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ipm

Inter-Process Messaging

The IPM library provides the low-level library for for sending messages between DUNE DAQ processes. IPM deals with messages consisting of arrays of bytes: higher-level concepts such as object serialization/deserialization will be handled by other libraries and processes building on IPM.

IPM provides two communication patterns:

  1. Sender/Receiver, a pattern in which one sender talks to one receiver

  2. Publisher/Subscriber, a pattern in which one sender talks to zero or more receivers. Each message goes to all subscribers

Users should interact with IPM via the interfaces dunedaq::ipm::Sender, dunedaq::ipm::Receiver and dunedaq::ipm::Subscriber, which are created using the factory functions dunedaq::ipm::makeIPM(Sender|Receiver|Subscriber), which each take a string argument giving the implementation type. The currently-available implementation types all use ZeroMQ, and are:

  • ZmqSender implementing dunedaq::ipm::Sender in the sender/receiver pattern

  • ZmqReceiver implementing dunedaq::ipm::Receiver

  • ZmqPublisher implementing dunedaq::ipm::Sender in the publisher/subscriber pattern

  • ZmqSubscriber implementing dunedaq::ipm::Subscriber

Basic example of the sender/receiver pattern:

// Sender side
std::shared_ptr<dunedaq::ipm::Sender> sender=dunedaq::ipm::makeIPMSender("ZmqSender");
sender->connect_for_sends({ {"connection_string", "tcp://127.0.0.1:12345"} });
void* message= ... ;
// Last arg is send timeout
sender->send(message, message_size, std::chrono::milliseconds(10));

// Receiver side
std::shared_ptr<dunedaq::ipm::Receiver> receiver=dunedaq::ipm::makeIPMReceiver("ZmqReceiver");
receiver->connect_for_receives({ {"connection_string", "tcp://127.0.0.1:12345"} });
// Arg is receive timeout
Receiver::Response response=receiver->receive(std::chrono::milliseconds(10));
// ... do something with response.data or response.metadata

Basic example of the publisher/subscriber pattern:

// Publisher side
std::shared_ptr<dunedaq::ipm::Sender> publisher=dunedaq::ipm::makeIPMSender("ZmqPublisher");
publisher->connect_for_sends({ {"connection_string", "tcp://127.0.0.1:12345"} });
void* message= ... ;
// Third arg is send timeout; last arg is topic for subscribers to subscribe to
publisher->send(message, message_size, std::chrono::milliseconds(10), "topic");

// Subscriber side
std::shared_ptr<dunedaq::ipm::Subscriber> subscriber=dunedaq::ipm::makeIPMReceiver("ZmqSubscriber");
subscriber->connect_for_receives({ {"connection_string", "tcp://127.0.0.1:12345"} });
subscriber->subscribe("topic");
// Arg is receive timeout
Receiver::Response response=subscriber->receive(std::chrono::milliseconds(10));
// ... do something with response.data or response.metadata

More complete examples can be found in the test/plugins directory.

API Diagram

Class Diagrams

Last git commit to the markdown source of this page:

Author: Eric Flumerfelt

Date: Thu Dec 8 13:48:36 2022 -0600

If you see a problem with the documentation on this page, please file an Issue at https://github.com/DUNE-DAQ/ipm/issues