Data::Chronicle::Reader - Provides reading from an efficient data storage for volatile and time-based data
This module contains helper methods which can be used to store and retrieve information on an efficient storage with below properties:
It is assumed that data to be stored are time-based meaning they change over time and the latest version is most important for us.
The module uses Redis cache to provide efficient data storage and retrieval.
In addition to caching every incoming data, it is also stored in PostgreSQL for future retrieval.
This modules hides all the details about distribution, caching, database structure and ... from developer. He only needs to call a method to save data and another method to retrieve it. All the underlying complexities are handled by the module.
There are three important methods this module provides:
set
Given a category, name and value stores the JSONified value in Redis and PostgreSQL database under "category::name" group and also stores current system time as the timestamp for the data (Which can be used for future retrieval if we want to get data as of a specific time). Note that the value MUST be either hash-ref or array-ref.
get
Given a category and name returns the latest version of the data according to current Redis cache
get_for
Given a category, name and timestamp returns version of data under "category::name" as of the given date (using a DB lookup).
my $d = get_some_log_data(); my $chronicle_w = Data::Chronicle::Writer->new( cache_writer => $writer, db_handle => $dbh); my $chronicle_r = Data::Chronicle::Reader->new( cache_reader => $reader, db_handle => $dbh); my $chronicle_r2 = Data::Chronicle::Reader->new( cache_reader => $hash_ref); #store data into Chronicle - each time we call `set` it will also store #a copy of the data for historical data retrieval $chronicle_w->set("log_files", "syslog", $d); #retrieve latest data stored for syslog under log_files category my $dt = $chronicle_r->get("log_files", "syslog"); #find historical data for `syslog` at given point in time my $some_old_data = $chronicle_r->get_for("log_files", "syslog", $epoch1);
cahce_reader can be an object which has `get` method used to fetch data. or it can be a plain hash-ref.
my $data = get("category1", "name1")
Query for the latest data under "category1::name1" from the cache reader. Will return `undef` if the data does not exist.
my $data = get_for("category1", "name1", 1447401505)
Query Pg archive for the data under "category1::name1" at or exactly before the given epoch/Date::Utility.
my $data = get_for_period("category1", "name1", 1447401505, 1447401900)
Query Pg historical data and return records whose date is between given period.
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Please report any bugs or feature requests to bug-data-chronicle at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Data-Chronicle. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
bug-data-chronicle at rt.cpan.org
You can find documentation for this module with the perldoc command.
perldoc Data::Chronicle::Reader
You can also look for information at:
RT: CPAN's request tracker (report bugs here)
http://rt.cpan.org/NoAuth/Bugs.html?Dist=Data-Chronicle
AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/Data-Chronicle
CPAN Ratings
http://cpanratings.perl.org/d/Data-Chronicle
Search CPAN
http://search.cpan.org/dist/Data-Chronicle/
To install Data::Chronicle, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Data::Chronicle
CPAN shell
perl -MCPAN -e shell install Data::Chronicle
For more information on module installation, please visit the detailed CPAN module installation guide.