In-Memory Data Grids Essentials. Oracle Coherence

Scalable eCommerce Platform Solutions
In-Memory Data Grids Essentials. Oracle Coherence
Vladimir Kondraschenko
Max Myslyvtsev

About me
Vladimir Kondraschenko
• Lead Java engineer
• More than 10 years of hands on experience in
– software design and coding
– technical leadership
– development management
vkondraschenko@griddynamics.com

Agenda
• Preconditions of using IMDG
• Architecture overview
– topology
– distributed cache layer
– local cache layer
• Cache operations
• Persistence integration
• Tips

Different Solutions
Coherence

Preconditions of Using IMDG
• Big amounts of data (10-100 GB)
• Low latency
• High availability
• Distributed calculations

Transport
Local Data
Architecture Layers
Transport
Local Data
Transport
Local Data
Shared Data

Scalable eCommerce Platform SolutionsScalable eCommerce Platform Solutions
Transport Layer
Discovery and communication

IMDG Topology

Discovery
• Multicast
• Well-known address

Discovery
• Multicast
New

Discovery
• Multicast
WKA
WKA
New

Communication
• Custom protocols over TCP or UDP
• Senior node
• Heartbeats
– Cluster heartbeats
– Node heartbeats
Senior

Node Departure
• TCP Ring
• IP monitor
• Timeout

Node Departure
• TCP Ring
• IP monitor
• Timeouts

Node Departure
• TCP Ring
• IP monitor
• Timeouts
Box1: IP 177.230.14.5
IP ping

Shared Data Layer
Cluster-wide data

Distributed Cache
Cluster
Client Node
Cache Interface
Storage Node
Data Storage
Cache Interface

Cache Topology
• Replicated
Storage 1
A
D
B
E
C
F
Storage 2
A
D
B
E
C
F
Storage 3
A
D
B
E
C
F
Storage 1
A
D
B
E
Storage 2
C
A
D
F
Storage 3
E
B
F
C
• Partitioned

Storage 3
Repartitioning
Storage 1
A
D
B
E
Storage 3
E
B
F
CE
Storage 2
C
A
D
FF
FCEB

CAP Theorem
C
A
P
Coherence Coherence

Get/Put/Remove, Query, Invocation, Map-Reduce
Cache operations

Key hashing
Cache Operations: Put/Get
Storage 1 Storage 2
Client
Primary A
A B C D E F
• Client knows responsible storage
– Key hash is used to find it
• Automatic backups
Backup A
Backup F Primary F

Storage 2Storage 2Storage 1
Cache Operations: Query
• Broadcast request
– Unless Query is Key-Associated
• All entries are evaluated
– Unless Indexes are used
field1=10 or field2>70field1=10 and key=A
key:
field1:
field2:
D
70
80
key:
field1:
field2:
C
50
60
key:
field1:
field2:
B
30
40
key:
field1:
field2:
D
70
80
key:
field1:
field2:
C
50
60
key:
field1:
field2:
B
30
40
key:
field1:
field2:
A
10
20

Cache Operations: Invocation/Entry Processor
• Task is serialized and distributed
– May contain additional data
• Configurable execution scope
– Specific nodes
– All nodes
– Nodes bound to data
Node 1 Node 2
Task Task
Client
Task

• Data-bound mapping
– By keys
– By Query
• Parallel execution
Storage 2Storage 1
key:
field1:
field2:
A
10
20
key:
field1:
field2:
B
30
40
key:
field1:
field2:
C
50
60
key:
field1:
field2:
D
70
80
Cache Operations: Map-Reduce
sum(field2) where field1>20
40 60 80
180
key:
field1:
field2:
A
10
20
140

Persistence integration

Synchronous Persistence Integration
• Read-through
• Write-through
StorageClient Durable
Storage
Data Grid
Client Durable
Storage
Data Grid
Storage

• Refresh-ahead
• Write-behind
Asynchronous Persistence Integration
Storage QueueClient Durable
Storage
Data Grid
Storage QueueClient Durable
Storage
Data Grid

Local Data Layer
Node-specific data

Storage Storage
Node
Near Caching
• Local access by primary key
• Lazy population
• Invalidation
– On entry change
– By timeout
Near Cache
Distributed Cache
A
A B

Continuous Caching
• Local access by any Query
• Eager population
• Near real-time data
Storage Storage
Node
Continuous Cache
Distributed Cache
A B
A B

Tips
Using Oracle Coherence in practice

Before integrating Oracle Coherence
• Do I really need IMDG or just a cache?
• How large my cluster should be?
• How much heap memory should be
configured for each node?
• What GC configuration to use?
• Do I have a relevant environment
to test my application?

Memory usage
Limit cache size
• By binary size (per node)
• By number of objects in cache (per node)
Estimate cache object memory consumption
• Use BinaryMemoryCalculator
• Remember about backup copies
• Cache listeners (near cache, custom)

Investigation & troubleshooting
• Coherence Management Framework (JMX)
– view cluster and nodes settings
– list caches (front and back) on each node
– view cache dynamic metrics
• Coherence command-line tool
– manage cache services
– manipulate cache data
• Profiling and heap analysis
– analyze heap dump
– analyze GC logs

Thank you!
Questions & Answers

References
• Workshop
– https://github.com/mmyslyvtsev/imdg-workshop
• Coherence Knowledge Base
– http://coherence.oracle.com
• Developers Guide
– http://docs.oracle.com/cd/E18686_01/coh.37/e18677/toc.htm
• Book
– http://www.amazon.com/Oracle-Coherence-3-5-Aleksandar-
Seovic/dp/1847196128

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