HiveServer2 was reconstructed and reimplemented to address limitations in the original HiveServer1 such as lack of concurrency, incomplete security implementations, and instability. HiveServer2 uses a multithreaded architecture where each client connection creates a new execution context including a session and operations. This allows HiveServer2 to associate a Hive execution context like the session and Driver with the thread serving each client request. The new Thrift interface in HiveServer2 also enables better support for common database features around authentication, authorization, and auditing compared to the original Thrift API in HiveServer1.

1. HiveServer2
Oct., 2013
Schubert Zhang

2. Hive Evolution
• Original
• Let users express their queries in a high-level language without having to
write MapReduce programs.
• Mainly target to ad-hoc queries.
• As a data tool, usually work in CLI mode.
• Now more …
• A parallel SQL DBMS that happens to use Hadoop for its storage and
execution layers.
• Ad-hoc + regular
• As a service …

3. Introduction
• Limitations of HiveServer1
•
•
•
•
Concurrency
Security
Client Interface
Stability
• Sessions/Currency
• Old Thrift API and server implementation
didn’t support currency.
• xDBC
• Old Thrift API didn’t support common xDBC
• Authentication/Authorization
• Incomplete implementations
• Auditing/Logging
HiveServer2:
• From hive-0.11 / CDH4.1
• Reconstructed and Re-implemented.
(HIVE-2935)
• HiveServer2 is a container for the Hive
execution engine (Driver).
• For each client connection, it creates a
new execution context (Connection and
Session) that serves Hive SQL requests
from the client.
• The new RPC interface enables the server
to associate this Hive execution context
with the thread serving the client’s
request.

4. Architecture
In fact,
Driver in
Operation
Context
System Arch.
Authentication Arch.
(don’t talk here)
http://blog.cloudera.com/blog/2013/07/how-hiveserver2-brings-security-and-concurrency-to-apache-hive/
@Cloudera

5. hiveServer2
Architecture:
Internal
Client-1
(main entry)
start
Thrift RPC Iface
Client-2
thriftCLIService
(TThreadPoolServer,
implements Client RPC Iface)
lIsten() and accept() new client connection, and process in each Thread)
• Core Contexts
• Connections
• Sessions
• Operations
• Operation Path …
Threads for Client Connections
…
call (ICLIService internal interface)
cliService
(Real implementations of
various operations)
open/close sessions, run operations in existing sessions …
HiveSession Interface
session
HiveConf, SessionState
sessionManager
backgroundOperationPool
runAsync
session
HiveConf, SessionState
operationManager
Threads for Async Operations
…
(handleToSessionMap)
...
...
session
HiveConf, SessionState
(handleToOperationMap)
create and run operations
SQLop
sync/async
create and run hive Driver
Hive Driver
op
op
...
op
SQLOp/SetOp/DfsOp/AddResourceOp/DeleteResourceOp ..
GetTypeInfoOp/GetCatalogsOp/GetSchemasOp/GetTablesOp/
GetTableTypesOp/GetColumnsOp/GetFunctionsOp ...

6. Architecture: Server Context
•
•
•
•
Client-1
Connection-1
(Thread)
Client
Connection (Thread)
Session (-> HiveConf, SessionState)
Operation (-> Driver)
Client-2
Connection-2
(Thread)
Session-12
• Usually, a client only opens one
Session in a Connection. (refer to JDBC
HiveDriver: HiveConnection)
Op-121
(SQL)
Driver
Session-11
Op-122
Op-123
(SQL)
Driver

7. Session
New Client API
SQL and Hive
Operation
• TCLIService.thrift
• Complete API
• Complete Database API
Hive
Command
Operation
DB Metadata
Operation
• Think about JDBC/ODBC
• To be compatible with
existing DB software
• Hive Specific API
• Best Practice
Operation for
Operation
• Client API vs. Internal
API
• Converting and Isolation
Get Result
OpenSession
CloseSession
ExecuteStatement
GetInfo *
GetTypeInfo
GetCatalogs
GetSchemas
GetTables
GetTableTypes
Client request to open a new session. A new HiveSession is created
in server and return a unique SessionHandler (UUID). All other calls
depend on this session.
Client request to close the session. Will also close and remove all
operations in this session.
Execute a HQL statement. SQLOp
Some SQL statement can be tagged “runAsync”, then it will be
executed in a dedicated Thread and return immediately.
SetOp,DfsOp,AddResourceOp,DeleteResourceOp
Get various global variables of Hive. (Key-Type->Value)
Get the detailed description and constraint of data type.
Do nothing so far.
Get schema from metastore.
Get table schema from metastore.
Get the table type, e.g. MANAGED_TABLE, EXTERNAL_TABLE,
VIRTUAL_VIEW, INDEX_TABLE.
GetColumns
Get columns of a table from metastore.
GetFunctions
Get the UDF functions.
GetOperationStatu Get state of an operation by opHandler, INITIALIZED/
s
RUNNING/FINISHED/CANCELED/CLOSED/ERROR/UNKNOWN/PENDI
NG.
CancelOperation
Cancel a RUNNING or PENDING operation by opHandler.
For SQLOp, do cleanup: close and destroy Hive Driver, delete temp
output files, and cancel the task running in the background thread…
CloseOperation
Remove this operation and close it: for SQLOp, do cleanup; for
HiveCommandOp, tearDownSessionIO.
GetResultSetMeta Get the resultset’s schema, such as the title columns.
data
FetchResults
Fetch the result rows from the real resultset.

8. Code
• Packages
• org.apache.hive.service …, top project of apache…
• Pros
• Clear Implementation
• Decoupling of HiveServer2 and HiveCore
• Decoupling of Thrift Client API and Internal Code
• Cons
•
•
•
•
Too many design pattern.
Somewhere, inconsistent principle.
Still not complete decoupling of HiveServer2 and HiveCore.
The JDBC Driver package/jar still relies on many other core code, such Hive->Hadoop and the
libs… (may be because of the support of Embedded Mode.)

9. Service
+state
CompositeService
Code
HiveServer2
AbstractService
+serviceList
+HiveConf: Global,set by init()
+addService()
+removeService()
+main(): 入口
+init()
+start()
+stop()
+register(): StateChangeListener
TCLIService.Iface
ThriftCLIService
ThrifyBinaryService
+cliService
ICLIService
TThreadPoolServer
+openSession()
+closeSession()
+getInfo()
+executeStatement()
+...()
+fetchResults()
CLIService
+sessionManager
FixedThreadPool
+OpenSession()
+CloseSession()
+GetInfo()
+ExecuteStatement()
+...()
+FetchResults()
OperationManager
+handleToOperation: HashMap
+newExecuteStatementOperation()
+newGetTypeInfoOperation()
+...()
+addOperation()
+removeOperation()
+getOperation()
+getOperationState()
+cancelOperation()
+closeOperation()
+getOperationNextRowSet()
+...()
SessionManager
+handleToSession: HashMap
+operationManager
+backgroundOperationPool
HiveSession
HiveSessionImpl
+sessionHandle
+hiveConf: new for each
+sessionState: new for each
+opHandleSet
+openSession()
+closeSession()
+getSession()
+...()
+submitBackgroundOperation()
Operation
+opHandle
+parentSession
+state
+getState()
+setState()
+run()
+getNextRowSet()
+close()
+cancel()
+...()
+getSessionHandle()
+getInfo()
+executeStatement()
+executeStatementAsync()
+...()
+fetchResults()
GetInfoOperation
ExecuteStatementOperation
SQLOperation
AddResourceOperation
DeleteResourceOpetation
DfsOperation
SetOperation
GetSchemasOperation
XXXOperation
This is just a quick view, may be not exact
in some detail, and intentionally missed
something not so important.

10. HiveCore and Depending
Hive
Env.?
• HiveConf
• Global instance
• Instance for each Session.
• Client can inject additional KeyValue style configurations when
OpenSession.
• Set an explicit session name(id) to
control the download directory
name.
• Hive SessionState
• Instance for each Session.
• Hive Driver
• Instance for each SQL Operation.
• Global static variables?
• ??
• SetOperation ->SetProcessor
• set env: variables can not be set.
• set system: global
System.getProperties().setProperty(..)
• We may forbid system setting? Or, only
administrator can do it?
• set hiveconf: instanced.
• set hivevar: instanced.
• Set: instanced
• AddResource and DeleteResourceOperation
• SessionState. add_resource/delete_resource
• DOWNLOADED_RESOURCES_DIR("hive.downlo
aded.resources.dir",
System.getProperty("java.io.tmpdir") +
File.separator + "${hive.session.id}_resources")
• DfsOperation
• Auth. With HDFS?

11. Handler (Identifier)
• SessionHandler
• OperationHandler
Theift IDL:
• Use UUID
struct THandleIdentifier {
// 16 byte globally unique identifier
// This is the public ID of the handle and
// can be used for reporting.
1: required binary guid,
Now, only the public ID is used, it’s OK.
// 16 byte secret generated by the server
// and used to verify that the handle is not
// being hijacked by another user.
2: required binary secret,
}

12. Configurations and Run
Config:
Run:
•
•
•
•
•
•
•
• Start HiveServer2
hive.server2.transport.mode = binary | http | https
hive.server2.thrift.port = 10000
hive.server2.thrift.bind.host
hive.server2.thrift.min.worker.threads = 5
hive.server2.thrift.max.worker.threads = 500
hive.server2.async.exec.threads = 50
hive.server2.async.exec.shutdown.timeout = 10
(seconds)
• hive.support.concurrency = true ???
• hive.zookeeper.quorum =
• …
• bin/hiveserver2 &
• Start CLI (use standard JDBC)
• bin/beeline
• !connect
jdbc:hive2://localhost:10000
• show tables;
• select * from tablename limit 10;

13. Interface and Clients
• RPC (TCLIService.thrift)
• Binary Protocol
• Http/https Protocol (to be researched)
• New JDBC Driver
• org.apache.hive.jdbc.HiveDriver
• URL: jdbc:hive2://hostname:10000/dbname… (jdbc:hive2://localhost:10000/default)
• Implemented more API features.
3party Client over JDBC:
• CLI
• Beeline based on SQLine
• IDE: SQuirreL SQL Client
• Web Client (e.g. H2 Web, etc.)

14. Client Tools: CLI
SQLine, Beeline

15. Client Tools: IDE SQuirreL SQL Client

16. Client Tools: Web Client

17. Think More …
• Thinking of XX as Platform
• Standard JDBC/ODBC
• RESTful API over HTTP, Web Service
• AWS Redshift, SimpleDB …
• Hive as a Service?
• http://www.qubole.com/
• Request Cluster, run SQL ad-hoc and Regularly, workflow and schedule.
• Language
• SQL, R, Pig
• Computing of Estimation, Probability …

18. Thank You!