## brcon2024 - 2024-08-08

   title: Deep C programming - UNIX philosophy in distributed offshore systems

  author: Anders Damsgaard (adc)

 contact: [email protected]
          gopher://adamsgaard.dk
          https://adamsgaard.dk

  slides: gopher://adamsgaard.dk/0/tmp/brcon2024_adc.md

## brcon2024 - 2024-08-08

   title: Deep C programming - UNIX philosophy in distributed offshore systems

  author: Anders Damsgaard (adc)

 contact: [email protected]
          gopher://adamsgaard.dk
          https://adamsgaard.dk
<marquee><blink>
  slides: gopher://adamsgaard.dk/tmp/brcon2024_adc.md
</blink></marquee>


## Previously..
* brcon2020: Energy efficient programming in science
* brcon2021: Unix principles for science simulations
* brcon2022: Est. Bitreich Arctic Vault
* brcon2023: Using Unix and Bitreich tools for preparing scientific papers
* Today: UNIX philosophy in distributed offshore systems
#pause
* Tomorrow: UNOX philosophy in Vitré

## Outline
* How we can benefit from hyped technology with true and tried principles
* Overview of the offshore system
* The talk transitions into hands-on exercises
* Ask questions along the way in #bitreich-con

## Danish Geotechnical Institute (geo.dk)
* ~250 employees in Lyngby and Aarhus, Denmark
* Geotechnical investigations (onshore/offshore)
* Environmental consultancy
* Laboratory tests
* Geodata analysis
* Geoscientific software development

#pause
-> New offshore rig built from the ground up

## Offshore geotechnical investigations
                       .*          +------------------+
                       \|\         |         ,_____.  |
                   _============.  |         |     |  |
                    \\# # # #/  |  | ._______|--|--|  |
                     |          +.,| |  Geo  .--|--|  |
             _---------------------|-+-------|--|--|--|\
               \  MS/Bitreich      |         +--|--+  | |
~~~~~~~~~~~~~~~~~\~~~~~~~~~~~~~~~~~~|~~~~~~~~~~~~~~~~~~|~|~~~~~~~~~~~~
                 \                 +------------------+''  ~
                  \_________________________________/--+ ~ . ~~
                                                           ~


    ><>

                         <><



----------------------------------------------------------------------


## Offshore geotechnical investigations
                       .*
                       \|\                   ,_____.
                   _============.            |     |
                    \\# # # #/  |    ._______|--|--|
                     |          +.,  |  Geo  .--|--|
             _---------------------+-+-------|--|--|---\
               \  MS/Bitreich                +--|--+    |
~~~~~~~~~~~~~~~~~\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|~~~~~~~~~~~~
                 \                                   .-''  ~
                  \_________________________________/--+ ~ . ~~
                                                           ~


    ><>

                         <><



----------------------------------------------------------------------



## Offshore geotechnical investigations
                       .*
                       \|\                   ,_____.
                   _============.            |     |
                    \\# # # #/  |    ._______|--|--|
                     |          +.,  |  Geo  |  |  |
             _---------------------+-+-------|--|--|---\
               \  MS/Bitreich                   |       |
~~~~~~~~~~~~~~~~~\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|~~~~~~~|~~~~~~~~~~~~
                 \                              |    .-''   ~
                  \_____________________________|___/--x~ ~ . ~~
                                             .--|--.        ~
                                             |  v  |
                                             +-----+
     ><>

                        <><



----------------------------------------------------------------------




## Offshore geotechnical investigations
                       .*
                       \|\                   ,_____.
                   _============.            |     |
                    \\# # # #/  |    ._______|--|--|
                     |          +.,  |  Geo  |  |  |
             _---------------------+-+-------|--|--|---\
               \  MS/Bitreich                   |       |
~~~~~~~~~~~~~~~~~\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|~~~~~~~|~~~~~~~~~~~~
                 \                              |    .-'~ ~ . ~~
                  \_____________________________|___/--x    ~
                                                |
                                                |
                                                |
      ><>                                       |
                                                |
                       <><                      |
                                                |
                                             .--|--.
                                             |  v  |
----------------------------------------------+-----+-----------------




## Offshore geotechnical investigations
                       .*
                       \|\                   ,_____.
                   _============.            |     |
                    \\# # # #/  |    ._______|--|--|
                     |          +.,  |  Geo  |  |  |
             _---------------------+-+-------|--|--|---\
               \  MS/Bitreich                   |       |
~~~~~~~~~~~~~~~~~\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|~~~~~~~|~~~~~~~~~~~~
                 \                              |    .-''   ~
                  \_____________________________|___/--x
                                                |
                                                |
                                                |
       ><>                                      |
                                                |
                      <><                       |
                                                |
                                             .--|--.
                                             |  |  |
----------------------------------------------+--|--+-----------------
                                                |
                                                |
                                                |
                                                v

## Offshore geotechnical investigations
                                        |               |
                                        |               |
                                        |               |
                                        |               |
                                        |               |
                                        |               |
                                        |               |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|~~~~~~~~~~~~~~~|~~~~~~~~~~~~
                                        |               |
                                        |               |
                                        |               |
                                        |               |
                                 ?      |               |
                               ><>      |               |
                                        |               |
                                        |               |  !
                                        |               |  <><
                                        |               |
                                        |               |
-----------------------------------------|---------------|------------
                                        |               |
                                        |               |
                                        |               |
                                        |               |
                                        |_______________|

https://www.mdpi.com/energies/energies-17-01964/article_deploy/html/images/energies-17-01964-g001.png

## Offshore systems overview
* Up to 800 sensors, usually 1-10 Hz
* SCADA, PLCs, environmental sensors, navigation, scientific results,
 calibration data, ...
* Control messages
* Asynchronous data streams
* Event driven logic
* Raw sensor output into physical units
* Aggregation of time series and combination of sources
* Time series databases
* Development project with many involved partners

## Approaches: Unix philosophy vs. Microsoft mentality
* Does the client know what they want?
* Do we know everything about what we want to solve?
* Do we know if our assumptions are valid, in particular in complex systems?
* Do we have full specifications?
* Should we produce a big integrated C# monolith to handle computations,
 flow, storage, logic?

#pause
   > yes no | head -n 5


## Data routing system
* MQTT: Message Queuing Telemetry Transport
* Started as a proprietary protocol for SCADA systems in O&G
* Lightweight, publish-subscribe network protocol
* Constrained devices and low-bandwidth, high-latency networks
* Publish/Subscribe Model: Decouples message producers from consumers
* Data accessible via network, not living internally in an obscure program

Specifications:
- MQTT v5.0:    https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-v5.0.html
- MQTT v3.1.1:  http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html
- https://github.com/mqtt/mqtt.org/wiki/Differences-between-3.1.1-and-5.0
- MQTT and TLS: https://www.rfc-editor.org/rfc/rfc9431.txt

## Central concepts
* Broker: Central server that routes messages
* Clients: Devices that publish or subscribe to one or more topics
* Messages: Data packets sent between clients via the broker
* Topics: Hierarchical and dynamic name space for message

Libs for many languages, e.g.,
       - https://github.com/eclipse/paho.mqtt.c
       - https://github.com/eclipse/paho.mqtt.golang

## DISCLAIMER

The coming exercises mainly to demonstrate fundamentals and principles

Most are suboptimal or bad practice

But, let's have some #fun ...

## MQTT use cases
* Home thermometers and weather stations (if you ask the web)
* IoT Devices: Smart homes, wearables, and industrial automation
* Mobile Applications: Real-time messaging and notifications
* Remote Monitoring: Environmental sensors, health monitoring
* Connected Vehicles: Telematics and fleet management

## MQTT messages
* TCP/IP
* Limit to message size configurable

* New subscribers receive only new messages (no backlog)
* Retained Messages: Last known good value for new subscribers
* Last Will and Testament (LWT): Notifies other clients about an ungraceful disconnection

* Quality of Service (QoS): Three levels to ensure message delivery
* QoS 0: At most once delivery (fire and forget)
* QoS 1: At least once delivery (acknowledged delivery)
* QoS 2: Exactly once delivery (assured delivery)

## Why MQTT for the offshore project?
* Hierarchial data structure through topics
* A node in the topic tree exists as soon as someone publishes or
 subscribes to it
* Data accessible via network and all clients can read or publish
 (by default)

#pause
   rig/sensor1/raw
   rig/sensor1/phys
   rig/sensor2/raw
   rig/sensor2/phys
   ...
   ship/navigation/easting
   ship/navigation/northing
   ...

## Topic examples
Wildcards: #, +   (subscribe only)

Subscription examples:
   1) rig/sensor1/raw
   2) ship/#: Subscribe to everything from the ship
   3) rig/+/phys: Subscribe to all physical values

## Example: Subscribe and publish
$ cat bin/timestamp     # in case you don't have ts(1)
#!/bin/sh
while read -r REPLY
do
   printf '%s %s\n' "$(date '+%Y-%m-%d %Z %H:%M:%S')" "$REPLY"
done
#pause
$ export MQTTURI='mqtt://bitreich:[email protected]:65431/'
#pause
$ mosquitto_sub -L "${MQTTURI}#" -v -t '#' | timestamp | grep -v hatesensor
#pause

$ date | mosquitto_pub -L "${MQTTURI}$(hostname)/$(whoami)" -l

## Reporting online status via last will and retain, reporting some metrics

gophers://duckless.org/0/tmp/mqtt-online

#!/bin/sh
online_topic="${ONLINE_TOPIC:-$(hostname)/online}"
mqtt_broker="${MQTT_BROKER:-mx2.adamsgaard.dk}"
mqtt_port="${MQTT_PORT:-65431}"
mqtt_user="${MQTT_USER:-bitreich}"
mqtt_password="${MQTT_PASSWORD:-bitreich}"
args="-h ${mqtt_broker} -p ${mqtt_port} -u ${mqtt_user} -P ${mqtt_password}"
mosquitto_pub ${args} -t "${online_topic}" -r -m "1"
while :
do
   printf '%s\t%s\t%s\t%s\n' "$(date +%s)" "$(date)" "$(hostname)" "$(uptime)"
   sleep 360
done | mosquitto_pub ${args} --will-topic "${online_topic}" \
   --will-retain --will-payload "0" -t "${online_topic}" -r -l

## Data structure on the network
Interact with data hierarchy via small modular clients.
Brings all benefits of UNIX design into play.

The tenents of the UNIX philosophy:

   - Small is beautiful
   - Make each program do one thing well
   - Build a prototype as soon as possible
   - Choose portability over efficiency
   - Store numerical data in flat ASCII files
   - Use software leverage to your advantage
   - Use shell scripts to increase leverage and portability
   - Avoid captive user interfaces
   - Make every program a filter

src: Make Gancarz 1995 "The UNIX Philosophy", ISBN 1-55558-123-4

## Distributed computing
Assign small modular programs to read stdin from topics and post their
result to another topic

* Rudimentary distributed computing
* Each program acts as a text filter
* Each program can contribute local data

(disclaimer: for 1:1 connections, netcat or named pipes over SSH is simpler)

Broker statistics: $SYS/broker
       mosquitto_sub -L "${MQTTURI}\$SYS/broker/#" -v

## Connecting stdin, stdout, and stderr with MQTT topics
Full script: gophers://duckless.org/0/tmp/mqtt-wrapper

   fifodir="$(mktemp -d)" || die 'mktemp'
   fin="${fifodir}/in"
   fout="${fifodir}/out"
   ferr="${fifodir}/err"
   mkfifo "$fin" "$fout" "$ferr" || die 'mkfifo'

#pause
   mosquitto_sub ${mosquitto_args} -t $subscribe_args >"${fin}" &
   mosquitto_pub ${mosquitto_args} -t "${output_topic}" -l <"${fout}" &
   mosquitto_pub ${mosquitto_args} -t "${error_topic}" -l <"${ferr}" &
   trap -- 'cleanup' ERR INT HUP EXIT CHLD

#pause
   while :
   do
       $runtime $runtime_args <"${fin}" >"${fout}" 2>"${ferr}"
   done

## Connecting stdin, stdout, and stderr with MQTT topics (cont.)

Works if input is continuously evaluated (i.e., does not wait for EOF)

       RUNTIME=bc ARGS="-l" sh -x ./mqtt-wrapper
       RUNTIME=sh ARGS="your-favorite-cgi-script" sh -x ./mqtt-wrapper
       RUNTIME=sh ARGS="your-sd-program" sh -x ./mqtt-wrapper

## Outlook
* Lots of possibilities coupling pub/sub with text streams
* Use existing client/broker implementations and libraries
* Minimal C implementation would be nice, aiming at a subset of features
* Represent topic structure with virtual file system representation
 (i.e., plan9 or /proc in linux)

## Challenge 0: Installing a MQTT broker/client
Mosquitto (mostly C, BSD-like license).
Pretty bloated, a minimal alternative would be nice.
You just need the client for these exercises.

   https://github.com/eclipse/mosquitto

Package names in common OS:

   OpenBSD  mosquitto           broker+client
   Arch     mosquitto           broker+client
   Gentoo   app-misc/mosquitto  broker+client
   Debian   mosquitto-clients   client

## Challenge agenda
First one to post a working solution will get points towards a
price.

## Challenge 1: Let's write a chat
Hints:

   mosquitto_pub(1): Publish a message to a named topic
       Useful flags:
           -d: Show debug info
           -l: Read messages from stdin (each line 1 message)
   mosquitto_sub(1): Subscribe to a path in the topic hierarchy
           -d: Show debug info
           -v: Print topic for each received message as first field

   Connection URI:
       -L 'mqtt://bitreich:[email protected]:65431/testtopic'

Let's use the message format: "nick\tmessage"

## Challenge 2: Write a script that records the chat
Hint: The '#' wild card

What is the best choice for a time stamp?
* Time as the sender reports it?
* Time as the subscriber sees it?

## Challenge 3: Let the data flow
Anyone has a funky data source?

* USB body thermometer?
* spoon -t
* while :; do printf '%s\t%s' "$(hostname)" "$(uptime)"; sleep 10; done
* ii/annna?
* vmstat(8)

Task: Publish some data and let the others guess what it is.
The funkier, the better.

Message format ideas:
   TSV, JSON, XLSX? sfeed(5)?
   VT100 control codes??

## Challenge 4: Raise an alert!
Set up a script that monitors one of the data sources, and triggers
an alert upon a condition (email, xmessage, log line, ...).

## Challenge 5: Make some gnuplot
Monitor one of the sensors from the previous, and create a continuously
updating gnuplot (-t dumb) with a rolling window.

## Challenge 6: Health check reporting
Write a script that monitors some gopher and reports their status to

       gopherstatus/<uri>
               up|down

## Challenge 7: Tamagotchi
Make script that imitates a virtual pet, expecting to be feed
"cookies" as messages on stdin every 30 s.

It should die if it gets to much or too little food.

Report its happyness to a topic with ASCII smileys.

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