Re: [Storagesync] Some preliminary investigations on ownCloud

2015-11-26 11:28 GMT+08:00 Fei Song <fsong@bjtu.edu.cn>:

> BTW, Based on the last sentence of last email:"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"
>
> The outcome he/she wanted might be just the links like
> http://cs3.ethz.ch/program.html :)
>
In another word, I think what I want finally might be a discussion about
"What is needed for the ISS: a sync protocol or a generalized API". Sorry
for the poor expression : )

Regards,
Linhui

>
>
> --------------
> Fei Song
> >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
> >
> >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
> >
> >It would be interesting to see if there is a potential for collaboration.
> Or maybe we already have some information you are looking for.
> >
> >Best regards,
> >
> >Jakub Moscicki
> >
> >—
> >
> >
> >On 25 Nov 2015, at 11:45, Linhui Sun <lh.sunlinh@gmail.com<mailto:
> lh.sunlinh@gmail.com>> 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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> >
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