phpman > perldoc > MongoDB::ChangeStream

NAME
    MongoDB::ChangeStream - A stream providing update information for collections.

VERSION
    version v2.2.2

SYNOPSIS
        $stream = $collection->watch( $pipeline, $options );
        while(1) {

            # This inner loop will only iterate until there are no more
            # changes available.
            while (my $change = $stream->next) {
                ...
            }
        }

DESCRIPTION
    This class models change stream results as returned by the "watch" in MongoDB::Collection
    method.

STREAM METHODS
  next
        $change_stream = $collection->watch(...);
        $change = $change_stream->next;

    Waits for the next change in the collection and returns it.

    Note: This method will wait for the amount of milliseconds passed as "maxAwaitTimeMS" to "watch"
    in MongoDB::Collection or the server's default wait-time. It will not wait indefinitely.

  get_resume_token
    Users can inspect the "_id" on each "ChangeDocument" to use as a resume token. But since MongoDB
    4.2, "aggregate" and "getMore" responses also include a "postBatchResumeToken". Drivers use one
    or the other when automatically resuming.

    This method retrieves the same resume token that would be used to automatically resume. Users
    intending to store the resume token should use this method to get the most up to date resume
    token.

    For instance:

        if ($local_change) {
            process_change($local_change);
        }

        eval {
            my $change_stream = $coll->watch([], { resumeAfter => $local_resume_token });
            while ( my $change = $change_stream->next) {
                $local_resume_token = $change_stream->get_resume_token;
                $local_change = $change;
                process_change($local_change);
            }
        };
        if (my $err = $@) {
            $log->error($err);
        }

    In this case the current change is always persisted locally, including the resume token, such
    that on restart the application can still process the change while ensuring that the change
    stream continues from the right logical time in the oplog. It is the application's
    responsibility to ensure that "process_change" is idempotent, this design merely makes a
    reasonable effort to process each change at least once.

SEE ALSO
    The Change Streams manual section <https://docs.mongodb.com/manual/changeStreams/>.

    The Change Streams specification
    <https://github.com/mongodb/specifications/blob/master/source/change-streams.rst>.

AUTHORS
    *   David Golden <david AT mongodb.com>

    *   Rassi <rassi AT mongodb.com>

    *   Mike Friedman <friedo AT friedo.com>

    *   Kristina Chodorow <k.chodorow AT gmail.com>

    *   Florian Ragwitz <rafl AT debian.org>

COPYRIGHT AND LICENSE
    This software is Copyright (c) 2020 by MongoDB, Inc.

    This is free software, licensed under:

      The Apache License, Version 2.0, January 2004