From f2251388ed3af0a564c0fbac9abe4934ef4dbf72 Mon Sep 17 00:00:00 2001
From: Neel Shah <neel.shah@sentry.io>
Date: Thu, 28 Nov 2024 12:00:31 +0100
Subject: [PATCH] Add mutex sync to SessionFlusher aggregates (#2469)

---
 CHANGELOG.md                              |  2 ++
 sentry-ruby/lib/sentry/session_flusher.rb | 12 ++++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 49d11bda1..6a88e9d8c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,8 @@
 - Fix `send_default_pii` handling in rails controller spans [#2443](https://github.com/getsentry/sentry-ruby/pull/2443)
   - Fixes [#2438](https://github.com/getsentry/sentry-ruby/issues/2438)
 - Fix `RescuedExceptionInterceptor` to handle an empty configuration [#2428](https://github.com/getsentry/sentry-ruby/pull/2428)
+- Add mutex sync to `SessionFlusher` aggregates [#2469](https://github.com/getsentry/sentry-ruby/pull/2469)
+  - Fixes [#2468](https://github.com/getsentry/sentry-ruby/issues/2468)
 
 ## 5.21.0
 
diff --git a/sentry-ruby/lib/sentry/session_flusher.rb b/sentry-ruby/lib/sentry/session_flusher.rb
index f992a3b20..8f0510832 100644
--- a/sentry-ruby/lib/sentry/session_flusher.rb
+++ b/sentry-ruby/lib/sentry/session_flusher.rb
@@ -10,6 +10,7 @@ def initialize(configuration, client)
       @pending_aggregates = {}
       @release = configuration.release
       @environment = configuration.environment
+      @mutex = Mutex.new
 
       log_debug("[Sessions] Sessions won't be captured without a valid release") unless @release
     end
@@ -18,7 +19,6 @@ def flush
       return if @pending_aggregates.empty?
 
       @client.capture_envelope(pending_envelope)
-      @pending_aggregates = {}
     end
 
     alias_method :run, :flush
@@ -42,11 +42,15 @@ def init_aggregates(aggregation_key)
     end
 
     def pending_envelope
-      envelope = Envelope.new
+      aggregates = @mutex.synchronize do
+        aggregates = @pending_aggregates.values
+        @pending_aggregates = {}
+        aggregates
+      end
 
+      envelope = Envelope.new
       header = { type: "sessions" }
-      payload = { attrs: attrs, aggregates: @pending_aggregates.values }
-
+      payload = { attrs: attrs, aggregates: aggregates }
       envelope.add_item(header, payload)
       envelope
     end