Add draw_timeline binary (#2688)

Cargo.lock

@@ -2170,6 +2170,7 @@ dependencies = [
  "serde_json",
  "serde_with",
  "signal-hook",
+ "svg_fmt",
  "tar",
  "tempfile",
  "thiserror",
@@ -3461,6 +3462,12 @@ version = "2.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
 
+[[package]]
+name = "svg_fmt"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fb1df15f412ee2e9dfc1c504260fa695c1c3f10fe9f4a6ee2d2184d7d6450e2"
+
 [[package]]
 name = "symbolic-common"
 version = "8.8.0"

Dockerfile

@@ -44,7 +44,7 @@ COPY . .
 # Show build caching stats to check if it was used in the end.
 # Has to be the part of the same RUN since cachepot daemon is killed in the end of this RUN, losing the compilation stats.
 RUN set -e \
-&& mold -run cargo build --bin pageserver --bin pageserver_binutils --bin safekeeper --bin proxy --locked --release \
+&& mold -run cargo build --bin pageserver --bin pageserver_binutils --bin draw_timeline_dir --bin safekeeper --bin proxy --locked --release \
     && cachepot -s
 
 # Build final image
@@ -65,6 +65,7 @@ RUN set -e \
 
 COPY --from=build --chown=neon:neon /home/nonroot/target/release/pageserver          /usr/local/bin
 COPY --from=build --chown=neon:neon /home/nonroot/target/release/pageserver_binutils /usr/local/bin
+COPY --from=build --chown=neon:neon /home/nonroot/target/release/draw_timeline_dir   /usr/local/bin
 COPY --from=build --chown=neon:neon /home/nonroot/target/release/safekeeper          /usr/local/bin
 COPY --from=build --chown=neon:neon /home/nonroot/target/release/proxy               /usr/local/bin
 

pageserver/Cargo.toml

@@ -67,6 +67,7 @@ remote_storage = { path = "../libs/remote_storage" }
 workspace_hack = { version = "0.1", path = "../workspace_hack" }
 close_fds = "0.3.2"
 walkdir = "2.3.2"
+svg_fmt = "0.4.1"
 
 [dev-dependencies]
 criterion = "0.4"

pageserver/src/bin/draw_timeline_dir.rs

@@ -0,0 +1,150 @@
+//! A tool for visualizing the arrangement of layerfiles within a timeline.
+//!
+//! It reads filenames from stdin and prints a svg on stdout. The image is a plot in
+//! page-lsn space, where every delta layer is a rectangle and every image layer is a
+//! thick line. Legend:
+//! - The x axis (left to right) represents page index.
+//! - The y axis represents LSN, growing upwards.
+//!
+//! Coordinates in both axis are compressed for better readability.
+//! (see https://medium.com/algorithms-digest/coordinate-compression-2fff95326fb)
+//!
+//! Example use:
+//! ```
+//! $ cd test_output/test_pgbench\[neon-45-684\]/repo/tenants/$TENANT/timelines/$TIMELINE
+//! $ ls | grep "__" | cargo run --release --bin draw_timeline_dir > out.svg
+//! $ firefox out.svg
+//! ```
+//!
+//! This API was chosen so that we can easily work with filenames extracted from ssh,
+//! or from pageserver log files.
+//!
+//! TODO Consider shipping this as a grafana panel plugin:
+//!      https://grafana.com/tutorials/build-a-panel-plugin/
+use anyhow::Result;
+use pageserver::repository::Key;
+use std::cmp::Ordering;
+use std::io::{self, BufRead};
+use std::{
+    collections::{BTreeMap, BTreeSet},
+    ops::Range,
+};
+use svg_fmt::{rectangle, rgb, BeginSvg, EndSvg, Fill, Stroke};
+use utils::{lsn::Lsn, project_git_version};
+
+project_git_version!(GIT_VERSION);
+
+// Map values to their compressed coordinate - the index the value
+// would have in a sorted and deduplicated list of all values.
+fn build_coordinate_compression_map<T: Ord + Copy>(coords: Vec<T>) -> BTreeMap<T, usize> {
+    let set: BTreeSet<T> = coords.into_iter().collect();
+
+    let mut map: BTreeMap<T, usize> = BTreeMap::new();
+    for (i, e) in set.iter().enumerate() {
+        map.insert(*e, i);
+    }
+
+    map
+}
+
+fn parse_filename(name: &str) -> (Range<Key>, Range<Lsn>) {
+    let split: Vec<&str> = name.split("__").collect();
+    let keys: Vec<&str> = split[0].split('-').collect();
+    let mut lsns: Vec<&str> = split[1].split('-').collect();
+    if lsns.len() == 1 {
+        lsns.push(lsns[0]);
+    }
+
+    let keys = Key::from_hex(keys[0]).unwrap()..Key::from_hex(keys[1]).unwrap();
+    let lsns = Lsn::from_hex(lsns[0]).unwrap()..Lsn::from_hex(lsns[1]).unwrap();
+    (keys, lsns)
+}
+
+fn main() -> Result<()> {
+    // Parse layer filenames from stdin
+    let mut ranges: Vec<(Range<Key>, Range<Lsn>)> = vec![];
+    let stdin = io::stdin();
+    for line in stdin.lock().lines() {
+        let range = parse_filename(&line.unwrap());
+        ranges.push(range);
+    }
+
+    // Collect all coordinates
+    let mut keys: Vec<Key> = vec![];
+    let mut lsns: Vec<Lsn> = vec![];
+    for (keyr, lsnr) in &ranges {
+        keys.push(keyr.start);
+        keys.push(keyr.end);
+        lsns.push(lsnr.start);
+        lsns.push(lsnr.end);
+    }
+
+    // Analyze
+    let key_map = build_coordinate_compression_map(keys);
+    let lsn_map = build_coordinate_compression_map(lsns);
+
+    // Initialize stats
+    let mut num_deltas = 0;
+    let mut num_images = 0;
+
+    // Draw
+    let stretch = 3.0; // Stretch out vertically for better visibility
+    println!(
+        "{}",
+        BeginSvg {
+            w: key_map.len() as f32,
+            h: stretch * lsn_map.len() as f32
+        }
+    );
+    for (keyr, lsnr) in &ranges {
+        let key_start = *key_map.get(&keyr.start).unwrap();
+        let key_end = *key_map.get(&keyr.end).unwrap();
+        let key_diff = key_end - key_start;
+        let lsn_max = lsn_map.len();
+
+        if key_start >= key_end {
+            panic!("Invalid key range {}-{}", key_start, key_end);
+        }
+
+        let lsn_start = *lsn_map.get(&lsnr.start).unwrap();
+        let lsn_end = *lsn_map.get(&lsnr.end).unwrap();
+
+        let mut lsn_diff = (lsn_end - lsn_start) as f32;
+        let mut fill = Fill::None;
+        let mut margin = 0.05 * lsn_diff; // Height-dependent margin to disambiguate overlapping deltas
+        let mut lsn_offset = 0.0;
+
+        // Fill in and thicken rectangle if it's an
+        // image layer so that we can see it.
+        match lsn_start.cmp(&lsn_end) {
+            Ordering::Less => num_deltas += 1,
+            Ordering::Equal => {
+                num_images += 1;
+                lsn_diff = 0.3;
+                lsn_offset = -lsn_diff / 2.0;
+                margin = 0.05;
+                fill = Fill::Color(rgb(0, 0, 0));
+            }
+            Ordering::Greater => panic!("Invalid lsn range {}-{}", lsn_start, lsn_end),
+        }
+
+        println!(
+            "    {}",
+            rectangle(
+                key_start as f32 + stretch * margin,
+                stretch * (lsn_max as f32 - (lsn_end as f32 - margin - lsn_offset)),
+                key_diff as f32 - stretch * 2.0 * margin,
+                stretch * (lsn_diff - 2.0 * margin)
+            )
+            .fill(fill)
+            .stroke(Stroke::Color(rgb(0, 0, 0), 0.1))
+            .border_radius(0.4)
+        );
+    }
+    println!("{}", EndSvg);
+
+    eprintln!("num_images: {}", num_images);
+    eprintln!("num_deltas: {}", num_deltas);
+
+    Ok(())
+}