NAME

       DBD::Gofer::Transport::Base - base class for DBD::Gofer client transports

SYNOPSIS

         my $remote_dsn = "..."
         DBI->connect("dbi:Gofer:transport=...;url=...;timeout=...;retry_limit=...;dsn=$remote_dsn",...)

       or, enable by setting the DBI_AUTOPROXY environment variable:

         export DBI_AUTOPROXY='dbi:Gofer:transport=...;url=...'

       which will force all DBI connections to be made via that Gofer server.

DESCRIPTION

       This is the base class for all DBD::Gofer client transports.

ATTRIBUTES

       Gofer transport attributes can be specified either in the attributes parameter of the
       connect() method call, or in the DSN string. When used in the DSN string, attribute names
       don't have the "go_" prefix.

   go_dsn
       The full DBI DSN that the Gofer server should connect to on your behalf.

       When used in the DSN it must be the last element in the DSN string.

   go_timeout
       A time limit for sending a request and receiving a response. Some drivers may implement
       sending and receiving as separate steps, in which case (currently) the timeout applies to
       each separately.

       If a request needs to be resent then the timeout is restarted for each sending of a
       request and receiving of a response.

   go_retry_limit
       The maximum number of times an request may be retried. The default is 2.

   go_retry_hook
       This subroutine reference is called, if defined, for each response received where
       $response->err is true.

       The subroutine is pass three parameters: the request object, the response object, and the
       transport object.

       If it returns an undefined value then the default retry behaviour is used. See "RETRY ON
       ERROR" below.

       If it returns a defined but false value then the request is not resent.

       If it returns true value then the request is resent, so long as the number of retries does
       not exceed "go_retry_limit".

RETRY ON ERROR

       The default retry on error behaviour is:

        - Retry if the error was due to DBI_GOFER_RANDOM. See L<DBI::Gofer::Execute>.

        - Retry if $request->is_idempotent returns true. See L<DBI::Gofer::Request>.

       A retry won't be allowed if the number of previous retries has reached "go_retry_limit".

TRACING

       Tracing of gofer requests and responses can be enabled by setting the "DBD_GOFER_TRACE"
       environment variable. A value of 1 gives a reasonably compact summary of each request and
       response. A value of 2 or more gives a detailed, and voluminous, dump.

       The trace is written using DBI->trace_msg() and so is written to the default DBI trace
       output, which is usually STDERR.

METHODS

       This section is currently far from complete.

   response_retry_preference
         $retry = $transport->response_retry_preference($request, $response);

       The response_retry_preference is called by DBD::Gofer when considering if a request should
       be retried after an error.

       Returns true (would like to retry), false (must not retry), undef (no preference).

       If a true value is returned in the form of a CODE ref then, if DBD::Gofer does decide to
       retry the request, it calls the code ref passing $retry_count, $retry_limit.  Can be used
       for logging and/or to implement exponential backoff behaviour.  Currently the called code
       must return using "return;" to allow for future extensions.

AUTHOR

       Tim Bunce, <http://www.tim.bunce.name>

LICENCE AND COPYRIGHT

       Copyright (c) 2007-2008, Tim Bunce, Ireland. All rights reserved.

       This module is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself. See perlartistic.

SEE ALSO

       DBD::Gofer, DBI::Gofer::Request, DBI::Gofer::Response, DBI::Gofer::Execute.

       and some example transports:

       DBD::Gofer::Transport::stream

       DBD::Gofer::Transport::http

       DBI::Gofer::Transport::mod_perl