[Unison-hackers] A rant about problems with dropbox -- thank you Unison!

[Ryan Newton]

Great!  I spoke too soon.  I was out of date -- I should have searched
and I'd have seen all those messages about fsmonitor.py ;-)...

Thanks,
   -Ryan

P.S.  The HEAD isn't building for me right this second, but is the
state of affairs still as laid out in the manual.  Namely, that the
implementation polls a watchfile every few seconds:

    http://www.cis.upenn.edu/~bcpierce/unison/download/releases/beta/unison-manual.html

Is there a reason that it polls and then sleeps for a few seconds?  If
the watchfile were a pipe couldn't the unison process just do blocking
reads against it to achieve better latency?  (Usually I use "-repeat
1" when I'm editing on one machine and compiling on another.)



On Tue, Feb 22, 2011 at 2:56 PM, Pierce Benjamin C.
<bcpierce at cis.upenn.edu> wrote:
>> I'm convinced that Unison could be the kernel of a great solution
>> here.  But in the past its been too much work for anyone to get
>> excited about doing cross-platform inotify-style file system
>> monitoring in particular.  Are there other open source projects from
>> which this functionality could be borrowed?  iFolder?
>
> Actually, this functionality is pretty close to working -- what it needs is for someone who cares about a particular platform to take it on and polish off a few remaining rough edges.  Moreover, this can be done with minimal OCaml knowledge, as the actual FS monitoring code is written in Python...
>
>    - B
>
>
> On Feb 21, 2011, at 8:58 AM, Ryan Newton wrote:
>
>> Thank you unison for *correctness*.
>>
>> We had a thread discussing dropbox back in October.  I was cautiously
>> optimistic then but now am more jaded after the abysmal way they
>> handle symlinks:
>>    http://parfunk.blogspot.com/2011/02/dropbox-semantics-oh-that-there-were.html
>>
>> Ironically, I end up recommending periodic unison to get the symlinks
>> right and then dropbox for day to day synchronization!  (Not a
>> pleasant solution.)  It's exactly as Benjamin Pierce says in the
>> message below -- unison fails safely and gets cross-platform right.
>> I've seen dropbox break both these rules so far.
>>
>> Ranting about the low quality of commercial synchronization solutions
>> has become a bit of a hobby.  For the sake of confirmation bias I
>> would love to hear other people's bad stories about commercial
>> synchronization solutions ;-) -- e.g. apple's iSync both lost my data
>> and got into a failure mode exhibiting exponential duplication.  It
>> seems as though many companies treat synchronization as just another
>> programming task and not worthy of deeper thought.
>>
>> BUT, Dropbox in particular still has a lot of draw -- super easy
>> setup, cloud storage, and the wonderful file-browser-as-GUI
>> methodology.
>>
>> I'm convinced that Unison could be the kernel of a great solution
>> here.  But in the past its been too much work for anyone to get
>> excited about doing cross-platform inotify-style file system
>> monitoring in particular.  Are there other open source projects from
>> which this functionality could be borrowed?  iFolder?
>>
>> -Ryan
>>
>> P.S. Also, if anyone were interested the nautilus-plugin for dropbox
>> is open-source and could be a starting point for file-browser
>> integration.
>>
>> P.P.S. I don't know about cloud storage.  I assume that S3 and google
>> storage use APIs that would make it difficult to ever unison-to-cloud
>> directly.  (Without maybe running an EC2 instance with a unison server
>> or something.)
>>
>>
>> On Mon, Oct 5, 2009 at 10:02 AM, Benjamin Pierce <bcpierce at cis.upenn.edu> wrote:
>>> I've been hearing some good things about DropBox too.  I'd love to
>>> know more about people's experiences with it, especially compared to
>>> Unison.
>>>
>>> Two things Unison is pretty good at are (1) failing safely when things
>>> go wrong and (2) getting the details of cross-platform synchronization
>>> right.  I doubt if I'll personally want switch to anything that
>>> doesn't do at least as good a job on both counts, so comments on these
>>> aspects of DropBox would be particularly interesting.
>>>
>>>    - Benjamin
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