[Kimchi-devel] [RFC] Improve task management for kimchi

[Sheldon]

On 06/27/2014 07:15 PM, Wen Wang wrote:
> Dear all,
> *
> **Problems:*
> Now our strategy  for long time operation is using task which the 
> browser needs to check up-to-date task status time by time until the 
> task ends. It's time consuming and less efficient. Also there exists 
> several problems when locating each task when doing debug generating 
> and storage pool as well as some new features that might use task 
> strategy in the future.
>
> *Solution*:
> As talked with Sheldon and Zhengsheng, we came up with a solution that 
> avoid browser checking status every 200ms. Also, we might need some 
> more labels in each task to provide more information when getting the 
> task like we might need to indicate which operation triggered certain 
> task. What's in our mind is to use the strategy that allow the server 
> inform browser about the task information. Our proposal is designed as 
> follows.
>
> 1) Browser needs to register to the back end to indicate which part 
> the result needs to reply to when the task finished.
> 2) The back end use broker to manage message distribution: when a task 
> is finished or experiencing an error, back end inform the browser 
> certain part of work is finished or error.
> 3) Using websocket of cherrypy to accomplish the message transfer.
Now let me elaborate above.

For Browser, it can be an event loop worker.
It can subscribe event message that users care to the back end broker.
listen the events from the broker and take some action for the event.

For back:
The broker should collect and store the events from everywhere.
The broker should dispatch the message to the client who subscribes it.
For some event, broker should determined whether it should dispatch to 
user.
Such a VM shutdown event, the broker just send it to the user who has 
the access permission. (Yu Xing's suggestion)
We had better define the event message format.

We had better to find an existing python lib for it. If no we should 
code it for ourself.
                                                            [ client1 ]
                                             care VM     |       ^
libvirt event -------------\        shutdown  |        |  VM shutdown
                                    \                         V |
event 1 -------- -------------------------->[   broker ]
                                   /                        ^ |  dispatch
event 2       ------------/                          |         |
                                           subscribe   |        V listen
                                                           [ client2 ]


For websocket:
There's also an issue about it. 
https://github.com/kimchi-project/kimchi/issues/22
The websocket is the pipe to connect the broker of the UI event worker.
We should support websocket proxying directly from the cherrypy server 
on its given port.
Zheng Sheng is working on it.  It can work on cherrypy. Seems something 
wrong with nginx.



>
> Best Regards
>
> Wang Wen
>
>
>
>
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-- 
Thanks and best regards!

Sheldon Feng(???)<shaohef at linux.vnet.ibm.com>
IBM Linux Technology Center

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