databridges_sio_client_lib 2.0.3

Databridges Python client Library

Databridges Python client Library

DataBridges makes it easy for connected devices and applications to communicate with each other in realtime in an efficient, fast, reliable and trust-safe manner. Databridges Python client library allows you to easily add realtime capabilities to your applications in record time.

Usage Overview

The following topics are covered:

• Supported platforms
• Installation
• Initialization
• Global Configuration
  • Required
  • Optional
• Connection
• Objects
• object:ConnectionState
  • Properties
  • Bind to connectionstate events
  • Functions
• object:Channel
  • Subscribe to Channel
  • Connect to Channel
  • Channel Information
  • Publish to Channel
  • Binding to events
  • System events for channel object
• object: rpc (Remote Procedure Call)
  • Connect to Server
  • Server Information
  • Execute Remote Procedure Call
  • System events for rpc object
• object:Cf (Client Function)
  • Properties
  • System events for cf object
• Change Log
• License

Supported platforms

Supports Python versions +3.6

Installation

You can use pip package manager to install the package.

pip3 install databridges_sio_client_lib

Note : Databridges library uses socket.io for websocket protocol management.

Initialization

from databridges_sio_client_lib import dBridges
from databridges_sio_client_lib.exceptions import dBError
dbridge = dBridges()

Global Configuration

Required

The following is the list of required connection properties before connecting to dataBridges network.

dbridge.auth_url = 'URL'
dbridge.appkey = 'APP_KEY'

You need to replace URL and APP_KEY with the actual URL and Application Key.

Properties	Description	Exceptions
auth_url	(string) Authentication url from dataBridges dashboard.	source: DBLIB_CONNECT code: INVALID_URL
appkey	(string) Application Key from dataBridges dashboard.	source: DBLIB_CONNECT code: INVALID_AUTH_PARAM

Optional

The following is the list of optional connection properties before connecting to dataBridges network.

dbridge.maxReconnectionRetries = 10
dbridge.maxReconnectionDelay = 120000 
dbridge.minReconnectionDelay = 1000 + Math.random() * 4000
dbridge.reconnectionDelayGrowFactor = 1.3
dbridge.minUptime = 200
dbridge.connectionTimeout = 10000
dbridge.autoReconnect = True
dbridge.cf.enable = False	

Properties	Default	Description
maxReconnectionDelay	10	(integer) The maximum delay between two reconnection attempts in seconds.
minReconnectionDelay	1000 + Math.random() * 4000	(integer) The initial delay before reconnection in milliseconds (affected by the reconnectionDelayGrowFactor value).
reconnectionDelayGrowFactor	1.3	(float) The randomization factor used when reconnecting (so that the clients do not reconnect at the exact same time after a server crash).
minUptime	200	(integer) Uptime before connected event is triggered, value in milliseconds.
connectionTimeout	10000	(integer) Number of milliseconds the application will wait for a connection to be established. If it fails it will emit a connection_error event.
maxReconnectionRetries	10	(integer) The number of reconnection attempts before giving up.
autoReconnect	true	(boolean) If false, application will not attempt reconnecting.
cf.enable	false	(boolean) Enable exposing client function for this connection. (Check Client Function section for details.)
access_token	function	(function) If you need custom authorization behavior for generating signatures for private/ presence/ system channels/rpc functions, you can provide your own access_token function.

Connection

Once the properties are set, use connect() function to connect to dataBridges Network.

try:
    await dbridge.connect()
except Exception as e:
	print("source: {0} ,  code: {1}, message: {2}".format(e.source , e.code , e.message))

Exceptions:

Source	Code	Message	Description
DBLIB_CONNECT	INVALID_URL		Value of dbridge.auth_url is not a valid dataBridges authentication URL.
DBLIB_CONNECT	INVALID_AUTH_PARAM		Value of dbridge.appkey is not a valid dataBridges application key.
DBLIB_CONNECT	INVALID_ACCESSTOKEN_FUNCTION		If "callback function" is not declared for authentication only while using private, presence or system channel/RPC functions. (Check Channel or RPC section for details.)
DBLIB_CONNECT	HTTP_	HTTP protocol reported message.	HTTP Errors returned during authentication process. HTTP Error code will be concatenated with HTTP_ in the err.code. eg. HTTP_501
DBLIB_CONNECT	INVALID_CLIENTFUNCTION		If "callback function" is not declared for client function or typeof() variable defined is not a "function". This is applicable only if clientFunction is enabled. (Check Client Function section for details.)

sessionid (string)

print("sessionid: {0}".format( dbridge.sessionid))

Making a connection provides the application with a new sessionid that is assigned by the server. This can be used to distinguish the application's own events. A change of state might otherwise be duplicated in the application. It is also stored within the connection, and used as a token for generating signatures for private/presence/system channels/rpc functions.

disconnect (function)

To close a connection use disconnect function. When a connection has been closed explicitly, no automatic reconnection will happen.

await dbridge.disconnect()

Objects

Object	Description
connectionstate	connectionstate object expose properties, functions and events to monitor and manage the health of dataBridges network connection.
channel	channel object exposes trust-safe flexible Pub/Sub messaging properties, functions and events to build realtime event messaging / event driven applications at scale.
rpc	rpc object exposes trust-safe properties, functions and events to provide reliable two-way messaging between multiple endpoints allowing you to build sophisticated asynchronous interactions.
cf	CF (Client-function) object is a special purpose RPC implementation to build command and control applications. CF object exposes properties, functions and events for command and control server applications to send messages to devices and application using dataBridges library in **trust-safe manner **, build smart update configuration system and implement **trust-safe ** actions for remote and automated management.

object:ConnectionState

Connectionstate object expose properties, functions and events to monitor and manage the health of dataBridges network connection.

Properties

The following is the list of connection state properties.

print(dbridge.connectionstate.state)
print(dbridge.connectionstate.isconnected)
print(dbridge.connectionstate.rttms)
print(dbridge.connectionstate.reconnect_attempt)

Property	Description
connectionstate.state	(String) Current state of dataBridges network connection . List of Return Values are detailed below.
connectionstate.isconnected	(Boolean) To verify if the application is still connected to the dataBridges network.
connectionstate.rttms	(integer) Latency in milliseconds between your application and the dataBridges router where your application is connected.
connectionstate.reconnect_attempt	(integer) Number of reconnection attempted as of now.

connectionstate.state

Return Values	Description
connecting	Your application is now attempting to connect to dataBridges network.
connected	The connection to dataBridges network is open and authenticated with your appkey.
connection_break	Indicates a network disconnection between application and dataBridges network. The library will initiate an automatic reconnection, if the reconnection property is set as true.
connect_error	The dataBridges network connection was previously connected and has now errored and closed.
disconnected	The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again.
reconnecting	Your application is now attempting to reconnect to dataBridges network as per properties set for reconnection.
reconnect_error	Reconnection attempt has errored.
reconnect_failed	The application will enter reconnect_failed state when all the reconnection attempts have been exhausted unsuccessfully. The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again
reconnected	The application has successfully re-connected to the dataBridges network, This state will follow connect_error or reconnect_error.

Bind to connectionstate events

Apart from retrieveing state of a dBrige connection, application can bind to connectionstate events.

You can use the following methods on connectionstate object to bind to events.

dbridge.connectionstate.bind(eventName, callable)
dbridge.connectionstate.unbind(eventName)
dbridge.connectionstate.unbind()

bind() on eventName has callback functions to be defined where you can write your own code as per requirement.

To stop listening to events use unbind(eventName) function.

To stop listening to all events use unbind() [without eventName] function.

Below are library events which can be bind to receive information about dataBridges network.

System events for connectionstate object

async def connecting():
    print("connecting")

async def reconnecting():
    print("reconnecting")

async def connection_break():
    print("connection_break")

async def state_change( data):
    print("state_change:", data)

async def connect_error( data):
    if isinstance(data, str):
        print("connect_error:" + str(data))
    if isinstance(data, dBError.dBError):
        print(data.code, data.source, data.message)

async def reconnect_error(data):
    if isinstance(data, str):
        print("reconnect_error:" + str(data))
    if isinstance(data, dBError.dBError):
        print(data.code, data.source, data.message)

async def reconnect_failed( data):
    print("reconnect_failed:", data)

async def reconnected():
    print("reconnected:")

async def rttpong(data=None):
    print("rttpong:", .dbridge.connectionstate.rttms)

async def disconnected():
    print("disconnected:")

async def connected():
    print("connected...")

try:
      dbridge.connectionstate.bind("connecting", connecting)
      dbridge.connectionstate.bind("reconnecting", reconnecting)
      dbridge.connectionstate.bind("connection_break", connection_break)
      dbridge.connectionstate.bind("state_change", state_change)
      dbridge.connectionstate.bind("connect_error", connect_error)
      dbridge.connectionstate.bind("reconnect_error", reconnect_error)
      dbridge.connectionstate.bind("reconnect_failed", reconnect_failed)
      dbridge.connectionstate.bind("reconnected", reconnected)
      dbridge.connectionstate.bind("rttpong", rttpong)
      dbridge.connectionstate.bind("connected", connected)
      dbridge.connectionstate.bind("disconnected", disconnected)
      
except Exception as e:
  	print(e.code, e.source, e.message)   

payload: (dberror object)

{
    "source": "DBLIB_CONNECT" , 			// (string) Error source
    "code": "RECONNECT_ATTEMPT_EXCEEDED",	// (string) Error code 
    "message": "" 							// (string) Error message if applicable.
}

Events	Parameters	Description
connecting		This event is triggered when your application is attempting to connect to dataBridges network.
connected		This event is triggered when connection to dataBridges network is open and authenticated with your appkey.
connection_break	payload	(dberror object) Indicates a network disconnection between application and dataBridges network. The library will initiate an automatic reconnection, if the reconnection property is set as true.
connect_error	payload	(dberror object) This event is triggered when the dataBridges network connection was previously connected and has now errored and closed.
disconnected		The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again.
reconnecting		This event is triggered when application is now attempting to reconnect to dataBridges network as per properties set for reconnection.
reconnect_error	payload	(dberror object) This event is triggered when reconnection attempt has errored.
reconnect_failed	payload	(dberror object) reconnect_failed event is triggered when all the reconnection attempts have been exhaused unsuccessfully. The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again.
reconnected		This event is triggered when the connection to dataBridges network is open and reconnected after connect_error or reconnect_error.
state_change	payload with payload.previous, payload.current	(dict) This event is triggered whenever there is any state changes in dataBridges network connection. Payload will have previous and current state of connection.
rttpong	payload	(integer) In Response to rttping() function call to dataBridges network, payload has latency in milliseconds between your application and the dataBridges router where your application is connected.

dberror:

Source	Code	Message	Description
DBLIB_CONNECT	RECONNECT_ATTEMPT_EXCEEDED		Triggered when reconnect_failed event is raised.
DBNET_CONNECT	DISCONNECT_REQUEST		Triggered when connect_error event is raised.
DBNET_CONNECT	RECONNECT_REQUEST		Triggered when connect_error, connection_break event is raised.
DBLIB_CONNECT	NETWORK_DISCONNECTED		Triggered when connect_error, reconnect_error event is raised.
DBLIB_CONNECT	INVALID_URL		Value of dbridge.auth_url is not a valid dataBridges authentication URL.
DBLIB_CONNECT	INVALID_AUTH_PARAM		Value of dbridge.appkey is not a valid dataBridges application key.
DBLIB_CONNECT	INVALID_ACCESSTOKEN_FUNCTION		If "callback function" is not declared for authentication only while using private, presence or system channel/RPC functions. (Check Channel or RPC section for details.)
DBLIB_CONNECT	HTTP_	HTTP protocol reported message.	HTTP Errors returned during authentication process. HTTP Error code will be concatenated with HTTP_ in the err.code. eg. HTTP_501
DBLIB_CONNECT	INVALID_CLIENTFUNCTION		If "callback function" is not declared for client function or typeof() variable defined is not a "function". This is applicable only if clientFunction is enabled. (Check Client Function section for details.)

Exceptions:

Source	Code	Description
DBLIB_CONNECT_BIND	INVALID_EVENTNAME	Invalid Event name. Not in defined events as above.
DBLIB_CONNECT_BIND	INVALID_CALLBACK	If "callback function" is not declared or typeof() variable defined is not a "function".

Functions

rttping()

This method is to understand the latency in milliseconds between your application and the dataBridges router where your application is connected. Event rttpong is triggered once response is received from dataBridges network. Bind to event:rttpong to retrieve the latency in ms.

# To get the last known Latency in milliseconds between your application and the dataBridges router where your application is connected.
# The dataBridges library exchanges rttms during the initial dataBridges network connection routine.
print(dbridge.connectionstate.rttms)

# To get the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
async def rttpong(self,  data=None):
 	print("rttpong:", data) 
    
try:
 	dbridge.connectionstate.bind("rttpong", rttpong)
except Exception as e:
 	print("source: {0} ,  code: {1}, message: {2}".format(e.source , e.code , e.message))

# Bind to rttpong, to get notified about the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
try:
 	dbridge.connectionstate.rttping()
except Exception as e:
 	print("source: {0} ,  code: {1}, message: {2}".format(e.source , e.code , e.message))

Exceptions:

Source	Code	Description
DBLIB_RTTPING	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.

---

object:Channel

channel object exposes trust-safe flexible Pub/Sub messaging properties, functions and events to build realtime event messaging / event driven applications at scale.

Concepts

• A message is attached to an event
• Group similar events into a channel
• Subscribe to a channel to receive all channel event messages.
• Publish event message to the channel and it will be sent to all the channel subscribers who are connected to dataBridges network and online.
• if you need to have an access controlled channel, prefix the channel name with pvt: , prs: and sys: .To subscribe to these type of channel. you will need to pass a trust-token when you subscribe to the channel. A trust-token is a JWT document created using a combination of channelname + sessionid + app.secret.
  • Use your existing access control, authorization and session identification rule-set, process and methods to create a trust-token instructing the dataBridges router to accept the pvt: prs: and sys: channel subscription, connection of from client application.
• Trust-tokens allows you to enable secured, access controlled and compliance driven realtime event driven messaging in your existing and new initiative applications.

dataBridges library supports 4 types of channel. The namespace is the 4 characters preceding the channelName (pvt:,prs:,sys:), identifying which type of channel the application is connecting to. If the channel type is pvt:,prs:,sys:, dataBridges library will use the access_token function to get the access encrypted token and will use it for all communication with this channel.

Channel Type	Channel Name Style	Description
Public	channelName	Public channel is used to send and receive messages that are to be publicly available. This channel type does not require any trust authorization token to subscribe. e.g channelName = mychannel
Private	**pvt:**channeName	Private channels is restricted channel. application will need to provide trust authorization token to subscribe and use Private channel. The dataBridges library will use the access_token function to get the trust authorization token. e.g channelName = pvt:mychannel
Presence	**prs:**channeName	Presence channels is a specialized private channel with additional feature of presence awareness. Subscribing to presence channel allows application to be notified of members joining / leaving the channel. Since Presence channel is a specialized version of Private channel, application will need to provide trust authorization token to subscribe and use Private channels. The dataBridges library will use the access_token function to get the trust authorization token. e.g channelName = prs:mychannel
System	**sys:**channeName	System channel is a specialized Presence channel to build command and control applications. Using System channel to create command and control server applications to send messages to devices and application using dataBridges library in **trust-safe manner **, build smart update configuration system and implement **trust-safe ** actions for remote and automated management. System channel allows application to send and receive messages with the server application (using dataBridges server library). Since System channel is a specialized version of Presence channel, application will need to provide trust authorization token to subscribe and use Private channels. The dataBridges library will use the access_token function to get the trust authorization token. e.g channelName = sys:systeminfo

dataBridges library provides 2 different ways to access any of above channel types based on usage.

Channel Type	Description
Subscribe to Channel	application that subscribes to a channel will receive messages and can send messages.
Connect to Channel	Where we have use-cases where application needs to only send messages and not interested to consume / receive channel messages, should connect to channel instead of subscribing to the channel.

Subscribe to Channel

Application that subscribes to a channel will receive messages and can send messages.

subscribe()

The default method for subscribing to a channel involves invoking the channel.subscribe function of your dataBridges object:

try:
    subscribed_channel =  await dbridge.channel.subscribe('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)

Parameter	Rules	Description
string	*channelName OR **pvt:**channelName OR **prs:**channelName OR **sys:*channelName	channelName to which subscription to be done.

Return Type	Description
object	channel object which events and related functions can be bound to.

Application can directly work with dataBridges object without using Channel object. Using this method application cannot publish any events.

try:
    await dbridge.channel.subscribe('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)

Exceptions:

Source	Code	Description
DBLIB_CHANNEL_SUBSCRIBE	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.
DBLIB_CHANNEL_SUBSCRIBE	INVALID_CHANNELNAME	Applicable for below conditions 1. channelName is not defined. 2. channelName validation error, typeof() channelName is not type string 3. channelName validation error, channelName fails a-zA-Z0-9\.:_- validation.
DBLIB_CHANNEL_SUBSCRIBE	INVALID_CHANNELNAME_LENGTH	channelName validation error, length of channelName greater than 64
DBLIB_CHANNEL_SUBSCRIBE	CHANNEL_ALREADY_SUBSCRIBED	channelName is already subscribed.

unsubscribe()

To unsubscribe from a subscribed channel, invoke the unsubscribe function of your dataBridges object. unsubscribe cannot be done on channel object.

try:
    dbridge.channel.unsubscribe('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)

Parameter	Rules	Description
string	*channelName OR **pvt:**channelName OR **prs:**channelName OR **sys:*channelName	channelName to which un-subscription to be done.

Return Type	Description
NA

Exceptions:

Source	Code	Description
DBLIB_CHANNEL_UNSUBSCRIBE	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.
DBLIB_CHANNEL_UNSUBSCRIBE	CHANNEL_NOT_SUBSCRIBED	channelName is not subscribed.
DBLIB_CHANNEL_UNSUBSCRIBE	INVALID_CHANNEL_TYPE	channelName is not subscribed, but it is in connected state.
DBLIB_CHANNEL_UNSUBSCRIBE	UNSUBSCRIBE_ALREADY_INITIATED	unsubscription to the channel is already initiated and hence the current unsubscribe command exited with exception.

Connect to Channel

Use-cases where application needs to only send channel messages and not interested to consume / receive channel messages, should connect to channel instead of subscribing to the channel.

connect()

The default method for connecting to a channel involves invoking the channel.connect function of your dataBridges object. Application cannot publish system events for which it has connected to.

try:
    connected_channel = dbridge.channel.connect('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)

Parameter	Rules	Description
string	*channelName OR **pvt:**channelName OR **prs:**channelName OR **sys:*channelName	channelName to which connection to be done.

Return Type	Description
object	channel object which events and related functions can be bound to.

Exceptions:

Source	Code	Description
DBLIB_CHANNEL_CONNECT	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.
DBLIB_CHANNEL_CONNECT	CHANNEL_ALREADY_CONNECTED	channelName is already connected.
DBLIB_CHANNEL_CONNECT	INVALID_CHANNELNAME	Applicable for below conditions 1. channelName is not defined. 2. channelName validation error, typeof() channelName is not type string 3. channelName validation error, length of channelName greater than 64 4. channelName validation error, channelName fails a-zA-Z0-9\.:_- validation. 5. if channelName contains : and first token is not pvt,prs,sys

disconnect()

To disconnect from a connected channel, invoke the disconnect function of your dataBridges object. disconnect cannot be done on channel object.

try:
    dbridge.channel.disconnect('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)

Parameter	Rules	Description
string	*channelName OR **pvt:**channelName OR **prs:**channelName OR **sys:*channelName	channelName to which disconnection to be done.

Return Type	Description
NA

Exceptions:

Source	Code	Description
DBLIB_CHANNEL_DISCONNECT	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.
DBLIB_CHANNEL_DISCONNECT	DISCONNECT_ALREADY_INITIATED	disconnect to the channel is already initiated and hence the current disconnect command exited with exception.
DBLIB_CHANNEL_DISCONNECT	INVALID_CHANNEL	channelName is not connected.
DBLIB_CHANNEL_DISCONNECT	INVALID_CHANNEL_TYPE	channelName is not connected, but it is in subscribed state.

Channel Information

isOnline()

dBridgeObject as well as channelObject provides a function to check if the channel is online. The best practice is to check the channel is online before publishing any message.

isonline = dbridge.channel.isOnline('mychannel')

isonline = subscribed_channel.isOnline()

Parameter	Rules	Description
string	*channelName OR **pvt:**channelName OR **prs:**channelName OR **sys:*channelName	channelName

Return Values	Description
boolean	Is the current status of channel online or offline.

list()

dBridgeObject provides a function to get list of successfully subscribed or connected channel.

channels = dbridge.channel.list()
#=> [{"name":  "mychannel" , "type": "subscribed/connect" ,  "isonline": True/False }]

Return Type	Description
array of dict	Array of channels subscribed or connected.

Dictionary contains below information.

Key	Description
name	(string) channelName of subscribed or connected channel.
type	(string) subscribed or connected
isonline	(boolean) Is the current status of channel online or offline.

getChannelName()

channelObject provides a function to get the channelName.

chName = channelobject.getChannelName()  

Return Type	Description
string	channelName of subscribed or connected channel.

Publish to Channel

Publish event-message using the publish function on an instance of the channel object.

A message is linked to an event and hence event-message. dataBridges allows you to bind to various events to create rich event driven processing flows

publish()

The default method for publishing to a channel involves invoking the channel.publish function of your channelObject.

try:
    channelObject.publish(eventname, payload, excludeSessionId, sourceId, seqno)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Best practice is to check the channel is online before publishing any message.
if channelObject.isOnline():
 	try:
  		channelObject.publish(eventname, payload, excludeSessionId, sourceId, seqno)
 	except dBError as e:
    	print(e.code, e.source, e.message) 

Parameter	Description
event	(string) event Name to which the message to be sent. event Name cannot start with dbridges:
payload	(string) Payload to be sent with the event.
seqno	(string) [optional] Message sequence number. This is optional parameter. seqno can be used by applications to manage message queue processing by the subscribers.

Return Values	Description
NA

Exceptions:

Source	Code	Description
DBLIB_CHANNEL_PUBLISH	INVALID_SUBJECT	Applicable for below conditions 1. event validation error, typeof() event is not type string 2. event validation error, event is not defined
DBLIB_CHANNEL_PUBLISH	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.

Binding to events

A message is linked to an event and hence event-message. dataBridges allows you to bind to various events to create rich event processing flows. An application needs to bind to event to process the received message.

You can use the following methods either on a channelObject, to bind to events on a particular channel; or on the dbridgeObject, to bind to events on all subscribed channels simultaneously.

bind and unbind

Bind to "event" on channel: payload and metadata is received.

# Binding to channel events on channelObject  
def eventFunction(payload ,  metadata):
  	print(payload , metadata)

try:
    channelObject.bind('eventName',  eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Binding to channel events on dbridgeObject 
try {
    dbridge.channel.bind('eventName', eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

Parameter	Description
event	(string) event Name to which binding to be done.

Callback parameters

payload:

(string) Payload data sent by the publisher.

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "event",				// (string) eventName 
    "sourcesysid": "", 					// (string) Sender system identity, applicable only for presence or system channel.
    "sqnum": "1",						// (string) user defined, sent during publish function.
    "sessionid": "", 					// (string) Sender sessionid, applicable only for presence or system channel.
    "intime": 1645554960732  			// (string) EPOC time of the sender at time of publish.
}

Exceptions:

Source	Code	Description
DBLIB_CONNECT_BIND	INVALID_EVENTNAME	eventName cannot be blank or null.
DBLIB_CONNECT_BIND	INVALID_CALLBACK	If "callback function" is not declared or typeof() variable defined is not a "function".
DBLIB_CHANNEL_CONNECT	INVALID_CHANNEL_TYPE_BINDING	Invalid Event name. This binding is not allowed in channel.connect.

Unbind behavior varies depending on which parameters you provide it with. For example:

#  Remove just `handler` of the `event` in the subscribed/connected channel 
channelObject.unbind("eventName",handler)

#  Remove all `handler` of the `event` in the subscribed/connected channel
channelObject.unbind("eventName")

# Remove all handlers for the all event in the subscribed/connected channel
channelObject.unbind()

#  Remove `handler` of the `event` for all events across all subscribed/connected channels
dbridge.channel.unbind("eventName",handler)

#  Remove all handlers of the `event` for all events across all subscribed/connected channels
dbridge.channel.unbind("eventName")

#  Remove all handlers for all events across all subscribed/connected channels
dbridge.channel.unbind()

bind_all and unbind_all

bind_all and unbind_all work much like bind and unbind, but instead of only firing callbacks on a specific event, they fire callbacks on any event, and provide that event in the metadata to the handler along with the payload. bind_all and unbind_all is not available for connected_channel i.e. dbridge.channel.connect() object.

# Binding to channel events on channelObject  
def eventFunction(payload ,  metadata):
  	print(payload , metadata)

try:
    channelObject.bind_all('eventName',  eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Binding to channel events on dbridgeObject 
try {
    dbridge.channel.bind_all('eventName', eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

Callback out parameter payload, metadata details are explained with each event below in this document.

Exceptions:

Source	Code	Description
DBLIB_CONNECT_BIND	INVALID_CALLBACK	If "callback function" is not declared or typeof() variable defined is not a "function".

unbind_all works similarly to unbind.

# Remove just `handler` across the channel 
channelObject.unbind_all(handler)

# Remove all handlers for the all event in the subscribed/connected channel
channelObject.unbind_all()

# Remove `handler` across the subscribed/connected channels
dbridge.channel.unbind_all(handler)

# Remove all handlers for all events across all subscribed/connected channels
dbridge.channel.unbind_all()

System events for channel object

There are a number of events which are triggered internally by the library, but can also be of use elsewhere. Below are the list of all events triggered by the library.

Below syntax is same for all system events.

# Binding to systemevent on channelObject  
def eventFunction(payload ,  metadata):
  	print(payload , metadata)
    
try:
    channelObject.bind_all('dbridges:subscribe.success',  eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Binding to systemevent on dbridgeObject 

try:
    dbridge.channel.bind_all('dbridges:subscribe.success', eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

dbridges:subscribe.success

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 			// (string) channelName to which subscription is done.
    "eventname": "dbridges:subscribe.success",// (string) eventName 
    "sourcesysid": "", 					// (string) Sender system identity, applicable only for presence or system channel.
    "sqnum": "1",						// (string) user defined, sent during publish function.
    "sessionid": "", 					// (string) Sender sessionid, applicable only for presence or system channel.
    "intime": 1645554960732  			// (string) EPOC time of the sender at time of publish.
}

dbridges:subscribe.fail

Callback parameters

payload: (dberror object)

{
    "source": "dberror.Source" , 		// (string) Error source, Refer dberror: for details
    "code": "dberror.Code",				// (string) Error code, Refer dberror: for details
    "message": "" 						// (string) Error message if applicable.
}

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:subscribe.fail",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:channel.online

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:channel.online",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:channel.offline

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:channel.offline",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:channel.removed

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:channel.removed",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:unsubscribe.success

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:unsubscribe.success",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:unsubscribe.fail

Callback parameters

payload: (dberror object)

{
    "source": "dberror.Source" , 		// (string) Error source, Refer dberror: for details
    "code": "dberror.Code",				// (string) Error code, Refer dberror: for details
    "message": "" 						// (string) Error message if applicable.
}

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:unsubscribe.fail",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:resubscribe.success

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:resubscribe.success",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:resubscribe.fail

Callback parameters

payload: (dberror object)

{
    "source": "dberror.Source" , 		// (string) Error source, Refer dberror: for details
    "code": "dberror.Code",				// (string) Error code, Refer dberror: for details
    "message": "" 						// (string) Error message if applicable.
}

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:resubscribe.fail",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:participant.joined

This will be triggered only for presence (prs:) and system (sys:) channel subscription.

Callback parameters

payload: (dict)

{
  "sessionid": "ydR27s3Z92yQw7wjGY2lX", 	// (string) Session id of the member who has subscribed/connected to channel
  "libtype": "nodejs", 						// (string) Library Lang of the member who has subscribed/connected to channel
  "sourceipv4": "0.0.0.0", 					// (string) IPv4 of the member who has subscribed/connected to channel
  "sourceipv6": "::1", 						// (string) Not Applicable in current version.
  "sysinfo": '{"sysid":"nameofcaller"}' 	// (string) System Info of the member who has subscribed/connected to channel
}

metadata (dict):

{
    "channelname": "prs:channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:participant.joined",// (string) eventName 
    "sourcesysid": "nameofcaller", 			// (string) Sys id of the member who has subscribed/connected to channel
    "sqnum": null,							// (string) 
    "sessionid": "ydR27s3Z92yQw7wjGY2lX", 	// (string) Session id of the member who has subscribed/connected to channel
    "intime": null	  						// (string) 
}

dbridges:participant.left

This will be triggered only for presence (prs:) and system (sys:) channel subscription.

Callback parameters

payload: (dict)

{
  "sessionid": "ydR27s3Z92yQw7wjGY2lX", 	// (string) Session id of the member who has subscribed/connected to channel
  "libtype": "nodejs", 						// (string) Library Lang of the member who has subscribed/connected to channel
  "sourceipv4": "0.0.0.0", 					// (string) IPv4 of the member who has subscribed/connected to channel
  "sourceipv6": "::1", 						// (string) Not Applicable in current version.
  "sysinfo": '{"sysid":"nameofcaller"}' 	// (string) System Info of the member who has subscribed/connected to channel
}

metadata (dict):

{
    "channelname": "prs:channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:participant.left",// (string) eventName 
    "sourcesysid": "nameofcaller", 			// (string) Sys id of the member who has subscribed/connected to channel
    "sqnum": null,							// (string) 
    "sessionid": "ydR27s3Z92yQw7wjGY2lX", 	// (string) Session id of the member who has subscribed/connected to channel
    "intime": null	  						// (string) 
}

dbridges:connect.success

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:connect.success",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:connect.fail

Callback parameters

payload: (dberror object)

{
    "source": "dberror.Source" , 		// (string) Error source, Refer dberror: for details
    "code": "dberror.Code",				// (string) Error code, Refer dberror: for details
    "message": "" 						// (string) Error message if applicable.
}

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:connect.fail",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:disconnect.success

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:disconnect.success",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:disconnect.fail

Callback parameters

payload: (dberror object)

{
    "source": "dberror.Source" , 		// (string) Error source, Refer dberror: for details
    "code": "dberror.Code",				// (string) Error code, Refer dberror: for details
    "message": "" 						// (string) Error message if applicable.
}

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:disconnect.fail",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:reconnect.success

Callback parameters

payload:

null

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:reconnect.success",// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

dbridges:reconnect.fail

Callback parameters

payload: (dberror object)

{
    "source": "dberror.Source" , 		// (string) Error source, Refer dberror: for details
    "code": "dberror.Code",				// (string) Error code, Refer dberror: for details
    "message": "" 						// (string) Error message if applicable.
}

metadata (dict):

{
    "channelname": "channelName" , 		// (string) channelName to which subscription is done.
    "eventname": "dbridges:reconnect.fail",				// (string) eventName 
    "sourcesysid": "", 					// (string) 
    "sqnum": "",						// (string) 
    "sessionid": "", 					// (string) 
    "intime": 	  						// (string) 
}

System events - payload (dberror object) - details:

Source	Code	Description
DBNET_CHANNEL_SUBSCRIBE	ERR_FAIL_ERROR	dataBridges network encountered error when subscribing to the channel.
DBNET_CHANNEL_SUBSCRIBE	ERR_ACCESS_DENIED	dBrdige network reported access violation with access_token function during subscription of this channel. Verify if appKey has sufficient publish grants. Login to management portal. Select Edit Key option and check Allow key to publish messages to public channels is selected.
DBLIB_CHANNEL_SUBSCRIBE	ACCESS_TOKEN	dbridge.access_token function returned error.
DBNET_CHANNEL_UNSUBSCRIBE	ERR_FAIL_ERROR	dataBridges network encountered error when unsubscribing to the channel.
DBNET_CHANNEL_UNSUBSCRIBE	ERR_ACCESS_DENIED	dataBridges network reported access violation with access_token function during unsubscribing of this channel. Verify if appKey has sufficient publish grants. Login to management portal. Select Edit Key option and check Allow key to publish messages to public channels is selected.
DBNET_CHANNEL_CONNECT	ERR_FAIL_ERROR	dataBridges network encountered error when subscribing to the channel.
DBNET_CHANNEL_CONNECT	ERR_ACCESS_DENIED	dataBridges network reported access violation with access_token function during subscription of this channel. Verify if appKey has sufficient publish grants. Login to management portal. Select Edit Key option and check Allow key to publish messages to public channels is selected.
DBLIB_CHANNEL_CONNECT	ACCESS_TOKEN	dbridge.access_token function returned error.
DBLIB_CHANNEL_DISCONNECT	ERR_FAIL_ERROR	dataBridges network encountered error when unsubscribing to the channel..
DBLIB_CHANNEL_DISCONNECT	ERR_ACCESS_DENIED	dataBridges network reported access violation with access_token function during unsubscribing of this channel. Verify if appKey has sufficient publish grants. Login to management portal. Select Edit Key option and check Allow key to publish messages to public channels is selected.

---

object: rpc (Remote Procedure Call)

rpc object exposes trust-safe properties, functions and events to provide reliable two-way messaging (request-response) between multiple endpoints allowing you to build sophisticated asynchronous interactions.

Concepts

• Client application allows you to execute RPC functions exposed by server applications.
• Client application is called CALLEE and the server application is called CALLER.
• Client application will execute a remote function by passing IN.paramter, and a timeout
  • The server application's corresponding function will be invoked with the IN.parameter and it will respond with response() or exception() which will be delivered back to the CALLEE client application by dataBridges network completing the request-response communication.
• Client application need not be aware about RPC servers identity and will only interact with RPC server namespace. The dataBridges network will intelligently route and load balance RPC call() to the RPC server application. The dataBridges network will automatically load balance multiple instance of server application exposing the same RPC endpoints.
• Trust-tokens are supported by RPC as well. You will need to pass a trust-token when you connect to the access controlled RPC endpoint. A trust-token is a JWT document created using a combination of rpc server endpoint / server name + sessionid + app.secret.
  • Use your existing access control, authorization and session identification rule-set, process and methods to create a trust-token instructing the dataBridges router to accept the pvt: prs: rpc endpoint/server connection of from client application.
• Trust-tokens allows you to enable secured, access controlled and compliance driven reliable two-way messaging (request-response) in your existing and new initiative applications.

Connect to Server

To use rpc functions, the application has to connect to the rpc endpoint/server. This is done using connect() function explained below.

connect()

The default method for connecting to a rpc endpoint/server involves invoking the rpc.connect function of your dataBridges object.

try:
     rpcClient = dbridge.rpc.connect('rpcServer')
except dBError as e:
 	print(e.code, e.source, e.message) 

Parameter	Rules	Description
string	*serverName OR **pvt:**serverName OR **prs:*serverName	serverName to which connection to be done.

Return Type	Description
object	rpcObject which events and related functions can be bound to.

Exceptions:

Source	Code	Message	Description
DBLIB_RPC_CONNECT	INVALID_SERVERNAME		Applicable for below conditions 1. serverName is not defined. 2. serverName validation error, length of serverName greater than 64 3. serverName validation error, serverName fails a-zA-Z0-9\.:_- validation. 4. serverName contains : and first token is not pvt,prs.
DBLIB_RPC_CONNECT	NETWORK_DISCONNECTED		Connection to dataBridges network is not active.
DBNET_RPC_CONNECT	ERR_FAIL_ERROR		dataBridges network encountered error during current operation.
DBNET_RPC_CONNECT	ERR_ACCESS_DENIED		dataBridges network reported access violation with access_token function during current operation. Verify if appKey has sufficient publish grants. Login to management portal. Select Edit Key option and check Allow key to access RPC functions is selected.

Server Information

isOnline()

rpcObject provides a function to check if the channel is online.

isonline = rpcClient.isOnline() 

Parameter	Rules	Description
string	*serverName OR **pvt:**serverName OR **prs:*serverName	serverName to which subscription to be done.

Return Values	Description
boolean	Is the current status of server connection online or offline.

getServerName()

rpcObject provides a function to get the serverName.

serverName = rpcClient.getServerName() 

Return Type	Description
string	serverName of connected rpcServer.

Execute Remote Procedure Call

call()

rpcObject call() function allows you to execute a remote function hosted by RPC endpoint / server using dataBridges server library

• passing function parameter as parameter
• while setting an time to live (TTL) for the response

The RPC call() functions supports multipart response (where the RPC function can send back multiple responses to a single RPC function call) along with exception routine.

def progress(response):
	print("multipart: " , response)

def onResult(response):
	print("response: ", response)

def onError(error):
	print(error.code, error.source, error.message)
  
try:
    p =  await rpcClient.call("functionName" ,  parameter , 10000, progress)
    p.then(onResult).catch(onError)
except dBError as e:
    print(e.code, e.source, e.message) 

# Below example how a application can connect to a RPC endpoint / Server called mathServer and use add, multiply functions.
try:
    myMathServer = dbridge.rpc.connect('mathServer');
except dBError as e:
    print(e.code, e.source, e.message) 

obj = { "num1":44.5, "num2":30};
inparam = json.dumps(obj);

try:
    p =  await myMathServer.call(add ,  inparam , 10000, progress)
    p.then(onResult).catch(onError)

    q =  await myMathServer.call(multiply ,  inparam , 10000, progress)
    q.then(onResult).catch(onError)
except dBError as e:
    print(e.code, e.source, e.message) 

Parameter	Expected Value	Description
functionName	functionname	(string) Function name as defined in rpc endpoint/ Server . Note - RPC endpoint / server can expose multiple rpc functions.
parameter	function parameter	(string) if multiple parameters to be passed, This can be done by putting it into array or json and stringify the object.
ttlms	1000	(integer) Time to live in millisecond, timeout value before the call() function throws error timeout.

Return Values	Description
string	Multipart or final response. in case of error, dberror object is returned.

Exceptions:

Source	Code	Description
DBNET_RPC_CALL	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.
DBNET_RPC_CALL	RESPONSE_TIMEOUT	call() response not received within defined ttlms.
DBLIB_RPC_CALL	ID_GENERATION_FAILED	Internal Library error.
DBNET_RPC_CALL	ERR_ACCESS_DENIED	dataBridges network reported access violation with access_token function during current operation. Verify if appKey has sufficient publish grants. Login to management portal. Select Edit Key option and check Allow key to access RPC functions is selected.
DBRPCCALLEE_RPC_CALL	ERR_error_code	This indicates an exception encountered by the remote RPC function. ERR_error_code will have the details.
DBNET_RPC_CALL	CLE_NR_10865	rpc endpoint / server disconnected from dataBridges network. Try again.
DBNET_RPC_CALL	CLE_NR_30391	rpc endpoint / server disconnected from dataBridges network. Try again.
DBNET_RPC_CALL	CLE_QX_41074	Cannot process the call() because the RPC server (in this case CALLEE) has exceeded outstanding pending rpc call() queue limit.
DBNET_RPC_CALL	CLE_QX_49467	Cannot process the call() because the RPC server (in this case CALLEE) has exceeded outstanding pending rpc call() queue limit.
DBNET_RPC_CALL	CLR_QX_39305	Cannot process the call() because the application (in this case CALLER) has exceeded outstanding pending rpc call() queue limit.
DBNET_RPC_CALL	CLR_QX_39824	Cannot process the call() because the application (in this case CALLER) has exceeded outstanding pending rpc call() queue limit.
DBNET_RPC_CALL	RE_28710	rpc endpoint / server disconnected from dataBridges network. Try again.
DBNET_RPC_CALL	AD_48621	Application does not have access to execute rpc functions.

System events for rpc object

There are a number of events which are triggered internally by the library, but can also be of use elsewhere. Below are the list of all events triggered by the library.

Below syntax is same for all system events.

#   Binding to systemevent on rpcObject  
try:
	rpcClient.bind("eventName", eventCallback)
except dBError as e:
    print(e.code, e.source, e.message) 

#  Binding to systemevent on rpcObject  
try:
   	dbridge.rpc.bind("eventName", eventCallback)
except dBError as e:
    print(e.code, e.source, e.message) 

bind_all and unbind_all

bind_all and unbind_all work much like bind and unbind, but instead of only firing callbacks on a specific event, they fire callbacks on any event, and provide that event in the metadata to the handler along with the payload.

# Binding to rpc events on rpcObject  
def eventFunction(payload ,  metadata):
  	print(payload , metadata)

try:
    rpcClient.bind_all('eventName',  eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Binding to rpc events on dbridgeObject 
try {
    dbridge.rpc.bind_all('eventName', eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

Callback out parameter payload, metadata details are explained with each event below in this document.

Exceptions:

Source	Code	Description
DBLIB_CONNECT_BIND	INVALID_CALLBACK	If "callback function" is not declared or typeof() variable defined is not a "function".

unbind_all works similarly to unbind.

# Remove just `handler` connected rpc server 
rpcClient.unbind_all(handler)

# Remove all handlers for the all event in the connected rpc server
rpcClient.unbind_all()

# Remove `handler` across the connected rpc servers
dbridge.rpc.unbind_all(handler)

# Remove all handlers for all events across all connected rpc servers
dbridge.rpc.unbind_all()

dridges:rpc.server.connect.success

Callback parameters

payload:

null

metadata (dict):

{
    "servername": "serverName" , 					// (string) serverName to which connection is done.
    "eventname": "dbridges:rpc.server.connect.success", // (string) eventName 
}

dbridges:rpc.server.connect.fail

Callback parameters

payload: (dberror object)

{
    "source": "DBLIB_RPC_CONNECT" , 	// (string) Error source
    "code": "ACCESS_TOKEN_FAIL",			// (string) Error code 
    "message": "" 							// (string) Error message if applicable.
}

metadata (dict):

{
    "servername": "serverName" , 				// (string) serverName to which connection is done.
    "eventname": "dbridges:rpc.server.connect.fail",// (string) eventName 
}

dbridges:rpc.server.online

Callback parameters

payload:

null

metadata (dict):

{
    "servername": "serverName" , 		   // (string) serverName to which connection is done.
    "eventname": "dbridges:rpc.server.online", // (string) eventName 
}

dbridges:rpc.server.offline

Callback parameters

payload:

null

metadata (dict):

{
    "servername": "serverName" , 					// (string) serverName to which connection is done.
    "eventname": "dbridges:rpc.server.offline",// (string) eventName 
}

dberror:

Source	Code	Message	Description
DBLIB_RPC_CONNECT	ACCESS_TOKEN_FAIL		Specific to private (pvt:) or presence (prs:) rpc call. Access token validation failed at dataBridges network.
DBLIB_RPC_CONNECT	ACCESS_DENIED	error_message	Specific to private (pvt:) or presence (prs:) rpc call. This is returned by the access_token function execution before call() is made.

---

object:Cf (Client Function)

CF (Client-function) object is a special purpose RPC | request-response implementation to build command and control applications. CF object exposes properties, functions and events for command and control server applications to send messages to devices and application using dataBridges library in **trust-safe manner **, build smart update configuration system and implement **trust-safe ** actions for remote and automated management.

CF REDUCES HUGE ENGINEERING TIME EFFORT REQUIRED TO DESIGN, BUILD AND MAINTAIN A ROBUST COMMAND-CONTROL INFRASTRUCTURE.

• A client function(s) is a callback function exposed by the client library as a RPC (remote procedure call).
• Server application (using dataBridges server library), can execute the CF function remotely.

Concepts

• CF (client-function) simplifies the comand and control type application design and maintenance.
• iOT and large distributed system requires a standard, secured and compliant method to send reliable request-response communication to the managed devices from authenticated and authorized Command-and-Control server applications. dataBridges CF allows you you to expose device functions and capabilities in a easy, secured manner allowing only authoirized dataBridges server applications to communicate with the devices, remote applications.
• Only server application using dataBridges server library + application key secret can execute CF functions exposed by remote devices.
  • The server application is called CALLER (the one executing cf.call() function)
  • The server application needs to know the sessionID of the device to which it needs to communicate.
  • The device application exposing command functions is called CALLEE. Only authenticated and authorized server application will be allowed to communicate with the device application for device / application management.

Properties

The following is the list of cf properties. These properties has to be set before dbridge.connect()

Property	Description
enable	(boolean) (default:false) If application wants to enable clientFunction functionality, this needs to be true else false.
functions	(function) A client function(s) is a callback function exposed by the client library as a RPC (remote procedure call).

enable:

You need to enable cf in the connection property.

dbridge.cf.enable = True

functions:

Application can expose callback function(s) as Client function (special case RPC | Request-Response). Server application using dataBridges server library can remotely execute the client functions. Each function needs to be registered with the library as a client function (CF), using dbridge.cf.regfn()where you can link the functionName to ClientFunctionName.

• The client application that exposes the client function is called a CALLEE.
• The server application that executes the client function is called a CALLER.

Functions can be defined either inside the property callback function or anywhere in the scope of application. Below code exhibits both ways of exposing the function.

# function is exposed outside the property callback function, but in the scope of application.
async def cfFunOutside(inparameter, response):
    try:
        response.tracker = True
        upTime = {"uptime": "13:34:30 up 8 days,  3:10,  1 user,  load average: 0.03, 0.11, 0.21"};
        response.next('retrieving system uptime')
        response.end(json,dumps(upTime))
        response.exception('INVALID_PARAM', 'Wrong parameter') 
    except dBError as e:
        print(e.code, e.source, e.message) 

async def cfFunctionBinder():
    async def cfFunInside(inparameter, response):
        #// function is exposed inside the property callback function.
        response.tracker = True
        try:
            response.tracker = True
            uName = {"uname": "Linux analysis 2.6.32-696.30.1.el6.x86_64 #1 SMP Tue May 22 03:28:18 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux"};
            response.next('retrieving uName')
            response.end(json.dumps(uName))
            response.exception('INVALID_PARAM', 'Wrong parameter') 
        except dBError as e:
            print(e.code, e.source, e.message) 

	try:
        dbridge.cf.regfn("isro", cfFunInside)
        dbridge.cf.regfn("nasa", cfFunOutside)
   	except dBError as e:
  		print(e.code, e.source, e.message) 

dbridge.cf.functions = cfFunctionBinder
# unbinding of function exposed by rpc functions
dbridge.cf.unregfn("nasa", cfFunOutside)

Below are parameters of the callback function which is exposed to clientfunctions.

Parameter	Description
payload	(string) The inParameter for the clientFunction.
response	(object) The library creates a response object unique for each client function call. The Response object has properties and function to return execution results of the function back to caller.

response: (object)

Properties/Function	Description
tracker	(boolean) This will enable response tracker, and event cf.response.tracker will be fired if any issue happens in sending back response to caller. Enable this property if your function needs a confirmation of reponse delivered to the caller.
id	(string) (readonly) Each client function execution is assigned a unique ID by the library. when the response tracker is enabled, the application can bind to an event cf.response.tracker to get the delivery notification. The event will indicate the delivery notification linked to this ID. Client application will need to maintain this ID to track the delivery notification.
next	(function) dataBridges CF (Special case RPC |request-response) supports mult-part response. Application can use response.next to send multi-part response to the caller.
end	(function) response.end is to send the final response to the caller. Once end is called, the object is closed and no more response can be sent.
exception	(function) Two parameter, return errorCode (string) ,errorMessage (string) is sent to caller. This will raise an exception at the caller library.

Exceptions:

Below exceptions are raised in the cf.regfn.

Source	Code	Description
DBLIB_CF_REGFN	INVALID_FUNCTION_NAME	Invalid Function name.
DBLIB_CF_REGFN	INVALID_CALLBACK	Callback is not a function or is not defined.

Below exceptions are raised on response object inside the registered function.

Source	Code	Description
DBLIB_CF_CALL	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.
DBLIB_CF_CALL	RESPONSE_OBJECT_CLOSED	Return response object is closed. Thus the function is unable to respond back to the call.

resetqueue()

dbridgeObject resetqueue() . The dataBridges network maintains in-process CF function execution status. resetqueue() informs the dataBridges network that all in-process CF function execution will be dropped by the application and response to be invalidated. Resetqueue() use case is intended to be used by application in its self health status management. Sometime due to the application process flow, the application can identify situation where it would like to ease its load by resettiing the CF function execution queue by sending resetqueue() message to dataBridges network and than closing all in-process CF function execution.

try:
    await dbridge.cf.resetqueue();
except dBError as e:
    print(e.code, e.source, e.message)

Exceptions:

Source	Code	Description
DBLIB_CF_CALL	NETWORK_DISCONNECTED	Connection to dataBridges network is not active.

System events for cf object

There are a number of events which are triggered internally by the library, but can also be of use elsewhere. Below are the list of all events triggered by the library.

Below syntax is same for all system events.

#  Binding to systemevent on dbridgeObject 
def eventFunction(payload,metadata):
   print(payload,metadata)

try:
    dbridge.cf.bind('eventName', eventFunction)
except dBError as e:
	print(e.code, e.source, e.message)

cf.response.tracker

Callback parameters

Return Values	Description
payload	(string) Tracker identifier. which is same as response.id
metadata	(string) Refer below table.

Error Identifier	Description
RE_12616	cf caller is disconnected from dataBridges network and hence cannot process response tracking.
RE_13151	cf caller is disconnected from dataBridges network and hence cannot process response tracking.
RE_30030	The cf client is disconnected from dataBridges network
RE_33635	The cf client is disconnected from dataBridges network

cf.callee.queue.exceeded

Callback parameters

payload: (dberror object)

{
    "source": "DBNET_CF_CALL" , 				// (string) Error source
    "code": "ERR_CALLEE_QUEUE_EXCEEDED",		// (string) Error code  
    "message": "" 								// (string) Error message if applicable.
}

metadata:

null

dberror:

Source	Code	Description
DBNET_CF_CALL	ERR_CALLEE_QUEUE_EXCEEDED	No new cf calls are being routed by the dataBridges network to the application because the application's current cf processing queue has already exceeded. Each application connection cannot exceed cf.queue.maximum. Refer to management console documentation for cf.queue.maximum details.

Change Log

• Change log: Changes in the recent versions

License

DataBridges Library is released under the Apache 2.0 license.

Copyright 2022 Optomate Technologies Private Limited.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.