On 6/9/2013 6:23 AM, Rahkonen Jukka wrote:
Hi,
This is so important thing to know that it should be mentioned in
http://www.mapserver.org/trunk/mapcache/seed.html I believe I am not
the only GeoWebCache users who experiment with MapCache and think
that MapCache can also do seeding/reseeding/truncating for an active
cache because that is the standard with GWC.
I tend to agree with you on this point. You might want to write a ticket
for this as a new feature with the use case(s) that you provided below.
That said, Thomas has been very busy and getting any priority on this
might need some funding.
The need to use seeding tool with inative cache makes me to wonder
how to implement partial updating of big cache like 1 TB in size in
production environment. The service can't be stopped for truncating
and reseeding. Making a copy of the active cache, truncating and
reseeding the copy and finally switching MapCache to use the
refreshed cache should work, but copying 1 TB of data is slow and
keeping an extra terabyte on a hosted disk is costly.
I guess that by using a GeoTIFF cache it would be possible to use the
seeding tool for creating a new cache from the updated areas. The
tiff files in the new cache are using the same naming convention and
therefore they could be copied on top of the outdated tiles in the
active cache and this could happen on-the-fly. Would this work?
The way I have updated my live cache in the past is:
1. update the source with new data
2. run a script to delete tiles in the cache for the updated area of
interest or 1/N of it if I want to do a multi-day N day update to spread
the load out
This is relatively safe, but runs the risk of an occasional tile getting
deleted while it is getting downloaded, but on the next refresh from the
client a new tile will get loaded.
I have also written a script (can't find it at the moment) that computes
the top-left tile in each metatile for a give area of interest and
request it from apache. This in effect creates a seeder that uses apache
to do the work and therefore works cooperatively with the live cache.
-Steve
-Jukka Rahkonen-
________________________________________ Stephen Woodbridge wrote:
In general, The seeder can not be run on an active cache because it
does
not coordinate tile generation with apache so if they both try to
create the same tiles things can get confusing and there is a chance
that an incomplete tile might get served with both writing the
resulting tile might be damaged.
-Steve W.
On 6/8/2013 3:41 PM, John D. Evans wrote:
Hi,
Thomas Bonfort wrote on 06/06/2013:
As for the root issue, are your tilesets fully preseeded or are
they populated on demand? KML superoverlays are organized in a
tree, i.e. to access a tile at zoom level N you first need to
access all parent tiles from level 0 to N-1; on an unseeded
tileset with a slow wms backend this might be a very long wait.
Also please check the apache error log for any mapcache related
messages.
Thanks for the input! Sorry for the delayed reply. My tiles had
been populated on demand but I finally found, installed, and ran
"mapcache_seed". It's now been running for 10+ hours now (*) but I
still get the same effect in Google Earth. (A very low-resolution
view displays when I'm zoomed out very far, but disappears as soon
as I try to zoom in.) Does the seeding have to be completely
finished before Google Earth can see beyond the top-level KML
tiles?
Thanks again.
- John E.
(*) I'm running this on a fairly puny virtual machine (2 cores); I
guess I should try seeding with 8 or 10 threads on an 8-core
machine. I will also try limiting my zoom levels (I suspect I'm
seeding 0-17 by default) and my spatial extent (I'm probably doing
the whole globe by default -- lots of blank tiles :-).
On 6 June 2013 05:19, John D. Evans <[email protected]
<mailto:[email protected]>> wrote:
Hello,
Not sure my earlier query made it to the list.
I'm using MapCache to serve for some satellite image products.
It sort of works: the tms and wmts browsers at /mapcache/demo
show full coverage of my data area, and let users zoom in to see
full resolution image mosaics. But the KML superoverlay (my
reason for using MapCache) only displays in Google Earth when I'm
zoomed very far out (so that the entire globe is not much bigger
than a golf ball on my screen). If I zoom in, the image usually
disappears; though sometimes when zoomed in I do see [only] the
right (east) half of my tileset, at a very low resolution.
Do you see anything wrong with my mapcache.xml (below)? Is there
anything else I should be checking?
(I'm using a simple disk cache in /tmp, with mod_mapcache from
the Ubuntu libmapcache 1.0.0-3 package; Mapserver 6.2.1 is on the
same machine, running in 64-bit Ubuntu 12.04. Mapserver works
fine, and reports no errors [I think]. My client is Google Earth
7.)
Thanks for taking a look,
- John D. Evans GST, Inc / Greenbelt, MD
Below is my mapcache.xml file (actually an excerpt of it: the
real one has more tilesets and sources).
<mapcache> <metadata> <title>my mapcache service</title>
<abstract>woot! this is a service abstract!</abstract>
</metadata>
<cache name="disk" type="disk"> <base>/tmp</base>
<symlink_blank/> </cache>
<format name="PNG_BEST" type ="PNG">
<compression>best</compression> </format> <format name="PNG_FAST"
type ="PNG"> <compression>fast</compression> </format>
<source name="CSPP_CloudPhase" type="wms"> <http>
<url>http://localhost/cgi-bin/mapserv?</url> </http> <getmap>
<params> <FORMAT>image/png</FORMAT>
<LAYERS>iicmocp_daily</LAYERS> <MAP>/raid/maps/viirs.map</MAP>
</params> </getmap> </source>
<tileset name="CSPP_Cloud_Phase_EDR"> <metadata> <title>VIIRS
Cloud Phase from NASA GSFC DRL</title> <abstract>Detailed
description goes here</abstract> </metadata>
<source>CSPP_CloudPhase</source> <cache>disk</cache>
<format>PNG</format> <grid>WGS84</grid> <metatile>2 2</metatile>
<expires>3600 <tel:3600></expires> <auto_expire>3600
<tel:3600></auto_expire> <!-- <metabuffer>10</metabuffer> -->
</tileset>
<default_format>PNG_FAST</default_format>
<service type="wms" enabled="true">
<full_wms>assemble</full_wms>
<resample_mode>bilinear</resample_mode>
<format>PNG_FAST</format> <!-- <maxsize>4096</maxsize> -->
</service>
<service type="wmts" enabled="true"/> <service type="tms"
enabled="true"/> <service type="kml" enabled="true"/> <service
type="gmaps" enabled="true"/> <service type="ve"
enabled="true"/> <service type="demo" enabled="true"/>
<lock_dir>/tmp</lock_dir> <errors>report</errors>
<threaded_fetching>true</threaded_fetching>
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