commit 5b86785c2b12f0b75ad5c581cd886db87c9b5977
Author: Olivier 'reivilibre <olivier@librepush.net>
Date:   Wed Mar 23 06:55:02 2022 +0000

    Initial version

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..7a53b1c
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+/target
+Cargo.lock
+
+.idea
\ No newline at end of file
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..8f9d77d
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "metrics-process-promstyle"
+authors = ["Olivier 'reivilibre'"]
+#
+version = "0.18.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+metrics = "0.18.1"
+procfs = "0.12.0"
+
+[dev-dependencies]
+metrics-exporter-prometheus = "0.9.0"
+tokio = { version = "1.17.0", features = ["macros", "rt-multi-thread"] }
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e6fd4ba
--- /dev/null
+++ b/README.md
@@ -0,0 +1,53 @@
+# `metrics-process-promstyle`: Prometheus-style process metrics for the `metrics` façade
+
+This crate provides Prometheus-style ['process metrics'][prom_process_metrics] for the backend-agnostic
+[`metrics`][metrics_crate] façade.
+
+Although these metrics use the conventional Prometheus names, they can be used with any `metrics`-compatible
+exporter!
+
+Process metrics are the following useful statistics:
+
+- CPU time
+- memory usage
+- start time of the process
+- number of threads
+
+[prom_process_metrics]: https://prometheus.io/docs/instrumenting/writing_clientlibs/#process-metrics
+[metrics_crate]: https://github.com/metrics-rs/metrics
+
+Unimplemented process metrics:
+
+- `process_open_fds`
+- `process_max_fds`
+- `process_virtual_memory_max_bytes`
+- `process_heap_bytes`
+
+
+## Usage
+
+Once your metrics exporter is set up, you can describe the process metrics using `describe()`.
+
+The `metrics` crate only provides for 'push'-style metrics; there's no way right now to emit statistics on demand.
+For that reason, this crate exposes a function called `emit_now()` which, as the name implies, emits the statistics when called.
+You'll need to call this occasionally (from a background thread or Tokio task etc, if necessary) to update the metrics.
+
+(One day, it should be as easy as enabling a feature in this crate and calling the necessary function to set up a timer for you.)
+
+See the `examples` directory for an example.
+
+
+## Licence
+
+See `LICENCE`: it's the MIT Licence.
+
+
+## Versioning
+
+For simplicity's sake, this crate will follow the major version number of `metrics`, so it's easy to tell that compatible versions are being used.
+This means that version `0.18.x` of this crate will be compatible with `metrics` `0.18.x`, and a hypothetical version `1.x.x` of this crate will be compatible with `metrics` `1.x.x`.
+
+
+## Contributions
+
+If you feel like you want to make a contribution, I would be very happy to accept.
diff --git a/examples/simple.rs b/examples/simple.rs
new file mode 100644
index 0000000..9bdce30
--- /dev/null
+++ b/examples/simple.rs
@@ -0,0 +1,29 @@
+use std::net::SocketAddr;
+use std::str::FromStr;
+use std::time::Duration;
+
+/// Demo for process-style metrics.
+/// Open up http://127.0.0.1:3333 whilst it's running to see!
+/// We must use Tokio as the Prometheus exporter requires to be called in a Tokio context...
+/// (this seems like a bug in `metrics-exporter-prometheus`...?).
+#[tokio::main]
+pub async fn main() {
+    metrics_exporter_prometheus::PrometheusBuilder::new()
+        .with_http_listener(SocketAddr::from_str("127.0.0.1:3333").unwrap())
+        .install()
+        .expect("Can't build Prometheus exporter");
+
+    // Describes the process metrics.
+    metrics_process_promstyle::describe();
+
+    std::thread::spawn(|| {
+        // 5 seconds is maybe too fast in real-life use.
+        std::thread::sleep(Duration::from_secs(5));
+
+        // Emits the process metrics.
+        metrics_process_promstyle::emit_now().expect("Failed to emit process metrics");
+    });
+
+    // Main program: sleep 2 minutes.
+    std::thread::sleep(Duration::from_secs(120));
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..4757234
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,75 @@
+use metrics::{describe_gauge, gauge, Unit};
+use procfs::process::Process;
+use procfs::{page_size, ticks_per_second, ProcResult};
+
+pub fn describe() {
+    describe_gauge!(
+        "process_cpu_seconds_total",
+        Unit::Seconds,
+        "Total user and system CPU time spent in seconds."
+    );
+    // TODO(feature): Getting the number of open file descriptors involves extra work
+    //     and I don't care *that* much about the metric for now anyway.
+    // describe_gauge!("process_open_fds", Unit::Count, "Number of open file descriptors.");
+    // TODO(feature): Getting the max number of file descriptors involves reading the limits file,
+    //     which is easy enough to implement but I don't care about the limit if there's no count of
+    //     open FDs (and may as well reduce the amount of work the collector needs to do).
+    // describe_gauge!("process_max_fds", Unit::Count, "Maximum number of open file descriptors.");
+    describe_gauge!(
+        "process_virtual_memory_bytes",
+        Unit::Bytes,
+        "Virtual memory size in bytes."
+    );
+    // TODO(feature): Couldn't immediately see where to get this one, and I don't usually rely on it.
+    // describe_gauge!("process_virtual_memory_max_bytes", Unit::Bytes, "Maximum amount of virtual memory available in bytes.");
+    describe_gauge!(
+        "process_resident_memory_bytes",
+        Unit::Bytes,
+        "Resident memory size in bytes."
+    );
+    // TODO(feature): counting heap bytes presumably needs access to the allocator.
+    //     I can see that breaking depending on which allocator is in use, so won't bother for now.
+    // describe_gauge!("process_heap_bytes", Unit::Bytes, "Process heap size in bytes.");
+    describe_gauge!(
+        "process_start_time_seconds",
+        Unit::Seconds,
+        "Start time of the process since unix epoch in seconds."
+    );
+    describe_gauge!(
+        "process_threads",
+        Unit::Count,
+        "Number of OS threads in the process."
+    );
+}
+
+pub fn emit_now() -> ProcResult<()> {
+    let boot_time_secs = procfs::boot_time_secs()?;
+
+    let this_process = Process::myself()?;
+
+    let total_time_ticks = this_process.stat.utime + this_process.stat.stime;
+    let ticks_per_second = ticks_per_second()?;
+
+    let rss_bytes = this_process.stat.rss * page_size()?;
+
+    let start_time_secs =
+        (this_process.stat.starttime as f64) / (ticks_per_second as f64) + boot_time_secs as f64;
+    let total_time_secs = (total_time_ticks as f64) / (ticks_per_second as f64);
+
+    let num_threads = this_process.stat.num_threads;
+
+    gauge!("process_cpu_seconds_total", total_time_secs);
+    // gauge!("process_open_fds", );
+    // gauge!("process_max_fds", );
+    gauge!(
+        "process_virtual_memory_bytes",
+        this_process.stat.vsize as f64
+    );
+    // gauge!("process_virtual_memory_max_bytes", );
+    gauge!("process_resident_memory_bytes", rss_bytes as f64);
+    // gauge!("process_heap_bytes", );
+    gauge!("process_start_time_seconds", start_time_secs);
+    gauge!("process_threads", num_threads as f64);
+
+    Ok(())
+}