This document discusses Apache Traffic Server internals and is presented by Phil Sorber, a principal engineer at Comcast and committer to ATS. The talk covers ATS's use of CPU, memory, storage and networking and how it utilizes abstractions. It provides a brief history of ATS and discusses its multi-threaded and asynchronous event-driven architecture.

1. Apache Traffic Server Internals
Phil Sorber - Comcast

2. How I learned to stop worrying
and love ATS

3. About Me
(Why you should listen to me)
• Principal Engineer @ Comcast on IpCDN team
• Committer to ATS
• Generally cool guy [citation needed]

4. About This Talk
(Why you shouldn’t leave just yet)
• CPU
• Memory
• Storage
• Network
• Abstractions

5. A brief History
• Inktomi (1996)
• Yahoo! (2002)
• Apache Incubator (2009)
• Apache TLP (2010)

6. CPU
• Multi-Threaded
• Asynchronous
• Event Driven
• Continuations
• CPU Affinity (NUMA)

7. CPU
(continued)

8. CPU
(continued)
• Thread Types
§ Net
§ AIO
§ Task
§ Accept
§ SSL
§ DNS
§ Remap
§ Plugins can also do thread things

9. Memory
• RAM Cache (not RAM disks)
• NUMA! NUMA!
• Freelists
§ Allocators
§ ClassAllocators (Global with atomics)
§ ProxyAllocators (Thread)
§ Arenas
• Huge Pages?

10. Memory
(continued)
Head
Version
Next Next Next

11. Memory
(continued)
Socket 1 Socket 2

12. Storage
• Raw Devices
• Unique Caches
• Distinct RAM Caches
• Consistent Hashing
• Circular Cache

13. Storage
(continued)
Vol 1 Vol 5Vol 4Vol 3Vol 2
RC
Consistent Hash
RC RC RC RC

14. Storage
(continued)
Vol 1 Vol 5Vol 4Vol 3Vol 2
RC
Consistent Hash
RC RC RC RC

15. Network
• Connection Pools
• Tiered Caches
• Parent Selection

16. Network
(continued)
Origin
Mid
2
Mid
1
Edge
2
Edge
3
Edge
1
Client
1
Client
2
Client
3
Client
4
Edge
4
Client
5
Client
6

17. Network
(continued)
Origin
Mid
2
Mid
1
Edge
2
Edge
3
Edge
1
Client
1
Client
2
Client
3
Client
4
Edge
4
Client
5
Client
6

18. Abstractions
• Processors
§ HostDB
§ DNS
§ Net
§ SSL
§ Cache
§ Remap
• State Machines
• Clustering

19. Abstractions
(continued)

20. Questions?
Seriously, ask some.
• Phil Sorber
• sorber@apache.org
• @PhilSorber
• http://trafficserver.apache.org
• #traffic-server on freenode (PSUdaemon)