From 09057984bf39d4e37506deaa5726099c0c6d89b9 Mon Sep 17 00:00:00 2001
From: Jakob Ackermann <jakob.ackermann@overleaf.com>
Date: Tue, 20 May 2025 11:26:00 +0100
Subject: [PATCH] [clsi] mark VM as unhealthy when detecting of-of-disk
 condition (#25721)

* [clsi] shed load when detecting out-of-disk condition

* [clsi] mark VM as unhealthy when detecting of-of-disk condition

GitOrigin-RevId: 25cda6785c0d973f50ec6206bee389804f35917e
---
 services/clsi/app.js                          | 14 +++++++---
 .../clsi/app/js/ProjectPersistenceManager.js  | 26 +++++++++++++++++--
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/services/clsi/app.js b/services/clsi/app.js
index 8de9d89b9b..872f612d9c 100644
--- a/services/clsi/app.js
+++ b/services/clsi/app.js
@@ -249,6 +249,9 @@ app.get('/health_check', function (req, res) {
   if (Settings.processTooOld) {
     return res.status(500).json({ processTooOld: true })
   }
+  if (ProjectPersistenceManager.isAnyDiskCriticalLow()) {
+    return res.status(500).json({ diskCritical: true })
+  }
   smokeTest.sendLastResult(res)
 })
 
@@ -296,9 +299,14 @@ const loadTcpServer = net.createServer(function (socket) {
     }
 
     const freeLoad = availableWorkingCpus - currentLoad
-    const freeLoadPercentage = Math.round(
-      (freeLoad / availableWorkingCpus) * 100
-    )
+    let freeLoadPercentage = Math.round((freeLoad / availableWorkingCpus) * 100)
+    if (ProjectPersistenceManager.isAnyDiskCriticalLow()) {
+      freeLoadPercentage = 0
+    }
+    if (ProjectPersistenceManager.isAnyDiskLow()) {
+      freeLoadPercentage = freeLoadPercentage / 2
+    }
+
     if (
       Settings.internal.load_balancer_agent.allow_maintenance &&
       freeLoadPercentage <= 0
diff --git a/services/clsi/app/js/ProjectPersistenceManager.js b/services/clsi/app/js/ProjectPersistenceManager.js
index e96a4591c3..41cdd07f4d 100644
--- a/services/clsi/app/js/ProjectPersistenceManager.js
+++ b/services/clsi/app/js/ProjectPersistenceManager.js
@@ -22,6 +22,9 @@ const fs = require('node:fs')
 // projectId -> timestamp mapping.
 const LAST_ACCESS = new Map()
 
+let ANY_DISK_LOW = false
+let ANY_DISK_CRITICAL_LOW = false
+
 async function collectDiskStats() {
   const paths = [
     Settings.path.compilesDir,
@@ -30,6 +33,8 @@ async function collectDiskStats() {
   ]
 
   const diskStats = {}
+  let anyDiskLow = false
+  let anyDiskCriticalLow = false
   for (const path of paths) {
     try {
       const { blocks, bavail, bsize } = await fs.promises.statfs(path)
@@ -45,10 +50,16 @@ async function collectDiskStats() {
       })
       const lowDisk = diskAvailablePercent < 10
       diskStats[path] = { stats, lowDisk }
+
+      const criticalLowDisk = diskAvailablePercent < 3
+      anyDiskLow = anyDiskLow || lowDisk
+      anyDiskCriticalLow = anyDiskCriticalLow || criticalLowDisk
     } catch (err) {
       logger.err({ err, path }, 'error getting disk usage')
     }
   }
+  ANY_DISK_LOW = anyDiskLow
+  ANY_DISK_CRITICAL_LOW = anyDiskCriticalLow
   return diskStats
 }
 
@@ -70,11 +81,22 @@ async function refreshExpiryTimeout() {
       break
     }
   }
+  Metrics.gauge(
+    'project_persistence_expiry_timeout',
+    ProjectPersistenceManager.EXPIRY_TIMEOUT
+  )
 }
 
 module.exports = ProjectPersistenceManager = {
   EXPIRY_TIMEOUT: Settings.project_cache_length_ms || oneDay * 2.5,
 
+  isAnyDiskLow() {
+    return ANY_DISK_LOW
+  },
+  isAnyDiskCriticalLow() {
+    return ANY_DISK_CRITICAL_LOW
+  },
+
   promises: {
     refreshExpiryTimeout,
   },
@@ -125,12 +147,12 @@ module.exports = ProjectPersistenceManager = {
       )
     })
 
-    // Collect disk stats frequently to have them ready the next time /metrics is scraped (60s +- jitter).
+    // Collect disk stats frequently to have them ready the next time /metrics is scraped (60s +- jitter) or every 5th scrape of the load agent (3s +- jitter).
     setInterval(() => {
       collectDiskStats().catch(err => {
         logger.err({ err }, 'low level error collecting disk stats')
       })
-    }, 50_000)
+    }, 15_000)
   },
 
   markProjectAsJustAccessed(projectId, callback) {