Hello,
Despite being one of "the mapcache devs", I have no answer to the second
question. This involves MapCache connection pool which uses APR pools
and which I am not familiar with:
https://github.com/MapServer/mapcache/blob/8b4d277df4f7951edd84e4fb8903dc544c3315a9/lib/connection_pool.c#L153
As for the first question, "d1" is not a magical value: this is just a
placeholder in the documentation for an actual default time value or
time interval.
https://mapserver.org/mapcache/dimensions.html?highlight=d1#configuring-a-time-dimension-using-an-explicit-back-end
Jerome
Le 18/01/2022 à 02:52, David Hoese a écrit :
Trygve,
Hello from outside the Pytroll community ;)
I can't answer your second question as I don't have much experience
with getCapabilities, but I think I have an answer for the first
question. My understanding for the `default` parameter was that that
was the returned time string if no times were returned by the query
(empty result). I have always expected this to be a normal time string
like 2022-01-01T12:00:00Z (to match your expected format. However, the
fact that you always get the oldest image when the default is "d1" is
surprising to me so I hope the mapcache devs can correct me.
As for the source code for this, I found that the default from the XML
goes into a dimension object as "default_value". It then gets set as
the default "requested_value" like here:
https://github.com/MapServer/mapcache/blob/447c0c6848fd101c11e6d54e451037e571117ef1/lib/tileset.c#L585
Going down the rabbit hole led me to here:
https://github.com/MapServer/mapcache/blob/447c0c6848fd101c11e6d54e451037e571117ef1/lib/dimension_pg.c#L265-L271
As far as I can tell "get_values_for_entry_query" is just the
"validate_query" query from your XML config. So somehow your validate
query with "dp1" input may be returning the oldest time in your
database. Just a guess. I'm interested in this answer, but definitely
not the best person to give it to you.
Dave
On 1/17/22 11:59, Trygve Aspenes wrote:
Hi there!
Slowly I'm getting mapserver/mapcache up running and looks now how to
improve things.
First: When I load a mapcache tileset with time dimension from a pg
db the oldest image is displayed in my client. Is it possible to
somehow get the newest image as default?
My tileset dimension look something like this:
<dimension type="postgresql" name="time" default="d1"
time="true" unit="ISO8601">
<connection>
host=mapserver-db user=$PGSQ_USERNAME
password=$PGSQ_PASSWORD dbname=mapserver port=5432
</connection>
<list_query>SELECT to_char(time,
'YYYY-MM-DD"T"HH24:MI:SS"Z"') FROM products where product_name='<some
product>' order by Id</list_query>
<validate_query>
SELECT
to_char(time,'YYYY-MM-DD"T"HH24:MI:SS"Z"') FROM products
WHERE time >= to_timestamp(:start_timestamp)
AND time <= to_timestamp(:end_timestamp)
AND product_name='<some product>'
ORDER BY time DESC
</validate_query>
</dimension>
I saw the `d1` default value in the documentation, but don't
understand of that is a dummy or an actual selector. I have grepped
around the source code, but could not see anything obvious.
Second: My client updates/fetch the getCapabilities of my mapcache
server every minute. Each time this is fetched the mapcache log is
filled with messages like:
mod_mapcache.c(164): [client ] tearing down pooled connection
(dim_<some product>_time) to make room, referer: <my client>
I dont understand why these connections is teared down every time
getCapabilites is requested.
I have looked in the documentation, but could not see how to control
this. But in the mapcache.xml.sample the connection pool config is
described. But adding this to my mapcache config does not remove
these tear downs.
<connection_pool>
<max_connections>2000</max_connections>
<time_to_live_us>120000000</time_to_live_us>
</connection_pool>
Any suggestions why this connection tear down is happening and if
there is something to do about it. It slows down the getCapabilities
request a bit, but if I add to many tileset I guess this will even
further slow down.
Thanks
Trygve Aspenes
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