Cassandra Community Webinar: Apache Cassandra Internals

CASSANDRA COMMUNITY WEBINARS AUGUST 2013
CASSANDRA
INTERNALS
Aaron Morton
@aaronmorton
Co-Founder & Principal Consultant
www.thelastpickle.com
Licensed under a Creative Commons Attribution-NonCommercial 3.0 New Zealand License

AboutThe Last Pickle
Work with clients to deliver and improve
Apache Cassandra based solutions.
Apache Cassandra Committer, DataStax MVP,
Hector Maintainer, 6+ years combined
Cassandra experience.
Based in New Zealand & Austin,TX.

Architecture
Code

Cassandra Architecture
API's
Cluster Aware
Cluster Unaware
Clients
Disk

Cassandra Cluster Architecture
API's
Cluster Aware
Cluster Unaware
Clients
Disk
API's
Cluster Aware
Cluster Unaware
Disk
Node 1 Node 2

Dynamo Cluster Architecture
API's
Dynamo
Database
Clients
Disk
API's
Dynamo
Database
Disk
Node 1 Node 2

Architecture
API
Dynamo
Database

APITransports
Thrift
Native Binary

ThriftTransport
//Custom TServer implementations
o.a.c.thrift.CustomTThreadPoolServer
o.a.c.thrift.CustomTNonBlockingServer
o.a.c.thrift.CustomTHsHaServer

Native BinaryTransport
Beta in Cassandra 1.2
Uses Netty
Enabled with
start_native_transport
(Disabled by default)

o.a.c.transport.Server.run()
//Setup the Netty server
new ExecutionHandler()
new NioServerSocketChannelFactory()
ServerBootstrap.setPipelineFactory()

o.a.c.transport.Message.Dispatcher.messageReceived()
//Process message from client
ServerConnection.validateNewMessage()
Request.execute()
ServerConnection.applyStateTransition()
Channel.write()

Messages
Deﬁned in the Native Binary
Protocol
$SRC/doc/native_protocol.spec

API Services
JMX
Thrift
CQL 3

JMX Management Beans
Spread around the code base.
Interfaces named *MBean

JMX Management Beans
Registered with names such as
org.apache.cassandra.db:
type=StorageProxy

o.a.c.thrift.CassandraServer
// Implements Thrift Interface
// Access control
// Input validation
// Mapping to/from Thrift and internal types

Thrift Interface
Thrift IDL
$SRC/interface/cassandra.thrift

o.a.c.thrift.CassandraServer.get_slice()
// get columns for one row
Tracing.begin()
ClientState cState = state()
cState.hasColumnFamilyAccess()
multigetSliceInternal()

CassandraServer.multigetSliceInternal()
// get columns for may rows
ThriftValidation.validate*()
// Create ReadCommands
getSlice()

CassandraServer.getSlice()
// Process ReadCommands
// return Thrift types
readColumnFamily()
thriftifyColumnFamily()

CassandraServer.readColumnFamily()
// Process ReadCommands
// Return ColumnFamilies
StorageProxy.read()

o.a.c.cql3.QueryProcessor
// Prepares and executes CQL3 statements
// Used by Thrift & Native transports
// Access control
// Input validation
// Returns transport.ResultMessage

CQL3 Grammar
ANTLR Grammar
$SRC/o.a.c.cql3/Cql.g

o.a.c.cql3.statements.ParsedStatement
// Subclasses generated by ANTLR
// Tracks bound term count
// Prepare CQLStatement
prepare()

o.a.c.cql3.statements.CQLStatement
checkAccess(ClientState state)
validate(ClientState state)
execute(ConsistencyLevel cl,
QueryState state,
List<ByteBuffer> variables)

statements.SelectStatement.RawStatement
// Implements ParsedStatement
// Input validation
prepare()

statements.SelectStatement.execute()
// Create ReadCommands
StorageProxy.read()

Dynamo Layer
o.a.c.service
o.a.c.net
o.a.c.dht
o.a.c.gms
o.a.c.locator
o.a.c.stream

o.a.c.service.StorageProxy
// Cluster wide storage operations
// Select endpoints & check CL available
// Send messages to Stages
// Wait for response
// Store Hints

o.a.c.service.StorageService
// Ring operations
// Track ring state
// Start & stop ring membership
// Node & token queries

o.a.c.service.IResponseResolver
preprocess(MessageIn<T> message)
resolve() throws
DigestMismatchException
RowDigestResolver
RowDataResolver
RangeSliceResponseResolver

Response Handlers / Callback
implements IAsyncCallback<T>
response(MessageIn<T> msg)

o.a.c.service.ReadCallback.get()
//Wait for blockfor & data
condition.await(timeout,
TimeUnit.MILLISECONDS)
throw ReadTimeoutException()
resolver.resolve()

o.a.c.service.StorageProxy.fetchRows()
getLiveSortedEndpoints()
new RowDigestResolver()
new ReadCallback()
MessagingService.sendRR()
---------------------------------------
ReadCallback.get() # blocking
catch (DigestMismatchException ex)
catch (ReadTimeoutException ex)

o.a.c.net.MessagingService.verb<<enum>>
MUTATION
READ
REQUEST_RESPONSE
TREE_REQUEST
TREE_RESPONSE
(And more...)

o.a.c.net.MessagingService.verbHandlers
new EnumMap<Verb,
IVerbHandler>(Verb.class)

o.a.c.net.IVerbHandler<T>
doVerb(MessageIn<T> message,
String id);

o.a.c.net.MessagingService.verbStages
new EnumMap<MessagingService.Verb,
Stage>(MessagingService.Verb.class)

o.a.c.net.MessagingService.receive()
runnable = new MessageDeliveryTask(
message, id, timestamp);
StageManager.getStage(
message.getMessageType());
stage.execute(runnable);

o.a.c.net.MessageDeliveryTask.run()
// If dropable and rpc_timeout
MessagingService.incrementDroppedMessag
es(verb);
MessagingService.getVerbHandler(verb)
verbHandler.doVerb(message, id)

Architecture
API Layer
Dynamo Layer
Database Layer

Database Layer
o.a.c.concurrent
o.a.c.db
o.a.c.cache
o.a.c.io
o.a.c.trace

o.a.c.concurrent.StageManager
stages = new EnumMap<Stage,
ThreadPoolExecutor>(Stage.class);
getStage(Stage stage)

o.a.c.concurrent.Stage
READ
MUTATION
GOSSIP
REQUEST_RESPONSE
ANTI_ENTROPY
(And more...)

o.a.c.db.Table
// Keyspace
open(String table)
getColumnFamilyStore(String cfName)
getRow(QueryFilter filter)
apply(RowMutation mutation,
boolean writeCommitLog)

o.a.c.db.ColumnFamilyStore
// Column Family
getColumnFamily(QueryFilter filter)
getTopLevelColumns(...)
apply(DecoratedKey key,
ColumnFamily columnFamily,
SecondaryIndexManager.Updater
indexer)

o.a.c.db.IColumnContainer
addColumn(IColumn column)
remove(ByteBuffer columnName)
ColumnFamily
SuperColumn

o.a.c.db.ISortedColumns
addColumn(IColumn column,
Allocator allocator)
removeColumn(ByteBuffer name)
ArrayBackedSortedColumns
AtomicSortedColumns
TreeMapBackedSortedColumns

o.a.c.db.Memtable
put(DecoratedKey key,
ColumnFamily columnFamily,
SecondaryIndexManager.Updater
indexer)
flushAndSignal(CountDownLatch latch,
Future<ReplayPosition>
context)

o.a.c.db.ReadCommand
getRow(Table table)
SliceByNamesReadCommand
SliceFromReadCommand

o.a.c.db.IDiskAtomFilter
getMemtableColumnIterator(...)
getSSTableColumnIterator(...)
IdentityQueryFilter
NamesQueryFilter
SliceQueryFilter

Summary
CustomTThreadPoolServer Message.Dispatcher
CassandraServer QueryProcessor
ReadCommand
StorageProxy
IResponseResolver
IAsyncCallback
MessagingService
IVerbHandler
Table ColumnFamilyStore IDiskAtomFilter
API
Dynamo
Database

Aaron Morton
@aaronmorton
Co-Founder & Principal Consultant
Licensed under a Creative Commons Attribution-NonCommercial 3.0 New Zealand License

Cassandra Community Webinar: Apache Cassandra Internals

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