Re: [Storagesync] Some preliminary investigations on ownCloud

[Linhui Sun <[e-mail]>]

Hi Jakub,

2015-11-26 1:50 GMT+08:00 Jakub Moscicki <[e-mail]>:

> Hello,
>
> What kind of outcome are you looking for with this analysis? Some research
> in this area has already been done or is being done as we speak
>
I think this is for the previous confusion that "why do we need the ISS
over the existing WebDAV". As we could find that many open source projects
are using WebDAV now (ownCloud is a popular example), we need to find out
whether WebDAV is sufficient for this kind of applications. IMO, the
developers for those applications might be the active users of the ISS
work, thus finding out what do they lack, what do they want is important.

>
> e.g. "A study of delta-sync and other optimisation in HTTP/Webdav
> synchonisation protocols"
>
> see "Technology and Research":
>
> http://cs3.ethz.ch/program.html
>
Actually I'm not talking about the efficiency or optimization here. What I
really want to say is the applicability. If we find the WebDAV is enough
and appropriate, then for ISS, a generalized API to access all services and
for collaboration would be better than a sync protocol.

>
> It would be interesting to see if there is a potential for collaboration.
> Or maybe we already have some information you are looking for.
>
The collaboration is really important but is based on the fact that many
providers are willing to use it. At the current stage, I think we need to
find someone who are willing to deploy and use the possible ISS work, maybe
ownCloud is a potential user : )

Regards,
Linhui

>
> Best regards,
>
> Jakub Moscicki
>
> —
>
>
> On 25 Nov 2015, at 11:45, Linhui Sun <[e-mail]> wrote:
>
> 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.
>
> 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).
>
> 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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