Eclipse Zenoh

The Eclipse Zenoh: Zero Overhead Pub/sub, Store/Query and Compute.

Zenoh (pronounce /zeno/) unifies data in motion, data at rest and computations. It carefully blends traditional pub/sub with geo-distributed storages, queries and computations, while retaining a level of time and space efficiency that is well beyond any of the mainstream stacks.

Check the website zenoh.io and the roadmap for more detailed information.

C++ API

The Zenoh C++ API are headers only C++ bindings for zenoh-c and zenoh-pico libraries.

C++ bindings are still under active development so the Zenoh team will highly appreciate any help in testing them on various platforms, system architecture, etc. and to report any issue you might encounter. This will help in greatly improving its maturity and robustness.

Requirements

The only hard requirement for building the library is a C++17-compliant compiler. Using the library requires either zenoh-c or zenoh-pico to be installed.

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How to build and install it

⚠️ WARNING ⚠️ : Zenoh and its ecosystem are under active development. When you build from git, make sure you also build from git any other Zenoh repository you plan to use (e.g. binding, plugin, backend, etc.). It may happen that some changes in git are not compatible with the most recent packaged Zenoh release (e.g. deb, docker, pip). We put particular effort in mantaining compatibility between the various git repositories in the Zenoh project.

To install zenoh-cpp do the following steps:

1. Clone the sources.

   git clone https://github.com/eclipse-zenoh/zenoh-cpp.git

2. Build and install.

   By default it is expected that you have zenoh-c installed. If you want to install for zenoh-pico backend or for both (or to not specify any backend), please set ZENOHCXX_ZENOHC or ZENOHCXX_ZENOHPICO Cmake variables toON or OFF accordingly. Notice that at least one of the backends is required for using the library and/or building tests and examples.

   Use option CMAKE_INSTALL_PREFIX for specifying installation location. Without this parameter installation is performed to default system location /usr/local which requires root privileges.

   mkdir build && cd build
   cmake .. -DCMAKE_INSTALL_PREFIX=~/.local # to configure only for zenoh-c backend
   cmake .. -DZENOHCXX_ZENOHC=OFF -DZENOHCXX_ZENOHPICO=ON  -DCMAKE_INSTALL_PREFIX=~/.local # to configure  only for zenoh-pico backend
   cmake .. -DZENOHCXX_ZENOHC=OFF -DZENOHCXX_ZENOHPICO=OFF  -DCMAKE_INSTALL_PREFIX=~/.local # to configure for none of the backends
   cmake .. -DZENOHCXX_ZENOHPICO=ON  -DCMAKE_INSTALL_PREFIX=~/.local # to configure for both backends
   cmake --install .

Building and running tests

By default it is expected that you have zenoh-c installed. If you want to build and run tests for zenoh-pico backend or for both, please set ZENOHCXX_ZENOHC or ZENOHCXX_ZENOHPICO Cmake variables toON or OFF accordingly.

To build tests run:

mkdir build && cd build
cmake ..  -DCMAKE_INSTALL_PREFIX=~/.local # to build tests only for zenoh-c backend
cmake .. -DZENOHCXX_ZENOHC=OFF -DZENOHCXX_ZENOHPICO=ON  -DCMAKE_INSTALL_PREFIX=~/.local # to build tests only for zenoh-pico backend
cmake .. -DZENOHCXX_ZENOHPICO=ON  -DCMAKE_INSTALL_PREFIX=~/.local # to build tests for both backends
cmake --build . --target tests
ctest

Notice that the output of cmake ../zenoh-cpp shows where zenoh-c and/or zenoh-pico the dependencies were found.

Building the Examples

Examples are splitted into two subdirectories. Subdirectory universal contains zenoh-cpp examples buildable with both zenoh-c and zenoh-pico backends. The zenohc subdirectory contains examples with zenoh-c specific functionality.

By default it is expected that you have zenoh-c installed. If you want to build examples for zenoh-pico backend or for both, please set ZENOHCXX_ZENOHC or ZENOHCXX_ZENOHPICO Cmake variables toON or OFF accordingly.

To build examples run:

cmake ..  -DCMAKE_INSTALL_PREFIX=~/.local # to build examples only for zenoh-c backend
cmake .. -DZENOHCXX_ZENOHC=OFF -DZENOHCXX_ZENOHPICO=ON  -DCMAKE_INSTALL_PREFIX=~/.local # to build examples only for zenoh-pico backend
cmake .. -DZENOHCXX_ZENOHPICO=ON  -DCMAKE_INSTALL_PREFIX=~/.local # to build examples for both backends
cmake --build . --target examples

Examples are placed into build/examples/zenohc and build/examples/zenohpico directories.

Running the examples

Change current directory to the variant you want (examples/zenohc or examples/zenohpico in the build directory).

See example sources for command line arguments (key expression, value, router address).

zenohc examples can work standalone, but for zenohpico examples the working zenoh router is required. So to run zenohpico examples download zenoh project and run the router (Rust should be installed):

git clone https://github.com/eclipse-zenoh/zenoh
cd zenoh
cargo run

Basic Pub/Sub Example

./z_sub

./z_pub

The z_pub should receive message sent by z_sub.

Queryable and Query Example

./z_queryable

./z_get

Queryable and Querier Example

./z_queryable

./z_querier

The z_querier should continuously send queries and receive replies from z_queryable.

Throughput Examples

./z_sub_thr_cpp

./z_pub_thr_cpp 1024

After 30-40 seconds delay the z_sub_thr will start to show the throughput measure results.

Library usage

Below are the steps to include zenoh-cpp into CMake project. See also examples/simple directory for short examples of CMakeLists.txt.

• include zenoh-c or zenoh-pico into your CMake project before dependency on zenoh-cpp itself. This is important as the library targets you need (zenohcxx::zenohpico, zenohcxx::zenohc::lib) are defined only if their backend library targets (zenohpico::lib and/or zenohc::lib are defined)

• include zenoh-cpp using find_package CMake function:

  find_package(zenohc) #if using zenoh-c backend
  find_package(zenohpico) #if using zenoh-pico backend
  find_package(zenohcxx)
  

• add dependency on zenoh-cpp to your project:

  target_link_libraries(yourproject PUBLIC zenohcxx::zenohc) #if using zenoh-c backend
  target_link_libraries(yourproject PUBLIC zenohcxx::zenohpico) #if using zenoh-pico backend
  

• include the zenoh.hxx header. All zenoh functionality is available under the namespace zenoh:

  #include "zenoh.hxx"
  using namespace zenoh;

Documentation

The documentation is on zenoh-cpp.readthedocs.io. Instruction how to build documentation locally is at docs/README.md.