Add Merge-Patch Support Handling

CHANGES_NEXT_RELEASE

@@ -1,2 +1,3 @@
+- Add NGSI-LD Merge-Patch Support Handling #1283
 - Update to offer NGSI-LD 1.6.1. Registrations #1302
 - Document removal of support for NGSI-LD 1.3.1 Interface

config.js

@@ -29,7 +29,12 @@ var config = {
     },
     server: {
         port: 4041,
-        host: '0.0.0.0'
+        host: '0.0.0.0',
+        ldSupport : {
+           null: true,
+           datasetId: true,
+           merge: false
+       }
     },
     authentication: {
         enabled: true,

doc/howto.md

@@ -430,6 +430,14 @@ iotAgentLib.setDataUpdateHandler(updateContextHandler);
 iotAgentLib.setDataQueryHandler(queryContextHandler);
 ```
 
+Where necessary, additional handlers to deal with command actuations and merge-patch operations may also be added when
+necessary.
+
+```javascript
+iotAgentLib.setCommandHandler(commandHandler);
+iotAgentLib.setMergePatchHandler(mergePatchHandler);
+```
+
 #### IOTA Testing
 
 In order to test it, we need to create an HTTP server simulating the device. The quickest way to do that may be using

doc/installationguide.md

@@ -72,6 +72,22 @@ overriding the group setting.
 }
 ```
 
+When connected to an **NGSI-LD** context broker, an IoT Agent is able to indicate whether it is willing to accept `null`
+values and also whether it is able to process the **NGSI-LD** `datasetId` metadata element. Setting these
+values to `false` will cause the IoT Agent to return a 400 **Bad Request** HTTP status code explaining that the IoT
+Agent does not support nulls or multi-attribute requests if they are encountered.
+
+```javascript
+{
+    baseRoot: '/',
+    port: 4041,
+    ldSupport : {
+      null: true,
+      datasetId: true
+    }
+}
+```
+
 -   **stats**: configure the periodic collection of statistics. Use `interval` in milliseconds to set the time between
     stats writings.
 
@@ -301,6 +317,8 @@ overrides.
 | IOTA_CB_NGSI_VERSION                 | `contextBroker.ngsiVersion`     |
 | IOTA_NORTH_HOST                      | `server.host`                   |
 | IOTA_NORTH_PORT                      | `server.port`                   |
+| IOTA_LD_SUPPORT_NULL                 | `server.ldSupport.null`         |
+| IOTA_LD_SUPPORT_DATASET_ID           | `server.ldSupport.datasetId`    |
 | IOTA_PROVIDER_URL                    | `providerUrl`                   |
 | IOTA_AUTH_ENABLED                    | `authentication.enabled`        |
 | IOTA_AUTH_TYPE                       | `authentication.type`           |

doc/usermanual.md

@@ -354,6 +354,83 @@ values.
 The handler is expected to call its callback once with no parameters (failing to do so may cause unexpected behaviors in
 the IoT Agent).
 
+##### iotagentLib.setCommandHandler()
+
+###### Signature
+
+```javascript
+function setCommandHandler(newHandler)
+```
+
+###### Description
+
+Sets the new user handler for registered entity commands. This handler will be called whenever a command request arrives, with
+the following parameters: (`id`, `type`, `service`, `subservice`, `attributes`, `callback`). The handler must retrieve
+all the corresponding information from the devices and return a NGSI entity with the requested values.
+
+The callback must be invoked with the updated Context Element, using the information retrieved from the devices. E.g.:
+
+```javascript
+callback(null, {
+    type: "TheType",
+    isPattern: false,
+    id: "EntityID",
+    attributes: [
+        {
+            name: "lumniscence",
+            type: "Lumens",
+            value: "432"
+        }
+    ]
+});
+```
+
+In the case of NGSI requests affecting multiple entities, this handler will be called multiple times, one for each
+entity, and all the results will be combined into a single response.  Only IoT Agents which deal with actuator devices will include a handler for commands.
+
+###### Params
+
+-   newHandler: User handler for command requests.
+
+##### iotagentLib.setMergePatchHandler()
+
+###### Signature
+
+```javascript
+function setMergePatchHandler(newHandler)
+```
+
+###### Description
+
+Sets the new user handler for NGSI-LD Entity [merge-patch](https://datatracker.ietf.org/doc/html/rfc7386) requests. This handler will be called whenever a merge-patch request arrives, with
+the following parameters: (`id`, `type`, `service`, `subservice`, `attributes`, `callback`). The handler must retrieve
+all the corresponding information from the devices and return a NGSI entity with the requested values.
+
+The callback must be invoked with the updated Context Element, using the information retrieved from the devices. E.g.:
+
+```javascript
+callback(null, {
+    type: "TheType",
+    isPattern: false,
+    id: "EntityID",
+    attributes: [
+        {
+            name: "lumniscence",
+            type: "Lumens",
+            value: "432"
+        }
+    ]
+});
+```
+
+In the case of NGSI-LD requests affecting multiple entities, this handler will be
+called multiple times. Since merge-patch is an advanced function, not all IoT Agents
+will include a handler for merge-patch.
+
+###### Params
+
+-   newHandler: User handler for merge-patch requests.
+
 ##### iotagentLib.setProvisioningHandler()
 
 ###### Signature

lib/commonConfig.js

@@ -158,7 +158,9 @@ function processEnvironmentVariables() {
         'IOTA_DEFAULT_ENTITY_NAME_CONJUNCTION',
         'IOTA_JSON_LD_CONTEXT',
         'IOTA_FALLBACK_TENANT',
-        'IOTA_FALLBACK_PATH'
+        'IOTA_FALLBACK_PATH',
+        'IOTA_LD_SUPPORT_NULL',
+        'IOTA_LD_SUPPORT_DATASET_ID'
     ];
     const iotamVariables = [
         'IOTA_IOTAM_URL',
@@ -263,6 +265,18 @@ function processEnvironmentVariables() {
         config.server.port = process.env.IOTA_NORTH_PORT;
     }
 
+    config.server.ldSupport = config.server.ldSupport || {null: true, datasetId: true, merge: false};
+
+    if (process.env.IOTA_LD_SUPPORT_NULL) {
+        config.server.ldSupport.null = process.env.IOTA_LD_SUPPORT_NULL === 'true';
+    }
+    if (process.env.IOTA_LD_SUPPORT_DATASET_ID) {
+        config.server.ldSupport.datasetId = process.env.IOTA_LD_SUPPORT_DATASET_ID === 'true';
+    }
+     if (process.env.IOTA_LD_SUPPORT_MERGE) {
+        config.server.ldSupport.datasetId = process.env.IOTA_LD_SUPPORT_MERGE === 'true';
+    }
+
     if (process.env.IOTA_PROVIDER_URL) {
         config.providerUrl = process.env.IOTA_PROVIDER_URL;
     }

lib/constants.js

@@ -60,6 +60,7 @@ module.exports = {
     SUBSERVICE_HEADER: 'fiware-servicepath',
     NGSI_LD_TENANT_HEADER: 'NGSILD-Tenant',
     NGSI_LD_PATH_HEADER: 'NGSILD-Path',
+    NGSI_LD_NULL: 'urn:ngsi-ld:null',
     //FIXME: check Keystone support this in lowercase, then change
     AUTH_HEADER: 'X-Auth-Token',
     X_FORWARDED_FOR_HEADER: 'x-forwarded-for',

lib/fiware-iotagent-lib.js

@@ -323,6 +323,7 @@ exports.getConfigurationSilently = groupConfig.getSilently;
 exports.findConfiguration = groupConfig.find;
 exports.setDataUpdateHandler = contextServer.setUpdateHandler;
 exports.setCommandHandler = contextServer.setCommandHandler;
+exports.setMergePatchHandler = contextServer.setMergePatchHandler;
 exports.setDataQueryHandler = contextServer.setQueryHandler;
 exports.setConfigurationHandler = contextServer.setConfigurationHandler;
 exports.setRemoveConfigurationHandler = contextServer.setRemoveConfigurationHandler;

lib/services/devices/deviceService.js

@@ -363,6 +363,7 @@ function registerDevice(deviceObj, callback) {
                     deviceObj.type = deviceData.type;
                     deviceObj.staticAttributes = deviceData.staticAttributes;
                     deviceObj.commands = deviceData.commands;
+                    deviceObj.lazy = deviceData.lazy;
                     if ('timestamp' in deviceData && deviceData.timestamp !== undefined) {
                         deviceObj.timestamp = deviceData.timestamp;
                     }

lib/services/devices/registrationUtils.js

@@ -314,6 +314,7 @@ function sendRegistrationsNgsiLD(unregister, deviceData, callback) {
     const properties = [];
     const lazy = deviceData.lazy || [];
     const commands = deviceData.commands || [];
+    const supportMerge = config.getConfig().server.ldSupport.merge;
 
     lazy.forEach((element) => {
         properties.push(element.name);
@@ -328,6 +329,9 @@ function sendRegistrationsNgsiLD(unregister, deviceData, callback) {
     if (commands.length > 0){
          operations.push('updateOps'); 
     }
+    if (supportMerge){
+        operations.push('mergeEntity'); 
+    }
 
     if (properties.length === 0) {
         logger.debug(context, 'Registration with Context Provider is not needed. Device without lazy atts or commands');