Unable to retrieve a federated, redirected context source using separate tenants.

[jason-fox]

Internally forwarding from an endpoint to itself twice is detected as a loop even when it is not.

Two (and a half) issues here -

1. A forwarding using two registrations with different contextSourceAlias but the same endpoint should not be a loop.
2. A forwarding using two registrations with different tentant but the same endpoint should not be a loop.
3. There is no indication in the response that a Loop may have occurred - Maybe add an NGSI-LD Warning header?

Create an Entity on the vet Tenant:

curl -iX POST \
  http://localhost:1026/ngsi-ld/v1/entities \
  -H 'Content-Type: application/ld+json' \
  -H 'NGSILD-Tenant: vet' \
  -d '{
    "id": "urn:ngsi-ld:Animal:cow103",
    "type": "Animal",
    "name": {
        "type": "Property",
        "value": "Buttercup"
    },
    "@context": "https://raw.githubusercontent.com/FIWARE/tutorials.Context-Providers/NGSI-LD/data-models/ngsi-context.jsonld"
}

Now add a registration on the farmer tenant

curl -L 'http://localhost:1026/ngsi-ld/v1/csourceRegistrations/' \
-H 'Link: <http://context/ngsi-context.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json' \
-H 'NGSILD-Tenant: farmer' \
-H 'Content-Type: application/json' \
-d '{
    "type": "ContextSourceRegistration",
    "information": [
        {
            "entities": [
                {
                    "type": "Animal"
                }
            ]
        }
    ],
    "contextSourceAlias": "VET",
    "tenant": "vet",
    "mode": "inclusive",
    "operations": [
        "federationOps"
    ],
    "endpoint": "http://orion:1026"
}'

The Entity can be viewed from the farmer tenant. ✅

curl -L 'http://localhost:1026/ngsi-ld/v1/entities/urn:ngsi-ld:Animal:cow103' \
-H 'Link: <http://context/ngsi-context.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json' \
-H 'Accept: application/ld+json' \
-H 'NGSILD-Tenant: farmer'

Result:

{
   "id": "urn:ngsi-ld:Animal:cow103",
    "type": "Animal",
   "name": {
        "type": "Property",
        "value": "Buttercup"
    }
}

Now add a second registration from the DEFAULT tenant

curl -L 'http://localhost:1026/ngsi-ld/v1/csourceRegistrations/' \
-H 'Link: <http://context/ngsi-context.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json' \
-H 'Content-Type: application/json' \
-d '{
    "type": "ContextSourceRegistration",
    "information": [
        {
            "entities": [
                {
                    "type": "Animal"
                }
            ]
        }
    ],
    "contextSourceAlias": "FARMER",
    "tenant": "farmer",
    "mode": "redirect",
    "operations": [
        "redirectionOps"
    ],
    "endpoint": "http://orion:1026"
}'

The Entity cannot be viewed from the DEFAULT tenant. ❌

curl -L 'http://localhost:1026/ngsi-ld/v1/entities/urn:ngsi-ld:Animal:cow103' \
-H 'Link: <http://context/ngsi-context.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json' \
-H 'Accept: application/ld+json' \
-H 'NGSILD-Tenant: farmer'

Result:

{
    "type": "https://uri.etsi.org/ngsi-ld/errors/ResourceNotFound",
    "title": "Entity not found",
    "detail": "urn:ngsi-ld:Animal:cow103"
}

[kzangeli]

Yes, this twisted!:) example hasn't been implemented yet ...
The tenant name hasn't been included in the Via header and thus, the second time it enters the broker, it's considered a loop.
Easy fix, just include the tenant name in the "Via item"