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=head1 NAME |
2 |
|
3 |
AnyEvent::DBI - asynchronous DBI access |
4 |
|
5 |
=head1 SYNOPSIS |
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|
7 |
use AnyEvent::DBI; |
8 |
|
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my $cv = AnyEvent->condvar; |
10 |
|
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my $dbh = new AnyEvent::DBI "DBI:SQLite:dbname=test.db", "", ""; |
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|
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$dbh->exec ("select * from test where num=?", 10, sub { |
14 |
my ($dbh, $rows, $rv) = @_; |
15 |
|
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$#_ or die "failure: $@"; |
17 |
|
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print "@$_\n" |
19 |
for @$rows; |
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|
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$cv->broadcast; |
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}); |
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|
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# asynchronously do sth. else here |
25 |
|
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$cv->wait; |
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|
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=head1 DESCRIPTION |
29 |
|
30 |
This module is an L<AnyEvent> user, you need to make sure that you use and |
31 |
run a supported event loop. |
32 |
|
33 |
This module implements asynchronous DBI access by forking or executing |
34 |
separate "DBI-Server" processes and sending them requests. |
35 |
|
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It means that you can run DBI requests in parallel to other tasks. |
37 |
|
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With DBD::mysql, the overhead for very simple statements |
39 |
("select 0") is somewhere around 50% compared to an explicit |
40 |
prepare_cached/execute/fetchrow_arrayref/finish combination. With |
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DBD::SQlite3, it's more like a factor of 8 for this trivial statement. |
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|
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=head2 ERROR HANDLING |
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|
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This module defines a number of functions that accept a callback |
46 |
argument. All callbacks used by this module get their AnyEvent::DBI handle |
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object passed as first argument. |
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|
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If the request was successful, then there will be more arguments, |
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otherwise there will only be the C<$dbh> argument and C<$@> contains an |
51 |
error message. |
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|
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A convenient way to check whether an error occurred is to check C<$#_> - |
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if that is true, then the function was successful, otherwise there was an |
55 |
error. |
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|
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=cut |
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|
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package AnyEvent::DBI; |
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|
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use common::sense; |
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|
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use Carp; |
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use Convert::Scalar (); |
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use AnyEvent::Fork (); |
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use CBOR::XS (); |
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|
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use AnyEvent (); |
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use AnyEvent::Util (); |
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|
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use Errno (); |
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|
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our $VERSION = '3.04'; |
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|
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=head2 METHODS |
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|
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=over 4 |
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|
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=item $dbh = new AnyEvent::DBI $database, $user, $pass, [key => value]... |
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|
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Returns a database handle for the given database. Each database handle |
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has an associated server process that executes statements in order. If |
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you want to run more than one statement in parallel, you need to create |
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additional database handles. |
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|
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The advantage of this approach is that transactions work as state is |
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preserved. |
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|
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Example: |
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|
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$dbh = new AnyEvent::DBI |
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"DBI:mysql:test;mysql_read_default_file=/root/.my.cnf", "", ""; |
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|
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Additional key-value pairs can be used to adjust behaviour: |
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|
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=over 4 |
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|
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=item on_error => $callback->($dbh, $filename, $line, $fatal) |
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|
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When an error occurs, then this callback will be invoked. On entry, C<$@> |
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is set to the error message. C<$filename> and C<$line> is where the |
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original request was submitted. |
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|
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If the fatal argument is true then the database connection is shut down |
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and your database handle became invalid. In addition to invoking the |
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C<on_error> callback, all of your queued request callbacks are called |
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without only the C<$dbh> argument. |
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|
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If omitted, then C<die> will be called on any errors, fatal or not. |
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|
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=item on_connect => $callback->($dbh[, $success]) |
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|
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If you supply an C<on_connect> callback, then this callback will be |
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invoked after the database connect attempt. If the connection succeeds, |
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C<$success> is true, otherwise it is missing and C<$@> contains the |
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C<$DBI::errstr>. |
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|
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Regardless of whether C<on_connect> is supplied, connect errors will result in |
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C<on_error> being called. However, if no C<on_connect> callback is supplied, then |
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connection errors are considered fatal. The client will C<die> and the C<on_error> |
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callback will be called with C<$fatal> true. |
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|
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When on_connect is supplied, connect error are not fatal and AnyEvent::DBI |
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will not C<die>. You still cannot, however, use the $dbh object you |
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received from C<new> to make requests. |
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|
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=item fork_template => $AnyEvent::Fork-object |
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|
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C<AnyEvent::DBI> uses C<< AnyEvent::Fork->new >> to create the database |
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slave, which in turn either C<exec>'s a new process (similar to the old |
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C<exec_server> constructor argument) or uses a process forked early (see |
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L<AnyEvent::Fork::Early>). |
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|
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With this argument you can provide your own fork template. This can be |
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useful if you create a lot of C<AnyEvent::DBI> handles and want to save |
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memory (And speed up startup) by not having to load C<AnyEvent::DBI> again |
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and again into your child processes: |
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|
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my $template = AnyEvent::Fork |
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->new # create new template |
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->require ("AnyEvent::DBI::Slave"); # preload AnyEvent::DBI::Slave module |
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|
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for (...) { |
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$dbh = new AnyEvent::DBI ... |
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fork_template => $template; |
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|
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=item timeout => seconds |
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|
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If you supply a timeout parameter (fractional values are supported), then |
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a timer is started any time the DBI handle expects a response from the |
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server. This includes connection setup as well as requests made to the |
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backend. The timeout spans the duration from the moment the first data |
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is written (or queued to be written) until all expected responses are |
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returned, but is postponed for "timeout" seconds each time more data is |
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returned from the server. If the timer ever goes off then a fatal error is |
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generated. If you have an C<on_error> handler installed, then it will be |
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called, otherwise your program will die(). |
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|
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When altering your databases with timeouts it is wise to use |
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transactions. If you quit due to timeout while performing insert, update |
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or schema-altering commands you can end up not knowing if the action was |
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submitted to the database, complicating recovery. |
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|
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Timeout errors are always fatal. |
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|
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=back |
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|
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Any additional key-value pairs will be rolled into a hash reference |
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and passed as the final argument to the C<< DBI->connect (...) >> |
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call. For example, to suppress errors on STDERR and send them instead to an |
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AnyEvent::Handle you could do: |
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|
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$dbh = new AnyEvent::DBI |
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"DBI:mysql:test;mysql_read_default_file=/root/.my.cnf", "", "", |
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PrintError => 0, |
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on_error => sub { |
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$log_handle->push_write ("DBI Error: $@ at $_[1]:$_[2]\n"); |
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}; |
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|
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=cut |
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|
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sub new { |
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my ($class, $dbi, $user, $pass, %arg) = @_; |
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|
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# we use our own socketpair, so we always have a socket |
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# available, even before the forked process exsist. |
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# this is mostly done so this module is compatible |
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# to versions of itself older than 3.0. |
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my ($client, $server) = AnyEvent::Util::portable_socketpair |
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or croak "unable to create AnyEvent::DBI communications pipe: $!"; |
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|
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AnyEvent::fh_unblock $client; |
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|
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my $fork = delete $arg{fork_template}; |
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|
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my %dbi_args = %arg; |
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delete @dbi_args{qw(on_connect on_error timeout fork_template exec_server)}; |
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|
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my $self = bless \%arg, $class; |
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|
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$self->{fh} = $client; |
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|
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my $rbuf; |
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my @caller = (caller)[1,2]; # the "default" caller |
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|
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$fork = $fork ? $fork->fork : AnyEvent::Fork->new |
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or croak "fork: $!"; |
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|
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$fork->require ("AnyEvent::DBI::Slave"); |
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$fork->send_arg ($VERSION); |
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$fork->send_fh ($server); |
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|
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# we don't rely on the callback, because we use our own |
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# socketpair, for better or worse. |
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$fork->run ("AnyEvent::DBI::Slave::serve", sub { }); |
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|
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{ |
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Convert::Scalar::weaken (my $self = $self); |
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|
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my $cbor = new CBOR::XS; |
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|
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$self->{rw} = AE::io $client, 0, sub { |
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my $len = Convert::Scalar::extend_read $client, $rbuf, 65536; |
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|
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if ($len > 0) { |
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# we received data, so reset the timer |
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$self->{last_activity} = AE::now; |
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|
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for my $res ($cbor->incr_parse_multiple ($rbuf)) { |
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last unless $self; |
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|
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my $req = shift @{ $self->{queue} }; |
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|
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if (defined $res->[0]) { |
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$res->[0] = $self; |
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$req->[0](@$res); |
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} else { |
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my $cb = shift @$req; |
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local $@ = $res->[1]; |
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$cb->($self); |
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$self->_error ($res->[1], @$req, $res->[2]) # error, request record, is_fatal |
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if $self; # cb() could have deleted it |
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} |
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|
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# no more queued requests, so become idle |
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if ($self && !@{ $self->{queue} }) { |
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undef $self->{last_activity}; |
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$self->{tw_cb}->(); |
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} |
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} |
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|
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} elsif (defined $len) { |
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# todo, caller? |
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$self->_error ("unexpected eof", @caller, 1); |
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} elsif ($! != Errno::EAGAIN) { |
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# todo, caller? |
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$self->_error ("read error: $!", @caller, 1); |
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} |
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}; |
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|
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$self->{tw_cb} = sub { |
262 |
if ($self->{timeout} && $self->{last_activity}) { |
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if (AE::now > $self->{last_activity} + $self->{timeout}) { |
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# we did time out |
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my $req = $self->{queue}[0]; |
266 |
$self->_error (timeout => $req->[1], $req->[2], 1); # timeouts are always fatal |
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} else { |
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# we need to re-set the timeout watcher |
269 |
$self->{tw} = AE::timer |
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$self->{last_activity} + $self->{timeout} - AE::now, |
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0, |
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$self->{tw_cb}, |
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; |
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} |
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} else { |
276 |
# no timeout check wanted, or idle |
277 |
undef $self->{tw}; |
278 |
} |
279 |
}; |
280 |
|
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$self->{ww_cb} = sub { |
282 |
$self->{last_activity} = AE::now; |
283 |
|
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my $len = syswrite $client, $self->{wbuf} |
285 |
or return delete $self->{ww}; |
286 |
|
287 |
substr $self->{wbuf}, 0, $len, ""; |
288 |
}; |
289 |
} |
290 |
|
291 |
$self->_req ( |
292 |
sub { |
293 |
return unless $self; |
294 |
$self->{child_pid} = $_[1]; |
295 |
}, |
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(caller)[1,2], |
297 |
"req_pid" |
298 |
); |
299 |
|
300 |
$self->_req ( |
301 |
sub { |
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return unless $self; |
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&{ $self->{on_connect} } if $self->{on_connect}; |
304 |
}, |
305 |
(caller)[1,2], |
306 |
req_open => $dbi, $user, $pass, %dbi_args |
307 |
); |
308 |
|
309 |
$self |
310 |
} |
311 |
|
312 |
sub _server_pid { |
313 |
shift->{child_pid} |
314 |
} |
315 |
|
316 |
sub kill_child { |
317 |
my $self = shift; |
318 |
|
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if (my $pid = delete $self->{child_pid}) { |
320 |
# kill and reap process |
321 |
my $kid_watcher; $kid_watcher = AE::child $pid, sub { |
322 |
undef $kid_watcher; |
323 |
}; |
324 |
kill TERM => $pid; |
325 |
} |
326 |
|
327 |
delete $self->{rw}; |
328 |
delete $self->{ww}; |
329 |
delete $self->{tw}; |
330 |
close delete $self->{fh}; |
331 |
} |
332 |
|
333 |
sub DESTROY { |
334 |
shift->kill_child; |
335 |
} |
336 |
|
337 |
sub _error { |
338 |
my ($self, $error, $filename, $line, $fatal) = @_; |
339 |
|
340 |
if ($fatal) { |
341 |
delete $self->{tw}; |
342 |
delete $self->{rw}; |
343 |
delete $self->{ww}; |
344 |
delete $self->{fh}; |
345 |
|
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# for fatal errors call all enqueued callbacks with error |
347 |
while (my $req = shift @{$self->{queue}}) { |
348 |
local $@ = $error; |
349 |
$req->[0]->($self); |
350 |
} |
351 |
$self->kill_child; |
352 |
} |
353 |
|
354 |
local $@ = $error; |
355 |
|
356 |
if ($self->{on_error}) { |
357 |
$self->{on_error}($self, $filename, $line, $fatal) |
358 |
} else { |
359 |
die "$error at $filename, line $line\n"; |
360 |
} |
361 |
} |
362 |
|
363 |
=item $dbh->on_error ($cb->($dbh, $filename, $line, $fatal)) |
364 |
|
365 |
Sets (or clears, with C<undef>) the C<on_error> handler. |
366 |
|
367 |
=cut |
368 |
|
369 |
sub on_error { |
370 |
$_[0]{on_error} = $_[1]; |
371 |
} |
372 |
|
373 |
=item $dbh->timeout ($seconds) |
374 |
|
375 |
Sets (or clears, with C<undef>) the database timeout. Useful to extend the |
376 |
timeout when you are about to make a really long query. |
377 |
|
378 |
=cut |
379 |
|
380 |
sub timeout { |
381 |
my ($self, $timeout) = @_; |
382 |
|
383 |
$self->{timeout} = $timeout; |
384 |
|
385 |
# reschedule timer if one was running |
386 |
$self->{tw_cb}->(); |
387 |
} |
388 |
|
389 |
sub _req { |
390 |
my ($self, $cb, $filename, $line) = splice @_, 0, 4, (); |
391 |
|
392 |
unless ($self->{fh}) { |
393 |
local $@ = my $err = 'no database connection'; |
394 |
$cb->($self); |
395 |
$self->_error ($err, $filename, $line, 1); |
396 |
return; |
397 |
} |
398 |
|
399 |
push @{ $self->{queue} }, [$cb, $filename, $line]; |
400 |
|
401 |
# re-start timeout if necessary |
402 |
if ($self->{timeout} && !$self->{tw}) { |
403 |
$self->{last_activity} = AE::now; |
404 |
$self->{tw_cb}->(); |
405 |
} |
406 |
|
407 |
$self->{wbuf} .= CBOR::XS::encode_cbor \@_; |
408 |
|
409 |
unless ($self->{ww}) { |
410 |
my $len = syswrite $self->{fh}, $self->{wbuf}; |
411 |
substr $self->{wbuf}, 0, $len, ""; |
412 |
|
413 |
# still any left? then install a write watcher |
414 |
$self->{ww} = AE::io $self->{fh}, 1, $self->{ww_cb} |
415 |
if length $self->{wbuf}; |
416 |
} |
417 |
} |
418 |
|
419 |
=item $dbh->attr ($attr_name[, $attr_value], $cb->($dbh, $new_value)) |
420 |
|
421 |
An accessor for the database handle attributes, such as C<AutoCommit>, |
422 |
C<RaiseError>, C<PrintError> and so on. If you provide an C<$attr_value> |
423 |
(which might be C<undef>), then the given attribute will be set to that |
424 |
value. |
425 |
|
426 |
The callback will be passed the database handle and the attribute's value |
427 |
if successful. |
428 |
|
429 |
If an error occurs and the C<on_error> callback returns, then only C<$dbh> |
430 |
will be passed and C<$@> contains the error message. |
431 |
|
432 |
=item $dbh->exec ("statement", @args, $cb->($dbh, \@rows, $rv)) |
433 |
|
434 |
Executes the given SQL statement with placeholders replaced by |
435 |
C<@args>. The statement will be prepared and cached on the server side, so |
436 |
using placeholders is extremely important. |
437 |
|
438 |
The callback will be called with a weakened AnyEvent::DBI object as the |
439 |
first argument and the result of C<fetchall_arrayref> as (or C<undef> |
440 |
if the statement wasn't a select statement) as the second argument. |
441 |
|
442 |
Third argument is the return value from the C<< DBI->execute >> method |
443 |
call. |
444 |
|
445 |
If an error occurs and the C<on_error> callback returns, then only C<$dbh> |
446 |
will be passed and C<$@> contains the error message. |
447 |
|
448 |
=item $dbh->stattr ($attr_name, $cb->($dbh, $value)) |
449 |
|
450 |
An accessor for the statement attributes of the most recently executed |
451 |
statement, such as C<NAME> or C<TYPE>. |
452 |
|
453 |
The callback will be passed the database handle and the attribute's value |
454 |
if successful. |
455 |
|
456 |
If an error occurs and the C<on_error> callback returns, then only C<$dbh> |
457 |
will be passed and C<$@> contains the error message. |
458 |
|
459 |
=item $dbh->begin_work ($cb->($dbh[, $rc])) |
460 |
|
461 |
=item $dbh->commit ($cb->($dbh[, $rc])) |
462 |
|
463 |
=item $dbh->rollback ($cb->($dbh[, $rc])) |
464 |
|
465 |
The begin_work, commit, and rollback methods expose the equivalent |
466 |
transaction control method of the DBI driver. On success, C<$rc> is true. |
467 |
|
468 |
If an error occurs and the C<on_error> callback returns, then only C<$dbh> |
469 |
will be passed and C<$@> contains the error message. |
470 |
|
471 |
=item $dbh->func ('string_which_yields_args_when_evaled', $func_name, $cb->($dbh, $rc, $dbi_err, $dbi_errstr)) |
472 |
|
473 |
This gives access to database driver private methods. Because they |
474 |
are not standard you cannot always depend on the value of C<$rc> or |
475 |
C<$dbi_err>. Check the documentation for your specific driver/function |
476 |
combination to see what it returns. |
477 |
|
478 |
Note that the first argument will be eval'ed to produce the argument list to |
479 |
the func() method. This must be done because the serialization protocol |
480 |
between the AnyEvent::DBI server process and your program does not support the |
481 |
passage of closures. |
482 |
|
483 |
Here's an example to extend the query language in SQLite so it supports an |
484 |
intstr() function: |
485 |
|
486 |
$cv = AnyEvent->condvar; |
487 |
$dbh->func ( |
488 |
q{ |
489 |
instr => 2, sub { |
490 |
my ($string, $search) = @_; |
491 |
return index $string, $search; |
492 |
}, |
493 |
}, |
494 |
create_function => sub { |
495 |
return $cv->send ($@) |
496 |
unless $#_; |
497 |
$cv->send (undef, @_[1,2,3]); |
498 |
} |
499 |
); |
500 |
|
501 |
my ($err,$rc,$errcode,$errstr) = $cv->recv; |
502 |
|
503 |
die $err if defined $err; |
504 |
die "EVAL failed: $errstr" |
505 |
if $errcode; |
506 |
|
507 |
# otherwise, we can ignore $rc and $errcode for this particular func |
508 |
|
509 |
=cut |
510 |
|
511 |
for my $cmd_name (qw(attr exec stattr begin_work commit rollback func)) { |
512 |
eval 'sub ' . $cmd_name . '{ |
513 |
my $cb = pop; |
514 |
splice @_, 1, 0, $cb, (caller)[1,2], "req_' . $cmd_name . '"; |
515 |
&_req |
516 |
}'; |
517 |
} |
518 |
|
519 |
=back |
520 |
|
521 |
=head1 SEE ALSO |
522 |
|
523 |
L<AnyEvent>, L<DBI>, L<Coro::Mysql>. |
524 |
|
525 |
=head1 AUTHOR AND CONTACT |
526 |
|
527 |
Marc Lehmann <schmorp@schmorp.de> (current maintainer) |
528 |
http://home.schmorp.de/ |
529 |
|
530 |
Adam Rosenstein <adam@redcondor.com> |
531 |
http://www.redcondor.com/ |
532 |
|
533 |
=cut |
534 |
|
535 |
1 |