Re: [Storagesync] Some preliminary investigations on ownCloud

["Fei Song" <[e-mail]>]

Hi Linhui,


--------------
Fei Song
>Hi Fei,
>
>2015-11-26 11:11 GMT+08:00 Fei Song <[e-mail]>:
>
>> Hi all
>>
>>
>> --------------
>> Fei Song
>> >Hi all,
>> >
>> >As I mentioned before, I think the developers could benefit from the IETF
>> >standards. The ownCloud (https://owncloud.org/) is just an example. It is
>> >developed for those who do not trust commercial storage services and want
>> >to build their own network-based storage services. The ownCloud is using
>> >WebDAV (RFC4918) to achieve the data sync. IMO, the WebDAV is designed for
>> >distributed work but not for the sync. Thus, I made some preliminary
>> >investigations on how the ownCloud uses WebDAV for sync purposes. A brief
>> >summary of what I've found is in the following, please correct me if I am
>> >wrong.
>> >
>> >I installed the ownCloud server (v8.2.1) on the CentOS7, and the client is
>> >a desktop client on Windows.
>> >
>> >1. To find whether there is a change to the synced directory, the client
>> >continuously sends PROPFIND to the server at regular intervals (around 34
>> >seconds under my observation). The server will respond a 207 Multi-Status
>> >Response to tell whether the main directory has been changed. To perform
>> >this regular check, the client will open a new TCP connection to send the
>> >PROPFIND, the server will close the existing TCP connection after
>> >responding the 207 Multi-Status Response. For the next check, the client
>> >will open another new TCP connection.
>>
>> I wonder whether these message you got had been encrypt or not.
>>
>The ownCloud suggests people use HTTPS, but you could also use the HTTP.
>And that is what I did.

Thanks!

>
>>
>> >
>> >2. Every time adding (or creating) a new file to the local folder, the
>> >client will open a new TCP connection (if there is no connection existing)
>> >to send the file asap. The client will first send several PROPFINDs to
>> find
>> >out which sub-directory has been changed. And then it sends the file using
>> >PUT. The server will respond a 201 Created Response and then terminate the
>> >connection. Currently, I haven't found any application layer chunking, all
>> >the segmentation are performed by TCP.
>> >
>> >3. Every time I delete (or rename) a file locally, the client will also
>> >open a new TCP connection to send several PROPFINDs to find out which file
>> >has been removed (or renamed). Then it will send DELETE (or MOVE). The
>> >server will respond a 204 No Content Response (or 201 Created Response)
>> and
>> >then terminate the connection.
>> >
>> >4. I open a file and frequently edit and save it (actually this is what I
>> >usually do with the Dropbox). The client will send the whole file to the
>> >server every time I save the file.
>> >
>> >To summarize, it seems that the ownCloud makes heavily use of PROPFIND to
>> >achieve the sync process. Each sync operation (e.g. upload, modify and
>> >etc.) will start with sending one or more PROPFINDs. And currently, if I
>> >add a file to the server (directly from the server side via web
>> interface),
>> >the client cannot find the change. I need to interrupt the sync and
>> recover
>> >it to make the client be aware of the change and download the newly added
>> >file. I'm not sure whether this is caused by the sync mechanism or an
>> >improper server configuration. I need to investigate this further and also
>> >how the ownCloud works for multiple clients (or devices).
>>
>> What do you mean by "directly from the server side via web interface".
>> If all the configuration were correct, do you want to identify that the
>> sync in
>> ownCloud is only unidirectional?
>>
>People could access to the ownCloud service via desktop, mobile client or
>web interface (i.e. browser), the point I want to say here is an operation
>on the server side cannot be detected automatically. I'm not sure whether
>I've configured the server correctly. But the sync is not unidirectional
>since after I recovering the sync, the client could download the asap.

I see, then there might be an option at the server side 
can sync the changes to the client automatically.


>
>>
>> >
>> >For ISS, I think ownCloud has demonstrated to some extent that similar
>> IETF
>> >protocols could be deployed and employed. The intention of this message is
>> >to investigate the current state of using WebDAV for sync purposes to see
>> >what needs to be improved here and whether we need new protocols.
>>
>>
>> >
>> >Comments are welcome : )
>> >
>> >Regards,
>> >Linhui
>> >
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