Initial Findings

It is found that the current Patch operation in CPS core can only update value of leaf nodes under a container node at a time.

Issues & Decisions:

NotesDecisions

 

As per discussion with stakeholder (DT), the following decisions were made:

  • Support for update operation across data trees is not of high priority.
  • But the error code returned when trying to update. multiple data trees should be made specific.
  • Team decision is to be taken regarding the new/updated error response.

 

After discussion in the CPS-sub team, following conclusions were made:

  • Use correct Error Code and Response Message, when updating multiple data nodes
  • As per CPS Exceptions and REST APIs HTTP Response Codes, the response code was set to 400 with appropriate message.
  • Update for single data node with root node xpath remains as it is.

After the investigation it was found that the reason behind the inconsistencies discovered was lack of support for Patch operation for multiple data nodes.

As per discussion in CPS sub team daily call it was decided to bring in support for Patch operation for multiple data nodes. As it would address all the inconsistencies discovered.

JSON Data Stored in CPS DB using POST operation.

The following JSON data was first stored in CPS DB:

{
  "multiple-data-tree:interface-A": {
    "host-name": "host",
    "interface": [
      {
        "name": "Interface-A",
        "address": "10.10.10.1",
        "subnet-mask": "255.255.255.0",
        "enabled": false
      }
    ],
    "domain": "false"
  },
  "multiple-data-tree:interface-B": {
    "interface": [
      {
        "name": "Interface-B",
        "address": "10.10.10.1",
        "subnet-mask": "255.255.255.0"
      }
    ]
  }
}

Analysis of Patch operation (Update node leaves)

Currently after multiple data trees are stored in CPS DB. On performing the Patch operation, with root node xpath "/", the first data tree is only updated by the Patch operation. To test this following scenarios were performed:

  1. Updating all data trees under an anchor with root node xPath "/"

    CURL request to update multiple leaves across multiple data trees 
    curl --location --request PATCH 'http://localhost:8080/cps/api/v1/dataspaces/testDataspace/anchors/sample/nodes?xpath=%2F' --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: Basic Y3BzdXNlcjpjcHNyMGNrcyE=' --header 'Cookie: JSESSIONID=node0iyclt1syzfqj28jzo5qc5gks1.node0' \
--data '{
  "multiple-data-tree:interface-A": {
    "host-name": "host-A",				   //value to be updated
    "interface": [						   
      {
        "name": "Interface-A",
        "address": "10.10.10.100",         
        "subnet-mask": "255.255.255.25",   
        "enabled": false
      }
    ],
    "domain": "true"
  },
  "multiple-data-tree:interface-B": {
    "interface": [						  
      {
        "name": "Interface-B",
        "address": "10.10.10.100",       //value to be updated
        "subnet-mask": "255.255.255.0"   //value to be updated
       }
    ]
  }
}'
    Response: 500 Server Error 
    {
    "status": "500 INTERNAL_SERVER_ERROR",
    "message": "could not execute statement; SQL [n/a]; nested exception is org.hibernate.exception.DataException: could not execute statement",
    "details": "Check logs for details."
}

    Reason: The following scenario would fail because CPS Patch operation only supports updating multiple leaves under one container node at a time. And here when we try to update multiple leaves present in two different containers the operations fails. 

    On performing Get operation we get the following JSON data, here none of the leaves are updated 
    [
    {
        "int:interface-A": {
            "domain": "false",
            "host-name": "host",
            "interface": [
                {
                    "name": "Interface-A",
                    "address": "10.10.10.1",
                    "enabled": false,
                    "subnet-mask": "255.255.255.0"
                }
            ]
        }
    },
    {
        "int:interface-B": {
            "interface": [
                {
                    "name": "Interface-B",
                    "address": "10.10.10.1",
                    "subnet-mask": "255.255.255.0"
                }
            ]
        }
    }
]

  2. Updating the data trees individually, leads to successful updation
    When updating multiple leaves present under individual data nodes the operation successfully executes.

    CURL request to update leaves under container data node 
    curl --location --request PATCH 'http://localhost:8080/cps/api/v1/dataspaces/testDataspace/anchors/sample/nodes?xpath=%2F' \
--header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: Basic Y3BzdXNlcjpjcHNyMGNrcyE=' --header 'Cookie: JSESSIONID=node0iyclt1syzfqj28jzo5qc5gks1.node0' \
--data '{
    "int:interface-A": {
      "domain": "true",			//value to be updated
      "host-name": "Host-A"	    //value to be updated
   
    }
  }'

    Response 200 OK

    Updated data after making get request 
    [
  {
    "int:interface-A": {
      "domain": "true",			//updated
      "host-name": "Host-A",	//updated
      "interface": [
        {
          "name": "Interface-A",
          "address": "10.10.10.200",		
          "enabled": true,					
          "subnet-mask": "255.255.255.0"
        }
      ]
    }
  }
]
    CURL request to update leaves of one list item in a list data node 
    curl --location --request PATCH 'http://localhost:8080/cps/api/v1/dataspaces/testDataspace/anchors/sample/nodes?xpath=%2Finterface-B' \
--header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: Basic Y3BzdXNlcjpjcHNyMGNrcyE=' --header 'Cookie: JSESSIONID=node0iyclt1syzfqj28jzo5qc5gks1.node0' \
--data '{
        "int:interface": {
            "name": "Interface-B",
            "address": "10.10.10.200",			//value to be updated
            "subnet-mask": "255.255.255.10"		//value to be updated
        }
    }'

    Response 200 OK

    Updated data after making get request 
    [
  {
    "int:interface-B": {
      "interface": [
        {
          "name": "Interface-B",
          "address": "10.10.10.200",		//updated
          "subnet-mask": "255.255.255.10"	//updated
        }
      ]
    }
  }
]

Inconsistencies with Patch Operation

When updating multiple data trees with only leaf nodes

Assuming the following data is in the data base, having one leaf in each data tree

{
  "first-container": {
    "a-leaf": "a-value"
  },
  "last-container": {
    "x-leaf": "x-value"
  }
}

An update operation is performed on both data trees as follows:

curl --location --request PATCH 'http://localhost:8080/cps/api/v1/dataspaces/testDataspace/anchors/multipleDataTree/nodes?xpath=%2F' --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: Basic Y3BzdXNlcjpjcHNyMGNrcyE=' --header 'Cookie: JSESSIONID=node0kglnliqz1tzc1g0x6opgrphei0.node0' \
--data '{
  "first-container": {
    "a-leaf": "a-new-value"
  },
  "last-container": {
    "x-leaf": "x-new-value"
  }
}'

On performing a get operation, it is noticed that only first data tree gets updated

[
  {
    "multiple-data-tree:last-container": {
      "x-leaf": "x-new-value"
    }
  },
  {
    "multiple-data-tree:first-container": {
      "a-leaf": "a-value"
    }
  }
]

When updating multiple list items under a list node, returns Status 200 but list data is not updated

(Note: This following finding was identified as an issue with list-nodes and not multiple data nodes. It is documented separately CPS-1383: Investigate CPS-Path for modifications of multiple fragments under an anchor.)




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