Hi Jens, you're certainly right about the format being subject to change -- in
BigCouch's master branch it's [3264, "g1AAA..."] to allow for sane sorting of
the sequences. Just an FYI.
The hex portion of the sequence is a Base64-encoded term_to_binary
representation of a covering set of shards. If you execute a
binary_to_term(couch_util:decodeBase64Url("g1AAA...")) on the two sequences in
that status string you'll see that the server replaced one of the shards in the
denominator with a replica. Perhaps one of the nodes in the cluster was
unavailable when the replication request was made. I'm afraid there's no good
way to do an equality comparison on the client when that happens. Under normal
operating conditions the two hex blobs should compare equal at the end of a
replication. Regards,
Adam
On Nov 29, 2011, at 5:07 PM, Jens Alfke wrote:
> CouchCocoa attempts to provide progress information about replications, so
> the app can display a progress bar or similar UI, or at least indicate when
> replication has completed. This is surprisingly difficult. I got it working
> well with regular CouchDB, but now I’m re-opening the can of worms because
> BigCouch doesn’t use integral sequence numbers and so the status messages
> provided by the replicator contain binary goop, for example:
>
> “status”: "Processed
> <<\"3264-g1AAAADzeJzLYWBgYMlgTmFQSElKzi9KdUhJMtLLTS3KLElMT9VLzskvTUnMK9HLSy3JAapkSmRIsv___39WEgMDsyGqNhM82pIcgGRSPUynDvEW5rEASYYGIAXUvB-s24F4eyG6D0B0Q-xWzgIA8ZZODg\">>
> /
> <<\"3264-g1AAAADzeJzLYWBgYMlgTmFQSElKzi9KdUhJMtLLTS3KLElMT9VLzskvTUnMK9HLSy3JAapkSmRIsv___39WEgMDsyGqNkM82pIcgGRSPUynDvEW5rEASYYGIAXUvB-s2wFVtwlB3QcguiF2K2cBAO-bTgs\">>
> changes”
>
> I’ve updated my parser to be able to tweeze out the two binary blobs, and I
> figured I could at least compare them for string equality to detect when the
> last change is processed. Unfortunately this doesn’t appear to work. The
> example above is the last status message I got in a pull from Cloudant;
> apparently it’s completed, because nothing else has been copied over in the
> 15 minutes since, but the two blobs are not exactly equal. (They are _almost_
> equal, up to the last 25 or so characters.)
>
> The unfortunate result is that in the iOS GrocerySync app, the replication
> progress bar gets stuck and never goes away.
>
> I realize that these blobs are probably deliberately opaque and their format
> Subject To Change Without Notice, but it would be helpful if I had some kind
> of heuristic about their current format that would at least let me detect
> when a replication has ended. Any suggestions?
>
> —Jens
>
