[OSM-talk] Missing data in rendering database on orm

[Toby Murray]

After talking a little bit about this on IRC with Tom and Sarah, it
appears this is related to a replication glitch that happened on
February 12th. It was mentioned on the developer mailing list:
https://lists.openstreetmap.org/pipermail/dev/2016-February/029087.html

The "minutely" changeset being talked about there actually contains
about 4 hours worth of changes due to some server problems that were
happening at the time. So anything that was uploaded during those 4
hours may be affected. I'm guessing the intersection of people
uploading at that time, people who land on orm instead of yevaud for
rendering and people who have actually noticed a glitch like this is
pretty small. (just me so far) But this problem could affect up to
about 340,000 objects in that diff. If objects are edited again, they
get fixed. Although if a way is edited that contains nodes that were
created during the 4 hour problem period there will still be problems
with the way until all of its child nodes are edited as well.

I was able to fix the gap I mentioned in my previous email by
uploading a diff that did nothing but bump the version number of the
way and all of its nodes.

To fix everything at once would probably take either re-applying the
last 2 weeks of diffs to orm or doing a full reimport of the rendering
database and I'm guessing that unless some other very visible problems
are discovered, that won't happen. And that is probably fine. This is
just the rendering after all. The actual OSM data is ok and over time
the number of errors will tend towards zero as things get edited. But
it is something to be aware of if you see something odd in the tiles.

I just hope this hasn't affected other consumers of minutely diffs. If
Roland hadn't discovered it quickly in the overpass database, it could
have led to some big problems.

Toby

On Sun, Feb 21, 2016 at 3:09 PM, Toby Murray <toby.murray at gmail.com> wrote:
> I noticed something weird in the tile rendering on osm.org a couple of
> days ago and after looking at several things it seems that one of the
> rendering servers (orm) is missing data. I'm wondering if I'm the only
> one to see this or if anyone else has noticed something similar.
>
> What I initially noticed was a gap in a road that should not have been
> there. It can be seen in this tile:
> http://orm.openstreetmap.org/16/15058/25351.png
>
> The data in the database was never in a state with a gap. I split the
> road to tag lane count. In the same upload the way coming in from the
> west was shortened and a new way was created. But on orm, only the
> shortening seems to have registered and the new way creation has
> apparently been dropped. Compare this tile to the same tile on yevaud:
> http://yevaud.openstreetmap.org/16/15058/25351.png
>
> You will see not only that the gap is filled in but yevaud also has
> several other features that are missing on orm.
>
> This is not a stale tile being served up from cache. These changes
> were made on the 16th and the tile has been rendered at least 3 times
> since then with the most recent being earlier today (on the 21st)
>
> The area this happened in is Wichita, KS:
> https://www.openstreetmap.org/#map=16/37.6864/-97.2828
>
> But you will only see the gap if you get routed to orm via the OSM DNS
> setup. See http://render.openstreetmap.org/ if you don't know which
> one you are being routed to (it will say either orm or yevaud in the
> first line)
>
> There is another gap if you pan west about two miles to the
> interstate. Here I split the way to add a maxheight tag. Other things
> I have uploaded since the 16th are showing up. It seems to be just
> that one changeset that got partially applied to the rendering
> database.
>
> Am I just really (un)lucky or has anyone else seen something similar?
>
> Toby