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Overview

CPS temporal data query will allow allows the user to fetch data based on multiple filtering criteria. This data can be used to create graphs and help the by an analytical system to take decisions.

Filtering

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Criteria

As it is time-series data, it can be filtered based on three main criteria:

Datetime

• Data after specified DateTime (To be supported in Istanbul Release)
• Data before specified

  Datetime 

• Data in last X hours 
• Data after a particular DateTime
Data before a particular DateTime 
• Last X network datarecords

DataTypes in CPS Core

• Dataspace & schema-

  set

  set (To be supported in Istanbul Release)

• Dataspace & anchoranchor (To be supported in Istanbul Release)
• Dataspace & multiple anchors - To improve performance, if there is a need to fetch data for multiple anchors.
• Dataspace

Payload (To be partially supported in Istanbul Release)

• Payload

  Based on a

  subsection or

  field in the payload. These criteria

  do

  need schema-set to be fixed to search in the same set of anchors. The

  payload will be passed in JSON format as it is more flexible and the user will not expect to implement functionality similar to cps-path query

  details of the format are defined here. 

We will implement only the basic APIs first and will add complex ones when required. 

Other

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Parameters 

There are other parameters, listed below, that can have an impact on the response. 

Assumptions

• Temporal database stores full information in the payload ( CPS-192: Design data store for Temporal Service). 
• It is possible that data stored for the different timestamps is the same, especially if the payload is used to filter data.
• Data in the response body will always contain the entire payload data.

Proposed APIs

...

Return data entries for an anchor after the specified Datetime, which matches the payload format.

...

Return data entries based on provided schema-set after the specified Datetime, which matches the payload format.

Approach 1 - GET

In the GET APIs, all the filtering parameters are passed as query parameter. 

...

Payload Filter Format 

Anchor
payloadFilterFormat payloadFilterFormat

The data can be filtered, using JSON format, on one  field at any level, but it is important to provide the entire path from the root. The below JSON is used as an example to explain the filtering format

{
  "idNearRTRIC": "1",
  "labels" : [ "cps", "ran"],
  "nestedObject": {
    "id": "4",
    "attributes": {
      "gNBDUId": 4.0,
      "gNBDUName": "gnduserver4",
      "gNBIdLength": 32.0
    }
  },
  "GNBDUFunction": [
    {
      "idGNBDUFunction": "5",
      "NRCellDU": [
        {
          "idNRCellDU": "13905",
          "attributes": {
            "nRPCI": 12.0,
            "nRTAC": 310.0,
            "cellLocalId": 13905.0
          }
        },
        {
          "idNRCellDU": "14655",
          "attributes": {
            "nRPCI": 12.0,
            "nRTAC": 310.0,
            "cellLocalId": 14655.0
          }
        }
      ],
      "attributes": {
        "gNBDUId": 5.0,
        "gNBDUName": "gnduserver5",
        "gNBIdLength": 32.0
      }
    }
  ]
}

The filtering scenarios and the format are defined below:

Proposed APIs

The GET Endpoints contains information about the anchors and the rest of the filtering criteria are passed as query parameter. The below-mentioned query parameters are supported by all endpoints.

1. after - timestamp ( ISO Format) to consider data created after the specified Timestamp
2. simplePayloadFilter - to define payload filtering criteria
3. pageNumber - to define the page number (required for pagination)
4. pageLimit - to limit the response size
5. pointInTime - to consider data changed or added before this time.
6. sort - to define the order of data in the result set

The response format for endpoints is the same and defined here

By Dataspace and Anchor

URL: GET /dataspaces/{dataspace-name}​/anchors/{anchor-name}​/history

Example: GET /dataspaces/{dataspace-name}​/anchors/{anchor-name}​/history?after=

...

2021-03-21T00:00:00-0:00&simplePayloadFilter={"

...

idNearRTRIC":"

...

1"}&

...

pageLimit=500

...

By Dataspace and Schema-set

...

URL: 

​GET /dataspaces/{dataspace-name}/

...

anchors/history?schemaSet={schemaset-name}

Example: GET /dataspaces/{dataspace-name}/anchors?schemaSet={schemaset-name}&after=2021-03-21T00:00:00-0:00&simplePayloadFilter={"idNearRTRIC":"1"}

Response 

Anchor
responseBody responseBody

...

...

{
  "nextRecordsLink": "cps-temporal/api/v1/dataspaces/{dataspace-name}/anchors/{anchor-name}/history?after=<epoch-time>&maxSize=1000&before=<epoch-time>&index=2&point-in-time=DATE2021-03-21T00:00:00-0:00&simplePayloadFilter={"idNearRTRIC":"1"}&pageLimit=500&pointInTime=2021-04-21T00:00:00-0:00&pageNumber=2",
  "previousRecordsLink": "cps-temporal/api/v1/dataspaces/{dataspace-name}/anchors/{anchor-name}/history?after=<epoch-time>&maxSize=1000&before=<epoch-time>&index=0&point-in-time=DATE2021-03-21T00:00:00-0:00&simplePayloadFilter={"idNearRTRIC":"1"}&pageLimit=500&pointInTime=2021-04-21T00:00:00-0:00&pageNumber=0",
  "records": [
    {
      "timestamp": "12345677888892021-03-21T00:00:00-0:00",
      "dataspace": "my-dataspace",
      "schemaSet": "my-schema-set",
      "anchor": "my-anchor",
      "data": {
        "status" : "UP"
      }
    }
  ]
}

Pros:

• Provides the ability to cache data based on URL. It is not relevant as data can change based on when the API is called.
• Can provide links for the next record and previous record link in the response itself.
• point-in-time can have the current timestamp as the default value because we can add it in the next record and previous record link as a part of the response.

Cons

• The payload is JSON can be a little longer and will not fit within the GET URL length limit.

Approach 2 - POST

As we are query data, POST is not intuitive but the search can be considered as a resource with different filtering criteria. We need only one API as the filtering criteria will be provided in the body, which allows the payload to be big if required.

API URL: cps-temporal/api/v1/filters?maxSize=1000&index=1 

Request Body

{
  "dataspaceName": "dataspace-001",
  "anchorName": "anchor-001",
  "schemaSetName": "schemaset-001",
  "after" : "2021-03-21T00:00:00-0:00",
  "pointInTime": "2021-04-21T00:00:00-0:00", // mandatory 
  "payload": {
    "status": "UP"
  }
}

 Response Body

[
  {
    "timestamp": "1234567788889",
    "dataspace": "my-dataspace",
    "schemaSet": "my-schema-set",
    "anchor": "my-anchor",
    "data": {
      "status": "UP"
    }
  }
]

Questions

1. Where to keep pagination related variables in the POST API?
2. GET Approach - Should we disable caching or ask the user to pass the point-in-time parameter value?

Open Items

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