databridges-sio-server-lib v2.0.3

Databridges Node.js server 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 Node.js 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
  • Channel Information
  • Publish to Channel
  • Send Message to Members / sessionID
  • Binding to events
  • System events for channel object
• object: rpc (Remote Procedure Call)
  • Initialize rpc Server
  • Register rpc functions
  • Register Server
  • Unregister Server
  • resetqueue()
  • System events for rpc server registration.
  • Server Information
  • Connect to Server
  • Execute Remote Procedure Call
• object:Cf (Client Function)
  • Execute Client Functions
  • Properties
• Change Log
• License

Supported platforms

Node.js version 10 or newer. (The current Long Term Support (LTS) release is an ideal starting point).

Installation

You can use NPM package manager to install the package.

npm install databridges-sio-server-lib --save

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

Initialization

const dbridge = require('databridges-sio-server-lib');
const dbridge = new 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';
dbridge.appsecret = 'APP_SECRET';

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

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; 

Connection

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

dbridge.connect().catch((err) => {
    console.log('dBridges Connection exception..', err.source, err.code, err.message);
});

Exceptions:

sessionid (string)

console.log(dbridge.sessionid);

Making a connection provides the application with a new sessionid that is assigned by the application. 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.

dbridge.disconnect();

Objects

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.

console.log(dbridge.connectionstate.state);
console.log(dbridge.connectionstate.isconnected);
console.log(dbridge.connectionstate.rttms);
console.log(dbridge.connectionstate.reconnect_attempt);

connectionstate.state

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, () => {});
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

dbridge.connectionstate.bind("connecting", () => {
    console.log('connecting');
});
dbridge.connectionstate.bind("reconnecting", () => {
    console.log('reconnecting', "reconnect_attempt=", dbridge.connectionstate.reconnect_attempt);
});
dbridge.connectionstate.bind("disconnected", () => {
    console.log('disconnected');
});
dbridge.connectionstate.bind("reconnected", () => {
    console.log('reconnected');
}); 
dbridge.connectionstate.bind("connection_break", (payload) => {
    console.log('connection_break', payload.source, payload.code, payload.message);
});
dbridge.connectionstate.bind("state_change", (payload) => {
    console.log('state_change', dbridge.connectionstate.state, payload);
});
dbridge.connectionstate.bind("connect_error", (payload) => {
    console.log('connect_error', payload.source, payload.code, payload.message); 
});
dbridge.connectionstate.bind("reconnect_error", (payload) => {
    console.log('reconnect_error', payload.source, payload.code, payload.message);
}); 
dbridge.connectionstate.bind("reconnect_failed", (payload) => {
    console.log('reconnect_failed', payload.source, payload.code, payload.message); 
});
dbridge.connectionstate.bind("rttpong", (payload) => {
    console.log('rttpong', payload, dbridge.connectionstate.rttms);
}); 
dbridge.connectionstate.bind("connected", () => { 
    console.log('connected');
});

payload: (dberror object)

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

dberror:

Exceptions:

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.
console.log(dbridge.connectionstate.rttms);

// To get the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
dbridge.connectionstate.rttping();

// Bind to rttpong, to get notified about the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
dbridge.connectionstate.bind("rttpong", (payload) => {
    console.log('rttpong', payload);
    //payload is an integer value is in millisecond which is same as dbridge.connectionstate.rttms.
});

Exceptions:

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: .
  • Note dataBridges have 2 seprate libraries (client lib, server lib). You are reading the server library api document.
    • Server lib uses app.key along with secret to get access to all channels including pvt: , prs: and sys: channels linked to the application.
    • Whereas application using client library (client application) will always need to pass a trust-token to access restricted channels (pvt: prs: sys: ) . A trust-token is a JWT document created using a combination of channelname + sessionid + app.secret. Trust token can be created by application having access to app.key's secret.
      • you can 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.

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 {
    const subscribed_channel = dbridge.channel.subscribe('mychannel');
} catch (err) {
    console.log(err.source, err.code, err.message);
}

Application can directly work with dataBridges object without using Channel object.

try {
    dbridge.channel.subscribe('mychannel');
} catch (err) {
    console.log(err.source, err.code, err.message);
}

Exceptions:

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');
} catch (err) {
    console.log(err.source, err.code, err.message);
}

Exceptions:

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.

const mychannel_isonline = dbridge.channel.isOnline('mychannel');

const mychannel_isonline = subscribed_channel.isOnline(); 

list()

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

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

Dictionary contains below information.

getChannelName()

channelObject provides a function to get the channelName.

const chName = channelobject.getChannelName() 

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 processing flows.

publish()

The default method for publishing user-defined events to a channel involves invoking the channel.publish function of your channelObject for which it has connected to OR using dbridgeObject giving the channelName as parameter.

Note: channel.publish is not allowed using channelObject subscribed to sys:* channel.

// Using dbridgeObject 
try {
    dbridge.channel.publish(channelName, event, payload, excludeSessionId, sourceId, seqno);
} catch (err) {
    console.log(err.source, err.code, err.message);
}
// Using channelObject 
try {
    channelObject.publish(event, payload, excludeSessionId, sourceId, seqno);
} catch (err) {
    console.log(err.source, err.code, err.message);
}
// Best practice is to check the channel is online before publishing any message.
if (channelObject.isOnline()) {
    try {
        channelObject.publish(event, payload, excludeSessionId, sourceId, seqno);
    } catch (err) {
        console.log(err.source, err.code, err.message);
    }
}

Exceptions:

Send Message to Members / sessionID

It's possible to send message to individual sessionId using the channel.sendmsg function on an instance of the channelObject or using dbridgeObject.

sendmsg()

The default method for send message user-defined events to a individual sessionId involves invoking the channel.sendmsg function of your channelObject for which it has connected to OR using dbridgeObject giving the channelName as parameter.

Note: channel.sendmsg is not allowed using channelObject subscribed to sys:* channel.

// Using dbridgeObject 
try {
    dbridge.channel.sendmsg(channelName, event, payload, toSessionId, sourceId, seqno);
} catch (err) {
    console.log(err.source, err.code, err.message);
}
// Using channelObject 
try {
    channelObject.sendmsg(event, payload, toSessionId, sourceId, seqno);
} catch (err) {
    console.log(err.source, err.code, err.message);
}

// Best practice is to check the channel is online before publishing any message.
if (channelObject.isOnline()) {
    try {
        channelObject.sendmsg(event, payload, toSessionId, sourceId, seqno);
    } catch (err) {
        console.log(err.source, err.code, err.message);
    }
}

Exceptions:

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 using Anonymous function.
try {
    channelObject.bind('eventName',  (payload, metadata) => {
        console.log(payload, metadata);
    });
} catch(err){
     console.log(err.source, err.code, err.message);
}

// Binding to channel events on dbridgeObject using Anonymous function.
try {
    dbridge.channel.bind('eventName', (payload, metadata) => {
    	console.log(payload, metadata);
	});
} catch(err){
     console.log(err.source, err.code, err.message);
}

// Binding to channel events on channelObject using user function.
const myEventHandler = (payload, metadata) =>{
	console.log(payload, metadata);
};

try {
    dbridge.channel.bind('eventName', myEventHandler);
} catch(err){
     console.log(err.source, err.code, err.message);
}

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:

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.

//  Binding to all channel events on channelObject  
try {
    channelObject.bind_all((payload, metadata) => {
        console.log(payload, metadata);
    });
} catch(err){
     console.log(err.source, err.code, err.message);
}

// Binding to all channel events on dbridgeObject 
try {
    dbridge.channel.bind_all((payload, metadata) => {
    	console.log(payload, metadata);
	});
} catch(err){
     console.log(err.source, err.code, err.message);
}

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

Exceptions:

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  
try {
    channelObject.bind('dbridges:subscribe.success', (payload, metadata) => {
        console.log( payload, metadata);
    });
} catch(err) {
     console.log(err.source, err.code, err.message);
}
//  Binding to systemevent on dbridgeObject  
try {
    dbridge.channel.bind('dbridges:subscribe.success', (payload, metadata) => {
        console.log( payload, metadata);
    });
} catch(err) {
     console.log(err.source, err.code, err.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 this 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 this 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) 
}

System events - payload (dberror object) - details:

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

• RPC endpoint / server (CALLEE)
  • Application using dataBridges server library can expose callback function(s) as a dataBridges rpc function.
  • Multiple callback function(s), can be exposed as rpc functions grouped together as an rpc endpoint / server.
  • To deploy access-controlled, trust-safe rpc endpoint / server, prefix the rpc server namespace with pvt: or prs:
    • Note dataBridges have 2 seprate libraries (client lib, server lib). You are reading the server library api document.
      • Server lib uses app.key along with secret to get access to rpc endpoint/server including pvt: , prs: access controlled rpc endpoint/server.
      • Whereas application using client library (client application) will always need to pass a trust-token to access restricted rpc endpoint/server (prefixed with pvt: prs:) . A trust-token is a JWT document created using a combination of channelname + sessionid + app.secret. Trust token can be created by application having access to app.key's secret.
        • you can 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 call() client application.
        • Trust-tokens allows you to enable secured, access controlled and compliance driven two-way messaging (request-response) between multiple endpoints allowing you to build sophisticated asynchronous interactions in your existing and new initiative applications.
• RPC clients (CALLER)
  • Both dataBridges client and server api's allow you to execute rpc function(s) exposed by rpc endpoint / server.
  • Appication consuming rpc function(s) is called CALLEE and the rpc endpoint/server application is called CALLER.
  • CALLEE application will execute a remote function by passing IN.paramter, and a timeout
    • The CALLER 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 application by dataBridges network completing the request-response communication.
  • CALLEE application need not be aware about RPC servers (CALLER) identity and will only interact with RPC server (CALLER) 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.

To expose rpc functions the application needs to register an rpc server and register callback functions to rpc server as rpc functions.

• The steps involved are :
  • Initialize rpc endpoint/server using init().
  • Register all rpc functions using regfn().
  • Register rpc endpoint/server with dataBridges network using register()

Initialize rpc Server

Initialize the server using rpc.init function of your dataBridges object. This will return an object to which all properties, functions and events are available.

Note : Application can have multiple rpc endpoint/server against a dataBridges object.

//lets create an rpc endpoint/server named missionControl and expose 2 functions called nasa and isro.

try {
    const missionControl = dbridge.rpc.init('missionControl');
} catch (err) {
    console.log(err.source, err.code, err.message);
}

Exceptions:

Register rpc functions

Application can expose callback function(s) as rpc functions. Application using dataBridges client/server library can remotely execute the rpc functions. Each function needs to be registered with the library as a rpc function, using rpc.regfn()where you can link the functionName to rpcFunctionName.

• The server application that exposes the rpc function is called a CALLEE.
• The client/server application that executes the rpc 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.
function rpcFuncOustide (payload, response) {
    try {
        response.tracker = true;
        response.next('This is Houston');
        response.end('message received by Houston');
        response.exception('INVALID_PARAM', 'Wrong parameter'); 
    } catch(err) {
        console.log(err.source, err.code, err.message);
    }
}

missionControl.functions = function () {
    // function is exposed inside the property callback function.
    function rpcFuncInside (payload, response) {
        try {
            response.tracker = true;
            response.next('This is Hassan');
            response.end('message received by Hassan');
            response.exception('INVALID_PARAM', 'Wrong parameter'); 
            console.log(response.id);
        } catch(err) {
            console.log(err.source, err.code, err.message);
        }
    }
    // registering function to be exposed by rpcServer
    try {
    	missionControl.regfn("nasa", rpcFuncOustide);
    	missionControl.regfn("isro", rpcFuncInside);
    } catch(err) {
    	console.log(err.source, err.code, err.message);
    }
}

// unregistering of function exposed by rpcServer
missionControl.unregfn("nasa", rpcFuncOustide);

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

payload: (object)

response: (object)

Exceptions:

Below exceptions are raised in the rpc.regfn.

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

Register Server

Register rpc endpoint/server with dataBridges network using register().

try {
    missionControl.register();
} catch (err) {
    console.log(err.source, err.code, err.message);
}

// Best practice is to check the channel is online before publishing any message.
if (dbridge.connectionstate.isconnected()) {
    try {
        missionControl.register();
    } catch (err) {
        console.log(err.source, err.code, err.message);
    }
}

Exceptions:

Unregister Server

rpcServer can be unregistered from dataBridges server library using unregister function of your rpcServerObject.

missionControl.unregister();

resetqueue()

dbridgeObject The dataBridges network maintains in-process rpc function execution status. resetqueue() informs the dataBridges network that all in-process rpc 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 rpc function execution queue by sending resetqueue() message to dataBridges network and than closing all in-process rpc function execution.

try {
    missionControl.resetqueue();
} catch(err) {
	console.log(err.source, err.code, err.message);
}

Exceptions:

System events for rpc server registration.

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 systemevents on rpcObject  
try {
    missionControl.bind('eventName',  (payload, metadata) => {
        console.log(payload, metadata);
    }