| Internet-Draft | RESTCONF Trace Context Headers | December 2024 |
| Gagliano, et al. | Expires 15 June 2025 | [Page] |
This document defines an extension to the RESTCONF protocol in order to support Trace Context propagation as defined by the W3C.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://github.com/netconf-wg/restconf-trace-ctx-headers/blob/gh-pages/draft-ietf-netconf-restconf-trace-ctx-headers.txt. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-netconf-restconf-trace-ctx-headers/.¶
Discussion of this document takes place on the NETCONF Working Group mailing list (mailto:netconf@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/netconf/. Subscribe at https://www.ietf.org/mailman/listinfo/netconf/.¶
Source for this draft and an issue tracker can be found at https://github.com/https://github.com/netconf-wg/restconf-trace-ctx-headers.¶
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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 track, analyze and debug operations such as configuration transactions, across multiple distributed systems.¶
The W3C has defined two HTTP headers (traceparent and tracestate) in [W3C-Trace-Context] for context propagation that are useful for distributed systems like the ones defined in section 4 of [RFC8309].¶
According to the W3C specification, each operation is uniquely identified by a "trace-id" field, and carries multiple metadata fields about the operation. Propagating this Trace Context between systems provides a coherent view of the entire operation as carried out by all involved systems.¶
In [I-D.draft-ietf-netconf-trace-ctx-extension], 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.¶
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.¶
Additionally, the document utilizes the following abbreviations:¶
OpenTelemetry protocol as defined by [OpenTelemetry]¶
Metrics, Events, Logs and Traces¶
A RESTCONF server that implements the Trace Context propagation mechanism defined in this document MUST support the Trace Context traceparent header as defined in [W3C-Trace-Context].¶
A RESTCONF server SHOULD support the Trace Context tracestate header as defined in [W3C-Trace-Context].¶
A RESTCONF server SHOULD follow the "Processing Model for Working with Trace Context" as specified in [W3C-Trace-Context]. Based on this processing model, it is NOT RECOMMENDED to reject an RPC because of the Trace Context header values.¶
If a server decides to reject an RPC because of the Trace Context header values, the server MUST return a RESTCONF 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-ietf-netconf-trace-ctx-extension] SHOULD be present in any error message from the server.¶
The RESTCONF protocol extension described in this document refers to the [W3C-Trace-Context] Trace Context capability. The W3C traceparent and tracestate 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.¶
[I-D.draft-ietf-netconf-trace-ctx-extension] 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.¶
The related document [I-D.draft-ietf-netconf-trace-ctx-extension] defines two YANG modules that are used when implementing the Trace Context concept, regardless of YANG-based protocol. These modules are completely empty, and therefore have very limited security considerations. Their purpose is only to indicate which Trace Context header versions the server supports using YANG Library [RFC8525].¶
The traceparent and tracestate headers make it easier to track and correlate the flow of requests and their downstream effect on other systems. This is indeed the whole point with these headers. This knowledge may be used by unauthorized entities to infer a map of a managed network.¶
All advice mentioned in the [W3C-Trace-Context] under the Privacy Considerations and Security Considerations also apply to this document.¶
The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].¶
This document has no IANA actions.¶
The authors would like to acknowledge the valuable implementation feedback from Christian Rennerskog and Per Andersson. Many thanks to Raul Rivas Felix, Alexander Stoklasa, Luca Relandini and Erwin Vrolijk for their help with the demos regarding integrations. The help and support from Med Boucadair, Jean Quilbeuf and Benoît Claise has also been invaluable to this work.¶
All examples from Appendix B of [RFC8040] could be recreated in this section by adding the new header described in this document. We selected one example from that document as reference.¶
To create a new "artist" resource within the "library" resource, a client might send the following request:¶
POST /restconf/data/example-jukebox:jukebox/library HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
traceparent: 00-405062f633be64ee006089dfca95a153-e021f9e263aad8e2-01
tracestate: vendorname1=opaqueValue1,vendorname2=opaqueValue2
{
"example-jukebox:artist" : [
{
"name" : "Foo Fighters"
}
]
}
¶
If the resource is created, the server might respond as follows:¶
HTTP/1.1 201 Created
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Location: https://example.com/restconf/data/\
example-jukebox:jukebox/library/artist=Foo%20Fighters
Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
ETag: "b3830f23a4c"
traceparent: 00-405062f633be64ee006089dfca95a153-e021f9e263aad8e2-01
tracestate: vendorname1=opaqueValue1,vendorname2=opaqueValue2
¶
[W3C-Trace-Context] specifies that a vendor may validate the tracestate header and that invalid headers may be discarded. Section 2.1 on Error handling (Section 2.1), states that servers may return an error. Let's assume that an implementation follows that behavior.¶
Example of a badly formated tracestate header using [RFC8040] example (Appendix B.2.1), in which a server receives the following:¶
POST /restconf/data/example-jukebox:jukebox/library HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
traceparent: 00-405062f633be64ee006089dfca95a153-e021f9e263aad8e2-01
tracestate: SomeBadFormatHere
{
"example-jukebox:artist" : [
{
"name" : "Foo Fighters"
}
]
}
¶
To which the server responds with an error message:¶
HTTP/1.1 400 Bad Request
Date: Thu, 20 Jun 2024 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" :
"Context traceparent header incorrectly formatted",
"error-info": {
"ietf-trace-context:trace-context-error-info" : {
"ietf-trace-context:meta-name" : "tracestate",
"ietf-trace-context:meta-value" :
"SomeBadFormatHere",
"ietf-trace-context:error-type" :
"ietf-trace-context:bad-format"
}
}
}
]
}
}
¶
Added WGLC comments¶
Changed namespaces and module name¶
Fix error in error response¶
Comments from Med Boucadair¶
Removed markdown formatting of tracestate and traceparent, as toolchain could not handle this properly¶
Removed references to RFC8341 (NACM) as the passage in the security considerations no longer need it¶
Rearranged text in introduction to include referenes in a more natural order¶
Removed several references to "we" and replaced with more neutral language¶
Clarified that everything described as MUST requirements in this document only apply to RESTCONF implementations that implement this document. Other RESTCONF implementations do not need to care about this document, it's an optional extension¶
Clarified that the YANG modules used by this document is defined by the sibling document for NETCONF¶
Lots of updated wording based on review feedback¶
Added Security considerations¶
Added Acknowledgements¶
Added several Normative references¶
Added links to latest document on github¶
Added RESTCONF example for success and error¶
Modified Error Handling to reflect better W3C alignment based on implementation feedback¶
Firmed up error handling and YANG-library to MUST-requirements¶