From 1d5f29885bacbaa931cbcc275d406ed1ef6f61bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20Adel=C3=B6w?= <freben@gmail.com>
Date: Mon, 5 Aug 2024 14:11:40 +0200
Subject: [PATCH] avoid excessive error listeners
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Signed-off-by: Fredrik Adelöw <freben@gmail.com>
---
 .changeset/tasty-ads-rescue.md                |  5 ++++
 .../src/entrypoints/cache/CacheManager.ts     | 28 +++++++++----------
 2 files changed, 19 insertions(+), 14 deletions(-)
 create mode 100644 .changeset/tasty-ads-rescue.md

diff --git a/.changeset/tasty-ads-rescue.md b/.changeset/tasty-ads-rescue.md
new file mode 100644
index 0000000000..d522856bdd
--- /dev/null
+++ b/.changeset/tasty-ads-rescue.md
@@ -0,0 +1,5 @@
+---
+'@backstage/backend-defaults': patch
+---
+
+Avoid excessive numbers of error listeners on cache clients
diff --git a/packages/backend-defaults/src/entrypoints/cache/CacheManager.ts b/packages/backend-defaults/src/entrypoints/cache/CacheManager.ts
index 89fabfe977..873bcf9648 100644
--- a/packages/backend-defaults/src/entrypoints/cache/CacheManager.ts
+++ b/packages/backend-defaults/src/entrypoints/cache/CacheManager.ts
@@ -111,23 +111,10 @@ export class CacheManager {
     return {
       getClient: (defaultOptions = {}) => {
         const clientFactory = (options: CacheServiceOptions) => {
-          const concreteClient = this.getClientWithTtl(
+          return this.getClientWithTtl(
             pluginId,
             options.defaultTtl ?? this.defaultTtl,
           );
-
-          // Always provide an error handler to avoid stopping the process.
-          concreteClient.on('error', (err: Error) => {
-            // In all cases, just log the error.
-            this.logger?.error('Failed to create cache client', err);
-
-            // Invoke any custom error handler if provided.
-            if (typeof this.errorHandler === 'function') {
-              this.errorHandler(err);
-            }
-          });
-
-          return concreteClient;
         };
 
         return new DefaultCacheClient(
@@ -149,11 +136,17 @@ export class CacheManager {
     return (pluginId, defaultTtl) => {
       if (!store) {
         store = new KeyvRedis(this.connection);
+        // Always provide an error handler to avoid stopping the process
+        store.on('error', (err: Error) => {
+          this.logger?.error('Failed to create redis cache client', err);
+          this.errorHandler?.(err);
+        });
       }
       return new Keyv({
         namespace: pluginId,
         ttl: defaultTtl,
         store,
+        emitErrors: false,
         useRedisSets: this.useRedisSets,
       });
     };
@@ -165,10 +158,16 @@ export class CacheManager {
     return (pluginId, defaultTtl) => {
       if (!store) {
         store = new KeyvMemcache(this.connection);
+        // Always provide an error handler to avoid stopping the process
+        store.on('error', (err: Error) => {
+          this.logger?.error('Failed to create memcache cache client', err);
+          this.errorHandler?.(err);
+        });
       }
       return new Keyv({
         namespace: pluginId,
         ttl: defaultTtl,
+        emitErrors: false,
         store,
       });
     };
@@ -180,6 +179,7 @@ export class CacheManager {
       new Keyv({
         namespace: pluginId,
         ttl: defaultTtl,
+        emitErrors: false,
         store,
       });
   }