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DBIx::Class::Storage::User:ContributedCPerl:Dotorage::DBI::Replicated::Pool(3)

NAME
       DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of
       replicants

SYNOPSIS
       This class is used internally by	DBIx::Class::Storage::DBI::Replicated.
       You shouldn't need to create instances of this class.

DESCRIPTION
       In a replicated storage type, there is at least one replicant to	handle
       the read-only traffic.  The Pool	class manages this replicant, or list
       of replicants, and gives	some methods for querying information about
       their status.

ATTRIBUTES
       This class defines the following	attributes.

   maximum_lag ($num)
       This is a number	which defines the maximum allowed lag returned by the
       "lag_behind_master" in DBIx::Class::Storage::DBI	method.	 The default
       is 0.  In general, this should return a larger number when the
       replicant is lagging behind its master, however the implementation of
       this is database	specific, so don't count on this number	having a fixed
       meaning.	 For example, MySQL will return	a number of seconds that the
       replicating database is lagging.

   last_validated
       This is an integer representing a time since the	last time the
       replicants were validated. It's nothing fancy, just an integer provided
       via the perl time built-in.

   replicant_type ($classname)
       Base class used to instantiate replicants that are in the pool.	Unless
       you need	to subclass DBIx::Class::Storage::DBI::Replicated::Replicant
       you should just leave this alone.

   replicants
       A hashref of replicant, with the	key being the dsn and the value
       returning the actual replicant storage.	For example, if	the $dsn
       element is something like:

	 "dbi:SQLite:dbname=dbfile"

       You could access	the specific replicant via:

	 $schema->storage->replicants->{'dbname=dbfile'}

       This attributes also supports the following helper methods:

       set_replicant($key=>$storage)
	   Pushes a replicant onto the HashRef under $key

       get_replicant($key)
	   Retrieves the named replicant

       has_replicants
	   Returns true	if the Pool defines replicants.

       num_replicants
	   The number of replicants in the pool

       delete_replicant	($key)
	   Removes the replicant under $key from the pool

   master
       Reference to the	master Storage.

METHODS
       This class defines the following	methods.

   connect_replicants ($schema,	Array[$connect_info])
       Given an	array of $dsn or connect_info structures suitable for
       connected to a database,	create an
       DBIx::Class::Storage::DBI::Replicated::Replicant	object and store it in
       the "replicants"	attribute.

   connect_replicant ($schema, $connect_info)
       Given a schema object and a hashref of $connect_info, connect the
       replicant and return it.

   _safely_ensure_connected ($replicant)
       The standard ensure_connected method with throw an exception should it
       fail to connect.	 For the master	database this is desirable, but	since
       replicants are allowed to fail, this behavior is	not desirable.	This
       method wraps the	call to	ensure_connected in an eval in order to	catch
       any generated errors.  That way a slave can go completely offline (e.g.
       the box itself can die) without bringing	down your entire pool of
       databases.

   _safely ($replicant,	$name, $code)
       Execute $code for operation $name catching any exceptions and printing
       an error	message	to the "<$replicant-"debugobj>>.

       Returns 1 on success and	undef on failure.

   connected_replicants
       Returns true if there are connected replicants.	Actually is overloaded
       to return the number of replicants.  So you can do stuff	like:

	 if( my	$num_connected = $storage->has_connected_replicants ) {
	   print "I have $num_connected	connected replicants";
	 } else	{
	   print "Sorry, no replicants.";
	 }

       This method will	actually test that each	replicant in the "replicants"
       hashref is actually connected, try not to hit this 10 times a second.

   active_replicants
       This is an array	of replicants that are considered to be	active in the
       pool.  This does	not check to see if they are connected,	but if they
       are not,	DBIC should automatically reconnect them for us	when we	hit
       them with a query.

   all_replicants
       Just a simple array of all the replicant	storages.  No particular order
       to the array is given, nor should any meaning be	derived.

   validate_replicants
       This does a check to see	if 1) each replicate is	connected (or
       reconnectable), 2) that is ->is_replicating, and	3) that	it is not
       exceeding the lag amount	defined	by "maximum_lag".  Replicants that
       fail any	of these tests are set to inactive, and	thus removed from the
       replication pool.

       This tests "all_replicants", since a replicant that has been previous
       marked as inactive can be reactivated should it start to	pass the
       validation tests	again.

       See DBIx::Class::Storage::DBI for more about checking if	a replicating
       connection is not following a master or is lagging.

       Calling this method will	generate queries on the	replicant databases so
       it is not recommended that you run them very often.

       This method requires that your underlying storage engine	supports some
       sort of native replication mechanism.  Currently	only MySQL native
       replication is supported.  Your patches to make other replication types
       work are	welcomed.

FURTHER	QUESTIONS?
       Check the list of additional DBIC resources.

COPYRIGHT AND LICENSE
       This module is free software copyright by the DBIx::Class (DBIC)
       authors.	You can	redistribute it	and/or modify it under the same	terms
       as the DBIx::Class library.

perl v5.32.1			DBIx::Class::Storage::DBI::Replicated::Pool(3)

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | METHODS | FURTHER QUESTIONS? | COPYRIGHT AND LICENSE

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