That's very helpful and just what I needed to know. Thanks, Bruce!<div><br clear="all"> -- John<br>
<br><br><div class="gmail_quote">On Tue, Sep 25, 2012 at 11:41 AM, Bruce Weertman <span dir="ltr"><<a href="mailto:bruce@iris.washington.edu" target="_blank">bruce@iris.washington.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
John:<br>
<br>
Good to hear from you.<br>
<br>
A few points about caching:<br>
<br>
* Yes ws-dataselect and ws-tracedsp do cache the data.<br>
<br>
* The cache is very specific to the request that you make.<br>
<br>
If you asked for some time period from some channel and then asked for exactly the same<br>
time period from the same channel, you would hit the cache and it should return much faster.<br>
If the second request's time range was just a fraction of a second different than there first's, you would not<br>
as there would then be two objects in the cache. This is because the 'token' to the cached objects<br>
are generated from hashes of request parameters. Changing a request in just the slightest<br>
way will generate a completely different hash.<br>
<br>
* ws-bulkdataselect does not cache data.<br>
<br>
* The underlying NFS filesystem which holds the archive and everything else we do here and the DMC<br>
does some caching of it's own. Going to datasets that are close to each other can result in sped up<br>
requests as a result. Performance may vary depending on many different factors including<br>
system load and how close to each other subsequent queries are.<br>
<br>
<br>
Hope that helps.<br>
<br>
Cheers,<br>
-Bruce<br>
<div><div class="h5"><br>
<br>
<br>
On Sep 25, 2012, at 11:17 AM, John D. West wrote:<br>
<br>
> Hello.<br>
><br>
> I am working on code that retrieves corrected traces from the DMC using the dataselect and tracedsp web services. I notice that a second retrieval of the same data is much, much faster, presumably because the data is being cached by the DMC web services. I am retrieving broadband 40Hz data in 60-hour increments.<br>
><br>
> Do these web services cache more data than I ask for? Can I speed up my requests by either sequentially asking for data for the same channel (i.e., ask for 60 hours of BHZ for a station, then ask for the next 60 hours, etc.) or by asking for multiple traces for the same time period (i.e., 60 hours of BHZ, then 60 hours of BHE & BHN for the same station & time span)?<br>
><br>
> Thanks!<br>
><br>
> -- John<br>
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</blockquote></div><br></div>