Single View Patch

info

This feature is supported from version 5.6.1 of the Single View Creator

Pre Requisites

To configure a Single View Creator dedicated to Single View Patch operations, some steps have to be followed:

• Set the env var KAFKA_PROJECTION_UPDATE_TOPICS with the comma separated list of the pr-update topics corresponding to the SV-Patch Projection.
• Configure the service to consume from Kafka (see the Consuming from Kafka section)
• Create a new ConfigMap with this Runtime Mount Path: /home/node/app/svTriggerHandlerCustomConfig
• Set the env var SV_TRIGGER_HANDLER_CUSTOM_CONFIG with the path to the main file defining SV-Patches actions, for example /home/node/app/svTriggerHandlerCustomConfig/svTriggerHandlerCustomConfig.json

Main Configuration

The main file, usually referred to as svTriggerHandlerCustomConfig.json, assign to each Projection one or more Patch Actions.

It is structured as following:

{
  "patchRules": [
    {
      "projection": "projection_A",
      "patchAction": "__fromFile__[customPatchForA.js]"
    },
    {
      "projection": "projection_B",
      "patchAction": "__fromFile__[customPatchForB.js]"
    },
    {
      "projection": "projection_B",
      "patchAction": "__fromFile__[secondCustomPatchForB.js]"
    }
  ]
}

Patch Action

In the same config map, we can insert the other files that are defined in the __fromFile__ directive of the patchActions field in the patchRules array from the svTriggerHandlerCustomConfig.json (in the above example, customPatchForA.js and customPatchForB.js).

They are structured as following:

'use strict'

module.exports = (logger, projection) => {
  logger.info('Function custom patch for projection A')
  return {
    filter: { 'sv-field': projection['projection-field'] },
    update: { $set: { 'sv-field-to-update': projection['changed-field'] } },
  }
}

A Patch Action works as follows: the MongoDB update object will be applied to all single view records matching the MongoDB query defined in the filter object.

Filtering which elements to update inside arrays

To patch fields of specific elements within an array, you can add the arrayFilters property inside the object returned by your patch action: this field behaves exactly like the arrayFilters option while using the positional operator $[].

'use strict'

module.exports = (logger, projection) => {
  logger.info('Function custom patch for projection A')
  return {
    filter: { 'sv-field': 'someValue' }, // This can be an empty object if needed
    update: {
      $set: {
        "array-field.$[item-name].array-item-field": projection['changed-field']
      }
    },
    arrayFilters: [{
      "item-name.array-item-field-id": projection['projection-A-field-id']
    }]
  }
}