From c839380694d93239187ec064c1688d933ffbb1da Mon Sep 17 00:00:00 2001
From: Nikos Vasileiou <nikosv@transifex.com>
Date: Thu, 29 Feb 2024 12:50:05 +0200
Subject: [PATCH] Add jitter to autosync functionality

---
 config/defaults.yml  | 6 ++++++
 src/helpers/utils.js | 2 +-
 src/queue/worker.js  | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/config/defaults.yml b/config/defaults.yml
index 9de849e..1e06080 100644
--- a/config/defaults.yml
+++ b/config/defaults.yml
@@ -50,6 +50,12 @@ settings:
   # TX__SETTINGS__AUTOSYNC_MIN=15
   autosync_min: 60
 
+  # A jitter to add to autosync functionality to randomly
+  # distribute cache invalidations over time. Cache will automatically
+  # invalidate at lastUpdate + autosync_min + random(autosync_jitter_min)
+  # TX__SETTINGS__AUTOSYNC_JITTER_MIN=15
+  autosync_jitter_min: 30
+
   # Optionally, a whitelist of project tokens. Set this value if you need
   # to limit access to only a subset of Native Project Tokens, vs having
   # CDS cache everything. e.g.
diff --git a/src/helpers/utils.js b/src/helpers/utils.js
index 69ac046..8f95e66 100644
--- a/src/helpers/utils.js
+++ b/src/helpers/utils.js
@@ -66,7 +66,7 @@ async function routerCacheHelper(req, res, key, filter, syncFunc, ...syncFuncPar
           sentContent = true;
         }
         // check for auto refresh
-        if ((Date.now() - rdata.ts) >= autoSyncMSec) {
+        if ((Date.now() - (rdata.ts + (rdata.ts_jitter || 0))) >= autoSyncMSec) {
           addJob();
         }
         break;
diff --git a/src/queue/worker.js b/src/queue/worker.js
index 41b54da..77da115 100644
--- a/src/queue/worker.js
+++ b/src/queue/worker.js
@@ -10,6 +10,7 @@ const { sendToTelemetry } = require('../telemetry');
 const pullSuccessExpireSec = config.get('settings:pull_success_cache_min') * 60;
 const pullErrorExpireSec = config.get('settings:pull_error_cache_min') * 60;
 const jobStatusCacheSec = config.get('settings:job_status_cache_min') * 60;
+const autoSyncJitterMin = config.get('settings:autosync_jitter_min') * 1;
 
 /**
  * Pull content from API syncer job
@@ -40,6 +41,7 @@ async function syncerPull(job) {
       registry.set(`cache:${key}`, {
         status: 'success',
         ts: Date.now(),
+        ts_jitter: _.random(autoSyncJitterMin) * 60 * 1000,
         etag,
         location,
         cacheKey,
@@ -70,6 +72,7 @@ async function syncerPull(job) {
         registry.set(`cache:${key}`, {
           status: 'error',
           ts: Date.now(),
+          ts_jitter: _.random(autoSyncJitterMin) * 60 * 1000,
           statusCode,
           statusMessage,
         }, pullErrorExpireSec),