Re: [Duplicity-talk] duplicity stalling intermittently

[Peter Schuller]

> Has anybody else seen anything like this? Or can anybody suggest where to
> look to find the problem? I'm running the latest duplicity version and have
> ample space on /tmp and (I think) no network problems so I'm not sure where
> to look next.

The "Stalled for too long, aborted copy" is coming from the duplicity backend 
(rather than scp directly). It happens when the backend has detected that scp 
has claimed itself to be "stalled" for a certain amount of time.

Unless there is a bug, it should only enter the "stalled" state as a result of 
scp actually outputting the word "stalled".

So, the first place I would look is to figure out what is going on with the 
scp session itself. First off, if you are able to 'catch it in the act' you 
can try manually copying the file to see if you can trigger it. Or if not 
just randombly grab a file of the same size as the duplicity volume size, and 
copy it a few times spread over time to see if you can trigger it that way. 
That is, if you want to be sure whether it can be triggered outside of 
duplicity.

The question is also whether you have any communication at all with the rsync 
account when this happens, or if it is just that one already established 
conneciton that dies.

Of course one reason it would stall would be a problem om the remote end, such 
that writing of the file is blocking. Presumably this has already been ruled 
out with rsync.net support.

Not sure what to suggest for an easy diagnosis. Perhaps try using -o 
ServerAliveInterval=5 -o ServerAliveCountMax=3 to make ssh trigger actual 
timeouts long before duplicity detects the stalled state. Would also be a way 
to show the problem appears with the underlying scp. 
(Use --ssh-options "ServerAliveInterval=5 ServerAliveCountMax=3" to duplicity 
to make it use this command line with scp)

-- 
/ Peter Schuller

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