Invalid JSON on GET request due to rounding error of decimal numbers

[FWuellhorst]

Bug description

• Orion version: 3.6.0
• MongoDB version 4.4
• Env variables or CLI parameters

      - ME_CONFIG_OPTIONS_EDITORTHEME=${ME_CONFIG_OPTIONS_EDITORTHEME:-ambiance}
      - ME_CONFIG_MONGODB_SERVER=${ME_CONFIG_MONGODB_SERVER:-mongodb}
      - ME_CONFIG_MONGODB_PORT=${ME_CONFIG_MONGODB_PORT:-27017}
      - ME_CONFIG_MONGODB_ENABLE_ADMIN=${ME_CONFIG_MONGODB_ENABLE_ADMIN:-true}
      - ME_CONFIG_MONGODB_AUTH_DATABASE=${ME_CONFIG_MONGODB_AUTH_DATABASE:-admin}

• Operating System or Docker Image used: docker v 20.10.16; fiware/orion:3.6.0

How to reproduce it

1. Create an entity with an attribute containing a number
2. Update the value of said attribute to e.g. 7.999999999536117
3. Get the entity via requests. I used the python requests package with the following settings:

url: 'http://some_ipv4:1026/v2/entities/abc'
{'options': <AttrsFormat.NORMALIZED: 'normalized'>}
{'User-Agent': 'python-requests/2.27.1', 'Accept-Encoding': 'gzip, deflate', 'Accept': '*/*', 'Connection': 'keep-alive', 'fiware-service': 'abc', 'fiware-servicepath': '/abc'}

4. Try to parse the return as json and get the JSONDecodeError:

....
"pressure": {
    "type": "Number",
    "value": 8.,
    "metadata": {
      "TimeInstant": {
        "type": "DateTime",
        "value": "2023-05-30T07:12:41.210Z"
      }
    }
  }

I know this is not a clear script to reproduce, but maybe it is already sufficient to reproduce. If the error does not occur on your side, I can invest the time and give a detailed script to reproduce.

Expected behavior
Either return 7.999999999536117 or 8.0 as the value for the attribute.

[fgalan]

Thanks for the report!

Reproduced with newest Orion version (3.8.0) in language-agnostic way. Creating entity this way:

$ curl localhost:1026/v2/entities -s -S -H 'Content-Type: application/json' -d @- <<EOF
{
  "id": "Room1",
  "type": "Room",
  "temperature": {
    "value": 7.999999999536117,
    "type": "Number"
  }
}
EOF

Getting the entity, wrong JSON:

$ curl localhost:1026/v2/entities/Room1 -s -S
{"id":"Room1","type":"Room","temperature":{"type":"Number","value":8.,"metadata":{}}}

Entity at DB is fine, so it is a problem in the rendering logic:

{
	"_id" : {
		"id" : "Room1",
		"type" : "Room",
		"servicePath" : "/"
	},
	"attrNames" : [
		"temperature"
	],
	"attrs" : {
		"temperature" : {
			"value" : 7.999999999536117,
			"type" : "Number",
			"creDate" : 1685460364.503991,
			"modDate" : 1685460364.503991,
			"mdNames" : [ ]
		}
	},
	"creDate" : 1685460364.503991,
	"modDate" : 1685460364.503991,
	"lastCorrelator" : "4a9735a6-fefe-11ed-bfdf-000c29583ca5"
}

[FWuellhorst]

Thanks for providing the code to reproduce this!

[fgalan]

Problem is here

void JsonObjectHelper::addNumber(const std::string& key, double value)
{
  if (!empty)
  {
    ss += ',';
  }
  ss += '"';
  ss += toJsonString(key);
  ss += "\":";
  ss +=  double2string(value);

  empty = false;

}

value is ok, but it is wronly rendered in the ss string,

So it seems double2string() function has flaws.

[fgalan]

PR #4354

[fgalan]

This issue should be fixed now in master branch.

@FWuellhorst could you tests using telefonicaiot/fiware-orion:latest dockerhub image to check it and provide feedback on this issue, please? Thanks!

[FWuellhorst]

@fgalan Yes, it does work for me! Thanks for the quick fix!
A short follow-up question: Is this orion version compatible with mongo:4.4 and iotagent-json:1.21.1?
It seems to work, but I don't want to run into troubles later on.

[fgalan]

A short follow-up question: Is this orion version compatible with mongo:4.4 and iotagent-json:1.21.1?

For questions about Orion, please use the proper channel, which is https://stackoverflow.com (using the "fiware-orion" label). Github issues are for other kind of items (bugs, feature requests, etc.).

Given the positive feedback in the previous comment (thanks!), I'm going to close this issue.