POE::Component::SimpleUser3Contributed Perl DocumePOE::Component::SimpleDBI(3)NAMEPOE::Component::SimpleDBI - Asynchronous non-blocking DBI calls in POE
made simple
SYNOPSIS
use POE;
use POE::Component::SimpleDBI;
# Create a new session with the alias we want
POE::Component::SimpleDBI->new( 'SimpleDBI' ) or die 'Unable to create the DBI session';
# Create our own session to communicate with SimpleDBI
POE::Session->create(
inline_states => {
_start => sub {
# Tell SimpleDBI to connect
$_[KERNEL]->post( 'SimpleDBI', 'CONNECT',
'DSN' => 'DBI:mysql:database=foobaz;host=192.168.1.100;port=3306',
'USERNAME' => 'FooBar',
'PASSWORD' => 'SecretPassword',
'EVENT' => 'conn_handler',
);
# Execute a query and return number of rows affected
$_[KERNEL]->post( 'SimpleDBI', 'DO',
'SQL' => 'DELETE FROM FooTable WHERE ID = ?',
'PLACEHOLDERS' => [ qw( 38 ) ],
'EVENT' => 'deleted_handler',
'INSERT_ID' => 0,
);
# Retrieve one row of information
$_[KERNEL]->post( 'SimpleDBI', 'SINGLE',
'SQL' => 'Select * from FooTable LIMIT 1',
'EVENT' => 'success_handler',
'BAGGAGE' => 'Some Stuff I want to keep!',
);
# We want many rows of information + get the query ID so we can delete it later
# Furthermore, disable prepare_cached on this query
my $id = $_[KERNEL]->call( 'SimpleDBI', 'MULTIPLE',
'SQL' => 'SELECT foo, baz FROM FooTable2 WHERE id = ?',
'PLACEHOLDERS' => [ qw( 53 ) ],
'EVENT' => 'multiple_handler',
'PREPARE_CACHED'=> 0,
);
# Quote something and send it to another session
$_[KERNEL]->post( 'SimpleDBI', 'QUOTE',
'SQL' => 'foo$*@%%sdkf"""',
'SESSION' => 'OtherSession',
'EVENT' => 'quote_handler',
);
# Changed our mind!
$_[KERNEL]->post( 'SimpleDBI', 'Delete_Query', $id );
# 3 ways to shutdown
# This will let the existing queries finish, then shutdown
$_[KERNEL]->post( 'SimpleDBI', 'shutdown' );
# This will terminate when the event traverses
# POE's queue and arrives at SimpleDBI
$_[KERNEL]->post( 'SimpleDBI', 'shutdown', 'NOW' );
# Even QUICKER shutdown :)
$_[KERNEL]->call( 'SimpleDBI', 'shutdown', 'NOW' );
},
# Define your request handlers here
'quote_handler' => \&FooHandler,
# And so on
},
);
ABSTRACT
This module simplifies DBI usage in POE's multitasking world.
This module is a breeze to use, you'll have DBI calls in your POE program
up and running in only a few seconds of setup.
This module does what XML::Simple does for the XML world.
If you want more advanced usage, check out:
POE::Component::LaDBI
DESCRIPTION
This module works its magic by creating a new session with POE, then
spawning off a child process to do the "heavy" lifting. That way, your
main POE process can continue servicing other clients. Queries are put
into a queue, and processed one at a time.
The standard way to use this module is to do this:
use POE;
use POE::Component::SimpleDBI;
POE::Component::SimpleDBI->new( ... );
POE::Session->create( ... );
POE::Kernel->run();
Starting SimpleDBI
To start SimpleDBI, just call it's new method:
POE::Component::SimpleDBI->new( 'ALIAS' );
This method will die on error or return success.
NOTE: The act of starting/stopping SimpleDBI fires off _child events,
read the POE documentation on what to do with them :)
This constructor accepts only 2 arguments.
Alias
This sets the session alias in POE.
The default is "SimpleDBI".
PREPARE_CACHED
This sets the global PREPARE_CACHED setting. This is a boolean value.
POE::Component::SimpleDBI->new( 'ALIAS', 0 );
The default is enabled.
Commands
There are a few commands you can trigger in SimpleDBI. They are
triggered via $_[KERNEL]->post( ... );
ID
All of the commands except for Delete_Query and shutdown return an id.
To get them, do this: my $id = $_[KERNEL]->call( 'SimpleDBI', ...
);
Afterwards, the id can be used to delete queries, look at Delete_Query
for more information.
Argument errors
All of the commands validate their arguments, and if an error happens (
missing argument, etc ), they will do either: - return undef and
forget that your request even existed - post to the SESSION/EVENT
with ERROR present in the data NOTE: The data will not have
an ID key present
Explanation of DO/SINGLE/MULTIPLE/QUOTE arguments
They are passed in via the $_[KERNEL]->post( ... );
NOTE: Capitalization is very important!
"SQL"
This is the actual SQL line you want SimpleDBI to execute. You can
put in placeholders, this module supports them.
"PLACEHOLDERS"
This is an array of placeholders.
You can skip this if your query does not utilize it.
"SESSION"
This is the session that will get the result
You can skip this, it defaults to the sending session
"EVENT"
This is the event, triggered whenever a query finished.
It will get a hash in ARG0, consult the specific queries on what
you will get.
NOTE: If the key 'ERROR' exists in the hash, then it will contain
the error string.
"BAGGAGE"
This is a special argument, you can "attach" any kind of baggage to
a query. The baggage will be kept by SimpleDBI and returned to the
Event handler intact.
This is good for storing data associated with a query like a client
object, etc.
You can skip this if your query does not utilize it.
"PREPARE_CACHED"
This was added recently, to override SimpleDBI's default behavior
of using the $dbh->prepare_cached() function. Setting this to false
will use $dbh->prepare() instead.
Some users reported problems with PostgreSQL. After investigation,
this turned out to be some bizarre OID caching issues when the
table was updated while the connection is alive. The quick work-
around is to reconnect to the database, but this was not a "sane"
solution.
This is a simple boolean value, and if this argument does not
exist, SimpleDBI will use the global setting when calling new().
"INSERT_ID"
This was added recently, to override SimpleDBI's default behavior
of using the $dbh->last_insert_id() function. Setting this to false
will disable retrieval of this value.
This is a simple boolean value, and if this argument does not
exist, SimpleDBI will default to true.
"CONNECT"
This tells SimpleDBI to connect to the database
NOTE: if we are already connected, it will be a success ( SimpleDBI will not disconnect then connect automatically )
Accepted arguments:
DSN -> The DBI DSN string, consult the DBI docs on what this is
USERNAME -> The username for the connection
PASSWORD -> The password for the connection
SESSION -> The session to send the results
EVENT -> The event to send the results
NOW -> Tells SimpleDBI to bypass the queue and connect NOW!
CLEAR -> Tells SimpleDBI to clear the queue and connect NOW!
AUTO_COMMIT -> The boolean value we will pass to DBI->connect ( defaults to true )
NOTE: if the DSN/USERNAME/PASSWORD/SESSION/EVENT does not exist, SimpleDBI assumes you wanted to use
the old connection and will use the cached values ( if you told it to DISCONNECT ).
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'CONNECT',
'DSN' => 'DBI:mysql:database=foobaz;host=192.168.1.100;port=3306',
'USERNAME' => 'MyUser',
'PASSWORD' => 'MyPassword',
'EVENT' => 'conn_handler',
'NOW' => 1,
);
The NOW/CLEAR arguments are special, they will tell SimpleDBI to bypass the request queue and connect NOW...
The CLEAR argument will also delete all the requests waiting in the queue, they will get an ERROR result
They both default to false, supply a boolean value to turn them on
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured
'GONE' => exists only if the server was disconnected and the reconnect failed
'ACTION' => 'CONNECT'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
}
Receiving this event without the ERROR key means SimpleDBI successfully connected and is waiting for queries
NOTE: You can do nifty things like:
$_[KERNEL]->post( 'SimpleDBI', 'CONNECT', 'DSN' => 'DBI:mysql:...', ... );
$_[KERNEL]->post( 'SimpleDBI', 'DO', ... );
$_[KERNEL]->post( 'SimpleDBI', 'SINGLE', ... );
$_[KERNEL]->post( 'SimpleDBI', 'DISCONNECT' );
$_[KERNEL]->post( 'SimpleDBI', 'CONNECT', 'DSN' => 'DBI:oracle:...', ... );
$_[KERNEL]->post( 'SimpleDBI', 'MULTIPLE', ... );
$_[KERNEL]->post( 'SimpleDBI', 'shutdown' );
They all will be executed in the right order!
As of 1.11 SimpleDBI now detects whether the backend lost the connection to the database server. The backend will
automatically reconnect if it happens, but if that fails, an error will be sent to the session/event specified here
with an extra key: 'GONE'. In this state SimpleDBI is deadlocked, any new queries will not be processed until a
CONNECT NOW event is issued! Keep in mind the SINGLE/etc queries WILL NOT receive an error if this happens, the error
goes straight to the CONNECT handler to keep it simple!
"DISCONNECT"
This tells SimpleDBI to disconnect from the database
NOTE: In the case that a DISCONNECT is issued when we are not connected, it will still succeed...
Accepted arguments:
SESSION -> The session to send the results
EVENT -> The event to send the results
NOW -> Tells SimpleDBI to bypass the queue and disconnect NOW!
CLEAR -> Tells SimpleDBI to clear the queue and disconnect NOW!
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'DISCONNECT',
'EVENT' => 'disconn_handler',
'NOW' => 1,
);
The NOW/CLEAR arguments are special, they will tell SimpleDBI to bypass the request queue and connect NOW...
The CLEAR argument will also delete all the requests waiting in the queue, they will get an ERROR result
They both default to false, supply a boolean value to turn them on
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured
'ACTION' => 'DISCONNECT'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
}
Receiving this event without the ERROR key means SimpleDBI successfully disconnected
BEWARE: There is the possibility of a deadlock:
$_[KERNEL]->post( 'SimpleDBI', 'CONNECT', ... );
$_[KERNEL]->post( 'SimpleDBI', 'MULTIPLE', ... );
$_[KERNEL]->post( 'SimpleDBI', 'DISCONNECT' );
$_[KERNEL]->post( 'SimpleDBI', 'DO', ... );
$_[KERNEL]->post( 'SimpleDBI', 'SINGLE', ... );
$_[KERNEL]->post( 'SimpleDBI', 'CONNECT' );
In this case, the DO/SINGLE queries will NEVER run until you issue a CONNECT with NOW enabled
"QUOTE"
This simply sends off a string to be quoted, and gets it back.
Accepted arguments:
SESSION -> The session to send the results
EVENT -> The event to send the results
SQL -> The string to be quoted
BAGGAGE -> Any extra data to keep associated with this query ( SimpleDBI will not touch it )
Internally, it does this:
return $dbh->quote( $SQL );
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'QUOTE',
SQL => 'foo$*@%%sdkf"""',
EVENT => 'quote_handler',
);
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured
'ACTION' => 'QUOTE'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
'SQL' => Original SQL inputted
'RESULT' => The quoted SQL
'PLACEHOLDERS' => Original placeholders ( may not exist if it was not provided )
'BAGGAGE' => whatever you set it to ( may not exist if it was not provided )
}
"DO"
This query is specialized for those queries where you UPDATE/DELETE/INSERT/etc.
THIS IS NOT FOR SELECT QUERIES!
Accepted arguments:
SESSION -> The session to send the results
EVENT -> The event to send the results
SQL -> The string to be quoted
PLACEHOLDERS -> Any placeholders ( if needed )
BAGGAGE -> Any extra data to keep associated with this query ( SimpleDBI will not touch it )
PREPARE_CACHED -> Boolean value ( if needed )
INSERT_ID -> Boolean value ( if needed )
Internally, it does this:
$sth = $dbh->prepare_cached( $SQL );
$rows_affected = $sth->execute( $PLACEHOLDERS );
return $rows_affected;
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'DO',
SQL => 'DELETE FROM FooTable WHERE ID = ?',
PLACEHOLDERS => [ 38 ],
EVENT => 'deleted_handler',
);
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured
'ACTION' => 'DO'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
'SQL' => Original SQL inputted
'RESULT' => Scalar value of rows affected
'PLACEHOLDERS' => Original placeholders ( may not exist if it was not provided )
'BAGGAGE' => whatever you set it to ( may not exist if it was not provided )
'INSERTID' => The insert ID - using $dbh->last_insert_id( undef, undef, undef, undef ) [ defaults to undef ]
}
"SINGLE"
This query is specialized for those queries where you will get exactly 1 result back.
Accepted arguments:
SESSION -> The session to send the results
EVENT -> The event to send the results
SQL -> The string to be quoted
PLACEHOLDERS -> Any placeholders ( if needed )
BAGGAGE -> Any extra data to keep associated with this query ( SimpleDBI will not touch it )
PREPARE_CACHED -> Boolean value ( if needed )
XXX Beware! I incorrectly stated that this returns lowercase rows, this is not true! XXX
Internally, it does this:
$sth = $dbh->prepare_cached( $SQL );
$sth->execute( $PLACEHOLDERS );
$result = $sth->fetchrow_hashref;
return $result;
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'SINGLE',
SQL => 'Select * from FooTable',
EVENT => 'success_handler',
SESSION => 'MySession',
);
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured
'ACTION' => 'SINGLE'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
'SQL' => Original SQL inputted
'RESULT' => Hash of columns - similar to fetchrow_hashref ( undef if no rows returned )
'PLACEHOLDERS' => Original placeholders ( may not exist if it was not provided )
'BAGGAGE' => whatever you set it to ( may not exist if it was not provided )
}
"MULTIPLE"
This query is specialized for those queries where you will get more than 1 result back.
XXX Keep in mind: the column names are all lowercased automatically! XXX
Accepted arguments:
SESSION -> The session to send the results
EVENT -> The event to send the results
SQL -> The string to be quoted
PLACEHOLDERS -> Any placeholders ( if needed )
BAGGAGE -> Any extra data to keep associated with this query ( SimpleDBI will not touch it )
PREPARE_CACHED -> Boolean value ( if needed )
Internally, it does this:
$sth = $dbh->prepare_cached( $SQL );
$sth->execute( $PLACEHOLDERS );
$sth->bind_columns( \( @$newdata{ @{ $sth->{'NAME_lc'} } } ) );
while ( $sth->fetch() ) {
push( @results, { @$newdata } );
}
return \@results;
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'MULTIPLE',
SQL => 'SELECT foo, baz FROM FooTable2 WHERE id = ?',
EVENT => 'multiple_handler',
PLACEHOLDERS => [ 53 ],
PREPARE_CACHED => 0,
);
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured
'ACTION' => 'MULTIPLE'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
'SQL' => Original SQL inputted
'RESULT' => Array of hash of columns - similar to array of fetchrow_hashref's ( undef if no rows returned )
'PLACEHOLDERS' => Original placeholders ( may not exist if it was not provided )
'BAGGAGE' => whatever you set it to ( may not exist if it was not provided )
}
"ATOMIC"
This query is specialized for those queries that you need to execute in a transaction. You supply an array of SQL queries,
and SimpleDBI will execute them all in a transaction block. No need to worry about AutoCommit, BEGIN, and END TRANSACTION!
You are supposed to pass an array of queries that normally would be executed in a DO-style query. Again, you cannot execute
SELECT queries in this type of command! Currently there is no control over prepare_cached for individual queries. It may be
added in a future release.
WARNING: It tripped me up on my testing when I realized this worked on Postgres but not MySQL. I forgot that I was testing
against MyISAM tables, which doesn't support transactions! ( it works nicely on InnoDB tables hah ) So, if this doesn't
"behave" properly for you please check your database tables!
Accepted arguments:
SESSION -> The session to send the results
EVENT -> The event to send the results
SQL -> The array of SQL queries
PLACEHOLDERS -> The array of placeholders ( if needed ) [ this is an AoA - array of arrays! ]
BAGGAGE -> Any extra data to keep associated with this query ( SimpleDBI will not touch it )
PREPARE_CACHED -> Boolean value ( if needed ) [ for all of the queries! ]
Internally, it does this:
eval {
$dbh->begin_work;
for my $idx ( 0 .. $#array ) {
if ( $prepare_cached ) {
$sth = $dbh->prepare_cached( $array[ $idx ] );
} else {
$sth = $dbh->prepare( $array[ $idx ] );
}
if ( defined $PLACEHOLDERS[ $idx ] ) {
$sth->execute( $PLACEHOLDERS[ $idx ] );
} else {
$sth->execute;
}
$sth->finish;
}
$dbh->commit;
};
if ( $@ ) {
eval { $dbh->rollback };
if ( $@ ) {
return ROLLBACK_FAILURE;
} else {
return COMMIT_FAILURE:
}
} else {
return SUCCESS;
}
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'ATOMIC',
SQL => [
'DELETE FROM FooTable WHERE ID = ?',
'UPDATE FooTable SET baz = ? WHERE bar = ?',
],
EVENT => 'atomic_handler',
PLACEHOLDERS => [ [ 53 ],
[ 5, 86 ]
],
);
The Event handler will get a hash in ARG0:
{
'ERROR' => exists only if an error occured ( ROLLBACK_FAILURE or COMMIT_FAILURE with explanation )
'ACTION' => 'ATOMIC'
'ID' => ID of the Query
'EVENT' => The event the query will respond to
'SESSION' => The session the query will respond to
'SQL' => Original SQL array inputted
'RESULT' => Either SUCCESS or in case of error, not exists
'PLACEHOLDERS' => Original placeholders ( may not exist if it was not provided )
'BAGGAGE' => whatever you set it to ( may not exist if it was not provided )
}
"Delete_Query"
Call this event if you want to delete a query via the ID.
Returns:
undef if it wasn't able to find the ID
0 if the query is currently being processed
1 if the query was successfully deleted
Here's an example on how to trigger this event:
$_[KERNEL]->post( 'SimpleDBI', 'Delete_Query', $queryID );
IF you really want to know the status, execute a call on the event and check the returned value.
"Clear_Queue"
This event will clear the entire queue except the running query, if there is one.
You can also pass in one argument -> the error string to be used instead of the default, 'Cleared the queue'
All the queries in the queue will return ERROR to their respective sessions/events
"shutdown"
$_[KERNEL]->post( 'SimpleDBI', 'shutdown' );
This will signal SimpleDBI to start the shutdown procedure.
NOTE: This will let all outstanding queries run!
SimpleDBI will kill it's session when all the queries have been processed.
you can also specify an argument:
$_[KERNEL]->post( 'SimpleDBI', 'shutdown', 'NOW' );
This will signal SimpleDBI to shutdown.
NOTE: This will NOT let the outstanding queries finish!
Any queries running will be lost!
Due to the way POE's queue works, this shutdown event will take some time to propagate POE's queue.
If you REALLY want to shut down immediately, do this:
$_[KERNEL]->call( 'SimpleDBI', 'shutdown', 'NOW' );
SimpleDBI Notes
This module is very picky about capitalization!
All of the options are uppercase, to avoid confusion.
You can enable debugging mode by doing this:
sub POE::Component::SimpleDBI::DEBUG () { 1 }
use POE::Component::SimpleDBI;
Also, this module will try to keep the SubProcess alive. if it dies,
it will open it again for a max of 5 retries.
You can override this behavior by doing this:
sub POE::Component::SimpleDBI::MAX_RETRIES () { 10 }
use POE::Component::SimpleDBI;
EXPORT
Nothing.
SEE ALSO
DBI
POE::Component::DBIAgent
POE::Component::LaDBI
POE::Component::EasyDBI
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc POE::Component::SimpleDBI
Websites
· AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/POE-Component-SimpleDBI
<http://annocpan.org/dist/POE-Component-SimpleDBI>
· CPAN Ratings
http://cpanratings.perl.org/d/POE-Component-SimpleDBI
<http://cpanratings.perl.org/d/POE-Component-SimpleDBI>
· RT: CPAN's request tracker
http://rt.cpan.org/NoAuth/Bugs.html?Dist=POE-Component-SimpleDBI
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=POE-Component-SimpleDBI>
· Search CPAN
http://search.cpan.org/dist/POE-Component-SimpleDBI
<http://search.cpan.org/dist/POE-Component-SimpleDBI>
· CPAN::Forum
http://www.cpanforum.com/dist/POE-Component-SimpleDBI
<http://www.cpanforum.com/dist/POE-Component-SimpleDBI>
Bugs
Please report any bugs or feature requests to
"bug-poe-component-simpledbi at rt.cpan.org", or through the web
interface at
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=POE-Component-SimpleDBI
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=POE-Component-
SimpleDBI>. I will be notified, and then you'll automatically be
notified of progress on your bug as I make changes.
Code Repository
This code is currently hosted on github.com under the account
"apocalypse". Please feel free to browse it and pull from it, or
whatever. If you want to contribute patches, please send me a diff or
prod me to pull from your repository :)
http://github.com/apocalypse/perl-poe-simpledbi/tree/master
<http://github.com/apocalypse/perl-poe-simpledbi/tree/master>
AUTHOR
Apocalypse <apocal@cpan.org>
COPYRIGHT AND LICENSE
Copyright 2009 by Apocalypse
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.14.1 2009-03-11 POE::Component::SimpleDBI(3)
