Pub/Sub

Get Started with Pub/ Sub in KubeMQ

Connect Your KubeMQ Cluster

To be able to communicate with KubeMQ interface ports running in Kubernetes cluster, a Port Forward of KubeMQ's ports is needed.

kubemqctl has a handy command that will do it for you:

kubemqctl set cluster proxy

A consumer can subscribe to the "hello-world" channel with one of the following methods.

Run the following kubemqctl command:

kubemqctl events rec hello-world

When connected, a stream of events messages will be shown in the console.

The following cURL command is using KubeMQ's REST interface:

curl --location --request GET "http://localhost:9090/subscribe/events?client_id=some_client_id&channel=some_channel&group=some_group&subscribe_type=events" \
  --header "Content-Type: application/json" \
  --data ""

Subscribe to Events in REST interface is using WebSocket for streaming (Push) events to the consumer. You will need to implement a WebSocket receiver accordingly.

The following .NET code snippet is using KubeMQ's .NET SDK with gRPC interface:

using System;

namespace PubSub_Subscribe_to_a_Channel
{
    class Program
    {
        static void Main(string[] args)
        {

            var ChannelName = "hello-world";
            var ClientID = "hello-world-subscriber";
            var KubeMQServerAddress = "localhost:50000";

            var  subscriber = new KubeMQ.SDK.csharp.Events.Subscriber(KubeMQServerAddress);
            try
            {
                subscriber.SubscribeToEvents(new KubeMQ.SDK.csharp.Subscription.SubscribeRequest
                {
                    Channel = ChannelName,
                    SubscribeType = KubeMQ.SDK.csharp.Subscription.SubscribeType.Events,
                    ClientID = ClientID

                }, (eventReceive) =>
                {

                    Console.WriteLine($"Event Received: EventID:{eventReceive.EventID} Channel:{eventReceive.Channel} Metadata:{eventReceive.Metadata} Body:{ KubeMQ.SDK.csharp.Tools.Converter.FromByteArray(eventReceive.Body)} ");
                },
                (errorHandler) =>                 
                {
                    Console.WriteLine(errorHandler.Message);
                });
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.WriteLine("press any key to close PubSub_Subscribe_to_a_Channel");
            Console.ReadLine();
        }  

    }
}

When executed, a stream of events messages will be shown in the console.

The following Java code snippet is using KubeMQ's Java SDK with gRPC interface:

package io.kubemq.sdk.examples.get_Started.pubSub_Subscribe_to_a_Channel;

import java.io.IOException;

import javax.net.ssl.SSLException;

import io.grpc.stub.StreamObserver;
import io.kubemq.sdk.basic.ServerAddressNotSuppliedException;
import io.kubemq.sdk.event.EventReceive;
import io.kubemq.sdk.event.Subscriber;
import io.kubemq.sdk.subscription.SubscribeRequest;
import io.kubemq.sdk.subscription.SubscribeType;
import io.kubemq.sdk.tools.Converter;

public class Program {

    public static void main(String[] args)  {


        String channelName = "hello-world", clientID = "hello-world-subscriber", kubeMQAddress = "localhost:50000";
        Subscriber subscriber = new Subscriber(kubeMQAddress);
        SubscribeRequest subscribeRequest = new SubscribeRequest();
        subscribeRequest.setChannel(channelName);
        subscribeRequest.setClientID(clientID);
        subscribeRequest.setSubscribeType(SubscribeType.Events); 

        StreamObserver<EventReceive> streamObserver = new StreamObserver<EventReceive>() {

            @Override
            public void onNext(EventReceive value) {
                try {
                    System.out.printf("Event Received: EventID: %d, Channel: %s, Metadata: %s, Body: %s",
                            value.getEventId(), value.getChannel(), value.getMetadata(),
                            Converter.FromByteArray(value.getBody()));
                } catch (ClassNotFoundException e) {
                    System.out.printf("ClassNotFoundException: %s",e.getMessage());
                    e.printStackTrace();
                } catch (IOException e) {
                    System.out.printf("IOException:  %s",e.getMessage());
                    e.printStackTrace();
                }

            }

            @Override
            public void onError(Throwable t) {
                System.out.printf("Event Received Error: %s", t.toString());
            }

            @Override
            public void onCompleted() {

            }
        };
        try {
            subscriber.SubscribeToEvents(subscribeRequest, streamObserver);
        } catch (SSLException e) {
            System.out.printf("SSLException: %s", e.toString());
            e.printStackTrace();
        } catch (ServerAddressNotSuppliedException e) {
            System.out.printf("ServerAddressNotSuppliedException: %s", e.toString());
         e.printStackTrace();
      }

    }
}

When executed, a stream of events messages will be shown in the console.

The following Go code snippet is using KubeMQ's Go SDK with gRPC interface:

package main
import (
   "context"
   "fmt"
   "github.com/kubemq-io/kubemq-go"
   "log"
)

func main() {
   ctx, cancel := context.WithCancel(context.Background())
   defer cancel()
   client, err := kubemq.NewClient(ctx,
      kubemq.WithAddress("localhost", 50000),
      kubemq.WithClientId("hello-world-subscriber"),
      kubemq.WithTransportType(kubemq.TransportTypeGRPC))
   if err != nil {
      log.Fatal(err)
   }
   defer client.Close()
   channelName := "hello-world"
   errCh := make(chan error)
   eventsCh, err := client.SubscribeToEvents(ctx, channelName, "", errCh)
   if err != nil {
      log.Fatal(err)
      return

   }
   for {
      select {
      case err := <-errCh:
         log.Fatal(err)
         return
      case event, more := <-eventsCh:
         if !more {
            fmt.Println("Event Received, done")
            return
         }
         log.Printf("Event Received:\nEventID: %s\nChannel: %s\nMetadata: %s\nBody: %s\n", event.Id, event.Channel, event.Metadata, event.Body)
      case <-ctx.Done():
         return
      }
   }
}

When executed, a stream of events messages will be shown in the console.

The following Python code snippet is using KubeMQ's Python SDK with gRPC interface:

from builtins import input
from random import randint
from kubemq.events.subscriber import Subscriber
from kubemq.tools.listener_cancellation_token import ListenerCancellationToken
from kubemq.subscription.subscribe_type import SubscribeType
from kubemq.subscription.events_store_type import EventsStoreType
from kubemq.subscription.subscribe_request import SubscribeRequest



def handle_incoming_events(event):
    if event:
        print("Subscriber Received Event: Metadata:'%s', Channel:'%s', Body:'%s tags:%s'" % (
            event.metadata,
            event.channel,
            event.body,
            event.tags
        ))

def handle_incoming_error(error_msg):
        print("received error:%s'" % (
            error_msg
        ))


if __name__ == "__main__":
    print("Subscribing to event on channel example")
    cancel_token=ListenerCancellationToken()


    # Subscribe to events without store
    subscriber = Subscriber("localhost:50000")
    subscribe_request = SubscribeRequest(
        channel="testing_event_channel",
        client_id="hello-world-subscriber",
        events_store_type=EventsStoreType.Undefined,
        events_store_type_value=0,
        group="",
        subscribe_type=SubscribeType.Events
    )
    subscriber.subscribe_to_events(subscribe_request, handle_incoming_events,handle_incoming_error,cancel_token)

    input("Press 'Enter' to stop Listen...\n")
    cancel_token.cancel()
    input("Press 'Enter' to stop the application...\n")

When executed, a stream of events messages will be shown in the console.

The following JS code snippet is using KubeMQ's NodeJS SDK with gRPC interface:

const kubemq = require('kubemq-nodejs');

let channelName = 'pubsub', clientID = 'hello-world-subscriber',
    kubeMQHost = 'localhost', kubeMQGrpcPort = '50000';

let sub = new kubemq.Subscriber(kubeMQHost, kubeMQGrpcPort, clientID, channelName);

sub.subscribeToEvents(msg => {
    console.log('Event Received: EventID:' + msg.EventID + ', Channel:' + msg.Channel + ' ,Metadata:' + msg.Metadata + ', Body:' + kubemq.byteToString(msg.Body));
}, err => {
    console.log('error:' + err)
})

The following PHP code snippet is using KubeMQ's REST interface:

<?php

$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => "http://localhost:9090/subscribe/events?client_id=some_client_id&channel=hello-world&group=some_group&subscribe_type=events",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => false,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_HTTPHEADER => array(
    "Content-Type: application/json"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
} ?>

Subscribe to Events in REST interface is using WebSocket for streaming (Push) events to the consumer. You will need to implement a WebSocket receiver accordingly.

The following Ruby code snippet is using KubeMQ's REST interface:

require "uri"
require "net/http"

url = URI("http://localhost:9090/subscribe/events?client_id=some_client_id&channel=hello-world&group=some_group&subscribe_type=events")

http = Net::HTTP.new(url.host, url.port)

request = Net::HTTP::Get.new(url)
request["Content-Type"] = "application/json"

response = http.request(request)
puts response.read_body

Subscribe to Events in REST interface is using WebSocket for streaming (Push) events to the consumer. You will need to implement a WebSocket receiver accordingly.

The following jQuery code snippet is using KubeMQ's REST interface:

var settings = {
  "url": "http://localhost:9090/subscribe/events?client_id=some_client_id&channel=hello-world&group=some_group&subscribe_type=events",
  "method": "GET",
  "timeout": 0,
  "headers": {
    "Content-Type": "application/json",
  },
};

$.ajax(settings).done(function (response) {
  console.log(response);
});

Subscribe to Events in REST interface is using WebSocket for streaming (Push) events to the consumer. You will need to implement a WebSocket receiver accordingly.

Publish to Event Channel

After you have subscribed to a hello-world channel, you can send your message to it.

Run the following kubemqctl command:

kubemqctl events send hello-world "Hi KubeMQ"

The following cURL command is using KubeMQ's REST interface:

curl --location --request POST "http://localhost:9090/send/event" 
  --header "Content-Type: application/json" 
  --data '{"EventID": "1234-5678-90","ClientID": "events-client-id","Channel": "events-channel","Metadata": "some-metadata","Body": "c29tZSBlbmNvZGVkIGJvZHk=","Store": false}'

A response for a successful command will look like this:

{
  "is_error": false,
  "message": "OK",
  "data": {
    "EventID": "1234-5678-90",
    "Sent": true
  }
}

The following .NET code snippet is using KubeMQ's .NET SDK with gRPC interface:

using System;

namespace PubSub_Publish_to_a_Channel
{
    class Program
    {
        static void Main(string[] args)
        {
            var ChannelName = "hello-wrold";
            var ClientID = "hello-world-sender";
            var KubeMQServerAddress = "localhost:50000";


            var channel = new KubeMQ.SDK.csharp.Events.Channel(new KubeMQ.SDK.csharp.Events.ChannelParameters
            {
                ChannelName = ChannelName,
                ClientID = ClientID,
                KubeMQAddress = KubeMQServerAddress
            });

            try
            {
                var result = channel.SendEvent(new KubeMQ.SDK.csharp.Events.Event()
                {                  
                    Body = KubeMQ.SDK.csharp.Tools.Converter.ToByteArray("hello kubemq - sending single event")
                });
                if (!result.Sent)
                {
                    Console.WriteLine($"Could not send single message:{result.Error}");                 
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);          
            }
        }
    }
}

The following Java code snippet is using KubeMQ's Java SDK with gRPC interface:

package io.kubemq.sdk.examples.get_Started.pubSub_Publish_to_a_Channel;

import java.io.IOException;

import javax.net.ssl.SSLException;

import io.kubemq.sdk.basic.ServerAddressNotSuppliedException;
import io.kubemq.sdk.event.Event;
import io.kubemq.sdk.event.Result;
import io.kubemq.sdk.tools.Converter;

public class Program {

    public static void main(String[] args)  {

        String channelName = "hello-world", clientID = "hello-world-subscriber", kubeMQAddress = "localhost:50000";

        io.kubemq.sdk.event.Channel chan = new io.kubemq.sdk.event.Channel(channelName, clientID, false, kubeMQAddress);

        Event event = new Event();
        try {
            event.setBody(Converter.ToByteArray("hello kubemq - sending single event"));
        } catch (IOException e) {

            e.printStackTrace();
        }

        try {
            Result res = chan.SendEvent(event);
        } catch (SSLException | ServerAddressNotSuppliedException e) {

            e.printStackTrace();
        }

    }
}

The following Go code snippet is using KubeMQ's Go SDK with gRPC interface:

package main
import (
   "context"
   "github.com/kubemq-io/kubemq-go"
   "log"
)

func main() {
   ctx, cancel := context.WithCancel(context.Background())
   defer cancel()
   client, err := kubemq.NewClient(ctx,
      kubemq.WithAddress("localhost", 50000),
      kubemq.WithClientId("hello-world-sender"),
      kubemq.WithTransportType(kubemq.TransportTypeGRPC))
   if err != nil {
      log.Fatal(err)
   }
   defer client.Close()
   channelName := "hello-world"
   err = client.E().
      SetId("some-id").
      SetChannel(channelName).
      SetMetadata("some-metadata").
      SetBody([]byte("hello kubemq - sending single event")).
      Send(ctx)
   if err != nil {
      log.Fatal(err)
   }

}

The following Python code snippet is using KubeMQ's Python SDK with gRPC interface:

import datetime

from kubemq.events.lowlevel.event import Event
from kubemq.events.lowlevel.sender import Sender

if __name__ == "__main__":

    publisher  = Sender("localhost:50000")
    event = Event(
        metadata="EventMetaData",
        body =("hello kubemq - sending single event").encode('UTF-8'),
        store=False,
        channel="testing_event_channel",
        client_id="hello-world-subscriber"
    )
    try:
        res = publisher.send_event(event)
        print(res)
    except Exception as err:
      print(
            "'error sending:'%s'" % (
                err
                        )
        )

The following JS code snippet is using KubeMQ's NodeJS SDK with gRPC interface:

const kubemq = require('kubemq-nodejs');
let channelName = 'pubsub', clientID = 'hello-world-subscriber',
    kubeMQHost = 'localhost', kubeMQGrpcPort = '50000';
const publisher = new kubemq.Publisher(kubeMQHost, kubeMQGrpcPort, clientID, channelName);
let event = new kubemq.Publisher.Event(kubemq.stringToByte('hello kubemq - sending single event'));
publisher.send(event).then(
    res => {
        console.log(res);
    }).catch(
        err => {
            console.log('error sending' + err)
        });

The following PHP code snippet is using KubeMQ's REST interface:

<?php

$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => "http://localhost:9090/send/event",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => false,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS =>"{\n    \"EventID\": \"1234-5678-90\",\n    \"ClientID\": \"events-client-id\",\n    \"Channel\": \"hello-world\",\n    \"Metadata\": \"some-metadata\",\n    \"Body\": \"c29tZSBlbmNvZGVkIGJvZHk=\",\n    \"Store\": false\n}",
  CURLOPT_HTTPHEADER => array(
    "Content-Type: application/json"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
} ?>

A response for a successful command will look like this:

{
  "is_error": false,
  "message": "OK",
  "data": {
    "EventID": "1234-5678-90",
    "Sent": true
  }
}

The following Ruby code snippet is using KubeMQ's REST interface:

require "uri"
require "net/http"

url = URI("http://localhost:9090/send/event")

https = Net::HTTP.new(url.host, url.port)
https.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Content-Type"] = "application/json"
request.body = "{\n    \"EventID\": \"1234-5678-90\",\n    \"ClientID\": \"events-client-id\",\n    \"Channel\": \"hello-world\",\n    \"Metadata\": \"some-metadata\",\n    \"Body\": \"c29tZSBlbmNvZGVkIGJvZHk=\",\n    \"Store\": false\n}"
response = https.request(request)
puts response.read_body

A response for a successful command will look like this:

{
  "is_error": false,
  "message": "OK",
  "data": {
    "EventID": "1234-5678-90",
    "Sent": true
  }
}

The following jQuery code snippet is using KubeMQ's REST interface:

var settings = {
  "url": "http://localhost:9090/send/event",
  "method": "POST",
  "timeout": 0,
  "headers": {
    "Content-Type": "application/json",
  },
  "data": "{\n    \"EventID\": \"1234-5678-90\",\n    \"ClientID\": \"events-client-id\",\n    \"Channel\": \"hello-world\",\n    \"Metadata\": \"some-metadata\",\n    \"Body\": \"c29tZSBlbmNvZGVkIGJvZHk=\",\n    \"Store\": false\n}",
};

$.ajax(settings).done(function (response) {
  console.log(response);
});

A response for a successful command will look like this:

{
  "is_error": false,
  "message": "OK",
  "data": {
    "EventID": "1234-5678-90",
    "Sent": true
  }
}

Demo

PreviousQueues NextRPC

Last updated 5 years ago

Was this helpful?

Connect Your KubeMQ Cluster

Subscribe to Events Channel

Publish to Event Channel

Demo