1. SEDA Java
Benjamin Tan
Team Leader@DBAppSecurity
Twitter: tanbamboo

2. Agenda
• SEDA
• Java
• Actor

3. SEDA
• SEDA: A new architecture for Internet services
• A general-purpose framework for high concurrency and
load conditioning
• Decomposes applications into stages separated by queues
• Adopt a structured approach to event-driven
concurrency
• To appear in the Eighteeth Symposium on Operating
Systems Principles (SOSP-18), Chateau Lake Louise,
Canada, October 21-24, 2001.
• http://www.cs.berkeley.edu/~mdw/

4. SEDA features
• Enable load conditioning
• Event queues allow inspection of request streams
• Can perform prioritization or filtering during heavy load
• Dynamic control for self-tuning resource management
• System observes application performance and tunes runtime parameters
• Apply control for graceful degradation
‣ Perform load shedding or degrade service under overload
• Simplify task of building highly-concurrent services
• Decouple load management from service complexity
• Use of stages supports modularity, code reuse, debugging
• Dynamic control shields apps from complexity of resource management

5. SEDA
Staged Event-Driven Architecture (SEDA)
file data
I/O
request
accept handle file
connection connection HTTP miss I/O
request cache
parse check miss
packet cache
packet packet
read send write
packet cache hit response packet
Decompose service into stages separated by queues
• Stage Queue
• Each stage performs a subset of request processing
• Stages internally event-driven, typically nonblocking
• Stage
• Queues introduce execution boundary for isolation and conditioning
Each stage contains a thread pool to drive stage execution
• However, threads are not exposed to applications
• Dynamic control grows/shrinks thread pools with demand
Stages may block if necessary

6. • Stage Queue
SEDA
•
•

7. •
•

8. Java
•
• CPU

9. Active List
•
ThreadLocal
• JUC concurrent

10. Counter
• AtomicInteger 1500EPS
1500
•
•

11. Java
• :
•
•
•

12. CPU
• CPU MEM Stage
CPU ( )
• IO Stage
CPU 3~5
HTTP

13. Actor
• SEDA
•
• Stage Queue
• Stage

14. Actor
• Actor
Context
• Actor Mailbox
• Topology Actor

15. Actor
• “self-heals, systems that never stop”
?
•
CPU ?