1DBIx::Class::Storage::DUBsIe:r:RCeopnltirciDabBtuIetxde::d::CPPloeaorslls(:3D:)oSctuomreangtea:t:iDoBnI::Replicated::Pool(3)
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NAME

6       DBIx::Class::Storage::DBI::Replicated::Pool - Manage a pool of
7       replicants
8

SYNOPSIS

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

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

20       This class defines the following attributes.
21
22   maximum_lag ($num)
23       This is a number which defines the maximum allowed lag returned by the
24       "lag_behind_master" in DBIx::Class::Storage::DBI method.  The default
25       is 0.  In general, this should return a larger number when the
26       replicant is lagging behind its master, however the implementation of
27       this is database specific, so don't count on this number having a fixed
28       meaning.  For example, MySQL will return a number of seconds that the
29       replicating database is lagging.
30
31   last_validated
32       This is an integer representing a time since the last time the
33       replicants were validated. It's nothing fancy, just an integer provided
34       via the perl time built-in.
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36   replicant_type ($classname)
37       Base class used to instantiate replicants that are in the pool.  Unless
38       you need to subclass DBIx::Class::Storage::DBI::Replicated::Replicant
39       you should just leave this alone.
40
41   replicants
42       A hashref of replicant, with the key being the dsn and the value
43       returning the actual replicant storage.  For example, if the $dsn
44       element is something like:
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46         "dbi:SQLite:dbname=dbfile"
47
48       You could access the specific replicant via:
49
50         $schema->storage->replicants->{'dbname=dbfile'}
51
52       This attributes also supports the following helper methods:
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54       set_replicant($key=>$storage)
55           Pushes a replicant onto the HashRef under $key
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57       get_replicant($key)
58           Retrieves the named replicant
59
60       has_replicants
61           Returns true if the Pool defines replicants.
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63       num_replicants
64           The number of replicants in the pool
65
66       delete_replicant ($key)
67           Removes the replicant under $key from the pool
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69   master
70       Reference to the master Storage.
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METHODS

73       This class defines the following methods.
74
75   connect_replicants ($schema, Array[$connect_info])
76       Given an array of $dsn or connect_info structures suitable for
77       connected to a database, create an
78       DBIx::Class::Storage::DBI::Replicated::Replicant object and store it in
79       the "replicants" attribute.
80
81   connect_replicant ($schema, $connect_info)
82       Given a schema object and a hashref of $connect_info, connect the
83       replicant and return it.
84
85   _safely_ensure_connected ($replicant)
86       The standard ensure_connected method with throw an exception should it
87       fail to connect.  For the master database this is desirable, but since
88       replicants are allowed to fail, this behavior is not desirable.  This
89       method wraps the call to ensure_connected in an eval in order to catch
90       any generated errors.  That way a slave can go completely offline (e.g.
91       the box itself can die) without bringing down your entire pool of
92       databases.
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94   _safely ($replicant, $name, $code)
95       Execute $code for operation $name catching any exceptions and printing
96       an error message to the "<$replicant-"debugobj>>.
97
98       Returns 1 on success and undef on failure.
99
100   connected_replicants
101       Returns true if there are connected replicants.  Actually is overloaded
102       to return the number of replicants.  So you can do stuff like:
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104         if( my $num_connected = $storage->has_connected_replicants ) {
105           print "I have $num_connected connected replicants";
106         } else {
107           print "Sorry, no replicants.";
108         }
109
110       This method will actually test that each replicant in the "replicants"
111       hashref is actually connected, try not to hit this 10 times a second.
112
113   active_replicants
114       This is an array of replicants that are considered to be active in the
115       pool.  This does not check to see if they are connected, but if they
116       are not, DBIC should automatically reconnect them for us when we hit
117       them with a query.
118
119   all_replicants
120       Just a simple array of all the replicant storages.  No particular order
121       to the array is given, nor should any meaning be derived.
122
123   validate_replicants
124       This does a check to see if 1) each replicate is connected (or
125       reconnectable), 2) that is ->is_replicating, and 3) that it is not
126       exceeding the lag amount defined by "maximum_lag".  Replicants that
127       fail any of these tests are set to inactive, and thus removed from the
128       replication pool.
129
130       This tests "all_replicants", since a replicant that has been previous
131       marked as inactive can be reactivated should it start to pass the
132       validation tests again.
133
134       See DBIx::Class::Storage::DBI for more about checking if a replicating
135       connection is not following a master or is lagging.
136
137       Calling this method will generate queries on the replicant databases so
138       it is not recommended that you run them very often.
139
140       This method requires that your underlying storage engine supports some
141       sort of native replication mechanism.  Currently only MySQL native
142       replication is supported.  Your patches to make other replication types
143       work are welcomed.
144

FURTHER QUESTIONS?

146       Check the list of additional DBIC resources.
147
149       This module is free software copyright by the DBIx::Class (DBIC)
150       authors. You can redistribute it and/or modify it under the same terms
151       as the DBIx::Class library.
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155perl v5.34.0                    DB2I0x2:1:-C0l7a-s2s2::Storage::DBI::Replicated::Pool(3)
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