[zeromq-dev] cppzmq revival and RFC on design goals and supported platforms

Simon.Giesecke at btc-ag.com Simon.Giesecke at btc-ag.com
Thu May 24 09:06:27 CEST 2018

Hi Gyorgy,

thanks for your mail!

Uniform sending could be implemented by providing a free send function which is overloaded for both message_t and multipart_t. There cannot be a member function of socket_t that accepts a multipart_t since the latter is in the upper layer (i.e. zmq_addon.hpp). If you would like to contribute this, this would be very welcome.

poller_t does not require casting a socket_t to the bare void * in the current master version. I am not sure when this was the case.

Best wishes

Von: zeromq-dev [mailto:zeromq-dev-bounces at lists.zeromq.org] Im Auftrag von Gyorgy Szekely
Gesendet: Mittwoch, 23. Mai 2018 21:10
An: ZeroMQ development list <zeromq-dev at lists.zeromq.org>
Betreff: Re: [zeromq-dev] cppzmq revival and RFC on design goals and supported platforms

Hi Simon,
This is great news! We're using cppzmq in a message broker and an accompanying communication library for 2 years now.

I fully agree with the declared goals. libzmq has a simple and concise API with object oriented mindset. It works well on its own, but cppzmq makes it a whole lot easier. What's particularly good about it:
- type safety and RAII: it's very straigtforward to think in classes that properly clean-up resources at destruction
- higher level functions: multipart messages are really nice, though the API is/was a bit inconsistent (socket.send(msg) vs, msg.send(socket))
- header only, it's very easy to use. Header only libraries usually mean template heavy monsters, but fortunately not in this case

What I personally really like is it's a thin wrapper and doesn't want to be more than libzmq. Methods usually map 1-to-1 to libzmq calls, there's no hidden trickery and the documentation at api.zeromq.org<https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fapi.zeromq.org&data=02%7C01%7Csimon.giesecke%40btc-ag.com%7Cc5bdddee6a524b60525408d5c0e0ca1f%7Cc064efb078954eebb406a40bc377bc7d%7C0%7C0%7C636626994076373759&sdata=XIYdEl3DMBXkTf7THghuQJGCbVCdsD7Wh%2Bjk8qXWDLU%3D&reserved=0> is fully relevant.

I haven't checked the recent updates (yet), but I found a few strange bits while working with cppzmq. Like the above mentioned sending inconsistency, or having to cast the socket to void* to use it in a pollset. Apart from that I completely agree with the direction. This is how a thin C++ wrapper should look like for a good base C API.

BTW, we're using the lib on Ubuntu16.04 64bit / G++ 5.3, no issues so far.


On Wed, May 23, 2018 at 6:07 PM, <Simon.Giesecke at btc-ag.com<mailto:Simon.Giesecke at btc-ag.com>> wrote:

Pawel Kurdybacha (kurdybacha) and me (sigiesec) have recently started to "revive" cppzmq (https://github.com/zeromq/cppzmq<https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fzeromq%2Fcppzmq&data=02%7C01%7Csimon.giesecke%40btc-ag.com%7Cc5bdddee6a524b60525408d5c0e0ca1f%7Cc064efb078954eebb406a40bc377bc7d%7C0%7C0%7C636626994076373759&sdata=Lb1zRKVGyijgPeUUDV1K4XUhKAwoMYd%2B0LB8v8YoZMY%3D&reserved=0>), the light-weight C++ wrapper around libzmq. We added CI for Windows/MSVC, Linux and MacOS, implemented tests, cleaned up the CMake infrastructure, formatted the source code consistently and added some overview documentation.

If you are using cppzmq or are interested in using it, we encourage you to have a look at the recent changes.

One particular point we would like to seek feedback on are the design goals, which have recently been documented for the first time. I tried to extrapolate them from the actual design, and from the reasons we chose to use cppzmq in comparison to other alternatives. These are part of the https://github.com/zeromq/cppzmq/blob/master/README.md<https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fzeromq%2Fcppzmq%2Fblob%2Fmaster%2FREADME.md&data=02%7C01%7Csimon.giesecke%40btc-ag.com%7Cc5bdddee6a524b60525408d5c0e0ca1f%7Cc064efb078954eebb406a40bc377bc7d%7C0%7C0%7C636626994076530008&sdata=qtIHTc0dYPpYWaDAgJO3kbLSrRRnLgf%2Fz8%2BK9hTY3oM%3D&reserved=0> file:

* cppzmq maps the libzmq C API to C++ concepts. In particular:
   * it is type-safe (the libzmq C API exposes various class-like concepts as void*)
   * it provides exception-based error handling (the libzmq C API provides errno-based error handling)
   * it provides RAII-style classes that automate resource management (the libzmq C API requires the user to take care to free resources explicitly)
* cppzmq is a light-weight, header-only binding. You only need to include the header file zmq.hpp (and maybe zmq_addon.hpp) to use it.
* zmq.hpp is meant to contain direct mappings of the abstractions provided by the libzmq C API, while zmq_addon.hpp provides additional higher-level abstractions.

We would like to here from you if you agree with these design goals. If you have any opposing views, proposals for improvement or extension of the design goals, please share them on the mailing list or by sending a PR.

Another part of the README is a section on the supported platforms. Please review this section, in particular if you do not use MacOS, Linux or Windows/MSVC with a recent compiler. If you successfully use a different platform, please send a PR to include this in the list of "Additional platforms that are known to work". Support for non-C++11 compilers is already partial only, and might be removed completely, unless there are users that still require such support.

Of course, you are also invited to contribute extensions, new features, cleanup, further tests, etc. to cppzmq.

Best regards

i.A. Simon Giesecke
BTC Business Technology Consulting AG
Kurfürstendamm 33
10719 Berlin
E-Mail: Simon.Giesecke at btc-ag.com<mailto:Simon.Giesecke at btc-ag.com>

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