restcmd - HTTP REST backend based CommandFacility

This implementation of the CommandFacility interface from cmdlib, is providing a way to send commands to applications via HTTP. This is carried out by the small web-server that this plugin carries. The server answers to HTTP POST requests, where the request body is the content of the command itself. The package ships a really lightweight Python script to send commands from the JSON files, that is located under the scripts directory.

Dependencies

The Pistache library is needed to build and run this plugin. At the moment, it's located under products_dev. The dependency is available under devevlopment products. Please pay attention to the build steps that include how to setup pistache from cvmfs.

Building and running examples:

• create a software work area
  • see the daq-buildtools instructions for how to do this
• clone this repo into your work/development area
  • cd <your_work_area>/sourcecode
  • git clone https://github.com/DUNE-DAQ/restcmd.git
  • cd ..
• build and install the software, as described in the daq-buildtools instructions
• run the demos in another shell. Do cd <your work area> and then set up the environment in the new shell as before. Rather than building, however, run:
  • restcmd_test_rest_app
    • the application will terminate in 20 seconds
    • from the first terminal, send commands via curl or with the more preferred send-restcmd.py

Running DAQ applications

To select this CommandFacility implementation, use the rest:// prefix for the application's commandFacility parameter as a URI. The URI is parsed, and the facility will listen to POST requests on the specified interface and port.

daq_application --name <it doesn't matter what your name is> --commandFacility rest://localhost:12345

Sending commands

With send-restcmd

The scripts directory also contains a command sender application based on Python3 and its Requests module. It is used on the following way:

send-recv-restcmd.py --file ./sourcecode/restcmd/test/test-init.json

The script can recognize multiple command objects in the same file, and send them one by one, with a configurable wait time between each send:

send-recv-restcmd.py --wait 3 --file ./sourcecode/restcmd/test/fdpc-commands.json

There is also an interactive mode. This requires typing the next command's ID from the set of commands that are available in the file:

send-recv-restcmd.py --interactive --file ./sourcecode/restcmd/test/fdpc-commands.json

To see details how to connect to different applications, have a look on the help:

send-recv-restcmd.py --help

With CURL

Sending commands with curl makes low-level debugging easier. Example of sending only a configuration command:

cmdfile=sourcecode/restcmd/test/test-init.json
curl --header "Content-Type: application/json" --header "X-Answer-Port: 12333" --request POST --data @$cmdfile http://localhost:12345/command

The command facility enforces the content type. The following will fail:

cmdfile=sourcecode/restcmd/test/test-init.json
curl --header "Content-Type: application/xml" --header "X-Answer-Port: 12333" --request POST --data @$cmdfile http://epdtdi103:12345/command