NAME

JLog::Reader - Perl extension for reading to a jlog journal.

SUMMARY

  use JLog::Reader;
  # create a new reader off the log directory
  $r = JLog::Reader->new($log);
  # open the log as the indicated subscriber
  $r->open($subscriber);
  while(my $line = $r->read) {
    # work with $line
  }
  # mark the seen records as read
  $r->checkpoint;

  use JLog::Reader;
  $r = JLog::Reader->new($log);
  $r->open($subscriber);
  # mark lines read as they are pulled off the queue
  $r->auto_checkpoint(1);
  while(my $line = $r->read) {
    # work with $line
  }

DESCRIPTION

JLog::Reader allows you to access a jlog queue for reader.

INTERFACE

Constructor

new

  $w = JLog::Reader->new( $path_to_jlog, [ $flags [, $size ] ] );

Instantiates a JLog writer object associated with the JLog directory.

$path_to_jlog: The directory for the JLog queue.
$flags: Optional flags, from 'Fcntl'. The default is O_CREAT.
$size: Optional size of the individual journal files.

Subscriber Management

These functions are inherited from JLog

add_subscriber

  $w->add_subscriber( $name, [ $flag ] );

Add a subscriber to the JLog queue.

$name: The name of the subscriber.
$flag: An optional flag dictating where the subscriber should be marked interested from. The default is JLog::JLOG_BEGIN. The other available option is JLog::JLOG_END.

remove_subscriber

  $w->remove_subscriber ( $name );

Remove a subscriber to the JLog queue.

$name: The name of the subscriber.

Reading From The Queue

open

  $w->open( $subscriber_name );

Opens the JLog for reading.

$subscriber_name: The name we want to subscribe under. This must previously have been registered as a log subscriber via add_subscriber().

read

  $message = $w->read;

Read the next message from the JLog queue.

checkpoint

  $r->checkpoint;

Checkpoint your read. This will notify the JLog that you have successfully read logs up to this point. If all registered subscribers have read to a certain point, the JLog system can remove the underlying data for the read messages.

auto_checkpoint( [ $val ] )

Returns (and optionally sets) the auto_checkpoint property. With auto-checkpointing enabled, JLog::Reader will automatically checkpoint whenever you call read().

$val: The value you wish to set auto_checkpointing to.

Internals

alter_journal_size

  $r->alter_journal_size( $size );

Set the size of the individual journal files.

$size: The desired size in bytes.

raw_size

  $size = $r->raw_size;

The size of the existing journal (including checkpointed but unpurged messages in the current journal file), in bytes.

  $r->rewind;

Rewind the jlog to the previous transaction id (when in an uncommitted state). This is useful for implementing a 'peek' style action.

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POD ERRORS

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