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.\" ========================================================================
.\"
.IX Title "Message::Passing::Role::HasErrorChain 3pm"
.TH Message::Passing::Role::HasErrorChain 3pm "2017-08-02" "perl v5.26.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
Message::Passing::Role::HasErrorChain \- A role for components which can report errors
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 4
\&    # Note this is an example package, and does not really exist!
\&    package Message::Passing::Output::ErrorAllMessages;
\&    use Moo;
\&    use namespace::clean \-except => \*(Aqmeta\*(Aq;
\&
\&    with qw/
\&        Message::Passing::Role::Output
\&        Message::Passing::Role::HasErrorChain
\&    /;
\&
\&    sub consume {
\&        my ($self, $message) = @_;
\&        $self\->error\->consume($message);
\&    }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Some components can create an error stream in addition to a message stream.
.SH "METHODS"
.IX Header "METHODS"
.SS "error"
.IX Subsection "error"
An attribute containing the error chain.
.PP
By default, this is a chain of:
.IP "Message::Passing::Filter::Encoder::JSON" 4
.IX Item "Message::Passing::Filter::Encoder::JSON"
.PD 0
.IP "Message::Passing::Output::STDOUT" 4
.IX Item "Message::Passing::Output::STDOUT"
.PD
.SH "WARNINGS"
.IX Header "WARNINGS"
.SS "\s-1ERROR CHAINS CAN LOOP\s0"
.IX Subsection "ERROR CHAINS CAN LOOP"
If you override the error chain output, be sure that the error chain does not go into your
normal log path! This is because if you suddenly have errors in your normal log path, and you
then start logging these errors, this causes more errors \- causing you to generate a message loop.
.SS "\s-1ENCODING IN ERROR CHAINS\s0"
.IX Subsection "ENCODING IN ERROR CHAINS"
If you emit something which cannot be encoded to an error chain then the encoding
error will likely be emitted by the error chain \- this can again cause loops and other
issues.
.PP
All components which use error chains should be very careful to output data which
they are entirely certain will be able to be encoded.
.SH "SPONSORSHIP"
.IX Header "SPONSORSHIP"
This module exists due to the wonderful people at Suretec Systems Ltd.
<http://www.suretecsystems.com/> who sponsored its development for its
VoIP division called SureVoIP <http://www.surevoip.co.uk/> for use with
the SureVoIP \s-1API\s0 \-
<http://www.surevoip.co.uk/support/wiki/api_documentation>
.SH "AUTHOR, COPYRIGHT AND LICENSE"
.IX Header "AUTHOR, COPYRIGHT AND LICENSE"
See Message::Passing.