This interface provides kdb+ users with the ability to interact with the Message Queuing Telemetry Transport (MQTT) messaging protocol. The interface is a thin wrapper for kdb+ around the eclipse/paho.mqtt.c C api.

This is part of the Fusion for kdb+ interface collection.

Kdb+ is the world's fastest time-series database, optimized for ingesting, analyzing and storing massive amounts of structured data. To get started with kdb+, please visit https://code.kx.com/q/learn/ for downloads and developer information. For general information, visit https://kx.com/

Message Queueing Telemetry Transport (MQTT) is a machine-to-machine/IOT connectivity protocol. It is designed to provide a lightweight publish/subscribe messaging protocol.

MQTT is used commonly for constrained devices with low-bandwidth, high-latency or unreliable networks.

• kdb+ ≥ 3.5 64-bit(Linux/MacOS/Windows) and 32-bit ARM
• paho.mqtt.c ≥ 1.3.2

Linux, MacOS and Windows users should complete the following steps

1. Download the latest release of the paho.mqtt.c C api for your system architecture, available here.
2. Unzip this release and move to a location appropriate for your system.
3. Set an environment variable $BUILD_HOME / %BUILD_HOME% pointing to the location of the installed and unzipped release.
4. Make the paho.mqtt.c api available to kdb.

For Linux and MacOS, add the location of the 'lib' directory to LD_LIBRARY_PATH/DYLD_LIBRARY_PATH as appropriate

## Linux
export LD_LIBRARY_PATH=$BUILD_HOME/lib/:$LD_LIBRARY_PATH

## MacOS
export DYLD_LIBRARY_PATH=$BUILD_HOME/lib/:$DYLD_LIBRARY_PATH

For Windows, create links to the paho dll's in the %QHOME%\w64 directory. e.g.

cd %QHOME%\w64
MKLINK paho-mqtt3a.dll %BUILD_HOME%\lib\paho-mqtt3a.dll
MKLINK paho-mqtt3as.dll %BUILD_HOME%\lib\paho-mqtt3as.dll
MKLINK paho-mqtt3c.dll %BUILD_HOME%\lib\paho-mqtt3c.dll
MKLINK paho-mqtt3cs.dll %BUILD_HOME%\lib\paho-mqtt3cs.dll

For 32-bit arm systems, there are currently no prebuilt releases available. As such, a user is required to build the PAHO C api from source following the instructions here.

It is recommended that a user install this interface through a release. This is completed in a number of steps

1. Ensure you have downloaded/installed the paho.mqtt.c C api following the instructions here
2. Download a release from here for your system architecture.
3. Install script hdf5.q to $QHOME, and binary file lib/libhdf5.(so|dll) to $QHOME/[mlw](64), by executing the following from the Release directory

## Linux/MacOS
chmod +x install.sh && ./install.sh

## Windows
install.bat

In order to successfully build and install this interface from source, the following environment variables must be set

1. BUILD_HOME = Location of a paho mqtt C api release
2. QHOME = Q installation directory (directory containing q.k)

• Create an out-of-source directory for the CMake and object files

mkdir cmake && cd cmake

• Generate the makefile (defaults to a generator for the native build system with a release target type)

cmake ..

• Build the interface shared object

make

• Create the installation package into sub-directory mqtt

make install

• Install the package (copies the shared object to$QHOME/[ml](64|32) )

cd mqtt && ./install.sh

From a Visual Studio command prompt:

• Create an out-of-source directory for the CMake and object files.

mkdir cmake && cd cmake

• Generate the VS solution

cmake ..

• Build the interface DLL and create the installation package into sub-directory mqtt

MSBuild.exe INSTALL.vcxproj /p:Configuration=Release /p:Platform=x64

• Install the package (copies the shared object to%QHOME%/w64 )

cd mqtt && install.bat

A sample docker file is provided in the docker_linux directory to create a CentOS 7 environment (including downloading the paho.mqtt.c 64 bit Linux release) before building and installing the kdb+ mqtt interface.

The BUILD_HOME and QHOME directories are specified at the top of mqtt_build.bat, which sets up the environment specified in Dockerfile.build and invokes mqtt_build.sh to build the library.

Documentation outlining the functionality available for this interface can be found here.

The mqtt interface is provided here under an Apache 2.0 license.

If you find issues with the interface or have feature requests, please consider raising an issue here.

If you wish to contribute to this project, please follow the contributing guide here.