ElasticSearch8.README.MD

Model:

Elasticsearch command for CLI: Elasticsearch (Is-A) EnvironmentAwareCommand (Is-A) Command

Bootstrap#init() A singleton Create Node & validate required things; and Node#start()

Node - represents a Node within a cluster

Environment { dataFiles,repoFiles:Path[], configFile,pluginsFile,modulesFile,shardDataFiel,binFile,logsFile,libFile,pidFile,tmpFile }

NodePath { path, indicesPath, FileStore } //Dir structure ${data.paths}/indices/{index.uuid}/{shard.id}

ShardLock ///** * A shard lock guarantees exclusive access to a shards data * directory. Internal processes should acquire a lock on a shard * before executing any write operations on the shards data directory. * * @see NodeEnvironment */

NodeEnvironment { NodePath[], sharedDataPath, locks:Lock[], ShardId->InternalShardLock } InternalShardLock { mutex:Semaphore, waitCount, ShardId } //an inner class.

//A component that holds all data paths for a single node.
  ShardId->InternalShardLock is synchronized. InternalShardId's waitCount is guarded by this map. 
 /**
 * Tries to lock the given shards ID. A shard lock is required to perform any kind of
 * write operation on a shards data directory like deleting files, creating a new index writer
 * or recover from a different shard instance into it. If the shard lock can not be acquired
 * /
                

   
   //A Node represent a node within a cluster ({@code cluster.name})//
   Node { Setting... , Environment, NodeEnvironment, NodeService, NamedWriteableRegistry }
        Node creates all the services required: NodeService, PluginsService, ResourceWatcherService, CircuitBreakerService, IngestService, UsageService, MetaStateService, IndicesService, MetaDataCreateIndexService, SearchService, SearchTransportService, TransportService, NetworkService, MetaDataIndexUpgradeService, ClusterInfoService, 
            PersistentTasksService, PersistentTasksClusterService, RepositoriesService, SnapshotsService, SnapshotShardsService, RestoreService, RerouteService
            Also creates Discovery
        
   DiscoveryNode { 
       String nodeName;
       String nodeId;
       String ephemeralId;
       String hostName;
       String hostAddress;
       TransportAddress address;
       Map<String, String> attributes;
       Version version;
       Set<DiscoveryNodeRole> roles;
   } //A discovery node represents a node that is part of the cluster.