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Trace Context

Trace Context header

For all transaction described in this implementation guide, the HTTP traceparent header is specified. This header is defined in the W3C Trace Context Recommendation.

The header value is made of four parts separated by dashes: the version, trace-id, parent-id and trace-flags. For example:

GET /request HTTP/1.1
traceparent: 00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-00

• The version is currently set to 00.
• The trace-id is a unique identifier for this transaction instance (i.e. an HTTP request and its response). It is a 16-byte array encoded as 32 hexadecimal characters, all lowercase.
• The parent-id is a unique identifier for this message. It is an 8-byte array, encoded as 16 hexadecimal characters, all lowercase.
• The trace-flags is used to communicate tracing flags with the consumer. This implementation guide specifies no requirements for this field, it is recommended using the value 00.

Each actor shall support the traceparent header. Grouped actors shall use the same trace-id value to correlate IHE transactions.

Actors of all transactions SHALL support the W3C Trace Context Recommendation and SHOULD send the HTTP header traceparent in requests.

Moreover, when serving incoming requests, each actor SHALL:

• Accept the HTTP header traceparent if it is contained in the incoming request, otherwise — generate it.
• Send the HTTP header traceparent in all requests induced by the incoming request, with the same value of the field trace id as for the incoming request.

Audit event requirements

The traceparent header value of the generated message SHALL be added to the generated Audit Event: for the client, the header value of the request; for the responder, the header value of the response. It is described as an AuditEvent.entity, with the type and roleelement as demonstrated below.

{
  "resourceType" : "AuditEvent",
  /* Rest of the AuditEvent */
  "entity" : [
    {
      "what" : {
        "identifier" : {
          "value" : "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-00"
        }
      },
      "type" : {
        "system" : "http://terminology.hl7.org/CodeSystem/audit-entity-type",
        "code" : "4",
        "display" : "Other"
      },
      "role" : {
        "system" : "http://terminology.hl7.org/CodeSystem/object-role",
        "code" : "26",
        "display" : "Processing Element"
      }
    }
  ]
}