monitor: compute image age from zfs creation property (#6)

monitor/src/get-snapshot-creation.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env zsh
+# usage: get-snapshot-creation.sh <pool/path/to/zvol@snapshot>
+set -euo pipefail -o bsdecho
+dataset_and_snapshot=$1; shift
+
+zfs get -Hpo value creation "$dataset_and_snapshot"

monitor/src/main.rs

@@ -403,10 +403,11 @@ fn monitor_thread() -> eyre::Result<()> {
                 busy,
                 excess_idle,
                 wanted,
+                image_age,
             },
         ) in profile_runner_counts.iter()
         {
-            info!("profile {key}: {healthy}/{target} healthy runners ({idle} idle, {reserved} reserved, {busy} busy, {started_or_crashed} started or crashed, {excess_idle} excess idle, {wanted} wanted)");
+            info!("profile {key}: image age {image_age:?}, {healthy}/{target} healthy runners ({idle} idle, {reserved} reserved, {busy} busy, {started_or_crashed} started or crashed, {excess_idle} excess idle, {wanted} wanted)");
         }
         for (_id, runner) in runners.iter() {
             runner.log_info();

monitor/src/profile.rs

@@ -1,13 +1,17 @@
-use std::process::Command;
+use std::{
+    process::Command,
+    time::{Duration, SystemTime, UNIX_EPOCH},
+};
 
-use jane_eyre::eyre;
+use jane_eyre::eyre::{self, Context};
 use serde::{Deserialize, Serialize};
 use tracing::{debug, info};
 
 use crate::{
     data::get_profile_data_path,
     libvirt::update_screenshot,
     runner::{Runner, Runners, Status},
+    zfs::snapshot_creation_time_unix,
     DOTENV,
 };
 
@@ -30,6 +34,7 @@ pub struct RunnerCounts {
     pub busy: usize,
     pub excess_idle: usize,
     pub wanted: usize,
+    pub image_age: Option<Duration>,
 }
 
 impl Profile {
@@ -96,6 +101,7 @@ impl Profile {
             busy: self.busy_runner_count(runners),
             excess_idle: self.excess_idle_runner_count(runners),
             wanted: self.wanted_runner_count(runners),
+            image_age: self.image_age().ok().flatten(),
         }
     }
 
@@ -166,6 +172,26 @@ impl Profile {
         }
     }
 
+    pub fn image_age(&self) -> eyre::Result<Option<Duration>> {
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .wrap_err("Failed to get current time")?;
+        let creation_time =
+            match snapshot_creation_time_unix(&self.base_vm_name, &self.base_image_snapshot) {
+                Ok(result) => result,
+                Err(error) => {
+                    debug!(
+                        self.base_vm_name,
+                        ?error,
+                        "Failed to get snapshot creation time"
+                    );
+                    return Ok(None);
+                }
+            };
+
+        Ok(Some(now - creation_time))
+    }
+
     pub fn update_screenshot(&self) {
         if let Err(error) = self.try_update_screenshot() {
             debug!(

monitor/src/settings.rs

@@ -20,7 +20,7 @@ pub struct Dotenv {
     pub github_api_suffix: String,
     pub libvirt_prefix: String,
     pub zfs_prefix: String,
-    // SERVO_CI_ZFS_CLONE_PREFIX not used
+    pub zfs_clone_prefix: String,
     pub monitor_data_path: Option<String>,
     // SERVO_CI_ZVOL_BLOCK_DEVICE_TIMEOUT not used
     pub monitor_poll_interval: Duration,
@@ -54,6 +54,7 @@ impl Dotenv {
             github_api_suffix: env_string("SERVO_CI_GITHUB_API_SUFFIX"),
             libvirt_prefix: env_string("SERVO_CI_LIBVIRT_PREFIX"),
             zfs_prefix: env_string("SERVO_CI_ZFS_PREFIX"),
+            zfs_clone_prefix: env_string("SERVO_CI_ZFS_CLONE_PREFIX"),
             monitor_data_path: env_option_string("SERVO_CI_MONITOR_DATA_PATH"),
             monitor_poll_interval: env_duration_secs("SERVO_CI_MONITOR_POLL_INTERVAL"),
             api_cache_timeout: env_duration_secs("SERVO_CI_API_CACHE_TIMEOUT"),

monitor/src/zfs.rs

@@ -1,9 +1,12 @@
 use core::str;
-use std::process::{Command, Stdio};
+use std::{
+    process::{Command, Stdio},
+    time::Duration,
+};
 
-use jane_eyre::eyre::{self, Context};
+use jane_eyre::eyre::{self, bail, eyre, Context, OptionExt};
 
-use crate::DOTENV;
+use crate::{shell::SHELL, DOTENV};
 
 pub fn list_runner_volumes() -> eyre::Result<Vec<String>> {
     let output = Command::new("../list-runner-volumes.sh")
@@ -26,3 +29,40 @@ pub fn list_runner_volumes() -> eyre::Result<Vec<String>> {
 
     Ok(result.collect())
 }
+
+pub fn snapshot_creation_time_unix(zvol_name: &str, snapshot_name: &str) -> eyre::Result<Duration> {
+    let dataset_and_snapshot = format!("{}/{zvol_name}@{snapshot_name}", DOTENV.zfs_clone_prefix);
+    let output = SHELL
+        .lock()
+        .map_err(|e| eyre!("Mutex poisoned: {e:?}"))?
+        .run(
+            include_str!("get-snapshot-creation.sh"),
+            [dataset_and_snapshot],
+        )?
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()?
+        .wait_with_output()?;
+    if !output.status.success() {
+        let stdout = str::from_utf8(&output.stdout)
+            .to_owned()
+            .map_err(|_| output.stdout.clone());
+        let stderr = str::from_utf8(&output.stderr)
+            .to_owned()
+            .map_err(|_| output.stderr.clone());
+        bail!(
+            "Command exited with status {}: stdout {:?}, stderr {:?}",
+            output.status,
+            stdout,
+            stderr
+        );
+    }
+    let result = str::from_utf8(&output.stdout)
+        .wrap_err("Failed to decode UTF-8")?
+        .strip_suffix('\n')
+        .ok_or_eyre("Failed to strip trailing newline")?
+        .parse::<u64>()
+        .wrap_err("Failed to parse as u64")?;
+
+    Ok(Duration::from_secs(result))
+}