Set up pycapa

You can use the pycapa tool to capture low-volume data flow.

Ensure you have installed Python 2.7
Older distributions, such as CentOS 6, that come with Python 2.6 installed, should install Python 2.7 within a virtual environment and then run Pycapa from within the virtual environment.
This installation assumes the following environment variables:
```
PYCAPA_HOME=/opt/pycapa
PYTHON27_HOME =/opt/rh/python27/root
```

Install system dependencies including the core development tools, Python libraries and header files, and Libpcap libraries and header files.
On CentOS 7+, you can install these requirements using the following command:
```
yum -y install "@Development tools" python-devel libpcap-devel
```
*** In a previous version of these installation instructions, we installed the following packages: epel-release, centos-release-scl, "@Development tools", python 27, python27-scldevel, python27-python-virtualenv libpcap-devel, and libselinux-python. The current installation lists much fewer packages. Are the rest of the packages no longer necessary? ***

Install Librdkafka at your chosen $PREFIX:

export PREFIX=/usr
wget https://github.com/edenhill/librdkafka/archive/v0.11.5.tar.gz   -O - | tar -xz
cd librdkafka-0.11.5/
./configure --prefix=$PREFIX
make
make install

Add Librdkafka to the dynamic library load path.

echo "$PREFIX/lib" >> /etc/ld.so.conf.d/pycapa.conf
ldconfig -v

Install Pycapa.
This step assumes that you already have the HCP source code installed on the host.
```
cd metron/metron-sensors/pycapa
pip install -r requirements.txt
python setup.py install
```

Start the pycapa packet capture producer:

cd ${PYCAPA_HOME}/pycapa-venv/bin
pycapa --producer --topic pcap -i $ETH_INTERFACE -k $KAFKA_HOST:6667