OpenTracing::interface::Span - A role that defines the Span interface
pacakge OpenTracing::Implementation::MyBackendService::Span; sub get_context { ... } sub overwrite_operation_name { ... } sub finish { ... } sub set_tag { ... } sub log_data { ... } sub set_baggage_item { ... } sub get_baggage_item { ... } BEGIN { use Role::Tiny::With; with 'OpenTracing::Interface::Span' if $ENV{OPENTRACING_INTERFACE}; } # check at compile time, perl -c will work 1;
This 'role' describes the interface for any OpenTracing Span implementation.
Span represents a unit of work executed on behalf of a trace.
Span
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.
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().
SpanContext
get_context()
my $span_context = $span->get_context;
none
An object of type SpanContext from OpenTracing::Types.
Changes the operation name.
$span->overwrite_operation_name( $operation_name );
The name of the operation-name, must be a string.
The span itself, for chaining purposes.
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).
finish()
If the span is already finished, a warning should be logged.
An explicit finish timestamp for the Span; if omitted, the current walltime is used implicitly.
The (finished) Span itself, for chaining purposes.
Adds a tag to the span
$span->set_tag( $tag_key => $tag_value );
If there is a pre-existing tag set for tag_key, it is overwritten.
tag_key
As an implementor, consider using "standard tags" listed in OpenTracing.io
If the Span is already finished, a warning should be logged.
Str
OpenTracing does not enforce any limitations though.
Value
Must be either a string, a boolean value, or a numeric type.
Adds a log record to the span
$span->log_data( $log_key1 => $log_value1, $log_key2 => $log_value2, ... );
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.
Returns either the corresponding baggage value, or undef when such a value was missing.
undef
my $baggage_value = $span->get_baggage_item( $baggage_key );
The value or undef when such a value was missing.
Describes the API definition for OpenTransport implementations written in the Perl5 language.
A library of Type::Tiny type constraints that provides Duck Type checks for all common elements that conform OpenTracing::Interface
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.
around
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.
To install OpenTracing::Interface, copy and paste the appropriate command in to your terminal.
cpanm
cpanm OpenTracing::Interface
CPAN shell
perl -MCPAN -e shell install OpenTracing::Interface
For more information on module installation, please visit the detailed CPAN module installation guide.