In CPS-341 the POST operation to create a new data node was updated to bring support for a multiple data trees under a single anchor (or a single root "/" node). In order to achieve this, the JSON data containing multiple data trees are parsed into a Collection of data nodes.
...
It is to be noted here that the methods used for GET operation are not limited to Get a Node API and are reused in other API's as well. All the APIS discussed below internally call the getFragmentWithoutDescendantsByXpath()to retrieve the data trees. This epic covers the impact on all the API's due to the above mentioned changes in CPS core.
A common task across the API's is to maintain backwards compatibility as well.
Get operation should return all the data trees under the root when xpath is set to "/"
after discussion with Toine Siebelink it was decided to give priority to the GET operation first, before heading for other API's. A discussion with the architects is to be scheduled to discuss upon the following points:
should a separate end point be created which returns all the data trees under the root node
impact of ongoing versioning issue with CPS on the above point and backwards compatibility
after discussion with the architects it was decided to have a v2 of the GET API and the v2 will return all the data nodes in an array
To implement V2 of Get Data Node API
New API to return all data nodes when xPath is set to root.
Existing functionality to be used when existing xPath is queried
should GET Data Node return a JSON array or JSON object in response for multiple data trees
as discussed in weekly meeting, it was decided that v2 of the GET API will return JSON Array and v1 will remain as is (that is returns single data node as JSON Object)
Update data node had inconsistencies where, updating leaf nodes for multiple container nodes would throw unexpected error.
And updating multiple list items in a list data node would cause partial update operation
After presenting the findings for patch operation and as per discussion in CPS sub team daily call, it was concluded that support for Patch operation for multiple data nodes would solve the inconsistencies found in the existing Patch operation.
Support for Patch for multiple data nodes to be implemented.
List of impacted API's
Operation
API
Issues
Possible Solution
GET
Anchor
getNode
getNode
Get a Node
should return all the data trees when xpath is set to root(/)
currently returns only the first data tree
modify the existing code for Get a Node API so it returns a List of fragment entities
this impacts other API's as well which make use of the Get operation
a separate API can be developed to return all the data trees, similar to Get all anchors and Get one anchor API in CPS
PUT
Replace a node with descendants
when the API is called with xpath set to "/", it will return all the data trees
once all the data trees are returned the PUT operation will be performed
if xpath is set to "/" and the number of data trees on which the replace operation is being performed is less than the total number of data trees the operation of retrieving all the data trees is not feasible
Replace list content
No issues were found in Delete DataNode API
Following tests were performed
replacing multiple Data Nodes under one container node
replacing multiple Data Nodes under multiple container nodes (under root node xpath)
when xpath is set to "/" the replace operation can return an error message
the user can specify the data tree for which Replace operation is to be performed, but the drawback of this approach is if the number of data trees on which replace operation is to be performed is significantly big
DELETE
Delete a datanode
when delete operation is performed with xpath set to root all the data trees must be deleted
PATCH
Update node leaves
when the API is called and xpath is set to "/", a get operation is executed internally to retrieve all the data trees first
once all the data trees are returned in a List the API proceeds to perform the Patch operation
if xpath is set to "/" and the number of data trees on which the patch operation is being performed is less than the total number of data trees the operation of retrieving all the data trees is not feasible
when xpath is set to "/" the patch operation can return an error message
the user can specify the data tree for which patch operation is to be performed, but the drawback of this approach is, when the number of data trees on which patch operation is to be performed is significantly big
PUT
Replace list content
when the API is called with xpath set to "/", it will return all the data trees
once all the data trees are returned the PUT operation will be performed
if xpath is set to / and the number of data trees on which the replace operation is being performed is less than the total number of data trees the operation of retrieving all the data trees is not feasible
this operation is to be performed on a list in an existing data tree. hence the possibility of multiple lists in multiple trees bring updated at same time is to be taken into consideration
when xpath is set to "/" the replace operation can return an error message
the user can specify the data tree for which Replace operation is to be performed, but the drawback of this approach is if the number of data trees on which replace operation is to be performed is significantly big
The existing GET operation
Code Block
//Returns single fragment entity
default FragmentEntity findFirstRootByDataspaceAndAnchor(@NonNull DataspaceEntity dataspaceEntity,
@NonNull AnchorEntity anchorEntity) {
return findRootsByDataspaceAndAnchor(dataspaceEntity.getId(), anchorEntity.getId()).stream().findFirst()
.orElseThrow(() -> new DataNodeNotFoundException(dataspaceEntity.getName(), anchorEntity.getName()));
The updated GET operation is as follows
...
No issues were found in Delete DataNode API
Following tests were performed:
Individual data nodes were deleted and the ones not deleted were retrieved successfully
When all data trees are deleted individually, the entire data node gets deleted from the DB eventually, i.e. an empty collection is not left behind when all data trees are deleted individually
When deleting using root node xpath, all container nodes are deleted.
PATCH
Anchor
patchAPI
patchAPI
Update node leaves
When the Patch operation is performed with xPath set to root node "/", then leaf value in all the modified data trees must be updated
Currently when updating container nodes using root node xPath, only the first data tree gets updated.
A detailed study on inconsistencies with Patch operation was documented in the following pages:
