# -*- perl -*- # # # DBD::Proxy - DBI Proxy driver # # # Copyright (c) 1997,1998 Jochen Wiedmann # # The DBD::Proxy module is free software; you can redistribute it and/or # modify it under the same terms as Perl itself. In particular permission # is granted to Tim Bunce for distributing this as a part of the DBI. # # # Author: Jochen Wiedmann # Am Eisteich 9 # 72555 Metzingen # Germany # # Email: joe@ispsoft.de # Phone: +49 7123 14881 # use strict; use Carp; require DBI; DBI->require_version(1.0201); use RPC::PlClient 0.2000; # XXX change to 0.2017 once it's released { package DBD::Proxy::RPC::PlClient; @DBD::Proxy::RPC::PlClient::ISA = qw(RPC::PlClient); sub Call { my $self = shift; if ($self->{debug}) { my ($rpcmeth, $obj, $method, @args) = @_; local $^W; # silence undefs Carp::carp("Server $rpcmeth $method(@args)"); } return $self->SUPER::Call(@_); } } package DBD::Proxy; use vars qw($VERSION $drh %ATTR); $VERSION = "0.2004"; $drh = undef; # holds driver handle once initialised %ATTR = ( # common to db & st, see also %ATTR in DBD::Proxy::db & ::st 'Warn' => 'local', 'Active' => 'local', 'Kids' => 'local', 'CachedKids' => 'local', 'PrintError' => 'local', 'RaiseError' => 'local', 'HandleError' => 'local', 'TraceLevel' => 'cached', 'CompatMode' => 'local', ); sub driver ($$) { if (!$drh) { my($class, $attr) = @_; $class .= "::dr"; $drh = DBI::_new_drh($class, { 'Name' => 'Proxy', 'Version' => $VERSION, 'Attribution' => 'DBD::Proxy by Jochen Wiedmann', }); $drh->STORE(CompatMode => 1); # disable DBI dispatcher attribute cache (for FETCH) } $drh; } sub CLONE { undef $drh; } sub proxy_set_err { my ($h,$errmsg) = @_; my ($err, $state) = ($errmsg =~ s/ \[err=(.*?),state=(.*?)\]//) ? ($1, $2) : (1, ' ' x 5); return $h->set_err($err, $errmsg, $state); } package DBD::Proxy::dr; # ====== DRIVER ====== $DBD::Proxy::dr::imp_data_size = 0; sub connect ($$;$$) { my($drh, $dsn, $user, $auth, $attr)= @_; my($dsnOrig) = $dsn; my %attr = %$attr; my ($var, $val); while (length($dsn)) { if ($dsn =~ /^dsn=(.*)/) { $attr{'dsn'} = $1; last; } if ($dsn =~ /^(.*?);(.*)/) { $var = $1; $dsn = $2; } else { $var = $dsn; $dsn = ''; } if ($var =~ /^(.*?)=(.*)/) { $var = $1; $val = $2; $attr{$var} = $val; } } my $err = ''; if (!defined($attr{'hostname'})) { $err .= " Missing hostname."; } if (!defined($attr{'port'})) { $err .= " Missing port."; } if (!defined($attr{'dsn'})) { $err .= " Missing remote dsn."; } # Create a cipher object, if requested my $cipherRef = undef; if ($attr{'cipher'}) { $cipherRef = eval { $attr{'cipher'}->new(pack('H*', $attr{'key'})) }; if ($@) { $err .= " Cannot create cipher object: $@."; } } my $userCipherRef = undef; if ($attr{'userkey'}) { my $cipher = $attr{'usercipher'} || $attr{'cipher'}; $userCipherRef = eval { $cipher->new(pack('H*', $attr{'userkey'})) }; if ($@) { $err .= " Cannot create usercipher object: $@."; } } return DBD::Proxy::proxy_set_err($drh, $err) if $err; # Returns undef my %client_opts = ( 'peeraddr' => $attr{'hostname'}, 'peerport' => $attr{'port'}, 'socket_proto' => 'tcp', 'application' => $attr{dsn}, 'user' => $user || '', 'password' => $auth || '', 'version' => $DBD::Proxy::VERSION, 'cipher' => $cipherRef, 'debug' => $attr{debug} || 0, 'timeout' => $attr{timeout} || undef, 'logfile' => $attr{logfile} || undef ); # Options starting with 'proxy_rpc_' are forwarded to the RPC layer after # stripping the prefix. while (my($var,$val) = each %attr) { if ($var =~ s/^proxy_rpc_//) { $client_opts{$var} = $val; } } # Create an RPC::PlClient object. my($client, $msg) = eval { DBD::Proxy::RPC::PlClient->new(%client_opts) }; return DBD::Proxy::proxy_set_err($drh, "Cannot log in to DBI::ProxyServer: $@") if $@; # Returns undef return DBD::Proxy::proxy_set_err($drh, "Constructor didn't return a handle: $msg") unless ($msg =~ /^((?:\w+|\:\:)+)=(\w+)/); # Returns undef $msg = RPC::PlClient::Object->new($1, $client, $msg); my $max_proto_ver; my ($server_ver_str) = eval { $client->Call('Version') }; if ( $@ ) { # Server denies call, assume legacy protocol. $max_proto_ver = 1; } else { # Parse proxy server version. my ($server_ver_num) = $server_ver_str =~ /^DBI::ProxyServer\s+([\d\.]+)/; $max_proto_ver = $server_ver_num >= 0.3 ? 2 : 1; } my $req_proto_ver; if ( exists $attr{proxy_lazy_prepare} ) { $req_proto_ver = ($attr{proxy_lazy_prepare} == 0) ? 2 : 1; return DBD::Proxy::proxy_set_err($drh, "DBI::ProxyServer does not support synchronous statement preparation.") if $max_proto_ver < $req_proto_ver; } # Switch to user specific encryption mode, if desired if ($userCipherRef) { $client->{'cipher'} = $userCipherRef; } # create a 'blank' dbh my $this = DBI::_new_dbh($drh, { 'Name' => $dsnOrig, 'proxy_dbh' => $msg, 'proxy_client' => $client, 'RowCacheSize' => $attr{'RowCacheSize'} || 20, 'proxy_proto_ver' => $req_proto_ver || 1 }); foreach $var (keys %attr) { if ($var =~ /proxy_/) { $this->{$var} = $attr{$var}; } } $this->SUPER::STORE('Active' => 1); $this; } sub DESTROY { undef } package DBD::Proxy::db; # ====== DATABASE ====== $DBD::Proxy::db::imp_data_size = 0; # XXX probably many more methods need to be added here # in order to trigger our AUTOLOAD to redirect them to the server. # (Unless the sub is declared it's bypassed by perl method lookup.) # See notes in ToDo about method metadata # The question is whether to add all the methods in %DBI::DBI_methods # to the corresponding classes (::db, ::st etc) # Also need to consider methods that, if proxied, would change the server state # in a way that might not be visible on the client, ie begin_work -> AutoCommit. sub commit; sub connected; sub rollback; sub ping; use vars qw(%ATTR $AUTOLOAD); # inherited: STORE / FETCH against this class. # local: STORE / FETCH against parent class. # cached: STORE to remote and local objects, FETCH from local. # remote: STORE / FETCH against remote object only (default). # # Note: Attribute names starting with 'proxy_' always treated as 'inherited'. # %ATTR = ( # see also %ATTR in DBD::Proxy::st %DBD::Proxy::ATTR, RowCacheSize => 'inherited', #AutoCommit => 'cached', 'FetchHashKeyName' => 'cached', Statement => 'local', Driver => 'local', dbi_connect_closure => 'local', Username => 'local', ); sub AUTOLOAD { my $method = $AUTOLOAD; $method =~ s/(.*::(.*)):://; my $class = $1; my $type = $2; #warn "AUTOLOAD of $method (class=$class, type=$type)"; my %expand = ( 'method' => $method, 'class' => $class, 'type' => $type, 'call' => "$method(\@_)", # XXX was trying to be smart but was tripping up over the DBI's own # smartness. Disabled, but left here in case there are issues. # 'call' => (UNIVERSAL::can("DBI::_::$type", $method)) ? "$method(\@_)" : "func(\@_, '$method')", ); my $method_code = q{ package ~class~; sub ~method~ { my $h = shift; local $@; my @result = wantarray ? eval { $h->{'proxy_~type~h'}->~call~ } : eval { scalar $h->{'proxy_~type~h'}->~call~ }; return DBD::Proxy::proxy_set_err($h, $@) if $@; return wantarray ? @result : $result[0]; } }; $method_code =~ s/\~(\w+)\~/$expand{$1}/eg; local $SIG{__DIE__} = 'DEFAULT'; my $err = do { local $@; eval $method_code.2; $@ }; die $err if $err; goto &$AUTOLOAD; } sub DESTROY { my $dbh = shift; local $@ if $@; # protect $@ $dbh->disconnect if $dbh->SUPER::FETCH('Active'); } sub disconnect ($) { my ($dbh) = @_; # Sadly the Proxy too-often disagrees with the backend database # on the subject of 'Active'. In the short term, I'd like the # Proxy to ease up and let me decide when it's proper to go over # the wire. This ultimately applies to finish() as well. #return unless $dbh->SUPER::FETCH('Active'); # Drop database connection at remote end my $rdbh = $dbh->{'proxy_dbh'}; if ( $rdbh ) { local $SIG{__DIE__} = 'DEFAULT'; local $@; eval { $rdbh->disconnect() } ; DBD::Proxy::proxy_set_err($dbh, $@) if $@; } # Close TCP connect to remote # XXX possibly best left till DESTROY? Add a config attribute to choose? #$dbh->{proxy_client}->Disconnect(); # Disconnect method requires newer PlRPC module $dbh->{proxy_client}->{socket} = undef; # hack $dbh->SUPER::STORE('Active' => 0); 1; } sub STORE ($$$) { my($dbh, $attr, $val) = @_; my $type = $ATTR{$attr} || 'remote'; if ($attr eq 'TraceLevel') { warn("TraceLevel $val"); my $pc = $dbh->{proxy_client} || die; $pc->{logfile} ||= 1; # XXX hack $pc->{debug} = ($val && $val >= 4); $pc->Debug("$pc debug enabled") if $pc->{debug}; } if ($attr =~ /^proxy_/ || $type eq 'inherited') { $dbh->{$attr} = $val; return 1; } if ($type eq 'remote' || $type eq 'cached') { local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $dbh->{'proxy_dbh'}->STORE($attr => $val) }; return DBD::Proxy::proxy_set_err($dbh, $@) if $@; # returns undef $dbh->SUPER::STORE($attr => $val) if $type eq 'cached'; return $result; } return $dbh->SUPER::STORE($attr => $val); } sub FETCH ($$) { my($dbh, $attr) = @_; # we only get here for cached attribute values if the handle is in CompatMode # otherwise the DBI dispatcher handles the FETCH itself from the attribute cache. my $type = $ATTR{$attr} || 'remote'; if ($attr =~ /^proxy_/ || $type eq 'inherited' || $type eq 'cached') { return $dbh->{$attr}; } return $dbh->SUPER::FETCH($attr) unless $type eq 'remote'; local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $dbh->{'proxy_dbh'}->FETCH($attr) }; return DBD::Proxy::proxy_set_err($dbh, $@) if $@; return $result; } sub prepare ($$;$) { my($dbh, $stmt, $attr) = @_; my $sth = DBI::_new_sth($dbh, { 'Statement' => $stmt, 'proxy_attr' => $attr, 'proxy_cache_only' => 0, 'proxy_params' => [], } ); my $proto_ver = $dbh->{'proxy_proto_ver'}; if ( $proto_ver > 1 ) { $sth->{'proxy_attr_cache'} = {cache_filled => 0}; my $rdbh = $dbh->{'proxy_dbh'}; local $SIG{__DIE__} = 'DEFAULT'; local $@; my $rsth = eval { $rdbh->prepare($sth->{'Statement'}, $sth->{'proxy_attr'}, undef, $proto_ver) }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; return DBD::Proxy::proxy_set_err($sth, "Constructor didn't return a handle: $rsth") unless ($rsth =~ /^((?:\w+|\:\:)+)=(\w+)/); my $client = $dbh->{'proxy_client'}; $rsth = RPC::PlClient::Object->new($1, $client, $rsth); $sth->{'proxy_sth'} = $rsth; # If statement is a positioned update we do not want any readahead. $sth->{'RowCacheSize'} = 1 if $stmt =~ /\bfor\s+update\b/i; # Since resources are used by prepared remote handle, mark us active. $sth->SUPER::STORE(Active => 1); } $sth; } sub quote { my $dbh = shift; my $proxy_quote = $dbh->{proxy_quote} || 'remote'; return $dbh->SUPER::quote(@_) if $proxy_quote eq 'local' && @_ == 1; # For the common case of only a single argument # (no $data_type) we could learn and cache the behaviour. # Or we could probe the driver with a few test cases. # Or we could add a way to ask the DBI::ProxyServer # if $dbh->can('quote') == \&DBI::_::db::quote. # Tim # # Sounds all *very* smart to me. I'd rather suggest to # implement some of the typical quote possibilities # and let the user set # $dbh->{'proxy_quote'} = 'backslash_escaped'; # for example. # Jochen local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $dbh->{'proxy_dbh'}->quote(@_) }; return DBD::Proxy::proxy_set_err($dbh, $@) if $@; return $result; } sub table_info { my $dbh = shift; my $rdbh = $dbh->{'proxy_dbh'}; #warn "table_info(@_)"; local $SIG{__DIE__} = 'DEFAULT'; local $@; my($numFields, $names, $types, @rows) = eval { $rdbh->table_info(@_) }; return DBD::Proxy::proxy_set_err($dbh, $@) if $@; my ($sth, $inner) = DBI::_new_sth($dbh, { 'Statement' => "SHOW TABLES", 'proxy_params' => [], 'proxy_data' => \@rows, 'proxy_attr_cache' => { 'NUM_OF_PARAMS' => 0, 'NUM_OF_FIELDS' => $numFields, 'NAME' => $names, 'TYPE' => $types, 'cache_filled' => 1 }, 'proxy_cache_only' => 1, }); $sth->SUPER::STORE('NUM_OF_FIELDS' => $numFields); $inner->{NAME} = $names; $inner->{TYPE} = $types; $sth->SUPER::STORE('Active' => 1); # already execute()'d $sth->{'proxy_rows'} = @rows; return $sth; } sub tables { my $dbh = shift; #warn "tables(@_)"; return $dbh->SUPER::tables(@_); } sub type_info_all { my $dbh = shift; local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $dbh->{'proxy_dbh'}->type_info_all(@_) }; return DBD::Proxy::proxy_set_err($dbh, $@) if $@; return $result; } package DBD::Proxy::st; # ====== STATEMENT ====== $DBD::Proxy::st::imp_data_size = 0; use vars qw(%ATTR); # inherited: STORE to current object. FETCH from current if exists, else call up # to the (proxy) database object. # local: STORE / FETCH against parent class. # cache_only: STORE noop (read-only). FETCH from private_* if exists, else call # remote and cache the result. # remote: STORE / FETCH against remote object only (default). # # Note: Attribute names starting with 'proxy_' always treated as 'inherited'. # %ATTR = ( # see also %ATTR in DBD::Proxy::db %DBD::Proxy::ATTR, 'Database' => 'local', 'RowsInCache' => 'local', 'RowCacheSize' => 'inherited', 'NULLABLE' => 'cache_only', 'NAME' => 'cache_only', 'TYPE' => 'cache_only', 'PRECISION' => 'cache_only', 'SCALE' => 'cache_only', 'NUM_OF_FIELDS' => 'cache_only', 'NUM_OF_PARAMS' => 'cache_only' ); *AUTOLOAD = \&DBD::Proxy::db::AUTOLOAD; sub execute ($@) { my $sth = shift; my $params = @_ ? \@_ : $sth->{'proxy_params'}; # new execute, so delete any cached rows from previous execute undef $sth->{'proxy_data'}; undef $sth->{'proxy_rows'}; my $rsth = $sth->{proxy_sth}; my $dbh = $sth->FETCH('Database'); my $proto_ver = $dbh->{proxy_proto_ver}; my ($numRows, @outData); local $SIG{__DIE__} = 'DEFAULT'; local $@; if ( $proto_ver > 1 ) { ($numRows, @outData) = eval { $rsth->execute($params, $proto_ver) }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; # Attributes passed back only on the first execute() of a statement. unless ($sth->{proxy_attr_cache}->{cache_filled}) { my ($numFields, $numParams, $names, $types) = splice(@outData, 0, 4); $sth->{'proxy_attr_cache'} = { 'NUM_OF_FIELDS' => $numFields, 'NUM_OF_PARAMS' => $numParams, 'NAME' => $names, 'cache_filled' => 1 }; $sth->SUPER::STORE('NUM_OF_FIELDS' => $numFields); $sth->SUPER::STORE('NUM_OF_PARAMS' => $numParams); } } else { if ($rsth) { ($numRows, @outData) = eval { $rsth->execute($params, $proto_ver) }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; } else { my $rdbh = $dbh->{'proxy_dbh'}; # Legacy prepare is actually prepare + first execute on the server. ($rsth, @outData) = eval { $rdbh->prepare($sth->{'Statement'}, $sth->{'proxy_attr'}, $params, $proto_ver) }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; return DBD::Proxy::proxy_set_err($sth, "Constructor didn't return a handle: $rsth") unless ($rsth =~ /^((?:\w+|\:\:)+)=(\w+)/); my $client = $dbh->{'proxy_client'}; $rsth = RPC::PlClient::Object->new($1, $client, $rsth); my ($numFields, $numParams, $names, $types) = splice(@outData, 0, 4); $sth->{'proxy_sth'} = $rsth; $sth->{'proxy_attr_cache'} = { 'NUM_OF_FIELDS' => $numFields, 'NUM_OF_PARAMS' => $numParams, 'NAME' => $names }; $sth->SUPER::STORE('NUM_OF_FIELDS' => $numFields); $sth->SUPER::STORE('NUM_OF_PARAMS' => $numParams); $numRows = shift @outData; } } # Always condition active flag. $sth->SUPER::STORE('Active' => 1) if $sth->FETCH('NUM_OF_FIELDS'); # is SELECT $sth->{'proxy_rows'} = $numRows; # Any remaining items are output params. if (@outData) { foreach my $p (@$params) { if (ref($p->[0])) { my $ref = shift @outData; ${$p->[0]} = $$ref; } } } $sth->{'proxy_rows'} || '0E0'; } sub fetch ($) { my $sth = shift; my $data = $sth->{'proxy_data'}; $sth->{'proxy_rows'} = 0 unless defined $sth->{'proxy_rows'}; if(!$data || !@$data) { return undef unless $sth->SUPER::FETCH('Active'); my $rsth = $sth->{'proxy_sth'}; if (!$rsth) { die "Attempt to fetch row without execute"; } my $num_rows = $sth->FETCH('RowCacheSize') || 20; local $SIG{__DIE__} = 'DEFAULT'; local $@; my @rows = eval { $rsth->fetch($num_rows) }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; unless (@rows == $num_rows) { undef $sth->{'proxy_data'}; # server side has already called finish $sth->SUPER::STORE(Active => 0); } return undef unless @rows; $sth->{'proxy_data'} = $data = [@rows]; } my $row = shift @$data; $sth->SUPER::STORE(Active => 0) if ( $sth->{proxy_cache_only} and !@$data ); $sth->{'proxy_rows'}++; return $sth->_set_fbav($row); } *fetchrow_arrayref = \&fetch; sub rows ($) { my $rows = shift->{'proxy_rows'}; return (defined $rows) ? $rows : -1; } sub finish ($) { my($sth) = @_; return 1 unless $sth->SUPER::FETCH('Active'); my $rsth = $sth->{'proxy_sth'}; $sth->SUPER::STORE('Active' => 0); return 0 unless $rsth; # Something's out of sync my $no_finish = exists($sth->{'proxy_no_finish'}) ? $sth->{'proxy_no_finish'} : $sth->FETCH('Database')->{'proxy_no_finish'}; unless ($no_finish) { local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $rsth->finish() }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; return $result; } 1; } sub STORE ($$$) { my($sth, $attr, $val) = @_; my $type = $ATTR{$attr} || 'remote'; if ($attr =~ /^proxy_/ || $type eq 'inherited') { $sth->{$attr} = $val; return 1; } if ($type eq 'cache_only') { return 0; } if ($type eq 'remote' || $type eq 'cached') { my $rsth = $sth->{'proxy_sth'} or return undef; local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $rsth->STORE($attr => $val) }; return DBD::Proxy::proxy_set_err($sth, $@) if ($@); return $result if $type eq 'remote'; # else fall through to cache locally } return $sth->SUPER::STORE($attr => $val); } sub FETCH ($$) { my($sth, $attr) = @_; if ($attr =~ /^proxy_/) { return $sth->{$attr}; } my $type = $ATTR{$attr} || 'remote'; if ($type eq 'inherited') { if (exists($sth->{$attr})) { return $sth->{$attr}; } return $sth->FETCH('Database')->{$attr}; } if ($type eq 'cache_only' && exists($sth->{'proxy_attr_cache'}->{$attr})) { return $sth->{'proxy_attr_cache'}->{$attr}; } if ($type ne 'local') { my $rsth = $sth->{'proxy_sth'} or return undef; local $SIG{__DIE__} = 'DEFAULT'; local $@; my $result = eval { $rsth->FETCH($attr) }; return DBD::Proxy::proxy_set_err($sth, $@) if $@; return $result; } elsif ($attr eq 'RowsInCache') { my $data = $sth->{'proxy_data'}; $data ? @$data : 0; } else { $sth->SUPER::FETCH($attr); } } sub bind_param ($$$@) { my $sth = shift; my $param = shift; $sth->{'proxy_params'}->[$param-1] = [@_]; } *bind_param_inout = \&bind_param; sub DESTROY { my $sth = shift; $sth->finish if $sth->SUPER::FETCH('Active'); } 1; __END__ =head1 NAME DBD::Proxy - A proxy driver for the DBI =head1 SYNOPSIS use DBI; $dbh = DBI->connect("dbi:Proxy:hostname=$host;port=$port;dsn=$db", $user, $passwd); # See the DBI module documentation for full details =head1 DESCRIPTION DBD::Proxy is a Perl module for connecting to a database via a remote DBI driver. See L for an alternative with different trade-offs. This is of course not needed for DBI drivers which already support connecting to a remote database, but there are engines which don't offer network connectivity. Another application is offering database access through a firewall, as the driver offers query based restrictions. For example you can restrict queries to exactly those that are used in a given CGI application. Speaking of CGI, another application is (or rather, will be) to reduce the database connect/disconnect overhead from CGI scripts by using proxying the connect_cached method. The proxy server will hold the database connections open in a cache. The CGI script then trades the database connect/disconnect overhead for the DBD::Proxy connect/disconnect overhead which is typically much less. I =head1 CONNECTING TO THE DATABASE Before connecting to a remote database, you must ensure, that a Proxy server is running on the remote machine. There's no default port, so you have to ask your system administrator for the port number. See L for details. Say, your Proxy server is running on machine "alpha", port 3334, and you'd like to connect to an ODBC database called "mydb" as user "joe" with password "hello". When using DBD::ODBC directly, you'd do a $dbh = DBI->connect("DBI:ODBC:mydb", "joe", "hello"); With DBD::Proxy this becomes $dsn = "DBI:Proxy:hostname=alpha;port=3334;dsn=DBI:ODBC:mydb"; $dbh = DBI->connect($dsn, "joe", "hello"); You see, this is mainly the same. The DBD::Proxy module will create a connection to the Proxy server on "alpha" which in turn will connect to the ODBC database. Refer to the L documentation on the C method for a way to automatically use DBD::Proxy without having to change your code. DBD::Proxy's DSN string has the format $dsn = "DBI:Proxy:key1=val1; ... ;keyN=valN;dsn=valDSN"; In other words, it is a collection of key/value pairs. The following keys are recognized: =over 4 =item hostname =item port Hostname and port of the Proxy server; these keys must be present, no defaults. Example: hostname=alpha;port=3334 =item dsn The value of this attribute will be used as a dsn name by the Proxy server. Thus it must have the format C, in particular it will contain colons. The I value may contain semicolons, hence this key *must* be the last and it's value will be the complete remaining part of the dsn. Example: dsn=DBI:ODBC:mydb =item cipher =item key =item usercipher =item userkey By using these fields you can enable encryption. If you set, for example, cipher=$class;key=$key (note the semicolon) then DBD::Proxy will create a new cipher object by executing $cipherRef = $class->new(pack("H*", $key)); and pass this object to the RPC::PlClient module when creating a client. See L. Example: cipher=IDEA;key=97cd2375efa329aceef2098babdc9721 The usercipher/userkey attributes allow you to use two phase encryption: The cipher/key encryption will be used in the login and authorisation phase. Once the client is authorised, he will change to usercipher/userkey encryption. Thus the cipher/key pair is a B based secret, typically less secure than the usercipher/userkey secret and readable by anyone. The usercipher/userkey secret is B private secret. Of course encryption requires an appropriately configured server. See . =item debug Turn on debugging mode =item stderr This attribute will set the corresponding attribute of the RPC::PlClient object, thus logging will not use syslog(), but redirected to stderr. This is the default under Windows. stderr=1 =item logfile Similar to the stderr attribute, but output will be redirected to the given file. logfile=/dev/null =item RowCacheSize The DBD::Proxy driver supports this attribute (which is DBI standard, as of DBI 1.02). It's used to reduce network round-trips by fetching multiple rows in one go. The current default value is 20, but this may change. =item proxy_no_finish This attribute can be used to reduce network traffic: If the application is calling $sth->finish() then the proxy tells the server to finish the remote statement handle. Of course this slows down things quite a lot, but is prefectly good for reducing memory usage with persistent connections. However, if you set the I attribute to a TRUE value, either in the database handle or in the statement handle, then finish() calls will be supressed. This is what you want, for example, in small and fast CGI applications. =item proxy_quote This attribute can be used to reduce network traffic: By default calls to $dbh->quote() are passed to the remote driver. Of course this slows down things quite a lot, but is the safest default behaviour. However, if you set the I attribute to the value 'C' either in the database handle or in the statement handle, and the call to quote has only one parameter, then the local default DBI quote method will be used (which will be faster but may be wrong). =back =head1 KNOWN ISSUES =head2 Unproxied method calls If a method isn't being proxied, try declaring a stub sub in the appropriate package (DBD::Proxy::db for a dbh method, and DBD::Proxy::st for an sth method). For example: sub DBD::Proxy::db::selectall_arrayref; That will enable selectall_arrayref to be proxied. Currently many methods aren't explicitly proxied and so you get the DBI's default methods executed on the client. Some of those methods, like selectall_arrayref, may then call other methods that are proxied (selectall_arrayref calls fetchall_arrayref which calls fetch which is proxied). So things may appear to work but operate more slowly than the could. This may all change in a later version. =head2 Complex handle attributes Sometimes handles are having complex attributes like hash refs or array refs and not simple strings or integers. For example, with DBD::CSV, you would like to write something like $dbh->{"csv_tables"}->{"passwd"} = { "sep_char" => ":", "eol" => "\n"; The above example would advice the CSV driver to assume the file "passwd" to be in the format of the /etc/passwd file: Colons as separators and a line feed without carriage return as line terminator. Surprisingly this example doesn't work with the proxy driver. To understand the reasons, you should consider the following: The Perl compiler is executing the above example in two steps: =over =item 1 The first step is fetching the value of the key "csv_tables" in the handle $dbh. The value returned is complex, a hash ref. =item 2 The second step is storing some value (the right hand side of the assignment) as the key "passwd" in the hash ref from step 1. =back This becomes a little bit clearer, if we rewrite the above code: $tables = $dbh->{"csv_tables"}; $tables->{"passwd"} = { "sep_char" => ":", "eol" => "\n"; While the examples work fine without the proxy, the fail due to a subtile difference in step 1: By DBI magic, the hash ref $dbh->{'csv_tables'} is returned from the server to the client. The client creates a local copy. This local copy is the result of step 1. In other words, step 2 modifies a local copy of the hash ref, but not the server's hash ref. The workaround is storing the modified local copy back to the server: $tables = $dbh->{"csv_tables"}; $tables->{"passwd"} = { "sep_char" => ":", "eol" => "\n"; $dbh->{"csv_tables"} = $tables; =head1 AUTHOR AND COPYRIGHT This module is Copyright (c) 1997, 1998 Jochen Wiedmann Am Eisteich 9 72555 Metzingen Germany Email: joe@ispsoft.de Phone: +49 7123 14887 The DBD::Proxy module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. In particular permission is granted to Tim Bunce for distributing this as a part of the DBI. =head1 SEE ALSO L, L, L =cut