From ba79df596644fae5718d3ce76ec10972d4a5071d Mon Sep 17 00:00:00 2001
From: Andras Schmelczer <andras@schmelczer.dev>
Date: Tue, 3 Feb 2026 21:46:01 +0000
Subject: [PATCH] Add grafana

---
 server-rs/Cargo.lock     | 346 +++++++++++++++++++++++++++++++++++++--
 server-rs/Cargo.toml     |   3 +
 server-rs/src/metrics.rs |  99 +++++++++++
 3 files changed, 435 insertions(+), 13 deletions(-)
 create mode 100644 server-rs/src/metrics.rs

diff --git a/server-rs/Cargo.lock b/server-rs/Cargo.lock
index a5e8a5f..381d16f 100644
--- a/server-rs/Cargo.lock
+++ b/server-rs/Cargo.lock
@@ -207,6 +207,28 @@ version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
 
+[[package]]
+name = "aws-lc-rs"
+version = "1.15.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b7b6141e96a8c160799cc2d5adecd5cbbe5054cb8c7c4af53da0f83bb7ad256"
+dependencies = [
+ "aws-lc-sys",
+ "zeroize",
+]
+
+[[package]]
+name = "aws-lc-sys"
+version = "0.37.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c34dda4df7017c8db52132f0f8a2e0f8161649d15723ed63fc00c82d0f2081a"
+dependencies = [
+ "cc",
+ "cmake",
+ "dunce",
+ "fs_extra",
+]
+
 [[package]]
 name = "axum"
 version = "0.8.8"
@@ -318,6 +340,12 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
+
 [[package]]
 name = "bytes"
 version = "1.11.0"
@@ -421,6 +449,15 @@ version = "0.7.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c3e64b0cc0439b12df2fa678eae89a1c56a529fd067a9115f7827f1fffd22b32"
 
+[[package]]
+name = "cmake"
+version = "0.1.57"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75443c44cd6b379beb8c5b45d85d0773baf31cce901fe7bb252f4eff3008ef7d"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "colorchoice"
 version = "1.0.4"
@@ -502,6 +539,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "core-foundation"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2a6cd9ae233e7f62ba4e9353e81a88df7fc8a5987b8d445b4d90c879bd156f6"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "core-foundation-sys"
 version = "0.8.7"
@@ -570,7 +617,7 @@ dependencies = [
  "crossterm_winapi",
  "document-features",
  "parking_lot",
- "rustix",
+ "rustix 1.1.3",
  "winapi",
 ]
 
@@ -615,6 +662,12 @@ dependencies = [
  "litrs",
 ]
 
+[[package]]
+name = "dunce"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "92773504d58c093f6de2459af4af33faa518c13451eb8f2b5698ed3d36e7c813"
+
 [[package]]
 name = "dyn-clone"
 version = "1.0.20"
@@ -711,6 +764,22 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28a80e3145d8ad11ba0995949bbcf48b9df2be62772b3d351ef017dff6ecb853"
 
+[[package]]
+name = "fmmap"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "687c574434dc6e3cd24a363fe0944711174f947fe71696fdc9a0ae046fe6e715"
+dependencies = [
+ "byteorder",
+ "bytes",
+ "enum_dispatch",
+ "fs4",
+ "memmap2",
+ "parse-display",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -747,6 +816,23 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "fs4"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c29c30684418547d476f0b48e84f4821639119c483b1eccd566c8cd0cd05f521"
+dependencies = [
+ "rustix 0.38.44",
+ "tokio",
+ "windows-sys 0.52.0",
+]
+
+[[package]]
+name = "fs_extra"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42703706b716c37f96a77aea830392ad231f44c9e9a67872fa5548707e11b11c"
+
 [[package]]
 name = "futures"
 version = "0.3.31"
@@ -950,6 +1036,12 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "hilbert_2d"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "705f81e042b11734af35c701c7f6b65f8a968a430621fa2c95e72e27f9f8be5c"
+
 [[package]]
 name = "home"
 version = "0.5.12"
@@ -1043,6 +1135,7 @@ dependencies = [
  "hyper",
  "hyper-util",
  "rustls",
+ "rustls-native-certs",
  "rustls-pki-types",
  "tokio",
  "tokio-rustls",
@@ -1305,6 +1398,12 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b6d2cec3eae94f9f509c767b45932f1ada8350c4bdb85af2fcab4a3c14807981"
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.4.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d26c52dbd32dccf2d10cac7725f8eae5296885fb5703b261f7d0a0739ec807ab"
+
 [[package]]
 name = "linux-raw-sys"
 version = "0.11.0"
@@ -1393,6 +1492,53 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "metrics"
+version = "0.24.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5d5312e9ba3771cfa961b585728215e3d972c950a3eed9252aa093d6301277e8"
+dependencies = [
+ "ahash",
+ "portable-atomic",
+]
+
+[[package]]
+name = "metrics-exporter-prometheus"
+version = "0.16.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd7399781913e5393588a8d8c6a2867bf85fb38eaf2502fdce465aad2dc6f034"
+dependencies = [
+ "base64",
+ "http-body-util",
+ "hyper",
+ "hyper-rustls",
+ "hyper-util",
+ "indexmap",
+ "ipnet",
+ "metrics",
+ "metrics-util",
+ "quanta",
+ "thiserror 1.0.69",
+ "tokio",
+ "tracing",
+]
+
+[[package]]
+name = "metrics-util"
+version = "0.19.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8496cc523d1f94c1385dd8f0f0c2c480b2b8aeccb5b7e4485ad6365523ae376"
+dependencies = [
+ "crossbeam-epoch",
+ "crossbeam-utils",
+ "hashbrown 0.15.5",
+ "metrics",
+ "quanta",
+ "rand 0.9.2",
+ "rand_xoshiro",
+ "sketches-ddsketch",
+]
+
 [[package]]
 name = "mime"
 version = "0.3.17"
@@ -1439,10 +1585,10 @@ dependencies = [
  "libc",
  "log",
  "openssl",
- "openssl-probe",
+ "openssl-probe 0.1.6",
  "openssl-sys",
  "schannel",
- "security-framework",
+ "security-framework 2.11.1",
  "security-framework-sys",
  "tempfile",
 ]
@@ -1537,6 +1683,12 @@ version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d05e27ee213611ffe7d6348b942e8f942b37114c00cc03cec254295a4a17852e"
 
+[[package]]
+name = "openssl-probe"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c87def4c32ab89d880effc9e097653c8da5d6ef28e6b539d313baaacfbafcbe"
+
 [[package]]
 name = "openssl-sys"
 version = "0.9.111"
@@ -1572,6 +1724,31 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "parse-display"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "287d8d3ebdce117b8539f59411e4ed9ec226e0a4153c7f55495c6070d68e6f72"
+dependencies = [
+ "parse-display-derive",
+ "regex",
+ "regex-syntax",
+]
+
+[[package]]
+name = "parse-display-derive"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fc048687be30d79502dea2f623d052f3a074012c6eac41726b7ab17213616b1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "regex",
+ "regex-syntax",
+ "structmeta",
+ "syn",
+]
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.2"
@@ -1623,6 +1800,21 @@ dependencies = [
  "array-init-cursor",
 ]
 
+[[package]]
+name = "pmtiles"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a83db53da21fbade9a8738bccb1ef54c405ef3db02b7fa81dfbd01933bc1a838"
+dependencies = [
+ "async-compression",
+ "bytes",
+ "fmmap",
+ "hilbert_2d",
+ "thiserror 2.0.18",
+ "tokio",
+ "varint-rs",
+]
+
 [[package]]
 name = "polars"
 version = "0.46.0"
@@ -1736,7 +1928,7 @@ dependencies = [
  "rayon",
  "regex",
  "strum_macros",
- "thiserror",
+ "thiserror 2.0.18",
  "version_check",
  "xxhash-rust",
 ]
@@ -1750,7 +1942,7 @@ dependencies = [
  "polars-arrow-format",
  "regex",
  "simdutf8",
- "thiserror",
+ "thiserror 2.0.18",
 ]
 
 [[package]]
@@ -2116,6 +2308,12 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "portable-atomic"
+version = "1.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c33a9471896f1c69cecef8d20cbe2f7accd12527ce60845ff44c153bb2a21b49"
+
 [[package]]
 name = "potential_utf"
 version = "0.1.4"
@@ -2152,6 +2350,9 @@ dependencies = [
  "clap",
  "h3o",
  "lasso",
+ "metrics",
+ "metrics-exporter-prometheus",
+ "pmtiles",
  "polars",
  "rayon",
  "regex",
@@ -2176,6 +2377,21 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "quanta"
+version = "0.12.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f3ab5a9d756f0d97bdc89019bd2e4ea098cf9cde50ee7564dde6b81ccc8f06c7"
+dependencies = [
+ "crossbeam-utils",
+ "libc",
+ "once_cell",
+ "raw-cpuid",
+ "wasi",
+ "web-sys",
+ "winapi",
+]
+
 [[package]]
 name = "quinn"
 version = "0.11.9"
@@ -2190,7 +2406,7 @@ dependencies = [
  "rustc-hash",
  "rustls",
  "socket2",
- "thiserror",
+ "thiserror 2.0.18",
  "tokio",
  "tracing",
  "web-time",
@@ -2211,7 +2427,7 @@ dependencies = [
  "rustls",
  "rustls-pki-types",
  "slab",
- "thiserror",
+ "thiserror 2.0.18",
  "tinyvec",
  "tracing",
  "web-time",
@@ -2315,6 +2531,15 @@ dependencies = [
  "rand 0.8.5",
 ]
 
+[[package]]
+name = "rand_xoshiro"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f703f4665700daf5512dcca5f43afa6af89f09db47fb56be587f80636bda2d41"
+dependencies = [
+ "rand_core 0.9.5",
+]
+
 [[package]]
 name = "raw-cpuid"
 version = "11.6.0"
@@ -2466,6 +2691,19 @@ version = "2.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "357703d41365b4b27c590e3ed91eabb1b663f07c4c084095e60cbed4362dff0d"
 
+[[package]]
+name = "rustix"
+version = "0.38.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fdb5bc1ae2baa591800df16c9ca78619bf65c0488b41b96ccec5d11220d8c154"
+dependencies = [
+ "bitflags",
+ "errno",
+ "libc",
+ "linux-raw-sys 0.4.15",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "rustix"
 version = "1.1.3"
@@ -2475,7 +2713,7 @@ dependencies = [
  "bitflags",
  "errno",
  "libc",
- "linux-raw-sys",
+ "linux-raw-sys 0.11.0",
  "windows-sys 0.61.2",
 ]
 
@@ -2485,6 +2723,7 @@ version = "0.23.36"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c665f33d38cea657d9614f766881e4d510e0eda4239891eea56b4cadcf01801b"
 dependencies = [
+ "aws-lc-rs",
  "once_cell",
  "ring",
  "rustls-pki-types",
@@ -2493,6 +2732,18 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "rustls-native-certs"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "612460d5f7bea540c490b2b6395d8e34a953e52b491accd6c86c8164c5932a63"
+dependencies = [
+ "openssl-probe 0.2.1",
+ "rustls-pki-types",
+ "schannel",
+ "security-framework 3.5.1",
+]
+
 [[package]]
 name = "rustls-pki-types"
 version = "1.14.0"
@@ -2509,6 +2760,7 @@ version = "0.103.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d7df23109aa6c1567d1c575b9952556388da57401e4ace1d15f79eedad0d8f53"
 dependencies = [
+ "aws-lc-rs",
  "ring",
  "rustls-pki-types",
  "untrusted",
@@ -2548,7 +2800,20 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "897b2245f0b511c87893af39b033e5ca9cce68824c4d7e7630b5a1d339658d02"
 dependencies = [
  "bitflags",
- "core-foundation",
+ "core-foundation 0.9.4",
+ "core-foundation-sys",
+ "libc",
+ "security-framework-sys",
+]
+
+[[package]]
+name = "security-framework"
+version = "3.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3297343eaf830f66ede390ea39da1d462b6b0c1b000f420d0a83f898bbbe6ef"
+dependencies = [
+ "bitflags",
+ "core-foundation 0.10.1",
  "core-foundation-sys",
  "libc",
  "security-framework-sys",
@@ -2673,6 +2938,12 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b2aa850e253778c88a04c3d7323b043aeda9d3e30d5971937c1855769763678e"
 
+[[package]]
+name = "sketches-ddsketch"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1e9a774a6c28142ac54bb25d25562e6bcf957493a184f15ad4eebccb23e410a"
+
 [[package]]
 name = "slab"
 version = "0.4.11"
@@ -2771,6 +3042,29 @@ version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
 
+[[package]]
+name = "structmeta"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e1575d8d40908d70f6fd05537266b90ae71b15dbbe7a8b7dffa2b759306d329"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "structmeta-derive",
+ "syn",
+]
+
+[[package]]
+name = "structmeta-derive"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "152a0b65a590ff6c3da95cabe2353ee04e6167c896b28e3b14478c2636c922fc"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "strum_macros"
 version = "0.26.4"
@@ -2841,7 +3135,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3c879d448e9d986b661742763247d3693ed13609438cf3d006f51f5368a5ba6b"
 dependencies = [
  "bitflags",
- "core-foundation",
+ "core-foundation 0.9.4",
  "system-configuration-sys",
 ]
 
@@ -2864,8 +3158,17 @@ dependencies = [
  "fastrand",
  "getrandom 0.3.4",
  "once_cell",
- "rustix",
- "windows-sys 0.52.0",
+ "rustix 1.1.3",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "thiserror"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6aaf5339b578ea85b50e080feb250a3e8ae8cfcdff9a461c9ec2904bc923f52"
+dependencies = [
+ "thiserror-impl 1.0.69",
 ]
 
 [[package]]
@@ -2874,7 +3177,18 @@ version = "2.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4288b5bcbc7920c07a1149a35cf9590a2aa808e0bc1eafaade0b80947865fbc4"
 dependencies = [
- "thiserror-impl",
+ "thiserror-impl 2.0.18",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
 ]
 
 [[package]]
@@ -3212,6 +3526,12 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ba73ea9cf16a25df0c8caa16c51acb937d5712a8429db78a3ee29d5dcacd3a65"
 
+[[package]]
+name = "varint-rs"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f54a172d0620933a27a4360d3db3e2ae0dd6cceae9730751a036bbf182c4b23"
+
 [[package]]
 name = "vcpkg"
 version = "0.2.15"
diff --git a/server-rs/Cargo.toml b/server-rs/Cargo.toml
index ccd4bab..06c7223 100644
--- a/server-rs/Cargo.toml
+++ b/server-rs/Cargo.toml
@@ -18,9 +18,12 @@ lasso = "0.7"
 rustc-hash = "2"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter", "fmt"] }
+metrics = "0.24"
+metrics-exporter-prometheus = "0.16"
 reqwest = { version = "0.12", features = ["rustls-tls"] }
 regex = "1"
 urlencoding = "2"
+pmtiles = { version = "0.12", features = ["mmap-async-tokio"] }
 
 [lints.clippy]
 min_ident_chars = "warn"
diff --git a/server-rs/src/metrics.rs b/server-rs/src/metrics.rs
new file mode 100644
index 0000000..46ddf04
--- /dev/null
+++ b/server-rs/src/metrics.rs
@@ -0,0 +1,99 @@
+use axum::body::Body;
+use axum::extract::Request;
+use axum::http::StatusCode;
+use axum::middleware::Next;
+use axum::response::{IntoResponse, Response};
+use metrics::{counter, gauge, histogram};
+use metrics_exporter_prometheus::{PrometheusBuilder, PrometheusHandle};
+use std::time::Instant;
+
+/// Initialize the Prometheus metrics exporter and return a handle for rendering metrics.
+pub fn init_metrics() -> PrometheusHandle {
+    PrometheusBuilder::new()
+        .install_recorder()
+        .expect("Failed to install Prometheus recorder")
+}
+
+/// Middleware to track HTTP request metrics.
+pub async fn track_metrics(request: Request<Body>, next: Next) -> Response {
+    let path = request.uri().path().to_string();
+    let method = request.method().to_string();
+
+    // Skip metrics endpoint itself to avoid recursion
+    if path == "/metrics" {
+        return next.run(request).await;
+    }
+
+    let start = Instant::now();
+    let response = next.run(request).await;
+    let duration = start.elapsed();
+
+    let status = response.status().as_u16().to_string();
+
+    // Normalize path for metrics (avoid high cardinality from dynamic segments)
+    let normalized_path = normalize_path(&path);
+
+    // Record metrics
+    histogram!("http_request_duration_seconds", "method" => method.clone(), "path" => normalized_path.clone(), "status" => status.clone())
+        .record(duration.as_secs_f64());
+
+    counter!("http_requests_total", "method" => method, "path" => normalized_path, "status" => status)
+        .increment(1);
+
+    response
+}
+
+/// Normalize paths to avoid high cardinality from dynamic segments.
+fn normalize_path(path: &str) -> String {
+    if path.starts_with("/api/tiles/") && !path.ends_with("style.json") {
+        return "/api/tiles/:z/:x/:y".to_string();
+    }
+    path.to_string()
+}
+
+/// Handler for the /metrics endpoint.
+pub async fn metrics_handler(handle: PrometheusHandle) -> impl IntoResponse {
+    // Update process metrics before rendering
+    update_process_metrics();
+
+    match handle.render() {
+        output if !output.is_empty() => (StatusCode::OK, output),
+        _ => (StatusCode::INTERNAL_SERVER_ERROR, "Failed to render metrics".to_string()),
+    }
+}
+
+/// Update process-level metrics (memory, etc.)
+fn update_process_metrics() {
+    #[cfg(target_os = "linux")]
+    {
+        if let Ok(status) = std::fs::read_to_string("/proc/self/status") {
+            for line in status.lines() {
+                if let Some(value) = line.strip_prefix("VmRSS:") {
+                    if let Some(kb) = parse_kb(value) {
+                        gauge!("process_resident_memory_bytes").set((kb * 1024) as f64);
+                    }
+                } else if let Some(value) = line.strip_prefix("VmSize:") {
+                    if let Some(kb) = parse_kb(value) {
+                        gauge!("process_virtual_memory_bytes").set((kb * 1024) as f64);
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[cfg(target_os = "linux")]
+fn parse_kb(value: &str) -> Option<u64> {
+    value
+        .trim()
+        .strip_suffix(" kB")
+        .or_else(|| value.trim().strip_suffix("kB"))
+        .and_then(|num| num.trim().parse().ok())
+}
+
+/// Record a custom gauge for data loading (call at startup).
+pub fn record_data_stats(property_count: usize, poi_count: usize, postcode_count: usize) {
+    gauge!("data_properties_loaded").set(property_count as f64);
+    gauge!("data_pois_loaded").set(poi_count as f64);
+    gauge!("data_postcodes_loaded").set(postcode_count as f64);
+}