FHIR to HL7v2 internal server error

[mklierman]

I'm attempting to use the sample template, ObservationBundle, to convert from FHIR to Hl7v2 and I'm getting a 500 internal server error. I'm able to convert from Hl7v2 to FHIR and JSON to FHIR without issues.

The application log shows:
Failed conversion request with HTTP Status 500 InternalServerError; TOP-LEVEL-ERROR: InternalServerError - Encountered an unexpected service error.; INNER ERROR: Code: TemplateRenderFailed, Message: 'An unexpected error was encountered while rendering the template: Error happened when rendering templates: Object reference not set to an instance of an object..', Exception: TemplateException; InnerException: RenderException - Code: TemplateRenderingError, Message: 'Error happened when rendering templates: Object reference not set to an instance of an object.'

This happens even if I use an empty input string like so:

{ "InputDataFormat": "Fhir", "RootTemplateName": "ObservationBundle", "InputDataString": "{} }

[kyclai]

Hi @mklierman,

I followed deployment-options.md to deploy a FHIR converter service with the default configuration. I then followed use-convert-web-apis.md to call APIs through the deployed FHIR converter service.

Sending the following POST request resulted in a successful HL7v2 response:

• Request URI: POST {{ _.service_url }}/convertToHl7v2?api-version=2024-05-01-preview
• Request body: (taken from the sample request body under this, except I removed the second Observation resource from the InputDataString for brevity)

  {
    "InputDataFormat": "Fhir",
    "RootTemplateName": "ObservationBundle",
    "InputDataString": "{\"resourceType\":\"Bundle\",\"id\":\"bundle-response-medsallergies\",\"type\":\"batch-response\",\"entry\":[{\"resource\":{\"resourceType\":\"Patient\",\"id\":\"example\",\"meta\":{\"versionId\":\"1\",\"lastUpdated\":\"2018-11-12T03:35:20.715Z\"},\"identifier\":[{\"use\":\"usual\",\"type\":{\"coding\":[{\"system\":\"http://terminology.hl7.org/CodeSystem/v2-0203\",\"code\":\"MR\"}]},\"system\":\"urn:oid:1.2.36.146.595.217.0.1\",\"value\":\"12345\",\"period\":{\"start\":\"2001-05-06\"},\"assigner\":{\"display\":\"AcmeHealthcare\"}}],\"active\":true,\"name\":[{\"use\":\"official\",\"family\":\"Chalmers\",\"given\":[\"Peter\",\"James\"]},{\"use\":\"usual\",\"given\":[\"Jim\"]},{\"use\":\"maiden\",\"family\":\"Windsor\",\"given\":[\"Peter\",\"James\"],\"period\":{\"end\":\"2002\"}}],\"telecom\":[{\"use\":\"home\"},{\"system\":\"phone\",\"value\":\"(03)55556473\",\"use\":\"work\",\"rank\":1},{\"system\":\"phone\",\"value\":\"(03)34105613\",\"use\":\"mobile\",\"rank\":2},{\"system\":\"phone\",\"value\":\"(03)55558834\",\"use\":\"old\",\"period\":{\"end\":\"2014\"}}],\"gender\":\"male\",\"birthDate\":\"1974-12-25\",\"_birthDate\":{\"extension\":[{\"url\":\"http://hl7.org/fhir/StructureDefinition/patient-birthTime\",\"valueDateTime\":\"1974-12-25T14:35:45-05:00\"}]},\"deceasedBoolean\":false,\"address\":[{\"use\":\"home\",\"type\":\"both\",\"text\":\"534ErewhonStPeasantVille,Rainbow,Vic3999\",\"line\":[\"534ErewhonSt\"],\"city\":\"PleasantVille\",\"district\":\"Rainbow\",\"state\":\"Vic\",\"postalCode\":\"3999\",\"period\":{\"start\":\"1974-12-25\"}}],\"contact\":[{\"relationship\":[{\"coding\":[{\"system\":\"http://terminology.hl7.org/CodeSystem/v2-0131\",\"code\":\"N\"}]}],\"name\":{\"family\":\"duMarché\",\"_family\":{\"extension\":[{\"url\":\"http://hl7.org/fhir/StructureDefinition/humanname-own-prefix\",\"valueString\":\"VV\"}]},\"given\":[\"Bénédicte\"]},\"telecom\":[{\"system\":\"phone\",\"value\":\"+33(237)998327\"}],\"address\":{\"use\":\"home\",\"type\":\"both\",\"line\":[\"534ErewhonSt\"],\"city\":\"PleasantVille\",\"district\":\"Rainbow\",\"state\":\"Vic\",\"postalCode\":\"3999\",\"period\":{\"start\":\"1974-12-25\"}},\"gender\":\"female\",\"period\":{\"start\":\"2012\"}}],\"managingOrganization\":{\"reference\":\"Organization/1\"}}},{\"resource\":{\"resourceType\":\"Observation\",\"id\":\"f001\",\"identifier\":[{\"use\":\"official\",\"system\":\"http://www.bmc.nl/zorgportal/identifiers/observations\",\"value\":\"6323\"}],\"status\":\"final\",\"code\":{\"coding\":[{\"system\":\"http://loinc.org\",\"code\":\"15074-8\",\"display\":\"Glucose[Moles/volume]inBlood\"}]},\"subject\":{\"reference\":\"Patient/f001\",\"display\":\"P.vandeHeuvel\"},\"effectiveDateTime\":\"2013-04-02T09:30:10+01:00\",\"issued\":\"2013-04-03T15:30:10+01:00\",\"performer\":[{\"reference\":\"Practitioner/f005\",\"display\":\"A.Langeveld\"}],\"valueQuantity\":{\"value\":6.3,\"unit\":\"mmol/l\",\"system\":\"http://unitsofmeasure.org\",\"code\":\"mmol/L\"},\"interpretation\":[{\"coding\":[{\"system\":\"http://terminology.hl7.org/CodeSystem/v3-ObservationInterpretation\",\"code\":\"H\",\"display\":\"High\"}]}],\"referenceRange\":[{\"low\":{\"value\":3.1,\"unit\":\"mmol/l\",\"system\":\"http://unitsofmeasure.org\",\"code\":\"mmol/L\"},\"high\":{\"value\":6.2,\"unit\":\"mmol/l\",\"system\":\"http://unitsofmeasure.org\",\"code\":\"mmol/L\"}}]}}]}"
  }
  

However, I'm also able to reproduce getting an InternalServerError if I send a POST request with an empty InputDataString, as you observed:

• Request URI: POST {{ _.service_url }}/convertToHl7v2?api-version=2024-05-01-preview
• Request body:

  {
    "InputDataFormat": "Fhir",
    "RootTemplateName": "ObservationBundle",
    "InputDataString": "{}"
  }
  

Passing in an empty InputDataString could be better handled with a more descriptive error message than returning an InternalServerError. However, the FHIR converter service expects non-empty input data to convert.
Some questions for you:

1. If you try the first request body that I provided above, does it still return an InternalServerError? If yes, I'd recommend double checking your configuration settings and maybe trying the default configuration to rule out other issues.
2. What's the original request body that you're using that returns an InternalServerError? I'd recommend double checking your InputDataString.