NAME

OpenTracing::Interface::Span - A role that defines the Span interface

SYNOPSIS

    pacakge OpenTracing::Implementation::MyBackendService::Span;
    
    sub get_context {
        ...
    }
    
    sub overwrite_operation_name {
        ...
    }
    
    sub finish {
        ...
    }
    
    sub add_tag {
        ...
    }
    
    sub add_tags {
        ...
    }
    
    sub get_tags {
        ...
    }
    
    sub log_data {
        ...
    }
    
    sub add_baggage_item {
        ...
    }
    
    sub add_baggage_items {
        ...
    }
    
    sub get_baggage_item {
        ...
    }
    
    sub get_baggage_items {
        ...
    }
    
    BEGIN {
        use Role::Tiny::With;
        with 'OpenTracing::Interface::Span'
    } # check at compile time, perl -c will work
    
    1;

DESCRIPTION

This 'role' describes the interface for any OpenTracing Span implementation.

Span represents a unit of work executed on behalf of a trace.

Examples of spans include a remote procedure call, or a in-process method call to a sub-component. Every span in a trace may have zero or more causal parents, and these relationships transitively form a DAG. It is common for spans to have at most one parent, and thus most traces are merely tree structures.

INSTANCE METHODS

get_context

Yields the SpanContext for this Span. Note that the return value of get_context() is still valid after a call to finish(), as is a call to get_context() after a call to finish().

    my $span_context = $span->get_context;
Parameter(s)

    none

Returns
SpanContext

The current (possibly changed> span context.

overwrite_operation_name

Changes the operation name.

    $span->overwrite_operation_name( $operation_name );
Required Positional Parameter(s)
operation_name, a required Str

The name of the span of work.

Returns
Invocant

The span itself, for chaining purposes.

finish

Sets the end timestamp and finalizes Span state.

    $span->finish;

or

    $span->finish( $epoch_timestamp );

With the exception of calls to get_context() (which are always allowed), finish() must be the last call made to any span instance, and to do otherwise leads to undefined behavior (but not returning an exception).

If the span is already finished, a warning should be logged.

Optional Positional Param(s)
epoch_timestamp, an optional PositiveOrZeroNum

An explicit finish timestamp for the span or, if omitted, the current walltime is used implicitly.

Returns
Invocant

The (finished) span object itself, for chaining purposes.

add_tag

Adds a single tag to the span.

    $span->add_tag( $tag_key => $tag_value );

If there is a pre-existing tag set for tag_key, it is overwritten.

As an implementor, consider using "standard tags" listed at OpenTracing.io

If the span has already finished, a warning should be logged.

Required Positional Parameter(s)
tag_key, a required Str

OpenTracing does not enforce any limitations though.

tag_value, as required Value

Must be either a string, a boolean value, or a numeric type.

Returns
Invocant

The span itself, for chaining purposes.

add_tags

Adds multiple tags to the span at the same time.

    $span->add_tags(
        $tag_key_1 => $tag_value_1,
        $tag_key_2 => $tag_value_2,
    );

See add_tag above.

get_tags

This will return a Hash of key/value pairs.

    my %tags = $span->get_tags;

It will return an empty list if there is no key/value pairs set.

Positional Parameter(s)

    none

Returns
Hash

A list of key/value pairs, not a hash reference!

log_data

Adds a log record to the span.

    $span->log_data(
        $log_key1 => $log_value1,
        $log_key2 => $log_value2,
        ...
    );
Cyclic Positional Parameter(s)
key, as Str
$value, as Str
Returns
Invocant

The span itself, for chaining purposes.

add_baggage_item

Sets a key:value pair on this Span and its SpanContext that also propagates to descendants of this Span.

    $span->set_bagagge_item(
        $baggage_key => $baggage_value
    );

Baggage items are key:value string pairs that apply to the given Span, its SpanContext, and all Spans which directly or transitively reference the local Span. That is, baggage items propagate in-band along with the trace itself.

Baggage items enable powerful functionality given a full-stack OpenTracing integration (for example, arbitrary application data from a mobile app can make it, transparently, all the way into the depths of a storage system), and with it some powerful costs: use this feature with care.

Use this feature thoughtfully and with care. Every key and value is copied into every local and remote child of the associated Span, and that can add up to a lot of network and cpu overhead.

Required Positional Parameter(s)
baggage_key, as required Str
baggage_value, as Value
Returns
Invocant

The span itself, for chaining purposes.

add_baggage_items

Sets multiple baggage_items at once.

    $span->set_bagagge_item(
        $baggage_key_1 => $baggage_value_1,
        $baggage_key_2 => $baggage_value_2,
    );

See add_baggage_item above.

get_baggage_item

Returns either the corresponding baggage value, or undef when such a value was missing.

    my $baggage_value = $span->get_baggage_item( $baggage_key );
Required Positional Parameters
baggage_key, a required Str
Returns
Maybe a Value

The value of the requested baggage item, or undef when such a value was missing.

get_baggage_items

This will return a Hash of key/value pairs.

    my %baggage_items = $span->get_baggage_items;

It will return an empty list if there is no key/value pairs set.

Positional Parameter(s)

    none

Returns
Hash

A list of key/value pairs, not a hash reference!

SEE ALSO

OpenTracing::Interface

Describes the API definition for OpenTransport implementations written in the Perl5 language.

OpenTracing::Types

A library of Type::Tiny type constraints that provides Duck Type checks for all common elements that conform OpenTracing::Interface

CAVEATS

This description is using around method modifiers that basically wraps them around the real implementation. These method modifiers provide a 'readable' and reusable interface, describing the inputs and outputs, using type constraints.

Consumers of this role, or implementors of the interface are MUST implement each method mentioned below. Not doing so will result in compilation errors.

Since this role does nothing else than checking input and output, it is useful during development. Most likely it can be switched off safely in production environments.

AUTHOR

Theo van Hoesel <tvanhoesel@perceptyx.com>

COPYRIGHT AND LICENSE

'OpenTracing API for Perl' is Copyright (C) 2019 .. 2021, Perceptyx Inc

This library is free software; you can redistribute it and/or modify it under the terms of the Artistic License 2.0.

This library is distributed in the hope that it will be useful, but it is provided "as is" and without any express or implied warranties.

For details, see the full text of the license in the file LICENSE.