From f791809614d377660bbd4dd0eb0a409564d41f89 Mon Sep 17 00:00:00 2001
From: Eric Mc Sween <5454374+emcsween@users.noreply.github.com>
Date: Thu, 16 Jan 2025 07:40:58 -0500
Subject: [PATCH] Merge pull request #22871 from
 overleaf/em-history-flush-metrics

History flush metrics

GitOrigin-RevId: eb8b357427942e9816ad92ccd46c0dd8a65ab939
---
 services/project-history/app/js/Metrics.js        | 15 +++++++++++++++
 .../project-history/app/js/UpdatesProcessor.js    |  7 +++++++
 2 files changed, 22 insertions(+)
 create mode 100644 services/project-history/app/js/Metrics.js

diff --git a/services/project-history/app/js/Metrics.js b/services/project-history/app/js/Metrics.js
new file mode 100644
index 0000000000..b51518963b
--- /dev/null
+++ b/services/project-history/app/js/Metrics.js
@@ -0,0 +1,15 @@
+// @ts-check
+
+import { prom } from '@overleaf/metrics'
+
+export const historyFlushDurationSeconds = new prom.Histogram({
+  name: 'history_flush_duration_seconds',
+  help: 'Duration of a history flush in seconds',
+  buckets: [0.05, 0.1, 0.2, 0.3, 0.5, 1, 2, 5, 10],
+})
+
+export const historyFlushQueueSize = new prom.Histogram({
+  name: 'history_flush_queue_size',
+  help: 'Size of the queue during history flushes',
+  buckets: prom.exponentialBuckets(1, 2, 10),
+})
diff --git a/services/project-history/app/js/UpdatesProcessor.js b/services/project-history/app/js/UpdatesProcessor.js
index df9ccf11ea..ad0dbc816b 100644
--- a/services/project-history/app/js/UpdatesProcessor.js
+++ b/services/project-history/app/js/UpdatesProcessor.js
@@ -15,6 +15,7 @@ import * as WebApiManager from './WebApiManager.js'
 import * as SyncManager from './SyncManager.js'
 import * as Versions from './Versions.js'
 import * as Errors from './Errors.js'
+import * as Metrics from './Metrics.js'
 import { Profiler } from './Profiler.js'
 
 const keys = Settings.redis.lock.key_schema
@@ -61,6 +62,7 @@ export function getRawUpdates(projectId, batchSize, callback) {
 
 // Process all updates for a project, only check project-level information once
 export function processUpdatesForProject(projectId, callback) {
+  const startTimeMs = Date.now()
   LockManager.runWithLock(
     keys.projectHistoryLock({ project_id: projectId }),
     (extendLock, releaseLock) => {
@@ -76,6 +78,11 @@ export function processUpdatesForProject(projectId, callback) {
         OError.tag(error)
       }
       ErrorRecorder.record(projectId, queueSize, error, callback)
+      if (queueSize > 0) {
+        const duration = (Date.now() - startTimeMs) / 1000
+        Metrics.historyFlushDurationSeconds.observe(duration)
+        Metrics.historyFlushQueueSize.observe(queueSize)
+      }
       // clear the timestamp in the background if the queue is now empty
       RedisManager.clearDanglingFirstOpTimestamp(projectId, () => {})
     }