Monitoring the Connection

Managing the interaction with the server is primarily the job of the client library but most of the libraries also provide some insight into what is happening under the covers.

For example, the client library may provide a mechanism to get the connection’s current status:

{% tabs %} {% tab title=”Go” %}

  1. nc, err := nats.Connect("demo.nats.io", nats.Name("API Example"))
  2. if err != nil {
  3.     log.Fatal(err)
  4. }
  5. defer nc.Close()
  7. getStatusTxt := func(nc *nats.Conn) string {
  8.     switch nc.Status() {
  9.     case nats.CONNECTED:
  10.         return "Connected"
  11.     case nats.CLOSED:
  12.         return "Closed"
  13.     default:
  14.         return "Other"
  15.     }
  16. }
  17. log.Printf("The connection is %v\n", getStatusTxt(nc))
  19. nc.Close()
  21. log.Printf("The connection is %v\n", getStatusTxt(nc))

{% endtab %}

{% tab title=”Java” %}

  1. Connection nc = Nats.connect("nats://demo.nats.io:4222");
  3. System.out.println("The Connection is: " + nc.getStatus());
  5. nc.close();
  7. System.out.println("The Connection is: " + nc.getStatus());

{% endtab %}

{% tab title=”JavaScript” %}

  1.   // you can find out where you connected:
  2. t.log(`connected to a nats server version ${nc.info.version}`);
  4. // or information about the data in/out of the client:
  5. const stats = nc.stats();
  6. t.log(`client sent ${stats.outMsgs} messages and received ${stats.inMsgs}`);

{% endtab %}

{% tab title=”Python” %}

  1. nc = NATS()
  3. await nc.connect(
  4.    servers=["nats://demo.nats.io:4222"],
  5.    )
  7. # Do something with the connection.
  9. print("The connection is connected?", nc.is_connected)
  11. while True:
  12.   if nc.is_reconnecting:
  13.     print("Reconnecting to NATS...")
  14.     break
  15.   await asyncio.sleep(1)
  17. await nc.close()
  19. print("The connection is closed?", nc.is_closed)

{% endtab %}

{% tab title=”Ruby” %}

  1. NATS.start(max_reconnect_attempts: 2) do |nc|
  2.   puts "Connect is connected?: #{nc.connected?}"
  4.   timer = EM.add_periodic_timer(1) do
  5.     if nc.closing?
  6.       puts "Connection closed..."
  7.       EM.cancel_timer(timer)
  8.       NATS.stop
  9.     end
  11.     if nc.reconnecting?
  12.       puts "Reconnecting to NATS..."
  13.       next
  14.     end
  15.   end
  16. end

{% endtab %} {% endtabs %}