（七）elasticsearch 源码之元数据CulsterState
1.概述
前面几篇讲述了es的许多重要的逻辑，这些逻辑都涉及到一个非常核心的类ClusterState，本文来看下ClusterState包括什么信息。
2.ClusterState
从注解中我们看到，CusterState表示整个集群的状态，其中的数据都是不可变的（除了RoutingTable），并且只能由master节点来更新。
CusterState 支持diff接口，用来生成增量信息。
主要字段如下：
// CulsterState
private final long version; // 版本号
private final String stateUUID; // 状态uuid
private final RoutingTable routingTable; // 路由表
private final DiscoveryNodes nodes; // 所有的发现节点
private final MetaData metaData; // 元数据
private final ClusterBlocks blocks; // 一些限制，用来阻止非法操作
private final ImmutableOpenMap<String, Custom> customs; // 自定义
private final ClusterName clusterName; // 集群名称
private final boolean wasReadFromDiff;
private final int minimumMasterNodesOnPublishingMaster;
// built on demand
private volatile RoutingNodes routingNodes; // 路由信息的copyRoutingTable 即全局的路由表，是索引路由表IndexRoutingTable的迭代器
public class RoutingTable implements Iterable<IndexRoutingTable>, Diffable<RoutingTable> {
public static final RoutingTable EMPTY_ROUTING_TABLE = builder().build();
private final long version;
// index to IndexRoutingTable map
private final ImmutableOpenMap<String, IndexRoutingTable> indicesRouting;索引路由表 IndexRoutingTable 是分片路由表 IndexShardRoutingTable的迭代器
public class IndexRoutingTable extends AbstractDiffable<IndexRoutingTable> implements Iterable<IndexShardRoutingTable> {
private final Index index; // 索引
private final ShardShuffler shuffler; // 洗牌器
// note, we assume that when the index routing is created, ShardRoutings are created for all possible number of
// shards with state set to UNASSIGNED
private final ImmutableOpenIntMap<IndexShardRoutingTable> shards; // 分片路由信息
private final List<ShardRouting> allActiveShards; // 所有活跃分片的路由信息IndexShardRoutingTable 包含了主分片和复制分片的信息
public class IndexShardRoutingTable implements Iterable<ShardRouting> {
final ShardShuffler shuffler; // 洗牌器
final ShardId shardId; // shard id is a int
final ShardRouting primary; // 主分片
final List<ShardRouting> primaryAsList;
final List<ShardRouting> replicas; // 复制分片
final List<ShardRouting> shards; // 分片
final List<ShardRouting> activeShards; // 活跃分片
final List<ShardRouting> assignedShards; // 已分配的分片
final Set<String> allAllocationIds;
final boolean allShardsStarted;DiscoveryNodes 表示所有发现节点
public class DiscoveryNodes extends AbstractDiffable<DiscoveryNodes> implements Iterable<DiscoveryNode> {
public static final DiscoveryNodes EMPTY_NODES = builder().build();
private final ImmutableOpenMap<String, DiscoveryNode> nodes; // 节点
private final ImmutableOpenMap<String, DiscoveryNode> dataNodes; // 数据节点
private final ImmutableOpenMap<String, DiscoveryNode> masterNodes; // master节点
private final ImmutableOpenMap<String, DiscoveryNode> ingestNodes;
private final String masterNodeId; // master节点id
private final String localNodeId; // 本地节点id
private final Version minNonClientNodeVersion;
private final Version maxNonClientNodeVersion;
private final Version maxNodeVersion;
private final Version minNodeVersion;public class DiscoveryNode implements Writeable, ToXContentFragment {
...
private final String nodeName; // 节点名称
private final String nodeId; // 节点id
private final String ephemeralId; // 临时id
private final String hostName; // 主机信息
private final String hostAddress;
private final TransportAddress address; // transport 地址
private final Map<String, String> attributes;
private final Version version;
private final Set<DiscoveryNodeRole> roles;MetaData代表元数据，包括一些配置，index mapping
public class MetaData implements Iterable<IndexMetaData>, Diffable<MetaData>, ToXContentFragment {
...
private final String clusterUUID; // cluster uuid
private final boolean clusterUUIDCommitted;
private final long version; // 版本号
private final CoordinationMetaData coordinationMetaData; // 节点发现元数据
private final Settings transientSettings; // 各类设置
private final Settings persistentSettings;
private final Settings settings;
private final DiffableStringMap hashesOfConsistentSettings;
private final ImmutableOpenMap<String, IndexMetaData> indices; // 索引元数据map
private final ImmutableOpenMap<String, IndexTemplateMetaData> templates; // 索引模版map
private final ImmutableOpenMap<String, Custom> customs; // 自定义map
private final transient int totalNumberOfShards; // Transient ? not serializable anyway? // 分片总数
private final int totalOpenIndexShards; // open的分片总数
private final String[] allIndices; // 所有的索引
private final String[] allOpenIndices; // 所有打开的索引
private final String[] allClosedIndices; // 所有关闭的索引
private final SortedMap<String, AliasOrIndex> aliasAndIndexLookup; // name -> alias/index mapClusterBlock表示在特定状态下对集群的一些禁止操作，比如在集群恢复阶段不可读写
public class ClusterBlocks extends AbstractDiffable<ClusterBlocks> {
public static final ClusterBlocks EMPTY_CLUSTER_BLOCK = new ClusterBlocks(emptySet(), ImmutableOpenMap.of());
private final Set<ClusterBlock> global; // 全局的block
private final ImmutableOpenMap<String, Set<ClusterBlock>> indicesBlocks; // 索引级别的block
private final EnumMap<ClusterBlockLevel, ImmutableLevelHolder> levelHolders; // 根据level对上面的block进行分类3.builder模式
ClusterState使用了builder模式，builder模式对于修改复杂的数据对象非常方便。先定义一个内部类，属性和数据对象相同
// ClusterState
public static class Builder {
private final ClusterName clusterName;
private long version = 0;
private String uuid = UNKNOWN_UUID;
private MetaData metaData = MetaData.EMPTY_META_DATA;
private RoutingTable routingTable = RoutingTable.EMPTY_ROUTING_TABLE;
private DiscoveryNodes nodes = DiscoveryNodes.EMPTY_NODES;
private ClusterBlocks blocks = ClusterBlocks.EMPTY_CLUSTER_BLOCK;
private final ImmutableOpenMap.Builder<String, Custom> customs;
private boolean fromDiff;
private int minimumMasterNodesOnPublishingMaster = -1;
public Builder(ClusterState state) {
this.clusterName = state.clusterName;
this.version = state.version();
this.uuid = state.stateUUID();
this.nodes = state.nodes();
this.routingTable = state.routingTable();
this.metaData = state.metaData();
this.blocks = state.blocks();
this.customs = ImmutableOpenMap.builder(state.customs());
this.minimumMasterNodesOnPublishingMaster = state.minimumMasterNodesOnPublishingMaster;
this.fromDiff = false;
}
...
public Builder metaData(MetaData metaData) {
this.metaData = metaData;
return this; // 返回当前builder对象
}
...
public ClusterState build() {
if (UNKNOWN_UUID.equals(uuid)) {
uuid = UUIDs.randomBase64UUID();
}
return new ClusterState(clusterName, version, uuid, metaData, routingTable, nodes, blocks, customs.build(),
minimumMasterNodesOnPublishingMaster, fromDiff); // 返回主类对象
}初始化和修改对象时进行链式修改，然后build，避免了传统的new, set, set...的写法
ClusterState initialClusterState = ClusterState.builder(ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
.metaData(metaData).routingTable(routingTable).nodes
(nb).build(); // 链式写法4.总结
本文简单描述了ClusterState的数据结果，展示了builder模式的运用。
