這個投影片有三個主軸： 第一個主軸是簡單的介紹各個元件，與如何快速試用 第二個主軸是介紹 openstack 架構與元件溝通方式 第二個主軸是介紹追蹤 openstack source code 的心得

1. Openstack 簡介
果凍

2. 簡介
● 任職於迎廣科技
○ python
○ openstack
● http://about.me/ya790206
● http://blog.blackwhite.
tw/
● https://github.
com/ya790206/call_seq

3. Openstack
● Build your own cloud.
● RESTful api
Openstack
iScsi libvirt LVM Open
vSwitch
other

4. trystack
● try openstack
● use your facebook id to login.
● http://trystack.org/

5. devstack
● build your development environment.
● mini config:
ADMIN_PASSWORD=secrete
DATABASE_PASSWORD=$ADMIN_PASSWORD
RABBIT_PASSWORD=$ADMIN_PASSWORD
SERVICE_PASSWORD=$ADMIN_PASSWORD
SERVICE_TOKEN=a682f596-76f3-11e3-b3b2-e716f9080d50
SCREEN_LOGDIR=$DEST/logs/screen

6. Component
● keystone -- auth and service catalog
● nova -- VM
● glance -- image service
● cinder -- block storage service
● swift -- object storage service
● neutron -- network

7. glance service:
● privide image
● support backend:
○ s3
○ swift
○ file system
cinder service:
● for instance
swift:
● object storage

8. other interesting project
● Trove -- database as a service
● Sahara -- provision a Hadoop cluster on top
of OpenStack
● taskflow
● oslo messaging

9. Common Requirement
SQLAlchemy
oslo.config
Paste
PasteDeploy
iso8601
greenlet
eventlet
Routes
WebOb
six

10. Threading Model
● green thread model(implemented through
using the Python eventlet and greenlet
libraries.
Python
VM
Openstack
thread
model
VM
M thread
M kernel
thread
M thread M thread
1 kernel
thread N kernel
thread
kernel layer
application layer

11. XXX-api
YYY-api
ZZZ-api
python-
XXXlib
python-
YYYlib
python-
ZZZlib
horizon
dashboard
REST api
REST api
REST api
REST api
function call
function call
function call
REST api
XXX-aaa
XXX-bbb
amqp
restapi
a
m
q
p
XXX-ccc
o
t
h
e
r

12. api.py: wsgi server(API or Controller)
rpcapi.py < = > manager.py
api.py
request for
RESTful api
python
call
rpcapi
.py
oslo.
messagi
ng
mana
ger.py

14. nova architecture

15. 有什麼問題，
中間加一層就
對了
● Mediates interactions between nova-
compute and the database.
● Security
○ nova-compute never access database directly.
● Ease of Upgrade
● Performance
○ Queries to the MySQL database will block the main
thread of a service.
○ scales horizontally
nova-conductor

17. Component Communications
● REST api:
○ nova-api -> keystone-api
○ glance-api -> glance-registry
● oslo.messaging(AMQP)
○ nova-api -> nova-compute
○ nova-api -> cinder-volume

18. REST api
glance/api/v1/images.py
glance/registry/client/v1/client.py
glance/registry/api/v1/images.py
rest
api

19. oslo.messaging
● support multi-endpoints.
● RPC Client <-> Server:
○ call
○ cast
● Notifier <-> Notification Listener
○ ceilometer
example code:
https://github.com/kgiusti/oslo-messaging-clients

20. openstack.taskflow
● workflow library.
● make task execution easy, consistent, and
reliable.
● flows can be stopped, resumed, and safely
reverted.

21. openstack.taskflow
● Tasks:
○ retry
○ revert
● Flows
○ revert
○ pattern:
■ Linear
■ Unordered
■ Directed acyclic graph
● Engines:
○ serial
○ parallel
○ worker-based

22. openstack.taskflow -- use case
task1: create server || rollback by delete
server
task2: create+attach volume || rollback by
delete volume

23. class CallJim(task.Task):
def execute(self, jim_number, *args, **kwargs):
print("Calling jim %s." % jim_number)
class CallJoe(task.Task):
def execute(self, joe_number, *args, **kwargs):
print("Calling joe %s." % joe_number)
flow = lf.Flow('simple-linear').add(
CallJim(),
CallJoe()
)
taskflow.engines.run(flow, store=dict(joe_number=444,
jim_number=555))

24. Example
https://github.
com/openstack/taskflow/blob/master/taskflo
w/examples/graph_flow.py
https://github.
com/openstack/taskflow/blob/master/taskflo
w/examples/reverting_linear.py

25. Trace Code Tip
● Document
● Database schema
● Basic data struct
● Entry point
● Test code
● Debug message.

26. Basic Data Struct
● for example:
○ django model for django
○ intobject.c for python intergrater.
○ glance models for openstack glance.

27. pyreverse
● UML tool for Python
● pyreverse -ASmy -k -o png main.py -p Main

28. Entry point
1. 由下而上(由樹見林）
a. traceback.extract_stack.
b. use debugger to show traceback.
2. 由上而下(由林見樹）
a. call_seq.

29. call_seq
● written by me.
● pip install git+https://github.
com/ya790206/call_seq
● trace you program how to run and generate
a report with json format.

30. from call_seq import CallSeq
trail = CallSeq()
trail.set_trace()
# the code you want to trace.
trail.unset_trace()
trail.dump_to_file('output.json')

31. "arguments": {},
"code": "test1()",
"file_name": "demo.py",
"lineno": 14,
"name": "test1",
"return": "<int>: 2",
"return_lineno": 10,
"seq": [
{
"arguments": {},
"code": "test2()",
"file_name": "demo.py",
"lineno": 9,
"return": "<NoneType>",
"return_lineno": 5,
"seq": []
}
]

33. Test Code
● 看看 function test 和 unit test
https://github.com.openstack.nova.blob.
master.nova.tests.test_flavors.py
https://github.com.openstack.cinder.blob.
master.cinder.tests.test_volume.py

34. 總結
● openstack: build you own cloud.
● communication:
○ REST api
○ oslo.messaging
● Trace Code Tip

35. 徵才
● 迎廣科技研發中心
● 尋找 openstack, python 的愛好者
● 聯絡方式： http://www.blackwhite.
tw/#/contact

36. Thank you

37. 雜記
● 此張投影片後的投影片內容為演講後所新增
內容，對前面的投影片內容做補充

38. 為何要介紹openstack元件？
● 站在巨人的肩上, 才能看的更遠
○ 利用現有軟體, 減少沒必要的程式開發
○ 利用已經有軟體, 創造更多價值

39. 為何要介紹 Common Requirement？
● 了解大型專案所採用的 library
● 如果我們要做 api server,但是不想浪費效能在無意
義的運算上。
○ 採用 django, bottle 對 api server 而言，太多餘
○ 直接寫 wsgi server 太痛苦
○ 可以模仿 openstack 用 paste, route, 和 webob 來
建立 api server。

40. ● 為 nova conductor 鋪路
為何介紹 Threading Model ？

41. ● 有問題，中間加一層就對了
● sql query 會影響 eventlet 效能(我不確定，文
件寫的)
為何介紹 nova conductor ？

42. ● 另一個 rpc library 的選擇
● 相似專案： zerorpc
為何介紹 oslo.messaging？

43. ● 類似 pipeline，或 sql transaction。
● 當工作失敗後，可以 rollback 動作。或是隔幾
秒重試，或是換不同的參數看看。
● 每個工作下可以擁有子任務，子任務可以循序
執行，平行執行等。
為何介紹 openstack.taskflow ？

44. ● 當你使用由下往上看（show traceback）的方
法時，這是一個很好的切入點。
為何要在 trace code tip 中提到 basic
data struct?

45. ● 因為茫茫程式碼海裡，不知道要從何下手
為何要由下往上看？

46. ● 要觀其大略，識大局
● 為何我要寫 call_seq:
○ 因為我懶得一個一個開檔案看程式碼
○ 既然程式都知道怎麼執行了，讓他告訴我也不是一件
過份的事
為何要由上往下看？