I think we're all on the same page here. The Standard report typically involves 14 file generations, so the function get_extension_list() will be invoked 14 times. If that's taking a long time, I would suggest trying to restructuring the SLE so the get_extension_list() invocation is not so expensive. For example, perhaps the parameters for the invocation could be stored in the object, but not actually do anything unless the tag is used (lazy evaluation). Or, if all 14 of those expensive invocations are identical, put it in __init__(), instead of get_extension_list(), then do it just once and store the results.
Of course, if the expensive calculation needs to be done for every template and they are all different, then there's no way around it. But, I find it hard to imagine such a case. -tk On Thu, Apr 5, 2018 at 6:58 AM, gjr80 <[email protected]> wrote: > Tom, > > Perhaps I am not understanding you correctly, but I have run into this > issue a number of times with a processing intensive SLE. Whether or not any > of the tags created by the SLE are used, the SLE is run in its entirety for > each template listed in the skin. For example, I have a SLE that returns > some rain related tags and it takes about 1 second for get_extension_list() > to execute. I included this SLE in the search_list_extensions list in the > Standard skin.conf. None of the tags returned by the SLE are used in any > template in the Standard skin, yet during the report cycle the SLE is > invoked 15 times in total taking a little over 15 seconds in total. > > I can understand that the TimeBinder 'chain' is more efficient in that > time consuming tasks such as db queries only occur if the tag is 'hit', but > not every SLE uses the TimeBinder chain approach. I think that is the issue > Rich is seeing (and I have encountered in the past) > > Gary > > On Thursday, 5 April 2018 22:47:06 UTC+10, Tom Keffer wrote: >> >> Hello, Rich. >> >> I'm afraid I'm not quite understanding your situation. >> >> There are 3 different occasions when your SLE may come into play: >> >> 1. When the Cheetah report generator starts up. This is when your SLE >> gets instantiated, that is, its __init__ function, if any, gets invoked. >> This happens only once per report generation. >> 2. When a template gets generated. This is when get_extension_list() >> is invoked, which happens once per template. For the standard search list >> that comes with weeWX, this is when the top of the tag chain (class >> TimeBinder), described in How tags work >> <http://weewx.com/docs/customizing.htm#how_tags_work>, gets created, >> however, the chain itself does not actually get chased. >> 3. When looking for a tag. The Cheetah template engine will probe all >> the search list extensions looking for a specific tag. It does this by >> calling __getattr__ repeatedly with the tag name as an argument --- a >> cheap >> call. If it finds a hit, then this is typically when the expensive stuff >> starts happening. Note that this probing will happen *for every tag*, >> whether your tag or not. But, the rest of the tag chain gets invoked only >> if Cheetah finds a hit. For the search list that comes with weeWX nothing >> expensive happens until the very end of the tag chain. That's when the >> database lookups start happening. >> >> You say your expensive calculation is happening 14 times. If you have 14 >> of your tags sprinkled throughout the templates, then this is unavoidable: >> 14 requests for your tag, 14 calculations. However, if you expect all 14 >> tags to produce the same results (an example would be $station.altitude) >> then you should be doing your calculation farther up the stack described >> above. Perhaps you should be doing the calculation in get_extension_list() >> or even __init__. >> >> I hope this make sense. If not, give us some more specifics. >> >> Cheers, >> >> -tk >> >> >> On Wed, Apr 4, 2018 at 10:26 PM, gjr80 <[email protected]> wrote: >> >>> Hi Rich, >>> >>> Unfortunately the SLEs are applied to each report in a skin. Can you >>> pull out the template concerned into its own skin and use the SLE in that >>> skin only? >>> >>> Gary >>> >>> >>> On Thursday, 5 April 2018 14:59:13 UTC+10, Rich Altmaier wrote: >>>> >>>> I'm creating a Report extension which is fairly expensive to >>>> calculate. When I add my extension to skin.conf, with the usual >>>> search_list_extensions under CheetahGenerator, I find my extension is >>>> invoked about 14 times, which costs many seconds. Is it possible to make >>>> a Report extension apply to a selected file generation, such as in >>>> generating index.html only? >>>> Thank you! >>>> Rich >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "weewx-user" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google Groups > "weewx-user" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
