Internet-Draft rc_trace July 2023
Gagliano, et al. Expires 7 January 2024 [Page]
Intended Status:
Standards Track
R. Gagliano
Cisco Systems
K. Larsson
Deutsche Telekom AG
J. Lindblad
Cisco Systems

RESTCONF Extension to support Trace Context Headers


This document extends the RESTCONF protocol in order to support trace context propagation as defined by the W3C.

About This Document

This note is to be removed before publishing as an RFC.

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Table of Contents

1. Introduction

Network automation and management systems commonly consist of multiple sub-systems and together with the network devices they manage, they effectively form a distributed system. Distributed tracing is a methodology implemented by tracing tools to follow, analyze and debug operations, such as configuration transactions, across multiple distributed systems. An operation is uniquely identified by a trace-id and through a trace context, carries some metadata about the operation. Propagating this "trace context" between systems enables forming a coherent view of the entire operation as carried out by all involved systems.

The W3C has defined two HTTP headers (traceparent and tracestate) for context propagation that are useful for distributed systems like the ones defined in [RFC8309]. The goal of this document is to adopt this W3C specification for the RESTCONF protocol.

This document does not define new HTTP extensions but makes those defined in [W3C-Trace-Context] optional headers for the RESTCONF protocol.

In [I-D.draft-rogaglia-netconf-trace-ctx-extension-03], the NETCONF protocol extension is defined and we will re-use several of the YANG and XML objects defined in that document for RESTCONF. Please refer to that document for additional context and example applications.

1.1. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT","SHOULD","SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2. RESTCONF Extensions

A RESTCONF server SHOULD support trace context traceparent header as defined in [W3C-Trace-Context].

A RESTCONF server SHOULD support trace context tracestate header as defined in [W3C-Trace-Context].

2.1. Errors handling

The RESTCONF server SHOULD follow the "Processing Model for Working with Trace Context" as specified in [W3C-Trace-Context].

If the server rejects the RPC because of the trace context headers values, the server MUST return an rpc-error with the following values:

  error-tag:      operation-failed
  error-type:     protocol
  error-severity: error

Additionally, the error-info tag SHOULD contain a relevant details about the error.

Finally, the sx:structure defined in [I-D.draft-rogaglia-netconf-trace-ctx-extension-03] SHOULD be present in any error message from the server.

Example of a badly formated trace context extension using [RFC8040] example B.2.1:

  POST /restconf/data/example-jukebox:jukebox/library HTTP/1.1
  Content-Type: application/yang-data+json
  traceparent: SomeBadFormatHere
  tracestate: OrSomeBadFormatHere

    "example-jukebox:artist" : [
        "name" : "Foo Fighters"

And the expected error message:

 HTTP/1.1 400 Bad Request
 Date: Tue, 20 Jun 2023 20:56:30 GMT
 Server: example-server
 Content-Type: application/yang-data+json

 { "ietf-restconf:errors" : {
     "error" : [
         "error-type" : "protocol",
         "error-tag" : "operation-failed",
         "error-severity" : "error",
         "error-message" :
         "OTLP traceparent attribute incorrectly formatted",
         "error-info": {
           "ietf-netconf-otlp-context:meta-name" : "traceparent",
           "ietf-netconf-otlp-context:meta-value" :
           "ietf-netconf-otlp-context:error-type" :

2.2. Trace Context header versionning

This extension refers to the [W3C-Trace-Context] trace context capability. The W3C traceparent and trace-state headers include the notion of versions. It would be desirable for a RESTCONF client to be able to discover the one or multiple versions of these headers supported by a server. We would like to achieve this goal avoiding the deffinition of new RESTCONF capabilities for each headers' version.

[I-D.draft-rogaglia-netconf-trace-ctx-extension-03] defines a pair YANG modules that SHOULD be included in the YANG library per [RFC8525] of the RESTCONF server supporting the RESTCONF Trace Context extension that will refer to the headers' supported versions. Future updates of this document could include additional YANG modules for new headers' versions.

3. Security Considerations

TODO Security

4. IANA Considerations

This document has no IANA actions.

5. Acknowledgments

We would like to acknowledge

6. References

6.1. Normative References

Gagliano, R., Larsson, K., and J. Lindblad, "NETCONF Extension to support Trace Context propagation", Work in Progress, Internet-Draft, draft-rogaglia-netconf-trace-ctx-extension-03, , <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., and R. Wilton, "YANG Library", RFC 8525, DOI 10.17487/RFC8525, , <>.
"W3C Recommendation on Trace Context", , <>.

6.2. Informative References

Wu, Q., Liu, W., and A. Farrel, "Service Models Explained", RFC 8309, DOI 10.17487/RFC8309, , <>.

Appendix A. Example RESTCONF calls


Appendix B. Changes (to be deleted by RFC Editor)

Appendix C. TO DO List (to be deleted by RFC Editor)

Authors' Addresses

Roque Gagliano
Cisco Systems
Avenue des Uttins 5
CH-1180 Rolle
Kristian Larsson
Deutsche Telekom AG
Jan Lindblad
Cisco Systems