Create the presentation

.gitignore

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+svg-inkscape/
+prometheus-exporter-rs.html
+prometheus-exporter-rs.pdf
+prometheus-exporter-rs.pyg
+prometheus-exporter-rs.tex

img/prometheus-icon-color.svg

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prometheus-exporter-rs.org

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+#+STARTUP: beamer
+#+OPTIONS: ':nil *:t -:t ::t <:t H:3 \n:nil ^:nil arch:headline
+#+OPTIONS: author:t broken-links:nil c:nil creator:nil
+#+OPTIONS: d:(not "LOGBOOK") date:t e:t email:nil f:t inline:t num:t
+#+OPTIONS: p:nil pri:nil prop:nil stat:t tags:t tasks:t tex:t
+#+OPTIONS: timestamp:t title:t toc:t todo:t |:t
+#+TITLE: @@latex:\includesvg[height=.25\textheight]{img/prometheus-icon-color}\hspace{1cm}\includesvg[height=.25\textheight]{img/rust-logo-blk}\newline @@Create a simple Prometheus Exporter with Rust
+#+SUBTITLE: From scratch to Debian package.
+#+DATE: \today
+#+AUTHOR: [[mailto:finga@onders.org][finga]]
+#+EMAIL: finga@onders.org
+#+DESCRIPTION: Create a simple Prometheus Exporter with Rust, from scratch to Debian package.
+#+LANGUAGE: en
+#+KEYWORDS: prometheus rust programming
+#+SELECT_TAGS: export
+#+EXCLUDE_TAGS: noexport
+#+CREATOR: Emacs 26.1 (Org mode 9.1.9)
+
+#+OPTIONS: H:2
+#+LATEX_CLASS: beamer
+#+LATEX_CLASS_OPTIONS: [aspectratio=1610]
+#+COLUMNS: %45ITEM %10BEAMER_env(Env) %10BEAMER_act(Act) %4BEAMER_col(Col) %8BEAMER_opt(Opt)
+#+LATEX_HEADER: \usepackage{svg}\hypersetup{colorlinks=true,linkcolor=black,urlcolor=gray}
+#+BEAMER_THEME: Frankfurt
+#+BEAMER_COLOR_THEME: seagull
+#+BEAMER_FONT_THEME:
+#+BEAMER_INNER_THEME:
+#+BEAMER_OUTER_THEME:
+#+BEAMER_HEADER: \institute[INST]{\href{https://onders.org}{onders.org}}
+
+* Objective
+
+** Objective
+
+*** Abstract
+    Acquire, (process)  and serve metrics.
+
+*** What we are actually going to do
+    Parse ~/proc/loadavg~ periodically and serve its latest values.
+
+*** Example content of ~/proc/loadavg~
+    #+begin_src
+0.13 0.14 0.09 1/273 3160
+    #+end_src
+
+** Create a new Project
+
+*** New Cargo Project
+    To begin we create a new Cargo project.
+    #+begin_src sh
+$ cargo new loadavg-exporter
+    #+end_src
+
+** Project settings
+   Add meta data to ~Cargo.toml~.
+
+*** ~Cargo.toml~
+    @@latex:\scriptsize@@
+    #+begin_src toml
+[package]
+name = "loadavg-exporter"
+version = "0.1.0"
+authors = ["finga <finga@onders.org>"]
+edition = "2021"
+description = "Prometheus exporter example to export the load average."
+readme = "README.md"
+license = "GPL-3.0-or-later"
+repository = "https://git.onders.org/finga/loadavg-exporter.git"
+keywords = ["prometheus", "metrics"]
+categories = ["command-line-utilities"]
+    #+end_src
+
+** Read from ~/proc/loadavg~
+*** ~src/main.rs~: Print content of ~/proc/loadavg~
+    @@latex:\scriptsize@@
+    #+begin_src rust
+use std::{
+    fs::File,
+    io::{BufRead, BufReader},
+    path::Path,
+};
+
+fn parse_loadavg<P>(filename: P)
+where
+    P: AsRef<Path>,
+{
+    let file = File::open(&filename).unwrap();
+    for line in BufReader::new(file).lines() {
+        println!("{}", line.unwrap());
+    }
+}
+
+fn main() {
+    parse_loadavg("/proc/loadavg")
+}
+    #+end_src
+
+** Use of =Result<T, E>=
+
+*** It is "just" an enum
+    @@latex:\scriptsize@@
+    #+begin_src rust
+enum Result<T, E> {
+    Ok(T),
+    Err(E),
+}
+    #+end_src
+
+*** How to use =Result=
+- ~Results~ "must" be used
+- There is the question mark operator: =?=
+- =?= can only be used in functions that return =Result=
+- For more see the docs[fn:result]
+- Historically the =?= operator replaces the =try!=[fn:try] macro
+
+** Set some ~clippy~ settings
+
+*** Create ~.cargo/config~
+    @@latex:\scriptsize@@
+#+begin_src
+[target.'cfg(feature = "cargo-clippy")']
+rustflags = [
+    "-Dwarnings",
+    "-Dclippy::pedantic",
+    "-Dclippy::nursery",
+    "-Dclippy::cargo",
+]
+#+end_src
+
+** Use ~anyhow~
+
+*** Add dependency to ~Cargo.toml~
+    @@latex:\scriptsize@@
+    #+begin_src toml
+[dependencies]
+anyhow = "1"
+    #+end_src
+
+*** Use ~anyhow~ where suitable
+    @@latex:\scriptsize@@
+    #+begin_src diff
++use anyhow::Result;
+ ...
+-fn parse_loadavg<P>(filename: P)
++fn parse_loadavg<P>(filename: P) -> Result<()>
+ ...
+-    let file = File::open(&filename).unwrap();
++    let file = File::open(&filename)?;
+     for line in BufReader::new(file).lines() {
+-        println!("{}", line.unwrap());
++        println!("{}", line?);
+     }
++    Ok(())
+ }
+...
+    #+end_src
+
+** Create an atomic for =f64=
+
+*** Create an atomic =f64= type
+    @@latex:\scriptsize@@
+    #+begin_src rust
+use std::sync::atomic::{AtomicU64, Ordering};
+
+#[derive(Default)]
+struct AtomicF64 {
+    storage: AtomicU64,
+}
+
+impl AtomicF64 {
+    fn store(&self, value: f64, ordering: Ordering) {
+        let as_u64 = value.to_bits();
+        self.storage.store(as_u64, ordering);
+    }
+
+    fn load(&self, ordering: Ordering) -> f64 {
+        let as_u64 = self.storage.load(ordering);
+        f64::from_bits(as_u64)
+    }
+}
+    #+end_src
+
+** What does the =#[derive(Default)]= attribute do?
+   This calls a procedural derive macro[fn:derive] to generate =AtomicF64::default()=.
+
+*** What is generated?
+    @@latex:\scriptsize@@
+    #+begin_src rust
+ #[automatically_derived]
+ #[allow(unused_qualifications)]
+ impl ::core::default::Default for AtomicF64 {
+     #[inline]
+     fn default() -> AtomicF64 {
+         AtomicF64 {
+             storage: ::core::default::Default::default(),
+         }
+     }
+ }
+    #+end_src
+
+** Create a storage for the metrics
+
+*** Create a struct to keep the metrics
+    @@latex:\scriptsize@@
+    #+begin_src rust
+#[derive(Default)]
+struct Metrics {
+    load_1: AtomicF64,
+    load_5: AtomicF64,
+    load_15: AtomicF64,
+}
+    #+end_src
+
+** Introduce logging
+
+*** How to configure logging from the outside?
+    - The =RUST_LOG= environment variable is the answer
+    - Use =RUST_LOG=trace cargo r= to set the log level to ~trace~ and
+      run the project
+    - Use =RUST_LOG=error,path::to::module=trace= to set the overall
+      log level to ~error~ and the log level of =path::to::module= to
+      ~trace~
+
+*** Add new dependencies in ~Cargo.toml~
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ [dependencies]
+ anyhow = "1"
++log = "0.4"
++env_logger = "0.9"
+    #+end_src
+
+** Introduce logging
+
+*** Generate some log messages
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ use anyhow::Result;
++use log::{debug, info};
+ use std::{
+     fs::File,
+     io::{BufRead, BufReader},
+...
+ fn parse_loadavg<P>(filename: P) -> Result<()>
+ where
+-    P: AsRef<Path>,
++    P: AsRef<Path> + std::fmt::Display,
+ {
++    debug!("Read load average from {}", filename);
+     let file = File::open(&filename)?;
+...
+ fn main() -> Result<()> {
++    env_logger::init();
++
++    info!("{} started", env!("CARGO_PKG_NAME"));
+     parse_loadavg("/proc/loadavg")?;
+    #+end_src
+
+** Parse the ~loadavg~ line
+
+*** Parse the fields
+    @@latex:\scriptsize@@
+    #+begin_src diff
+-fn parse_loadavg<P>(filename: P) -> Result<()>
++fn parse_loadavg<P>(filename: P, metrics: Arc<Metrics>) -> Result<()>
+ ...
+     let file = File::open(&filename)?;
+-    for line in BufReader::new(file).lines() {
+-        println!("{}", line?);
++    let mut data = String::new();
++
++    BufReader::new(file).read_to_string(&mut data)?;
++    let data = data.trim();
++    trace!("Data to parse: {}", data);
++    let fields: Vec<&str> = data.split(' ').collect();
++
++    if fields.len() != 5 {
++        bail!(
++            "Expected to read 5 space separated fields from {}",
++            filename
++        );
+     }
+     ...
+    #+end_src
+
+** Store the parsed values in our =Metrics= struct
+
+*** Before returning we store the gathered data
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ fn parse_loadavg<P>(filename: P, metrics: Arc<Metrics>) -> Result<()>
+ where
+     P: AsRef<Path> + std::fmt::Display,
+ {
+     ...
++    trace!("Parsed fields: {:?}", fields);
++
++    metrics
++        .load_1
++        .store(fields[0].parse::<f64>()?, Ordering::Relaxed);
++    metrics
++        .load_5
++        .store(fields[1].parse::<f64>()?, Ordering::Relaxed);
++    metrics
++        .load_15
++        .store(fields[2].parse::<f64>()?, Ordering::Relaxed);
++
+     Ok(())
+ }
+    #+end_src
+
+** Introduce =tokio=[fn:tokio]
+   @@latex:\scriptsize@@
+*** Add =tokio= to =Cargo.toml=
+#+begin_src diff
+ ...
++tokio = { version = "1", features = ["macros", "time", "rt-multi-thread"] }
+#+end_src
+
+*** Add =use= statements to bring utilities into scope
+#+begin_src diff
+ use anyhow::{bail, Result};
+ use log::{debug, info, trace};
+ use std::{
+     fs::File,
+     io::{BufReader, Read},
+     path::Path,
+     sync::{
+         atomic::{AtomicU64, Ordering},
+         Arc,
+     },
++    time::Duration,
+ };
++use tokio::time::sleep;
+#+end_src
+
+** Periodically poll the data from =/proc/loadavg=
+
+*** Call the loadavg parser in an infinite loop and sleep
+    @@latex:\scriptsize@@
+    #+begin_src rust
+async fn poll_loadavg<P>(filename: P, interval: u64, metrics: Arc<Metrics>) -> Result<()>
+where
+    P: AsRef<Path> + std::fmt::Display,
+{
+    debug!("Reading {} every {} seconds", filename, interval);
+
+    loop {
+        trace!("Polling loadavg from {}", filename);
+        parse_loadavg(&filename, metrics.clone())?;
+        sleep(Duration::from_secs(interval)).await;
+    }
+}
+    #+end_src
+
+** Make =main= use =tokio=
+
+*** And adopt our =main()= to use it
+    @@latex:\scriptsize@@
+    #+begin_src diff
+-fn main() -> Result<()> {
++#[tokio::main]
++async fn main() -> Result<()> {
+     ...
+-    parse_loadavg("/proc/loadavg", Arc::clone(&metrics))?;
++    poll_loadavg("/proc/loadavg", 5, Arc::clone(&metrics)).await?;
+    #+end_src
+
+** What is =#[tokio::main]=?
+
+*** It is syntactic sugar as following:
+    @@latex:\scriptsize@@
+#+begin_src rust
+#[tokio::main]
+async fn main() {
+    println!("hello");
+}
+#+end_src
+
+*** ... just generates this:
+    @@latex:\scriptsize@@
+#+begin_src rust
+fn main() {
+    let mut rt = tokio::runtime::Runtime::new().unwrap();
+    rt.block_on(async {
+        println!("hello");
+    })
+}
+#+end_src
+
+** Serve the metrics data
+
+*** Add dependencies to =Cargo.toml=...
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ [dependencies]
+ ...
++axum = "0.5"
+ ...
+    #+end_src
+
+*** and import further necessities in our program...
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ use anyhow::{bail, Result};
++use axum::{routing::get, Extension, Router, Server};
+ use log::{debug, info, trace};
+ use std::{
+     fs::File,
+     io::{BufReader, Read},
++    net::{IpAddr, Ipv4Addr, SocketAddr},
+     path::Path,
+ ...
+ };
+-use tokio::time::sleep;
++use tokio::{spawn, time::sleep, try_join};
+    #+end_src
+
+** Generate the response string
+
+*** Create the served metrics data
+    @@latex:\scriptsize@@
+    #+begin_src rust
+#[allow(clippy::unused_async)]
+async fn serve_metrics(Extension(metrics): Extension<Arc<Metrics>>) -> String {
+    format!(
+        r"# HELP System load (1m).
+# TYPE load_1 gauge
+load_1 {}
+# HELP System load (5m).
+# TYPE load_5 gauge
+load_5 {}
+# HELP System load (15m).
+# TYPE load_15 gauge
+load_15 {}
+",
+        metrics.load_1.load(Ordering::Relaxed),
+        metrics.load_5.load(Ordering::Relaxed),
+        metrics.load_15.load(Ordering::Relaxed),
+    )
+}
+    #+end_src
+
+** Create a =Router= to route and serve the http endpoint
+
+*** Basically thats our http listener
+    @@latex:\scriptsize@@
+    #+begin_src rust
+async fn listen_http(address: IpAddr, port: u16, metrics: Arc<Metrics>) -> Result<()> {
+    let app = Router::new()
+        .route("/metrics", get(serve_metrics))
+        .layer(Extension(metrics));
+    let addr = SocketAddr::from((address, port));
+    debug!("Listening on {}:{}", address, port);
+    Ok(Server::bind(&addr).serve(app.into_make_service()).await?)
+}
+    #+end_src
+
+** Read from file and serve http asynchronously
+
+*** Poll loadavg, listen for http and return on error
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ #[tokio::main]
+ async fn main() -> Result<()> {
+     ...
+-    poll_loadavg("/proc/loadavg", 5, Arc::clone(&metrics)).await?;
++
++    let (poller, listener) = try_join!(
++        spawn(poll_loadavg("/proc/loadavg", 5, Arc::clone(&metrics))),
++        spawn(listen_http(
++            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
++            8000,
++            Arc::clone(&metrics),
++        )),
++    )?;
++    poller?;
++    listener?;
+
+     Ok(())
+ }
+    #+end_src
+
+** Early Conclusion
+   This concludes the first step of creating a small prometheus
+   exporter.
+
+*** Note
+    We could have created a more simple solution without using =tokio=
+    and by parsing ~/proc/loadavg~ on each request. Still, this shows
+    a bit of =tokio= and further might not appliciable when slightly
+    more complex requirements are needed.
+
+** The Finishing
+   Although this example already works here are some additional steps
+   to improve certain aspects.
+
+*** Further improvements
+    - Parse command line arguments with ~clap~: The Command Line
+      Argument Parser
+    - Use ~cargo-deb~ to generate a Debian Package
+    - Cross compile the project for other architectures
+
+* ~clap~
+
+** Parse command line arguments with ~clap~
+
+*** What is ~clap~
+    - There are several ways of how ~clap~ can be used (derive,
+      builder, etc..)
+    - Documentation: [[https://docs.rs/clap/latest/clap/]]
+    - Examples: [[https://github.com/clap-rs/clap/tree/master/examples]]
+
+** Add build dependencies for ~clap~
+
+*** Add ~clap~ dependencies to ~Cargo.toml~
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ axum = "0.5"
++clap = { version = "3", features = ["derive"] }
+    #+end_src
+
+** Have a struct holding all arguments
+
+*** Create a struct which holds all arguments
+    @@latex:\scriptsize@@
+    #+begin_src rust
+#[derive(Parser)]
+#[clap(about, version, author)]
+struct Args {
+    /// The path to the file to parse the load average parameters.
+    #[clap(short, long, default_value = "/proc/loadavg")]
+    file: String,
+    /// The intervall how often the file is queried
+    #[clap(short, long, default_value = "10")]
+    interval: u64,
+    /// The IPv4 or IPv6 address where the metrics are served.
+    #[clap(short, long, default_value = "127.0.0.1")]
+    address: IpAddr,
+    /// The port where the metrics are served.
+    #[clap(short, long, default_value = "9111")]
+    port: u16,
+    /// Produce verbose output, multiple -v options increase the verbosity
+    #[clap(short, long, global = true, parse(from_occurrences))]
+    verbose: u8,
+}
+    #+end_src
+
+** Make use of the new arguments
+
+*** Parse the arguments and set the log level accordingly
+    @@latex:\scriptsize@@
+    #+begin_src diff
+ #[tokio::main]
+ async fn main() -> Result<()> {
+-    env_logger::init();
++    let cli = Cli::parse();
++
++    env_logger::Builder::from_env(env_logger::Env::default().default_filter_or(
++        match cli.verbose {
++            0 => "error",
++            1 => "warn",
++            2 => "info",
++            3 => "debug",
++            _ => "trace",
++        },
++    ))
++    .init();
+    #+end_src
+
+** Make use of the new arguments
+
+*** Pass the argument values to the procedures
+    @@latex:\scriptsize@@
+    #+begin_src diff
+     let (poller, listener) = try_join!(
+-        spawn(poll_loadavg("/proc/loadavg", 5, Arc::clone(&metrics))),
+-        spawn(listen_http(
+-            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+-            8000,
+-            Arc::clone(&metrics),
+-        )),
++        spawn(poll_loadavg(cli.file, cli.interval, Arc::clone(&metrics))),
++        spawn(listen_http(cli.address, cli.port, Arc::clone(&metrics))),
+     )?;
+     poller?;
+     listener?;
+    #+end_src
+
+* Debian Package
+
+** Build a Debian Package with the help of ~cargo-deb~
+
+*** Create ~debian/service~
+    @@latex:\scriptsize@@
+    #+begin_src
+[Unit]
+Description=Load average Prometheus exporter
+
+[Service]
+Restart=always
+EnvironmentFile=/etc/default/loadavg-exporter
+ExecStart=/usr/bin/loadavg-exporter $ARGS
+Type=simple
+ProtectSystem=strict
+PrivateDevices=yes
+PrivateUsers=yes
+RestrictNamespaces=yes
+
+[Install]
+WantedBy=multi-user.target
+    #+end_src
+
+** Build a Debian Package with the help of ~cargo-deb~
+
+*** Create ~debian/default~
+    @@latex:\scriptsize@@
+    #+begin_src
+ARGS=""
+# loadavg-exporter supports the following options:
+#  -a, --address <ADDRESS>      The IPv4 or IPv6 address where the metrics are served
+#                               [default: 127.0.0.1]
+#  -f, --file <FILE>            The path to the file to parse the load average parameters
+#                               [default: /proc/loadavg]
+#  -i, --interval <INTERVAL>    The intervall how often the file is queried [default: 10]
+#  -p, --port <PORT>            The port where the metrics are served [default: 9112]
+#  -v, --verbose                Produce verbose output, multiple -v options increase the
+#                               verbosity
+    #+end_src
+
+** Build a Debian Package with the help of ~cargo-deb~
+
+*** Add the ~package.metadata.deb~ section to ~Cargo.toml~
+    @@latex:\scriptsize@@
+    #+begin_src toml
+[package.metadata.deb]
+extended-description = "Load average Prometheus exporter."
+section = "utility"
+maintainer-scripts = "debian/"
+systemd-units = { enable = true }
+assets = [
+    ["target/release/loadavg-exporter", "usr/bin/", "755"],
+    ["debian/default", "etc/default/loadavg-exporter", "644"],
+]
+    #+end_src
+
+* Cross compile
+
+** Cross compile for aarch64/arm64
+You need to have the right compiler dependencies installed, on Debian
+that is: ~dummy~
+
+*** Add targets to ~.cargo/config~
+    @@latex:\scriptsize@@
+    #+begin_src
+[target.armv7-unknown-linux-gnueabihf]
+linker = "arm-linux-gnueabihf-gcc"
+
+[target.aarch64-unknown-linux-gnu]
+linker = "aarch64-linux-gnu-gcc"
+    #+end_src
+
+* Examples
+
+** Example 1: MightyOhm Geiger Counter
+*** Abstract
+    A sensor connected to a system to log the sensor data.
+
+*** Technology
+    - [[https://mightyohm.com/blog/products/geiger-counter/][MightyOhm Geiger Counter]]
+    - [[https://www.raspberrypi.com/products/raspberry-pi-3-model-b-plus/][RaspberryPi 3 Model B+]]
+    - [[https://prometheus.io/][Prometheus]]
+    - [[https://grafana.com/][Grafana]]
+    - [[https://www.rust-lang.org/][Rust]]
+
+** Example 1: Sensor
+
+*** Reading Data from the Sensor
+    The Geiger Counter's serial port is connected to the UART port of
+    the Pi. So our program need to listen on the serial line to
+    receive the Data
+
+** Example 1: Prometheus
+*** Prometheus Exporter
+    In order to pipe the Data to Prometheus we will open a port to
+    listen for incomming http requests to respond with the sensors
+    data.
+
+# ** Reading from the Serial Line
+#     To start with reading data from the serial line we use the
+#     ~serialport~ crate. So we do need to add it to the projects
+#     dependencies.
+# *** ~Cargo.toml~
+#     #+begin_src toml
+#     [dependencies]
+#     serialport = "4.1"
+#     #+end_src
+# ***                                                       :B_ignoreheading:
+# :PROPERTIES:
+# :BEAMER_env: ignoreheading
+# :END:
+#     And take a look at the ~seralport~
+#     documentation[fn:serialport_docs] and a simple
+#     example[fn:serialport_example_receive] about how to read from the
+#     serial line.
+
+** Example 2: DHT11 Exporter
+
+* Footnotes
+[fn:result] =Result= docs: [[https://doc.rust-lang.org/std/result/]]
+[fn:try] =try!= docs: https://doc.rust-lang.org/std/macro.try.html
+[fn:derive] [[https://doc.rust-lang.org/reference/procedural-macros.html#derive-macros][https://doc.rust-lang.org/reference/procedural-macros.html]]
+[fn:tokio] https://tokio.rs/
+
+# [fn:serialport_docs] [[https://docs.rs/serialport/latest/serialport/][~serialport~ docs]]
+# [fn:serialport_example_receive] [[https://github.com/serialport/serialport-rs/blob/main/examples/receive_data.rs][~serialport-rs/examples/receive_data.rs~]]