Session Management

/**
 * Session manager for Spark SQL with HiveServer2 compatibility
 * Manages client sessions and their SQL contexts
 */
class SparkSQLSessionManager(hiveServer: HiveServer2, sqlContext: SQLContext) extends SessionManager(hiveServer) {
  /**
   * Open a new client session with optional impersonation
   * @param protocol Thrift protocol version
   * @param username Client username
   * @param passwd Client password
   * @param ipAddress Client IP address
   * @param sessionConf Session-specific configuration
   * @param withImpersonation Whether to enable user impersonation
   * @param delegationToken Delegation token for authentication
   * @return SessionHandle identifying the new session
   */
  def openSession(
    protocol: TProtocolVersion,
    username: String,
    passwd: String,
    ipAddress: String,
    sessionConf: java.util.Map[String, String],
    withImpersonation: Boolean,
    delegationToken: String
  ): SessionHandle
  
  /**
   * Close an existing session and clean up resources
   * @param sessionHandle Handle identifying the session to close
   */
  def closeSession(sessionHandle: SessionHandle): Unit
  
  /**
   * Set configuration parameters for a SQL context
   * @param conf The SQL context to configure
   * @param confMap Configuration key-value pairs
   */
  def setConfMap(conf: SQLContext, confMap: java.util.Map[String, String]): Unit
}

import org.apache.spark.sql.hive.thriftserver.SparkSQLSessionManager
import org.apache.hive.service.rpc.thrift.TProtocolVersion
import scala.collection.JavaConverters._

// Create session manager
val sessionManager = new SparkSQLSessionManager(hiveServer, SparkSQLEnv.sqlContext)

// Open a new session
val sessionConf = Map(
  "spark.sql.adaptive.enabled" -> "true",
  "spark.sql.adaptive.coalescePartitions.enabled" -> "true"
).asJava

val sessionHandle = sessionManager.openSession(
  protocol = TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V10,
  username = "spark_user",
  passwd = "",
  ipAddress = "192.168.1.100",
  sessionConf = sessionConf,
  withImpersonation = false,
  delegationToken = null
)

// Use the session...
// Close the session when done
sessionManager.closeSession(sessionHandle)

/**
 * Handle identifying a client session
 */
class SessionHandle extends Handle {
  /**
   * Create a new session handle
   * @param handleId Unique handle identifier
   * @param protocol Thrift protocol version
   */
  public SessionHandle(HandleIdentifier handleId, TProtocolVersion protocol)
  
  /**
   * Get the protocol version for this session
   * @return TProtocolVersion used by the session
   */
  public TProtocolVersion getProtocolVersion()
  
  /**
   * Check if this session handle equals another
   * @param other Handle to compare with
   * @return true if handles are equal
   */
  public boolean equals(Object other)
  
  /**
   * Get string representation of the handle
   * @return String representation for logging/debugging
   */
  public String toString()
}

/**
 * Base handle class providing unique identification
 */
abstract class Handle {
  /**
   * Get the unique identifier for this handle
   * @return HandleIdentifier containing UUID and secret
   */
  public HandleIdentifier getHandleIdentifier()
}

/**
 * Unique identifier containing UUID and secret
 */
class HandleIdentifier {
  /**
   * Get the public UUID part of the identifier
   * @return UUID for this identifier
   */
  public UUID getPublicId()
  
  /**
   * Get the secret part of the identifier
   * @return UUID secret for security
   */
  public UUID getSecretId()
}

/**
 * Supported Thrift protocol versions
 */
enum TProtocolVersion {
  HIVE_CLI_SERVICE_PROTOCOL_V1,   // Original HiveServer2 protocol
  HIVE_CLI_SERVICE_PROTOCOL_V2,   // Added async operations
  HIVE_CLI_SERVICE_PROTOCOL_V3,   // Added get/set operations
  HIVE_CLI_SERVICE_PROTOCOL_V4,   // Added delegation tokens
  HIVE_CLI_SERVICE_PROTOCOL_V5,   // Added primary keys support
  HIVE_CLI_SERVICE_PROTOCOL_V6,   // Added cross reference support
  HIVE_CLI_SERVICE_PROTOCOL_V7,   // Enhanced metadata operations
  HIVE_CLI_SERVICE_PROTOCOL_V8,   // Added result set schema info
  HIVE_CLI_SERVICE_PROTOCOL_V9,   // Added query ID support
  HIVE_CLI_SERVICE_PROTOCOL_V10   // Latest version with all features
}

// Check protocol version capabilities
val sessionHandle = sessionManager.openSession(
  TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V10, // Use latest version
  "username", "", "127.0.0.1", Map.empty.asJava, false, null
)

val protocolVersion = sessionHandle.getProtocolVersion()
println(s"Session using protocol: $protocolVersion")

// Handle different protocol versions
protocolVersion match {
  case TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V10 =>
    // All features available
    println("Using latest protocol with full feature support")
  case v if v.getValue >= TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V6.getValue =>
    // Cross reference support available
    println("Cross reference operations supported")
  case _ =>
    // Limited functionality
    println("Using older protocol with limited features")
}

// Common session configuration parameters
val sessionConfig = Map(
  // Spark SQL configuration
  "spark.sql.adaptive.enabled" -> "true",
  "spark.sql.adaptive.coalescePartitions.enabled" -> "true", 
  "spark.sql.adaptive.skewJoin.enabled" -> "true",
  "spark.sql.execution.arrow.pyspark.enabled" -> "true",
  
  // Hive compatibility settings
  "hive.exec.dynamic.partition" -> "true",
  "hive.exec.dynamic.partition.mode" -> "nonstrict",
  "hive.support.concurrency" -> "false",
  
  // Session-specific settings
  "spark.sql.session.timeZone" -> "UTC",
  "spark.sql.warehouse.dir" -> "/spark-warehouse",
  "spark.sql.catalogImplementation" -> "hive"
).asJava

// Session states and lifecycle
abstract class SessionManager {
  /**
   * Initialize the session manager
   * @param hiveConf Hive configuration
   */
  def init(hiveConf: HiveConf): Unit
  
  /**
   * Start the session manager service
   */
  def start(): Unit
  
  /**
   * Stop the session manager and close all sessions
   */
  def stop(): Unit
  
  /**
   * Get session by handle
   * @param sessionHandle Handle identifying the session
   * @return HiveSession instance or null if not found
   */
  def getSession(sessionHandle: SessionHandle): HiveSession
}

import org.apache.hive.service.cli.session.HiveSession

// Session lifecycle management
val sessionManager = new SparkSQLSessionManager(hiveServer, sqlContext)

try {
  // Initialize and start
  sessionManager.init(hiveConf)
  sessionManager.start()
  
  // Open session
  val sessionHandle = sessionManager.openSession(
    TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V10,
    "user", "pass", "127.0.0.1", sessionConf, false, null
  )
  
  // Get session object for advanced operations
  val session = sessionManager.getSession(sessionHandle)
  if (session != null) {
    println(s"Session user: ${session.getUserName}")
    println(s"Session database: ${session.getCurrentDatabase}")
  }
  
  // Close session
  sessionManager.closeSession(sessionHandle)
  
} finally {
  // Clean shutdown
  sessionManager.stop()
}

// User impersonation configuration
val impersonationConfig = Map(
  "hive.server2.enable.doAs" -> "true",
  "hadoop.proxyuser.spark.hosts" -> "*",
  "hadoop.proxyuser.spark.groups" -> "*"
).asJava

// Open session with impersonation
val sessionHandle = sessionManager.openSession(
  protocol = TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V10,
  username = "spark",          // Service user
  passwd = "",
  ipAddress = "127.0.0.1",
  sessionConf = impersonationConfig,
  withImpersonation = true,    // Enable impersonation
  delegationToken = "actual_user_token"  // Token for actual user
)

/**
 * Exception thrown during session operations
 */
class HiveSQLException extends SQLException {
  public HiveSQLException(String reason, String sqlState, int vendorCode)
  public HiveSQLException(String reason, String sqlState, Throwable cause)
}

/**
 * Common error scenarios in session management
 */
// Session creation errors
public static final String SESSION_CREATION_ERROR = "08006";
public static final String INVALID_SESSION_HANDLE = "HY000";
public static final String SESSION_ALREADY_CLOSED = "HY010";
public static final String AUTHENTICATION_FAILED = "28000";

import org.apache.hive.service.cli.HiveSQLException

try {
  val sessionHandle = sessionManager.openSession(
    TProtocolVersion.HIVE_CLI_SERVICE_PROTOCOL_V10,
    username, password, ipAddress, sessionConf, false, null
  )
  
  // Session operations...
  
} catch {
  case e: HiveSQLException if e.getSqlState == "28000" =>
    println("Authentication failed")
  case e: HiveSQLException if e.getSqlState == "08006" =>
    println("Session creation failed")
  case e: HiveSQLException =>
    println(s"Session error: ${e.getMessage} (${e.getSqlState})")
}

// Session monitoring through Spark metrics
val activeSessionCount = sessionManager.getOpenSessionCount()
val sessionInfo = sessionManager.getSessionInfo(sessionHandle)

// Access session details
session.getCreationTime()     // When session was created
session.getLastAccessTime()   // Last activity timestamp  
session.getUserName()         // Session username
session.getCurrentDatabase()  // Current database context
session.getSessionConf()      // Session configuration