Ability to detect connect / disconnect with push / pull sockets about jeromq HOT 7 CLOSED

Basically it is not easy getting the list of connected peer in ZMQ without a lock. This would have a negative impact on its performance.

The monitor approach might be still the best option. At a point the monitor call was improved at libzmq, but jeromq is a little behind of the change.

We need to improve the jeromq monitor code together by investigating how libzmq works.

from jeromq.

Hi what I am really looking for is the following scenario:

1. I have a point to point connection between 2 servers (push / pull).
2. If the server peer goes down I want the app to be notified so that it
   stops sending requests.

Not sure how to accomplish this with ZMQ
Chase

On Tue, May 14, 2013 at 8:48 AM, Dongmin Yu [email protected]:

Basically it is not easy getting the list of connected peer in ZMQ without
a lock. This would have a negative impact on its performance.

The monitor approach might be still the best option. At a point the
monitor call was improved at libzmq, but jeromq is a little behind of the
change.

We need to improve the jeromq monitor code together by investigating how
libzmq works.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/61#issuecomment-17880766
.

from jeromq.

The classic answer to this question is, this isn't the ZeroMQ/JeroMQ
layer's work, you should do that on top using the right mix of heartbeats
and socket patterns. There is lots of discussion of this in the Guide.

It's still the right answer: knowing too much about peers breaks the
abstractions. Over time we may learn how to do this correctly but we're not
there yet. The monitor approach is not the right approach.

-Pieter

On Tue, May 14, 2013 at 5:52 PM, cwolfinger [email protected]:

Hi what I am really looking for is the following scenario:

1. I have a point to point connection between 2 servers (push / pull).
2. If the server peer goes down I want the app to be notified so that it
   stops sending requests.

Not sure how to accomplish this with ZMQ
Chase

On Tue, May 14, 2013 at 8:48 AM, Dongmin Yu [email protected]:

Basically it is not easy getting the list of connected peer in ZMQ
without
a lock. This would have a negative impact on its performance.

The monitor approach might be still the best option. At a point the
monitor call was improved at libzmq, but jeromq is a little behind of
the
change.

We need to improve the jeromq monitor code together by investigating how
libzmq works.

—
Reply to this email directly or view it on GitHub<
https://github.com/zeromq/jeromq/issues/61#issuecomment-17880766>
.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/61#issuecomment-17885271
.

from jeromq.

Thank you for the clarification. I was missing this point.

On Tue, May 14, 2013 at 11:37 AM, Pieter Hintjens
[email protected]:

The classic answer to this question is, this isn't the ZeroMQ/JeroMQ
layer's work, you should do that on top using the right mix of heartbeats
and socket patterns. There is lots of discussion of this in the Guide.

It's still the right answer: knowing too much about peers breaks the
abstractions. Over time we may learn how to do this correctly but we're
not
there yet. The monitor approach is not the right approach.

-Pieter

On Tue, May 14, 2013 at 5:52 PM, cwolfinger [email protected]:

Hi what I am really looking for is the following scenario:

1. I have a point to point connection between 2 servers (push / pull).
2. If the server peer goes down I want the app to be notified so that it
   stops sending requests.

Not sure how to accomplish this with ZMQ
Chase

On Tue, May 14, 2013 at 8:48 AM, Dongmin Yu [email protected]:

Basically it is not easy getting the list of connected peer in ZMQ
without
a lock. This would have a negative impact on its performance.

The monitor approach might be still the best option. At a point the
monitor call was improved at libzmq, but jeromq is a little behind of
the
change.

We need to improve the jeromq monitor code together by investigating
how
libzmq works.

—
Reply to this email directly or view it on GitHub<
https://github.com/zeromq/jeromq/issues/61#issuecomment-17880766>
.

—
Reply to this email directly or view it on GitHub<
https://github.com/zeromq/jeromq/issues/61#issuecomment-17885271>
.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/61#issuecomment-17892172
.

from jeromq.

@cwolfinger right, you don't have fully trust ZMQ monitoring as it doesn't reflect the networking, server and application status. If you still want to use monitoring as a helper for status check, say logging, please refer

https://github.com/zeromq/jeromq/blob/master/src/test/java/zmq/TestMonitor.java

Actually it should be revised but as a interim solution, you can try

Here's a sudo code

push_sock.monitor("inproc://my-monitor", ZMQ.EVENT_ALL);
new Runnable() {
      void run() {
            monitor_sock = ctx.socket(ZMQ.PAIR);
            monitor_sock.connect("inproc://my-monitor");
            while (true) {
                  byte[] event = monitor_sock.recv();    //  4bytes-event-type, 1byte-address-length, length bytes address, 1byte-flag, optional-integer(errno)                    
                  // do your stuff like logging
            }
      }
}.start();

from jeromq.

@miniway I'm using your monitor example above to watch messages on a PULL socket accumulate in receive buffer, I want to take action before HWM is exceeded, but there's no event generated when a message is received. I only see events on peer connect and other things, but no events generated, is that normal?

    final ZContext ctx = new ZContext();        
    Socket pull = ctx.createSocket(ZMQ.PULL);
    pull.bind("tcp://*:5555");
            pull.monitor("inproc://events", ZMQ.EVENT_ALL);

    Socket push = ctx.createSocket(ZMQ.PUSH);

    Runnable r = new Runnable() {
           public void run() {
            Socket monitor_sock = ctx.createSocket(ZMQ.PAIR);
            monitor_sock.connect("inproc://events");
            while (true) {
                  byte[] event = monitor_sock.recv();                 
                  //just dump event as string
                  log( new String(event));
            }
        }
    };
    (new Thread(r)).start();

    push.setSndHWM(100);
    push.connect("tcp://localhost:5555");
    push.send("hello");
    push.send("world");

Output:
?? tcp://localhost:555?? //for initial connect

from jeromq.

@raffian It is normal. There's no event related with HWM.

If you want to handle HWM, try sending messages with ZMQ_DONTWAIT or ZMQ_SNDTIMEO=1. The send method will return false incase of HWM.

from jeromq.