usermanual.md

Library Functions

• Stats Registry
• Alarm module
• Transactions
• Library overview
• Function reference

Stats Registry

The library provides a mechanism for the periodic reporting of stats related to the library's work. In order to activate the use of the periodic stats, it must be configured in the config file, as described in the Configuration section.

The Stats Registry holds two dictionaries, with the same set of stats. For each stat, one of the dictionaries holds the historical global value and the other one stores the value since the last value reporting (or current value).

The stats library currently stores only the following values:

• deviceCreationRequests: number of Device Creation Requests that arrived to the API (no matter the result).
• deviceRemovalRequests: number of Removal Device Requests that arrived to the API (no matter the result).
• measureRequests: number of times the ngsiService.update() function has been invoked (no matter the result).

More values will be added in the future to the library. The applications using the library can add values to the Stats Registry just by using the following function:

iotagentLib.statsRegistry.add('statName', statIncrementalValue, callback);

The first time this function is invoked, it will add the new stat to the registry. Subsequent calls will add the value to the specified stat both to the current and global measures. The stat will be cleared in each interval as usual.

Alarm module

The library provide an alarm module that can be used to track through the logs alarms raised in the IoTAgent. This module provides:

• Two functions to raise and release and alarm (raise() and release()): every alarm is identified by a name and a description. When the alarm is raised, an error with the text Raising [%s] is logged. When the alarm is released, the corresponding text, Releasing [%s] is logged. If an alarm is raised multiple times, it is only logged once. If its released multiple times it is only released once. Releasing a non-existing alarm has no effect.

• Functions to list all the raised alarms and clean all the alarms (list() and clean()).

• A function to instrument other functions, so when one of that functions return an error, an alarm is raised, and when it returns a success an alarm is ceased (intercept()).

All this functions can be accessed through the .alarms attribute of the library.

Transactions

The library implements a concept of transactions, in order to follow the execution flow the library follows when treating requests entering both from the North and the South ports of the IoT Agent.

To follow the transactions, a new Domain is created for each incoming request; in the case of requests received on the North Port of the IoT Agent, this domain is automatically created by a Express middleware, and no further action is needed from the user. For the case of requests received on the South Port of the IoT Agent, the user is responsible of creating an stopping the transaction, using the ensureSouthboundDomain and finishSouthBoundTransaction. In this case, the transaction will last from the invocation to the former to the invocation of the latter.

The Transaction Correlator is used along all the IoT Platform to follow the trace of a transaction between multiple components. To do so, in all the HTTP requests sent to other components of the platform, a custom header named Fiware-Correlator is sent with the correlator of the transaction that generated the request. If a component of the platform receives a request containing this header that starts a transaction, the component will create the transaction with the received correlator, instead of creating a new one. If the header is not present or the transaction originates in the component, the transaction ID in this component will be used as the correlator.

During the duration of a transaction, all the log entries created by the code will write the current Transaction ID and correlator for the operation being executed.

Library overview

In order to use the library, add the following dependency to your package.json file:

"iotagent-node-lib": "*"

In order to use this library, first you must require it:

var iotagentLib = require('iotagent-node-lib');

The library supports four groups of features, one for each direction of the communication: client-to-server and server-to-client (and each flow both for the client and the server). Each feature set is defined in the following sections.

Function reference

iotagentLib.activate()

Signature

function activate(newConfig, callback)

Description

Activates the IoT Agent to start listening for NGSI Calls (acting as a Context Provider). It also creates the device registry for the IoT Agent (based on the deviceRegistry.type configuration option).

Params

• newConfig: Configuration of the Context Server (described in the Configuration section).

iotagentLib.deactivate()

Signature

function deactivate(callback)

Description

Stops the HTTP server.

Params

iotagentLib.register()

Signature

function registerDevice(deviceObj, callback)

Description

Register a new device in the IoT Agent. This registration will also trigger a Context Provider registration in the Context Broker for all its lazy attributes.

The device Object can have the following attributes:

• id: Device ID of the device.
• type: type to be assigned to the device.
• name: name that will be used for the Entity representing the device in the Context Broker.
• service: name of the service associated with the device.
• subservice: name of the subservice associated with th device.
• lazy: list of lazy attributes with their types.
• active: list of active attributes with their types.
• staticAttributes: list of NGSI attributes to add to the device entity 'as is' in updates, queries and registrations.
• internalAttributes: optional section with free format, to allow specific IoT Agents to store information along with the devices in the Device Registry.

The device id and type are required fields for any registration. The rest of the attributes are optional, but, if they are not present in the function call arguments, the type must be registered in the configuration, so the service can infer their default values from the configured type. If an optional attribute is not given in the parameter list and there isn't a default configuration for the given type, a TypeNotFound error is raised.

If the device has been previously preprovisioned, the missing data will be completed with the values from the registered device.

Params

• deviceObj: object containing all the information about the device to be registered (mandatory).

iotagentLib.unregister()

Signature

function unregisterDevice(id, service, subservice, callback)

Description

Unregister a device from the Context broker and the internal registry.

Params

• id: Device ID of the device to register.
• service: Service of the device to unregister.
• subservice: Subservice inside the service for the unregistered device.

iotagentLib.update()

Signature

function update(entityName, attributes, typeInformation, token, callback)

Description

Makes an update in the Device's entity in the context broker, with the values given in the 'attributes' array. This array should comply to the NGSI's attribute format.

Params

• entityName: Name of the entity to register.
• attributes: Attribute array containing the values to update.
• typeInformation: Configuration information for the device.
• token: User token to identify against the PEP Proxies (optional).

iotagentLib.setCommandResult()

Signature

function setCommandResult(entityName, resource, apikey, commandName, commandResult, status, deviceInformation, callback)

Description

Update the result of a command in the Context Broker. The result of the command has two components: the result of the command itself will be represented with the suffix _result in the entity while the status is updated in the attribute with the _info suffix.

Params

• entityName: Name of the entity holding the command.
• resource: Resource name of the endpoint the device is calling.
• apikey: Apikey the device is using to send the values (can be the empty string if none is needed).
• commandName: Name of the command whose result is being updated.
• commandResult: Result of the command in string format.
• deviceInformation: Device information, including security and service information. (optional).

iotagentLib.listDevices()

Signature

function listDevices(callback)
function listDevices(limit, offset, callback)
function listDevices(service, subservice, limit, offset, callback)

Description

Return a list of all the devices registered in the specified service and subservice. This function can be invoked in three different ways:

• with just one parameter (the callback)
• with three parameters (service, subservice and callback)
• or with five parameters (including limit and offset).

Params

• service: service from where the devices will be retrieved.
• subservice: subservice from where the devices will be retrieved.
• limit: maximum number of results to retrieve (optional).
• offset: number of results to skip from the listing (optional).

iotagentLib.setDataUpdateHandler()

Signature

function setDataUpdateHandler(newHandler)

Description

Sets the new user handler for Entity update requests. This handler will be called whenever an update request arrives with the following parameters: (id, type, service, subservice, attributes, callback). The handler is in charge of updating the corresponding values in the devices with the appropriate protocol.

Once all the updates have taken place, the callback must be invoked with the updated Context Element. E.g.:

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.

Params

• newHandler: User handler for update requests

iotagentLib.setDataQueryHandler()

Signature

function setDataQueryHandler(newHandler)

Description

Sets the new user handler for Entity query requests. This handler will be called whenever a query 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.:

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.

Params

• newHandler: User handler for query requests.

iotagentLib.setNotificationHandler()

Signature

function setNotificationHandler(newHandler)

Description

Sets the new handler for incoming notifications. The notifications are sent by the Context Broker based on the IoT Agent subscriptions created with the subscribe() function.

The handler must adhere to the following signature:

function mockedHandler(device, data, callback)

The device parameter contains the device object corresponding to the entity whose changes were notified with the incoming notification. Take into account that multiple entities may be modified with each single notification. The handler will be called once for each one of those entities.

The data parameter is an array with all the attributes that were requested in the subscription and its respective 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.setProvisioningHandler()

Signature

function setProvisioningHandler (newHandler)

Description

Sets the new user handler for the provisioning of devices. This handler will be called every time a new device is created.

The handler must adhere to the following signature:

function(newDevice, callback)

The newDevice parameter will contain the newly created device. The handler is expected to call its callback with no parameters (this handler should only be used for reconfiguration purposes of the IoT Agent).

iotagentLib.setRemoveDeviceHandler()

Signature

function setRemoveDeviceHandler(newHandler)

Description

Sets the new user handler for the removal of a device. This handler will be called every time a device is removed.

The handler must adhere to the following signature:

function(deviceToDelete, callback)

The deviceToDelete parameter will contain the device to be deleted. The handler is expected to call its callback with no parameters (this handler should only be used for reconfiguration purposes of the IoT Agent).

iotagentLib.setConfigurationHandler()

Signature

function setConfigurationHandler(newHandler)

Description

Sets the new user handler for the configuration updates. This handler will be called every time a new configuration is created or an old configuration is updated.

The handler must adhere to the following signature:

function(newConfiguration, callback)

The newConfiguration parameter will contain the newly created configuration. The handler is expected to call its callback with no parameters (this handler should only be used for reconfiguration purposes of the IoT Agent).

For the cases of multiple updates (a single Device Configuration POST that will create several device groups), the handler will be called once for each of the configurations (both in the case of the creations and the updates).

The handler will be also called in the case of updates related to configurations. In that situation, the newConfiguration parameter contains also the fields needed to identify the configuration to be updated, i.e., service, subservice, resource and apikey.

iotagentLib.setRemoveConfigurationHandler()

Signature

function setRemoveConfigurationHandler(newHandler)

Description

Sets the new user handler for the removal of configuratios. This handler will be called every time a configuration is removed.

The handler must adhere to the following signature:

function(configurationToDelete, callback)

The configurationToDelete parameter will contain the configuration to be deleted. The handler is expected to call its callback with no parameters (this handler should only be used for reconfiguration purposes of the IoT Agent).

iotagentLib.getDevice()

Signature

function getDevice(deviceId, service, subservice, callback)

Description

Retrieve all the information about a device from the device registry.

Params

• deviceId: ID of the device to be found.
• service: Service for which the requested device.
• subservice: Subservice inside the service for which the device is requested.

iotagentLib.getDeviceByName()

Signature

function getDeviceByName(deviceName, service, subservice, callback)

Description

Retrieve a device from the registry based on its entity name.

Params

• deviceName: Name of the entity associated to a device.
• service: Service the device belongs to.
• subservice: Division inside the service.

iotagentLib.getDevicesByAttribute()

Signature

function getDevicesByAttribute(attributeName, attributeValue, service, subservice, callback)

Description

Retrieve all the devices having an attribute named name with value value.

Params

• name: name of the attribute to match.
• value: value to match in the attribute.
• service: Service the device belongs to.
• subservice: Division inside the service.

iotagentLib.retrieveDevice()

Signature

function retrieveDevice(deviceId, apiKey, callback)

Description

Retrieve a device from the device repository based on the given APIKey and DeviceID, creating one if none is found for the given data.

Params

• deviceId: Device ID of the device that wants to be retrieved or created.
• apiKey: APIKey of the Device Group (or default APIKey).

iotagentLib.mergeDeviceWithConfiguration()

Signature

function mergeDeviceWithConfiguration(fields, defaults, deviceData, configuration, callback)

Description

Complete the information of the device with the information in the configuration group (with precedence of the device). The first argument indicates what fields would be merged.

Params

• fields: Fields that will be merged.
• defaults: Default values fot each of the fields.
• deviceData: Device data.
• configuration: Configuration data.

iotagentLib.getConfiguration()

Signature

function getConfiguration(resource, apikey, callback)

Description

Gets the device group identified by the given (resource, apikey) pair.

Params

• resource: representation of the configuration in the IoT Agent (dependent on the protocol) .
• apikey: special key the devices will present to prove they belong to a particular configuration.

iotagentLib.findConfiguration()

Signature

function findConfiguration(service, subservice, callback)

Description

Find a device group based on its service and subservice.

Params

• service: name of the service of the configuration.
• subservice: name of the subservice of the configuration.

iotagentLib.getEffectiveApiKey()

Signature

function getEffectiveApiKey(service, subservice, type, callback)

Description

Get the API Key for the selected service if there is any, or the default API Key if a specific one does not exist.

Params

• service: Name of the service whose API Key we are retrieving.
• subservice: Name of the subservice whose API Key we are retrieving.
• type: Type of the device.

iotagentLib.subscribe()

Signature

function subscribe(device, triggers, content, callback)

Description

Creates a subscription for the IoTA to the entity representing the selected device.

Params

• device: Object containing all the information about a particular device.
• triggers: Array with the names of the attributes that would trigger the subscription
• content: Array with the names of the attributes to retrieve in the notification.

iotagentLib.unsubscribe()

Signature

function unsubscribe(device, id, callback)

Description

Removes a single subscription from the selected device, identified by its ID.

Params

• device: Object containing all the information about a particular device.
• id: ID of the subscription to remove.

iotagentLib.ensureSouthboundDomain()

Signature

function ensureSouthboundTransaction(context, callback)

Description

Ensures that the current operation is executed inside a transaction with all the information needed for the appropriate platform logging: start date, transaction ID and correlator in case one is needed. If the function is executed in the context of a previous transaction, just the context is changed (and the Transaction ID and start time are kept).

Params

• context: New context data for the transaction.

iotagentLib.finishSouthBoundTransaction()

Signature

function finishSouthboundTransaction(callback)

Description

Terminates the current transaction, if there is any, cleaning its context.

iotagentLib.startServer()

Signature

function startServer(newConfig, iotAgent, callback)

Description

Start the HTTP server either in single-thread or multi-thread (multi-core) based on the value of multiCore variable (described in the Configuration section). If the value is False (either was directly specified False in the config.js or it was not specified and by default is assigned False), it is a normal (single-thread) behaviour. Nevertheless, if multiCore is True, the IoTAgent is executed in multi-thread environment.

The number of parallel processes is calculated based on the number of available CPUs. In case of some of the process unexpectedly dead, a new process is created automatically to keep always the maximum of them working in parallel.

Note: startServer() initializes the server but it does not activate the library. The function in the Node Lib will call the iotAgent.start() in order to complete the activation of the library. Therefore, it is expected that the IoT Agent implement the iotAgent.start() function with the proper invocation to the iotAgentLib.activate().

Params

• newConfig: Configuration of the Context Server (described in the Configuration section).
• iotAgent: The IoT Agent Objects, used to start the agent.
• callback: The callback function.

iotagentLib.request()

Signature

function request(options, callback)

Description

Make a direct HTTP request using the underlying request library (currently got), this is useful when creating agents which use an HTTP transport for their southbound commands, and removes the need for the custom IoT Agent to import its own additional request library

Params

• options: definition of the request (see got options for more details). The following attributes are currently exposed.
  • method - HTTP Method
  • searchParams - query string params
  • qs - alias for query string params
  • headers
  • responseType - either text or json. json is the default
  • json - a supplied JSON object as the request body
  • body - any ASCII text as the request body. It takes precedence over json if both are provided at the same time (not recommended).
  • url - the request URL
  • uri - alternative alias for the request URL.
• callback: The callback currently returns an error Object, the response and body. The body is parsed to a JSON object if the responseType is JSON.

Generic middlewares

This collection of utility middlewares is aimed to be used to north of the IoT Agent Library, as well as in other HTTP-based APIs of the IoT Agents. All the middlewares follow the Express convention of (req, res, next) objects, so this information will not be repeated in the descriptions for the middleware functions. All the middlewares can be added to the servers using the standard Express mechanisms.

iotagentLib.middlewares.handleError()

Signature

function handleError(error, req, res, next)

Description

Express middleware for handling errors in the IoTAs. It extracts the code information to return from the error itself returning 500 when no error code has been found.

iotagentLib.middlewares.traceRequest()

Signature

function traceRequest(req, res, next)

Description

Express middleware for tracing the complete request arriving to the IoTA in debug mode.

iotagentLib.middlewares.changeLogLevel()

Signature

function changeLogLevel(req, res, next)

Description

Changes the log level to the one specified in the request.

iotagentLib.middlewares.ensureType()

Signature

function ensureType(req, res, next)

Description

Ensures the request type is one of the supported ones.

iotagentLib.middlewares.validateJson()

Signature

function validateJson(template)

Description

Generates a Middleware that validates incoming requests based on the JSON Schema template passed as a parameter.

Returns an Express middleware used in request validation with the given template.

Params

• template: JSON Schema template to validate the request.

iotagentLib.middlewares.retrieveVersion()

Signature

function retrieveVersion(req, res, next)

Description

Middleware that returns all the IoTA information stored in the module.

iotagentLib.middlewares.setIotaInformation()

Signature

function setIotaInformation(newIoTAInfo)

Description

Stores the information about the IoTAgent for further use in the retrieveVersion() middleware.

Params

• newIoTAInfo: Object containing all the IoTA Information.