Hi Dirk,

Are there any issues with the backend today? I’m not able to sync either from 
my desktop or mobile (also over 4G).


— Attilla

> On 19 Apr 2021, at 22:58, Dirk Hohndel via subsurface 
> <[email protected]> wrote:
> 
> Hi Jason,
> 
> Thanks for the feedback. Yes, the new DNS records now have much longer TTL 
> and are therefore more likely to be cached.
> I also made some subtle changes to the logic when we first attempt to connect 
> and actually try to start writing to the cloud that might make a difference 
> there.
> 
> /D
> 
>> On Apr 19, 2021, at 1:50 PM, Jason Bramwell  wrote:
>> 
>> Many thanks as always.
>>  
>> I used to see a ‘feature’ where the first attempt to load Subsurface would 
>> fall back to using the local cache and i’d have to close/reopen Subsurface 
>> to get it to connect to the cloud storage, Linux diagnosed this as likely 
>> slow DNS lookup, very brief testing (I do mean very brief) seems to indicate 
>> that this is no longer the save now and it ‘just works’.
>>  
>> Jason
>>  
>> Sent from Mail for Windows 10
>>  
>> From: Dirk Hohndel via subsurface
>> Sent: 19 April 2021 21:00
>> To: Subsurface Mailing List
>> Subject: redundant cloud servers
>>  
>>  
>> Over the past couple of weeks I quietly moved the cloud server backend and 
>> the authentication database out of my home network and back into the public 
>> cloud.
>> The fact that apparently no one noticed and nothing broke was rather 
>> encouraging :-)
>>  
>> I then setup a second cloud server in the public cloud, this one in Europe 
>> (actually, Frankfurt, Germany).
>>  
>> A few minutes ago I merged a pull request that adds a couple of interesting 
>> new features to both Subsurface and Subsurface-mobile:
>>  
>> - geo based choice of cloud server (those in the Americas should end up 
>> using the US server, everyone else should get directed to the European 
>> server), which is intended to be completely transparent to the user.
>> I.e., unless you explicitly look for it, you shouldn't notice (or care) 
>> which server you are using
>> - hot failover between the two servers (so if the server that you have used 
>> before is unavailable, Subsurface and Subsurface-mobile should try the other 
>> one - and the implementation makes it easy to add more servers if that 
>> appears useful)
>>  
>> The two servers are automatically kept in sync in the background. I can 
>> create one extremely artificial case where there is a fairly short 
>> (generally sub one second in my tests) window for a race condition. A user 
>> would have to have two different devices that are synced to different 
>> servers (for example because they took their phone with them on an overseas 
>> dive trip), that have made conflicting changes to the dive log, and the user 
>> would then have to cause a save to the cloud on both devices within the 
>> roughly one second window. Forcing that race turned out to be fairly hard 
>> because the mobile app does a few other things before storing the data to 
>> the cloud - so for testing I ended up using two instances of Subsurface and 
>> synchronized clicks... really -- not a realistic scenario.
>>  
>> If this were to happen, I will get an automated email alert and fixing the 
>> problem isn't really hard - but I wanted to give a full disclosure of the 
>> issues that I am aware of.
>>  
>> What would help right now if people tested all this.
>> So far I have not had the time to make new beta versions of 
>> Subsurface-mobile, but as I said, it's actually easier to test on the 
>> desktop.
>>  
>> /D
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