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With ZeroMQ I had the worst possible results and experience. Honestly much of what it claims is bogus. It is highly optimized for certain cases and utterly usel

With ZeroMQ I had the worst possible results and experience. Honestly much of what it claims is bogus. It is highly optimized for certain cases and utterly useless for distributed systems. Try and find out in PUB/SUB what the IP addresses of the subscribers are. Not possible. In many cases you will be much better off learning TCP/IP yourself. In the mentioned case you simply iterate over the vector of subscribers - much more powerful and the sane default. It seems at some point people confused internal networking solutions with the Internet.

PieterH 10y ago
If you try to use ZeroMQ to replace TCP with the same semantics, then no, it won't work.
- bachback 10y ago
  How should ZeroMQ replace TCP? Internet runs on TCP/IP (last time I checked). In private networks many problems of public networks don't appear. I'm aware that organisations use it for their internal systems. As soon as one bridges to the outside world, one is going to hit with a problem.
  - PieterH 10y ago
    ZeroMQ is a messaging layer that runs over numerous network protocols (TCP, UDP, PGM, TIPC,...), as well as inter-process and inter-thread. It provides abstractions (like pub-sub) that work over all these protocols, and it shows the developer the abstraction using a socket-like API. In practice you build services which are internally composed and scaled using threads and processes, and which talk to each other over plain (unencrypted) protocols, e.g. TCP between boxes, IPC between processes on the same box. And when you need to talk to the outside world you build bridges that can speak any protocol you like, such as HTTP, or ZeroMQ's encrypted TCP protocol (CurveZMQ). From the developer's point of view, it's mostly transparent. Obviously you need security infrastructure, e.g. key/certificate management. You can build entire ZeroMQ applications using only encrypted TCP and they will run on public infrastructure. You can develop and test the same apps on a laptop. You might run the same code using IPC on a laptop, and CurveZMQ over the Internet. So though ZeroMQ definitely uses TCP as one of its transport protocols, it's not a replacement for it. Which means that doing things like asking for the IP address of a peer make no sense. What's the IP address of a thread, or another process on the same box? If you need identity information, you should not use the transport protocol for that.
kchoudhu 10y ago
The ZeroMQ documentation is pretty up front about the need for you to build those pieces yourself. It would appear you chose the wrong tool for your requirements.
- bachback 10y ago
  ZeroMQ wants to be a neutral wrapper in any language but in the end its a C++ library enforcing C++ concepts. You can't map in a straightforward way process concepts from C++ to other languages (also the OS and VM sits in between that). In the end its just mapping programming logic to state machines. There are much better ways to do this and end up with something much more powerful (with first class meta-programming).
  - PieterH 10y ago
    ZeroMQ has native stacks in Java, C#, Erlang, C. Also C++.
  - sidlls 10y ago
    I've found ZeroMQ to be an immensely useful and powerful library for certain kinds of distributed queueing applications. It's just a library, not an entire application or web framework to drop practically pre-dictated code into. Also what "c++ concepts" does it enforce and how? And why is that a bad thing?
vegabook 10y ago
it is trivially easy for any node to broadcast its IP address to the whole network periodically (in my case every 2 seconds) using a separate thread and UDP. Using this technique I have rock solid ZeroMQ topology that reconnects with max downtime about 2.5 seconds (because I broadcast every 2 sdconds) for any single node failure. I agree that this functionality could be better implemented in zmq but using this simple technique, the rest of zmq becomes amazing. In Python: import socket import time cs = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) cs.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1) cs.setsockopt(SOL_SOCKET, SO_BROADCAST, 1) while True: cs.sendto('Node ID', ('255.255.255.255', 54545)) time.sleep(4) Everybody listening on the same on port 54545 without knowing Node ID's IP address will get these messages which includes the broadcaster IP address. import socket s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM) s.bind(('',54545)) m=s.recvfrom(1024) print m[0] This is a very useful technique when using ZeroMQ generally as you can broadcast services without knowning any IP address so they can come up and down on new addresses if / when necessary.
- mej10 10y ago
  This would be great, but I don't think it works on AWS -- I don't think they support broadcast.
  - kchoudhu 10y ago
    My ZeroMQ components all register themselves in a database when coming and going. This makes it trivially easy to find where stuff is just by running a bog simple database query. Lots of ways to skin this cat...
    - vegabook 10y ago
      indeed, with the small caveat that you now need to know the database's IP address, thereby introducing a failure point / master IP point. My solution is completely IP address agnostic. Indeed you could run my version even with DHCP for all nodes.
      - 10y ago

PieterH 10y ago

If you try to use ZeroMQ to replace TCP with the same semantics, then no, it won't work.

bachback 10y ago
How should ZeroMQ replace TCP? Internet runs on TCP/IP (last time I checked). In private networks many problems of public networks don't appear. I'm aware that organisations use it for their internal systems. As soon as one bridges to the outside world, one is going to hit with a problem.
- PieterH 10y ago
  ZeroMQ is a messaging layer that runs over numerous network protocols (TCP, UDP, PGM, TIPC,...), as well as inter-process and inter-thread. It provides abstractions (like pub-sub) that work over all these protocols, and it shows the developer the abstraction using a socket-like API. In practice you build services which are internally composed and scaled using threads and processes, and which talk to each other over plain (unencrypted) protocols, e.g. TCP between boxes, IPC between processes on the same box. And when you need to talk to the outside world you build bridges that can speak any protocol you like, such as HTTP, or ZeroMQ's encrypted TCP protocol (CurveZMQ). From the developer's point of view, it's mostly transparent. Obviously you need security infrastructure, e.g. key/certificate management. You can build entire ZeroMQ applications using only encrypted TCP and they will run on public infrastructure. You can develop and test the same apps on a laptop. You might run the same code using IPC on a laptop, and CurveZMQ over the Internet. So though ZeroMQ definitely uses TCP as one of its transport protocols, it's not a replacement for it. Which means that doing things like asking for the IP address of a peer make no sense. What's the IP address of a thread, or another process on the same box? If you need identity information, you should not use the transport protocol for that.

kchoudhu 10y ago

The ZeroMQ documentation is pretty up front about the need for you to build those pieces yourself. It would appear you chose the wrong tool for your requirements.

bachback 10y ago
ZeroMQ wants to be a neutral wrapper in any language but in the end its a C++ library enforcing C++ concepts. You can't map in a straightforward way process concepts from C++ to other languages (also the OS and VM sits in between that). In the end its just mapping programming logic to state machines. There are much better ways to do this and end up with something much more powerful (with first class meta-programming).
- PieterH 10y ago
  ZeroMQ has native stacks in Java, C#, Erlang, C. Also C++.
- sidlls 10y ago
  I've found ZeroMQ to be an immensely useful and powerful library for certain kinds of distributed queueing applications. It's just a library, not an entire application or web framework to drop practically pre-dictated code into. Also what "c++ concepts" does it enforce and how? And why is that a bad thing?

vegabook 10y ago

it is trivially easy for any node to broadcast its IP address to the whole network periodically (in my case every 2 seconds) using a separate thread and UDP. Using this technique I have rock solid ZeroMQ topology that reconnects with max downtime about 2.5 seconds (because I broadcast every 2 sdconds) for any single node failure. I agree that this functionality could be better implemented in zmq but using this simple technique, the rest of zmq becomes amazing. In Python: import socket import time cs = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) cs.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1) cs.setsockopt(SOL_SOCKET, SO_BROADCAST, 1) while True: cs.sendto('Node ID', ('255.255.255.255', 54545)) time.sleep(4) Everybody listening on the same on port 54545 without knowing Node ID's IP address will get these messages which includes the broadcaster IP address. import socket s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM) s.bind(('',54545)) m=s.recvfrom(1024) print m[0] This is a very useful technique when using ZeroMQ generally as you can broadcast services without knowning any IP address so they can come up and down on new addresses if / when necessary.

mej10 10y ago
This would be great, but I don't think it works on AWS -- I don't think they support broadcast.
- kchoudhu 10y ago
  My ZeroMQ components all register themselves in a database when coming and going. This makes it trivially easy to find where stuff is just by running a bog simple database query. Lots of ways to skin this cat...
  - vegabook 10y ago
    indeed, with the small caveat that you now need to know the database's IP address, thereby introducing a failure point / master IP point. My solution is completely IP address agnostic. Indeed you could run my version even with DHCP for all nodes.
    - 10y ago