Geo::Coder::Many - Module to tie together multiple Geo::Coder::* modules
Geo::Coder::Many is based on Geo::Coder::Multiple, but tries to be more flexible about how the wrapped geocoders are used.
Amongst other things, Geo::Coder::Many adds geocoder precision information, alternative scheduling methods (weighted random, and ordered list), timeouts for geocoders which are failing, and optional callbacks for result filtering and picking.
General steps for using Geo::Coder::Many:
new
add_geocoder
geocode
Suppose the geocoders we want to use are called 'Locatorize' and 'WhereIzIt'.
use Geo::Coder::Locatorize; use Geo::Coder::WhereIzIt; use Geo::Coder::Many; use Geo::Coder::Many::Util qw( country_filter ); # Create the Geo::Coder::Many object, telling it to use a 'weighted random' # scheduling method my $options = { cache => $cache_object, scheduler_type => 'WRR', }; my $geocoder_many = Geo::Coder::Many->new( $options ); # Create and add a geocoder my $Locatorize = Geo::Coder::Locatorize->new( appid => 'mY_loCat0r1Ze_iD' ); my $Locatorize_options = { geocoder => $Locatorize, daily_limit => 2500, }; $geocoder_many->add_geocoder( $Locatorize_options ); # Create and add a second geocoder my $WhereIzIt = Geo::Coder::WhereIzIt->new( apikey => 'mY_WhERiz1t_kEy' ); my $WhereIzIt_options = { geocoder => $WhereIzIt, daily_limit => 4000, }; $geocoder_many->add_geocoder( $WhereIzIt_options ); # Use a filter callback from Geo::Coder::Many::Util $geocoder_many->set_filter_callback(country_filter('United Kingdom')); # Use a built-in picker callback $geocoder_many->set_picker_callback('max_precision'); my $result = $geocoder_many->geocode( { location => '82 Clerkenwell Road, London' } ); if (defined $result) { print "Country: ", $result->{country}, "\n"; print "Longitude: ", $result->{longitude}, "\n"; print "Latitude: ", $result->{latitude}, "\n"; print "Location: ", $result->{location}, "\n"; print "Response code: ", $result->{response_code}, "\n"; print "Address: ", $result->{address}, "\n"; print "Precision: ", $result->{precision}, "\n"; print "Geocoder: ", $result->{geocoder}, "\n"; } else { print "Failed to geocode!\n"; }
Constructs a new Geo::Coder::Many object and returns it. Options should be provided as the entries of a hash reference, as follows:
KEY VALUE ----------- -------------------- cache Cache object reference (optional) normalize_code_ref A normalization code ref (optional) scheduler_type Name of the scheduler type to use (default: WRR) use_timeouts Whether to time out failing geocoders (default: false)
If no cache option is specified, no caching will be done for the geocoding results.
cache
normalize_code_ref is a code reference which is used to normalize location strings to ensure that all cache keys are normalized for correct lookup.
normalize_code_ref
scheduler_type specifies how load balancing should be done.
scheduler_type
Scheduling schemes currently available are:
Round-robin scheduling, weighted by the daily_limit values for the geocoders (The same behaviour as Geo::Coder::Multiple)
A strict preferential ordering by daily_limit - the geocoder with the highest limit will always be used. If that fails, the next highest will be used, and so on.
Geocoders will be picked at random, each with probability proportional to its specified daily_limit.
Other scheduling schemes can be implemented by sub-classing Geo::Coder::Many::Scheduler or Geo::Coder::Many::UniquenessScheduler.
If use_timeouts is true, geocoders that are unsuccessful will not be queried again for a set amount of time. The timeout period will increase exponentially for every successive consecutive failure.
use_timeouts
This method adds a geocoder to the list of possibilities.
Before any geocoding can be performed, at least one geocoder must be added to the list of available geocoders.
If the same geocoder is added twice, only the instance added first will be used. All other additions will be ignored.
KEY VALUE ----------- -------------------- geocoder geocoder object reference (required) daily_limit geocoder source limit per 24 hour period (required)
geocoder should be a reference to a Geo::Coder::Something object, where 'Something' is a supported geocoder type. For a geocoder to be supported, it needs to have a corresponding Geo::Coder::Many::Something adapter module.
geocoder
Note that daily_limit is just treated as guideline for the chosen scheduler, and will not necessarily be strictly obeyed.
daily_limit
Sets the callback used for filtering results. By default, all results are passed through. If a callback is set, only results for which the callback returns true are passed through. The callback takes one argument: a Response object to be judged for fitness. It should return true or false, depending on whether that Response is deemed suitable for consideration by the picker.
Sets the callback used for result picking. This determines which single result will actually be returned by the geocode method. By default, the first valid result (that has passed the filter callback, if one was set) is returned.
As an alternative to passing a subroutine reference, you can pass a scalar with a name that refers to one of the built-in callbacks. An empty string or 'first' sets the behaviour back to the default: accept the first result that is offered. 'max_precision' fetches all results and chooses the one with the greatest precision value.
The picker callback has two arguments: a reference to an array of the valid results that have been collected so far, and a value that is true if there are more results available and false otherwise. The callback should return a single result from the list, if one is acceptable. If none are acceptable, the callback may return undef, indicating that more results to pick from are desired. If these are available, the picker will be called again once they have been added to the results array.
Note that since geocoders are not (currently) queried in parallel, a picker that requires lots of results to make a decision may take longer to return a value.
my $options = { location => $location, results_cache => $cache, }; my $found_location = $geocoder_many->geocode( $options );
Arguments should be provided in a hash reference with the following entries:
KEY VALUE ----------- -------------------- location location string to pass to geocoder results_cache reference to a cache object; will override the default no_cache if set, the result will not be retrieved or set in cache (off by default) wait_for_retries if set, the method will wait until it's sure all geocoders have been tried (off by default)
This method is the basis for the class, it will retrieve result from cache first, and return if cache hit.
If the cache is missed, the geocode method is called, with the location as the argument, on the next available geocoder object in the sequence.
If called in an array context all the matching results will be returned, otherwise the first result will be returned.
A matching address will have the following keys in the hash reference.
KEY VALUE ----------- -------------------- response_code integer response code (see below) address matched address latitude latitude of matched address longitude longitude of matched address country country of matched address (not available for all geocoders) geocoder source used to lookup address location the original query string precision scalar ranging from 0.0 to 1.0, denoting the granularity of the result (undef if not known)
The geocoder key will contain a string denoting which geocoder returned the results (eg, 'locatorize').
The response_code key will contain the response code. The possible values are:
response_code
200 Success 210 Success (from cache) 401 Unable to find location 402 All geocoder limits reached (not yet implemented)
geocode will return undef if none of the geocoders that were tried produced a result that satisfied the filter and picker callbacks.
Takes a result hash and a Response object and mashes them into a single flat hash, allowing results from different geocoders to be more easily assimilated
Given a name and a list of mappings from names to code references, do a fuzzy lookup of the name and return the appropriate subroutine.
Checks that a response is defined and has a valid response code,
Check a response passes the filter callback (if one is set).
Returns a list of the geocoders that have been added to the Many geocoder.
Requests the next geocoder from the scheduler and looks it up in the geocoders hash.
Assigns weights to the current geocoders, and initialises the scheduler as appropriate.
Returns an instance of the currently-set scheduler, with the specified geocoders.
Set the list of cache objects
Test the cache to ensure it has 'get', 'set' and 'remove' methods
Store the result in the cache
Check the cache to see if the data is available
Use the provided normalize_code_ref callback (if one is set) to return a normalized string to use as a cache key.
All cache objects used must support 'get', 'set' and 'remove' methods.
The input (location) string is expected to be in utf-8. Incorrectly encoded strings will make for unreliable geocoding results. All strings returned will be in utf-8. returned latitude and longitude co-ordinates will be in WGS84 format.
In the case of an error, this module will print a warning and then may call die().
The Geo::Coder::* modules added to the geocoding source list must have a geocode method which takes a single location string as an argument.
Currently supported Geo::Coder::* modules are:
Geo::Coder::Bing Geo::Coder::Google Geo::Coder::Mapquest Geo::Coder::Multimap Geo::Coder::OSM Geo::Coder::PlaceFinder Geo::Coder::Yahoo
Originally Dan Horgan (http://search.cpan.org/~danhgn/) This module is maintained by the team members of Lokku Ltd. (http://www.lokku.com)
Geo::Coder::Many was originally based on Geo::Coder::Multiple, which unfortunately seems to no longer be maintained (by Alistair Francis http://search.cpan.org/~friffin/)
Patches are welcome! Please send any code or feedback to cpan@lokku.com
A number of the feature ideas are taken directly from Tim Bunce's blog:
http://blog.timbunce.org/2010/06/09/high-quality-multi-source-geocoding-in-perl/
(Needless to say, neither he nor anybody else should be held responsible for any deficiencies in the implementation!)
If reducing your dependancy on geo information providers is your thing- and really, who doesn't enjoy breaking dependancy? - you'll probably enjoy Mapstraction - http://www.mapstraction.com
Copyright 2010 Lokku Ltd <cpan@lokku.com>
Parts taken from Geo::Coder::Multiple are copyright 2009 Alistair Francis <opensource@alizta.com>
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10 or, at your option, any later version of Perl 5 you may have available.
To install Geo::Coder::Many, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Geo::Coder::Many
CPAN shell
perl -MCPAN -e shell install Geo::Coder::Many
For more information on module installation, please visit the detailed CPAN module installation guide.