DBIx-Connector-Retry-MySQL

MySQL-specific DBIx::Connector with retry support


License
Artistic-2.0

Documentation

NAME

DBIx::Connector::Retry::MySQL - MySQL-specific DBIx::Connector with retry support

VERSION

version v1.0.0

SYNOPSIS

my $conn = DBIx::Connector::Retry::MySQL->new(
    connect_info  => [ 'dbi:Driver:database=foobar', $user, $pass, \%args ],
    retry_debug   => 1,
    timer_options => {
        # Default options from Algorithm::Backoff::RetryTimeouts
        max_attempts          => 8,
        max_actual_duration   => 50,
        jitter_factor         => 0.1,
        timeout_jitter_factor => 0.1,
        adjust_timeout_factor => 0.5,
        min_adjust_timeout    => 5,
        # ...among others
    },
);

# Keep retrying/reconnecting on errors
my ($count) = $conn->run(ping => sub {
    $_->do('UPDATE foobar SET updated = 1 WHERE active = ?', undef, 'on');
    $_->selectrow_array('SELECT COUNT(*) FROM foobar WHERE updated = 1');
});

my ($count) = $conn->txn(fixup => sub {
    $_->selectrow_array('SELECT COUNT(*) FROM barbaz');
});

# Plus everything else in DBIx::Connector::Retry and DBIx::Connector

DESCRIPTION

DBIx::Connector::Retry::MySQL is a subclass of DBIx::Connector::Retry that will explicitly retry on MySQL-specific transient error messages, as identified by DBIx::ParseError::MySQL, using Algorithm::Backoff::RetryTimeouts as its retry algorithm. This connector should be much better at handling deadlocks, connection errors, and Galera node flips to ensure the transaction always goes through.

It is essentially a DBIx::Connector version of DBIx::Class::Storage::DBI::mysql::Retryable.

INHERITED ATTRIBUTES

This inherits all of the attributes of DBIx::Connector::Retry:

connect_info

mode

disconnect_on_destroy

max_attempts

Unlike "max_attempts" in DBIx::Connector::Retry, this is just an alias to the value in "timer_options".

As such, it has a slightly adjusted default of 8.

retry_debug

Like retry_debug, this turns on debug warnings for retries. But, this module has a bit more detail in the messages.

retry_handler

Since the whole point of the module is the retry-handling code, this attribute cannot be set.

failed_attempt_count

Unlike "failed_attempt_count" in DBIx::Connector::Retry, this is just an alias to the value in the internal timer object.

exception_stack

NEW ATTRIBUTES

timer_class

The class used for delay and timeout setting calculations. By default, it's Algorithm::Backoff::RetryTimeouts, but you can use a sub-class of this, if you so choose, provided that it has a similar interface.

timer_options

Controls all of the options passed to the timer constructor, using "timer_class" as the object.

aggressive_timeouts

Boolean that controls whether to use some of the more aggressive, query-unfriendly timeouts:

  • mysql_read_timeout

    Controls the timeout for all read operations. Since SQL queries in the middle of sending its first set of row data are still considered to be in a read operation, those queries could time out during those circumstances.

    If you're confident that you don't have any SQL statements that would take longer than the timeout settings (or at least returning results before that time), you can turn this option on. Otherwise, you may experience longer-running statements going into a retry death spiral until they hit the final timeout and die.

  • wait_timeout

    Controls how long the MySQL server waits for activity from the connection before timing out. While most applications are going to be using the database connection pretty frequently, the MySQL default (8 hours) is much much longer than the mere seconds this engine would set it to.

Default is off. Obviously, this setting makes no sense if max_actual_duration within "timeout_options" is disabled.

parse_error_class

The class used for MySQL error parsing. By default, it's DBIx::ParseError::MySQL, but you can use a sub-class of this, if you so choose, provided that it has a similar interface.

enable_retry_handler

Boolean to enable the retry handler. The default is, of course, on. This can be turned off to temporarily disable the retry handler.

CAVEATS

$dbh settings

See "$dbh settings" in DBIx::Connector::Retry.

Savepoints and nested transactions

See "Savepoints and nested transactions" in DBIx::Connector::Retry.

Connection modes

Due to the caveats of "Fixup mode" in DBIx::Connector::Retry, fixup mode is changed to just act like no_ping mode. However, no_ping mode is safer to use in this module because it comes with the same retry protections as the other modes. Certain retries, such as connection/server errors, come with an explicit disconnect to make sure it starts back up with a clean slate.

In ping mode, the DB will be pinged on the first try. If the retry explicitly disconnected, the connector will simply connect back to the DB and run the code, without a superfluous ping.

AUTHOR

Grant Street Group developers@grantstreet.com

COPYRIGHT AND LICENSE

This software is Copyright (c) 2020 - 2021 by Grant Street Group.

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)