackendClause(List<String> hostPorts) {
+    // be in free state is not owned by any cluster
+    protected boolean isFree;
+
+    public AddBackendClause(List<String> hostPorts, boolean isFree) {
         super(hostPorts);
+        this.isFree = isFree;
     }
 
     @Override
@@ -35,4 +39,13 @@ public String toSql() {
         }
         return sb.toString();
     }
+
+
+    public void setFree(boolean isFree) {
+        this.isFree = isFree;
+    }   
+
+    public boolean isFree() {
+        return this.isFree;
+    } 
 }
diff --git a/fe/src/com/baidu/palo/catalog/Catalog.java b/fe/src/com/baidu/palo/catalog/Catalog.java
@@ -4422,14 +4422,6 @@ public void createCluster(CreateClusterStmt stmt) throws DdlException {
     }
 
     private void unprotectCreateCluster(Cluster cluster) {
-        if (cluster.getName().equalsIgnoreCase(SystemInfoService.DEFAULT_CLUSTER)) {
-            if (cluster.getBackendIdList().isEmpty()) {
-                isDefaultClusterCreated = true;
-                // ignore default_cluster
-                return;
-            }
-        }
-
         final Iterator<Long> iterator = cluster.getBackendIdList().iterator();
         while (iterator.hasNext()) {
             final Long id = iterator.next();
@@ -4921,12 +4913,24 @@ public Set<BaseParam> getMigrations() {
 
     public long loadCluster(DataInputStream dis, long checksum) throws IOException, DdlException {
         if (Catalog.getCurrentCatalogJournalVersion() >= FeMetaVersion.VERSION_30) {
-            int dbCount = dis.readInt();
-            checksum ^= dbCount;
-            for (long i = 0; i < dbCount; ++i) {
+            int clusterCount = dis.readInt();
+            checksum ^= clusterCount;
+            for (long i = 0; i < clusterCount; ++i) {
                 final Cluster cluster = new Cluster();
                 cluster.readFields(dis);
                 checksum ^= cluster.getId();
+
+                // BE is in default_cluster when added , therefore it is possible that the BE 
+                // in default_clsuter are not the latest because cluster cant't be updated when 
+                // loadCluster is after loadBackend.  
+                List<Long> latestBackendIds = systemInfo.getClusterBackendIds(cluster.getName());
+                if (cluster.getName().equalsIgnoreCase(SystemInfoService.DEFAULT_CLUSTER)) {
+                    cluster.setBackendIdList(latestBackendIds);
+                } else {
+                    // The cluster has the same number of be as systeminfo recorded
+                    Preconditions.checkState(latestBackendIds.size() == cluster.getBackendIdList().size());
+                }
+
                 final InfoSchemaDb db = new InfoSchemaDb(cluster.getName());
                 db.setClusterName(cluster.getName());
                 idToDb.put(db.getId(), db);
@@ -4951,28 +4955,27 @@ private void initDefaultCluster() {
         cluster.setName(SystemInfoService.DEFAULT_CLUSTER);
         cluster.setId(id);
 
-        if (backendList.size() != 0) {
-            // make sure one host hold only one backend.
-            Set<String> beHost = Sets.newHashSet();
-            for (Backend be : defaultClusterBackends) {
-                if (beHost.contains(be.getHost())) {
-                    // we can not handle this situation automatically.
-                    LOG.error("found more than one backends in same host: {}", be.getHost());
-                    System.exit(-1);
-                } else {
-                    beHost.add(be.getHost());
-                }
+        // make sure one host hold only one backend.
+        Set<String> beHost = Sets.newHashSet();
+        for (Backend be : defaultClusterBackends) {
+            if (beHost.contains(be.getHost())) {
+                // we can not handle this situation automatically.
+                LOG.error("found more than one backends in same host: {}", be.getHost());
+                System.exit(-1);
+            } else {
+                beHost.add(be.getHost());
             }
+        }
 
-            // we create default_cluster only if we had existing backends.
-            // this could only happend when we upgrade Palo from version 2.4 to 3.x.
-            cluster.setBackendIdList(backendList);
-            unprotectCreateCluster(cluster);
-            for (Database db : idToDb.values()) {
-                db.setClusterName(SystemInfoService.DEFAULT_CLUSTER);
-                cluster.addDb(db.getFullName(), db.getId());
-            }
+        // we create default_cluster to meet the need for ease of use, because
+        // most users hava no multi tenant needs.
+        cluster.setBackendIdList(backendList);
+        unprotectCreateCluster(cluster);
+        for (Database db : idToDb.values()) {
+            db.setClusterName(SystemInfoService.DEFAULT_CLUSTER);
+            cluster.addDb(db.getFullName(), db.getId());
         }
+
         // no matter default_cluster is created or not,
         // mark isDefaultClusterCreated as true
         isDefaultClusterCreated = true;

diff --git a/fe/src/com/baidu/palo/cluster/Cluster.java b/fe/src/com/baidu/palo/cluster/Cluster.java
@@ -51,7 +51,7 @@ public class Cluster implements Writable {
     private Long id;
     private String name;
     // backend which cluster own
-    private List<Long> backendIdList;
+    private Set<Long> backendIdSet;
 
     private Set<Long> userIdSet;
     private Set<String> userNameSet;
@@ -66,7 +66,7 @@ public class Cluster implements Writable {
 
     public Cluster() {
         this.rwLock = new ReentrantReadWriteLock(true);
-        this.backendIdList = new LinkedList<Long>();
+        this.backendIdSet = Sets.newHashSet();
         this.userIdSet = Sets.newHashSet();
         this.userNameSet = Sets.newHashSet();
         this.linkDbNames = Maps.newHashMap();
@@ -79,7 +79,7 @@ public Cluster(String name, long id) {
         this.name = name;
         this.id = id;
         this.rwLock = new ReentrantReadWriteLock(true);
-        this.backendIdList = new LinkedList<Long>();
+        this.backendIdSet = Sets.newHashSet();
         this.userIdSet = Sets.newHashSet();
         this.userNameSet = Sets.newHashSet();
         this.linkDbNames = Maps.newHashMap();
@@ -230,36 +230,36 @@ public boolean isWriteLockHeldByCurrentThread() {
     }
 
     public int getClusterCapacity() {
-        return backendIdList.size();
+        return backendIdSet.size();
     }
 
     public List<Long> getBackendIdList() {
-        return Lists.newArrayList(backendIdList);
+        return Lists.newArrayList(backendIdSet);
     }
 
     public void setBackendIdList(List<Long> backendIdList) {
         writeLock();
         try {
-            this.backendIdList = backendIdList;
+            this.backendIdSet = Sets.newHashSet(backendIdList);
         } finally {
             writeUnlock();
         }
     }
 
-    public void addBackend(long id) {
+    public void addBackend(long backendId) {
         writeLock();
         try {
-            this.backendIdList.add(id);
+            this.backendIdSet.add(backendId);
         } finally {
             writeUnlock();
         }
     }
 
-    public void addBackends(List<Long> backends) {
+    public void addBackends(List<Long> backendIds) {
         writeLock();
         try {
-            this.backendIdList.addAll(backends);
-        } finally {
+            this.backendIdSet.addAll(backendIds);
+       } finally {
             writeUnlock();
         }
     }
@@ -285,8 +285,8 @@ public void write(DataOutput out) throws IOException {
         out.writeLong(id);
         Text.writeString(out, name);
 
-        out.writeLong(backendIdList.size());
-        for (Long id : backendIdList) {
+        out.writeLong(backendIdSet.size());
+        for (Long id : backendIdSet) {
             out.writeLong(id);
         }
 
@@ -329,9 +329,8 @@ public void readFields(DataInput in) throws IOException {
         Long len = in.readLong();
         while (len-- > 0) {
             Long id = in.readLong();
-            backendIdList.add(id);
+            backendIdSet.add(id);
         }
-
         int count = in.readInt();
         while (count-- > 0) {
             dbNames.add(Text.readString(in));
@@ -362,7 +361,7 @@ public void readFields(DataInput in) throws IOException {
     public void removeBackend(long removedBackendId) {
         writeLock();
         try {
-            backendIdList.remove((Long)removedBackendId);
+            backendIdSet.remove((Long)removedBackendId);
         } finally {
             writeUnlock();
         }
@@ -371,7 +370,7 @@ public void removeBackend(long removedBackendId) {
     public void removeBackends(List<Long> removedBackendIds) {
         writeLock();
         try {
-            backendIdList.remove(removedBackendIds);
+            backendIdSet.remove(removedBackendIds);
         } finally {
             writeUnlock();
         }