Pub/Sub

​
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:
1
kubemqctl set cluster proxy
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Subscribe to Events Channel
A consumer can subscribe to the "hello-world" channel with one of the following methods.
kubemqctl
curl
.Net
Java
Go
Python
Node
PHP
Ruby
jquery
Run the following kubemqctl command:
1
kubemqctl events rec hello-world
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When connected, a stream of events messages will be shown in the console.
The following cURL command is using KubeMQ's REST interface:
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curl --location --request GET "http://localhost:9090/subscribe/events?client_id=some_client_id&channel=some_channel&group=some_group&subscribe_type=events" \
2
  --header "Content-Type: application/json" \
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  --data ""
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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:
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using System;
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​
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namespace PubSub_Subscribe_to_a_Channel
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{
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    class Program
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    {
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        static void Main(string[] args)
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        {
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​
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            var ChannelName = "hello-world";
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            var ClientID = "hello-world-subscriber";
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            var KubeMQServerAddress = "localhost:50000";
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​
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            var  subscriber = new KubeMQ.SDK.csharp.Events.Subscriber(KubeMQServerAddress);
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            try
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            {
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                subscriber.SubscribeToEvents(new KubeMQ.SDK.csharp.Subscription.SubscribeRequest
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                {
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                    Channel = ChannelName,
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                    SubscribeType = KubeMQ.SDK.csharp.Subscription.SubscribeType.Events,
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                    ClientID = ClientID
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​
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                }, (eventReceive) =>
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                {
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​
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                    Console.WriteLine(quot;Event Received: EventID:{eventReceive.EventID} Channel:{eventReceive.Channel} Metadata:{eventReceive.Metadata} Body:{ KubeMQ.SDK.csharp.Tools.Converter.FromByteArray(eventReceive.Body)} ");
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                },
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                (errorHandler) =>                 
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                {
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                    Console.WriteLine(errorHandler.Message);
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                });
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            }
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            catch (Exception ex)
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            {
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                Console.WriteLine(ex.Message);
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            }
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            Console.WriteLine("press any key to close PubSub_Subscribe_to_a_Channel");
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            Console.ReadLine();
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        }  
40
​
41
    }
42
}
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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:
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package io.kubemq.sdk.examples.get_Started.pubSub_Subscribe_to_a_Channel;
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​
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import java.io.IOException;
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​
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import javax.net.ssl.SSLException;
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​
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import io.grpc.stub.StreamObserver;
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import io.kubemq.sdk.basic.ServerAddressNotSuppliedException;
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import io.kubemq.sdk.event.EventReceive;
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import io.kubemq.sdk.event.Subscriber;
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import io.kubemq.sdk.subscription.SubscribeRequest;
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import io.kubemq.sdk.subscription.SubscribeType;
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import io.kubemq.sdk.tools.Converter;
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​
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public class Program {
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​
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    public static void main(String[] args)  {
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​
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​
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        String channelName = "hello-world", clientID = "hello-world-subscriber", kubeMQAddress = "localhost:50000";
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        Subscriber subscriber = new Subscriber(kubeMQAddress);
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        SubscribeRequest subscribeRequest = new SubscribeRequest();
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        subscribeRequest.setChannel(channelName);
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        subscribeRequest.setClientID(clientID);
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        subscribeRequest.setSubscribeType(SubscribeType.Events); 
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​
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        StreamObserver<EventReceive> streamObserver = new StreamObserver<EventReceive>() {
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​
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            @Override
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            public void onNext(EventReceive value) {
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                try {
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                    System.out.printf("Event Received: EventID: %d, Channel: %s, Metadata: %s, Body: %s",
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                            value.getEventId(), value.getChannel(), value.getMetadata(),
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                            Converter.FromByteArray(value.getBody()));
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                } catch (ClassNotFoundException e) {
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                    System.out.printf("ClassNotFoundException: %s",e.getMessage());
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                    e.printStackTrace();
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                } catch (IOException e) {
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                    System.out.printf("IOException:  %s",e.getMessage());
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                    e.printStackTrace();
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                }
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​
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            }
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​
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            @Override
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            public void onError(Throwable t) {
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                System.out.printf("Event Received Error: %s", t.toString());
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            }
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​
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            @Override
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            public void onCompleted() {
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​
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            }
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        };
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        try {
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            subscriber.SubscribeToEvents(subscribeRequest, streamObserver);
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        } catch (SSLException e) {
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            System.out.printf("SSLException: %s", e.toString());
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            e.printStackTrace();
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        } catch (ServerAddressNotSuppliedException e) {
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            System.out.printf("ServerAddressNotSuppliedException: %s", e.toString());
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         e.printStackTrace();
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      }
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​
65
    }
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}
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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:
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package main
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import (
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   "context"
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   "fmt"
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   "github.com/kubemq-io/kubemq-go"
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   "log"
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)
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​
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func main() {
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   ctx, cancel := context.WithCancel(context.Background())
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   defer cancel()
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   client, err := kubemq.NewClient(ctx,
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      kubemq.WithAddress("localhost", 50000),
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      kubemq.WithClientId("hello-world-subscriber"),
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      kubemq.WithTransportType(kubemq.TransportTypeGRPC))
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   if err != nil {
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      log.Fatal(err)
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   }
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   defer client.Close()
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   channelName := "hello-world"
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   errCh := make(chan error)
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   eventsCh, err := client.SubscribeToEvents(ctx, channelName, "", errCh)
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   if err != nil {
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      log.Fatal(err)
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      return
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​
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   }
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   for {
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      select {
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      case err := <-errCh:
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         log.Fatal(err)
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         return
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      case event, more := <-eventsCh:
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         if !more {
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            fmt.Println("Event Received, done")
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            return
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         }
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         log.Printf("Event Received:\nEventID: %s\nChannel: %s\nMetadata: %s\nBody: %s\n", event.Id, event.Channel, event.Metadata, event.Body)
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      case <-ctx.Done():
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         return
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      }
42
   }
43
}
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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:
1
from builtins import input
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from random import randint
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from kubemq.events.subscriber import Subscriber
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from kubemq.tools.listener_cancellation_token import ListenerCancellationToken
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from kubemq.subscription.subscribe_type import SubscribeType
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from kubemq.subscription.events_store_type import EventsStoreType
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from kubemq.subscription.subscribe_request import SubscribeRequest
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​
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​
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​
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def handle_incoming_events(event):
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    if event:
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        print("Subscriber Received Event: Metadata:'%s', Channel:'%s', Body:'%s tags:%s'" % (
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            event.metadata,
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            event.channel,
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            event.body,
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            event.tags
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        ))
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​
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def handle_incoming_error(error_msg):
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        print("received error:%s'" % (
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            error_msg
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        ))
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​
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​
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if __name__ == "__main__":
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    print("Subscribing to event on channel example")
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    cancel_token=ListenerCancellationToken()
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​
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​
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    # Subscribe to events without store
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    subscriber = Subscriber("localhost:50000")
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    subscribe_request = SubscribeRequest(
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        channel="testing_event_channel",
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        client_id="hello-world-subscriber",
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        events_store_type=EventsStoreType.Undefined,
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        events_store_type_value=0,
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        group="",
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        subscribe_type=SubscribeType.Events
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    )
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    subscriber.subscribe_to_events(subscribe_request, handle_incoming_events,handle_incoming_error,cancel_token)
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​
43
    input("Press 'Enter' to stop Listen...\n")
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    cancel_token.cancel()
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    input("Press 'Enter' to stop the application...\n")
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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:
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const kubemq = require('kubemq-nodejs');
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​
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let channelName = 'pubsub', clientID = 'hello-world-subscriber',
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    kubeMQHost = 'localhost', kubeMQGrpcPort = '50000';
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​
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let sub = new kubemq.Subscriber(kubeMQHost, kubeMQGrpcPort, clientID, channelName);
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​
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sub.subscribeToEvents(msg => {
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    console.log('Event Received: EventID:' + msg.EventID + ', Channel:' + msg.Channel + ' ,Metadata:' + msg.Metadata + ', Body:' + kubemq.byteToString(msg.Body));
10
}, err => {
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    console.log('error:' + err)
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})
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The following PHP code snippet is using KubeMQ's REST interface:
1
<?php
2
​
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$curl = curl_init();
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​
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curl_setopt_array($curl, array(
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  CURLOPT_URL => "http://localhost:9090/subscribe/events?client_id=some_client_id&channel=hello-world&group=some_group&subscribe_type=events",
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  CURLOPT_RETURNTRANSFER => true,
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  CURLOPT_ENCODING => "",
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  CURLOPT_MAXREDIRS => 10,
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  CURLOPT_TIMEOUT => 0,
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  CURLOPT_FOLLOWLOCATION => false,
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  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
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  CURLOPT_CUSTOMREQUEST => "GET",
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  CURLOPT_HTTPHEADER => array(
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    "Content-Type: application/json"
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  ),
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));
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​
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$response = curl_exec($curl);
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$err = curl_error($curl);
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​
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curl_close($curl);
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​
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if ($err) {
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  echo "cURL Error #:" . $err;
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} else {
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  echo $response;
28
} ?>
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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:
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require "uri"
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require "net/http"
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​
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url = URI("http://localhost:9090/subscribe/events?client_id=some_client_id&channel=hello-world&group=some_group&subscribe_type=events")
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​
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http = Net::HTTP.new(url.host, url.port)
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​
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request = Net::HTTP::Get.new(url)
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request["Content-Type"] = "application/json"
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​
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response = http.request(request)
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puts response.read_body
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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:
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var settings = {
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  "url": "http://localhost:9090/subscribe/events?client_id=some_client_id&channel=hello-world&group=some_group&subscribe_type=events",
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  "method": "GET",
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  "timeout": 0,
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  "headers": {
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    "Content-Type": "application/json",
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  },
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};
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​
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$.ajax(settings).done(function (response) {
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  console.log(response);
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});
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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.
kubemqctl
curl
.Net
Java
Go
Python
Node
PHP
Ruby
jquery
Run the following kubemqctl command:
1
kubemqctl events send hello-world "Hi KubeMQ"
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The following cURL command is using KubeMQ's REST interface:
1
curl --location --request POST "http://localhost:9090/send/event" 
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  --header "Content-Type: application/json" 
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  --data '{"EventID": "1234-5678-90","ClientID": "events-client-id","Channel": "events-channel","Metadata": "some-metadata","Body": "c29tZSBlbmNvZGVkIGJvZHk=","Store": false}'
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A response for a successful command will look like this:
1
{
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  "is_error": false,
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  "message": "OK",
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  "data": {
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    "EventID": "1234-5678-90",
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    "Sent": true
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  }
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}
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The following .NET code snippet is using KubeMQ's .NET SDK with gRPC interface:
1
using System;
2
​
3
namespace PubSub_Publish_to_a_Channel
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{
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    class Program
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    {
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        static void Main(string[] args)
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        {
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            var ChannelName = "hello-wrold";
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            var ClientID = "hello-world-sender";
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            var KubeMQServerAddress = "localhost:50000";
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​
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​
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            var channel = new KubeMQ.SDK.csharp.Events.Channel(new KubeMQ.SDK.csharp.Events.ChannelParameters
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            {
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                ChannelName = ChannelName,
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                ClientID = ClientID,
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                KubeMQAddress = KubeMQServerAddress
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            });
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​
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            try
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            {
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                var result = channel.SendEvent(new KubeMQ.SDK.csharp.Events.Event()
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                {                  
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                    Body = KubeMQ.SDK.csharp.Tools.Converter.ToByteArray("hello kubemq - sending single event")
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                });
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                if (!result.Sent)
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                {
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                    Console.WriteLine(quot;Could not send single message:{result.Error}");                 
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                }
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            }
32
            catch (Exception ex)
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            {
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                Console.WriteLine(ex.Message);          
35
            }
36
        }
37
    }
38
}
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The following Java code snippet is using KubeMQ's Java SDK with gRPC interface:
1
package io.kubemq.sdk.examples.get_Started.pubSub_Publish_to_a_Channel;
2
​
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import java.io.IOException;
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​
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import javax.net.ssl.SSLException;
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​
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import io.kubemq.sdk.basic.ServerAddressNotSuppliedException;
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import io.kubemq.sdk.event.Event;
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import io.kubemq.sdk.event.Result;
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import io.kubemq.sdk.tools.Converter;
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​
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public class Program {
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​
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    public static void main(String[] args)  {
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​
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        String channelName = "hello-world", clientID = "hello-world-subscriber", kubeMQAddress = "localhost:50000";
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​
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        io.kubemq.sdk.event.Channel chan = new io.kubemq.sdk.event.Channel(channelName, clientID, false, kubeMQAddress);
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​
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        Event event = new Event();
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        try {
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            event.setBody(Converter.ToByteArray("hello kubemq - sending single event"));
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        } catch (IOException e) {
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​
25
            e.printStackTrace();
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        }
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​
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        try {
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            Result res = chan.SendEvent(event);
30
        } catch (SSLException | ServerAddressNotSuppliedException e) {
31
​
32
            e.printStackTrace();
33
        }
34
​
35
    }
36
}
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The following Go code snippet is using KubeMQ's Go SDK with gRPC interface:
1
package main
2
import (
3
   "context"
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   "github.com/kubemq-io/kubemq-go"
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   "log"
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)
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​
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func main() {
9
   ctx, cancel := context.WithCancel(context.Background())
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   defer cancel()
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   client, err := kubemq.NewClient(ctx,
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      kubemq.WithAddress("localhost", 50000),
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      kubemq.WithClientId("hello-world-sender"),
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      kubemq.WithTransportType(kubemq.TransportTypeGRPC))
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   if err != nil {
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      log.Fatal(err)
17
   }
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   defer client.Close()
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   channelName := "hello-world"
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   err = client.E().
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      SetId("some-id").
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      SetChannel(channelName).
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      SetMetadata("some-metadata").
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      SetBody([]byte("hello kubemq - sending single event")).
25
      Send(ctx)
26
   if err != nil {
27
      log.Fatal(err)
28
   }
29
​
30
}
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The following Python code snippet is using KubeMQ's Python SDK with gRPC interface:
1
import datetime
2
​
3
from kubemq.events.lowlevel.event import Event
4
from kubemq.events.lowlevel.sender import Sender
5
​
6
if __name__ == "__main__":
7
​
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    publisher  = Sender("localhost:50000")
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    event = Event(
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        metadata="EventMetaData",
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        body =("hello kubemq - sending single event").encode('UTF-8'),
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        store=False,
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        channel="testing_event_channel",
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        client_id="hello-world-subscriber"
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    )
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    try:
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        res = publisher.send_event(event)
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        print(res)
19
    except Exception as err:
20
      print(
21
            "'error sending:'%s'" % (
22
                err
23
                        )
24
        )
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The following JS code snippet is using KubeMQ's NodeJS SDK with gRPC interface:
1
const kubemq = require('kubemq-nodejs');
2
let channelName = 'pubsub', clientID = 'hello-world-subscriber',
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    kubeMQHost = 'localhost', kubeMQGrpcPort = '50000';
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const publisher = new kubemq.Publisher(kubeMQHost, kubeMQGrpcPort, clientID, channelName);
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let event = new kubemq.Publisher.Event(kubemq.stringToByte('hello kubemq - sending single event'));
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publisher.send(event).then(
7
    res => {
8
        console.log(res);
9
    }).catch(
10
        err => {
11
            console.log('error sending' + err)
12
        });
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The following PHP code snippet is using KubeMQ's REST interface:
1
<?php
2
​
3
$curl = curl_init();
4
​
5
curl_setopt_array($curl, array(
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  CURLOPT_URL => "http://localhost:9090/send/event",
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  CURLOPT_RETURNTRANSFER => true,
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  CURLOPT_ENCODING => "",
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  CURLOPT_MAXREDIRS => 10,
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  CURLOPT_TIMEOUT => 0,
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  CURLOPT_FOLLOWLOCATION => false,
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  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
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  CURLOPT_CUSTOMREQUEST => "POST",
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  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}",
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  CURLOPT_HTTPHEADER => array(
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    "Content-Type: application/json"
17
  ),
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));
19
​
20
$response = curl_exec($curl);
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$err = curl_error($curl);
22
​
23
curl_close($curl);
24
​
25
if ($err) {
26
  echo "cURL Error #:" . $err;
27
} else {
28
  echo $response;
29
} ?>
Copied!
A response for a successful command will look like this:
1
{
2
  "is_error": false,
3
  "message": "OK",
4
  "data": {
5
    "EventID": "1234-5678-90",
6
    "Sent": true
7
  }
8
}
Copied!
The following Ruby code snippet is using KubeMQ's REST interface:
1
require "uri"
2
require "net/http"
3
​
4
url = URI("http://localhost:9090/send/event")
5
​
6
https = Net::HTTP.new(url.host, url.port)
7
https.use_ssl = true
8
​
9
request = Net::HTTP::Post.new(url)
10
request["Content-Type"] = "application/json"
11
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}"
12
response = https.request(request)
13
puts response.read_body
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A response for a successful command will look like this:
1
{
2
  "is_error": false,
3
  "message": "OK",
4
  "data": {
5
    "EventID": "1234-5678-90",
6
    "Sent": true
7
  }
8
}
Copied!
The following jQuery code snippet is using KubeMQ's REST interface:
1
var settings = {
2
  "url": "http://localhost:9090/send/event",
3
  "method": "POST",
4
  "timeout": 0,
5
  "headers": {
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    "Content-Type": "application/json",
7
  },
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  "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}",
9
};
10
​
11
$.ajax(settings).done(function (response) {
12
  console.log(response);
13
});
Copied!
A response for a successful command will look like this:
1
{
2
  "is_error": false,
3
  "message": "OK",
4
  "data": {
5
    "EventID": "1234-5678-90",
6
    "Sent": true
7
  }
8
}
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Demo
Queues
RPC
Last modified 2yr ago
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Contents
Connect Your KubeMQ Cluster
Subscribe to Events Channel
Publish to Event Channel
Demo