=encoding utf-8

=head1 NAME

ngx_otel_module - Module ngx_otel_module




=head1



The C<ngx_otel_module> module (1.23.4) provides
L<OpenTelemetry|https://opentelemetry.io>
distributed tracing support.
The module supports
L<W3C|https://w3c.github.io/trace-context>
context propagation and OTLPE<sol>gRPC export protocol.





The source code of the module is available
L<here|https://github.com/nginxinc/nginx-otel>.
Download and install instructions are available
L<here|https://github.com/nginxinc/nginx-otel/blob/main/README.md>.





The module is also available in a prebuilt
C<nginx-module-otel>
L<package|linux_packages>
since 1.25.3
and in C<nginx-plus-module-otel> package
as part of our
commercial subscription.




=head1 Example Configuration




    
    load_module modules/ngx_otel_module.so;
    
    events {
    }
    
    http {
    
        otel_exporter {
            endpoint localhost:4317;
        }
    
        server {
            listen 127.0.0.1:8080;
    
            location / {
                otel_trace         on;
                otel_trace_context inject;
    
                proxy_pass http://backend;
            }
        }
    }






=head1 Directives

=head2 otel_exporter


otel_exporter { B<...> }



B<context:> I<http>





Specifies OTel data export parameters:


=over



=item C<endpoint>




the address of OTLPE<sol>gRPC endpoint that will accept telemetry data.



=item C<interval>




the maximum interval between two exports,
by default is C<5> seconds.



=item C<batch_size>




the maximum number of spans to be sent in one batch per worker,
by default is C<512>.



=item C<batch_count>




the number of pending batches per worker,
spans exceeding the limit are dropped,
by default is C<4>.




=back


Example:

    
    otel_exporter {
        endpoint    localhost:4317;
        interval    5s;
        batch_size  512;
        batch_count 4;
    }









=head2 otel_service_name


B<syntax:> otel_service_name I<I<C<name>>>


B<default:> I<unknown_service:nginx>


B<context:> I<http>





Sets the
“L<C<service.name>|https://opentelemetry.io/docs/reference/specification/resource/semantic_conventions/#service>”
attribute of the OTel resource.







=head2 otel_trace


B<syntax:> otel_trace I<C<on> E<verbar>
        C<off> E<verbar>
        C<$variable>>


B<default:> I<off>


B<context:> I<http>


B<context:> I<server>


B<context:> I<location>





Enables or disables OpenTelemetry tracing.
The directive can also be enabled by specifying a variable:

    
    split_clients "$otel_trace_id" $ratio_sampler {
                  10%              on;
                  *                off;
    }
    
    server {
        location / {
            otel_trace         $ratio_sampler;
            otel_trace_context inject;
            proxy_pass         http://backend;
        }
    }









=head2 otel_trace_context


B<syntax:> otel_trace_context I<C<extract> E<verbar>
        C<inject> E<verbar>
        C<propagate> E<verbar>
        C<ignore>>


B<default:> I<ignore>


B<context:> I<http>


B<context:> I<server>


B<context:> I<location>





Specifies how to propagate
L<traceparentE<sol>tracestate|https://www.w3.org/TR/trace-context/#design-overview> headers:


=over



=item C<extract>




uses an existing trace context from the request,
so that the identifiers of
a trace and
the parent span
are inherited from the incoming request.



=item C<inject>




adds a new context to the request, overwriting existing headers, if any.



=item C<propagate>




updates the existing context
(combines L</extract> and L</inject>).



=item C<ignore>




skips context headers processing.




=back









=head2 otel_span_name


B<syntax:> otel_span_name I<I<C<name>>>



B<context:> I<http>


B<context:> I<server>


B<context:> I<location>





Defines the name of the OTel
L<span|https://opentelemetry.io/docs/concepts/observability-primer/#spans>.
By default, it is a name of the location for a request.
The name can contain variables.







=head2 otel_span_attr


B<syntax:> otel_span_attr I<I<C<name>> I<C<value>>>



B<context:> I<http>


B<context:> I<server>


B<context:> I<location>





Adds a custom OTel span attribute.
The value can contain variables.







=head1 Default span attributes



The following L<span attributes|https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md>
are added automatically:


=over




=item *

C<http.method>



=item *

C<http.target>



=item *

C<http.route>



=item *

C<http.scheme>



=item *

C<http.flavor>



=item *

C<http.user_agent>



=item *

C<http.request_content_length>



=item *

C<http.response_content_length>



=item *

C<http.status_code>



=item *

C<net.host.name>



=item *

C<net.host.port>



=item *

C<net.sock.peer.addr>



=item *

C<net.sock.peer.port>



=back






=head1 Embedded Variables




=over



=item C<$otel_trace_id>




the identifier of the trace the current span belongs to,
for example, C<56552bc4daa3bf39c08362527e1dd6c4>



=item C<$otel_span_id>




the identifier of the current span,
for example, C<4c0b8531ec38ca59>



=item C<$otel_parent_id>




the identifier of the parent span,
for example, C<dc94d281b0f884ea>



=item C<$otel_parent_sampled>




the “C<sampled>” flag of the parent span,
can be “C<1>” or “C<0>”




=back