From 330baa6cc39bffca1159e5eb05a834f03d757de9 Mon Sep 17 00:00:00 2001
From: "Zaiming (Stone) Shi" <zmstone@gmail.com>
Date: Fri, 19 Jan 2024 17:44:49 +0100
Subject: [PATCH] docs: add changelog for #12326

---
 changes/ce/feat-12326.en.md | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 changes/ce/feat-12326.en.md

diff --git a/changes/ce/feat-12326.en.md b/changes/ce/feat-12326.en.md
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+Add session registration history.
+
+Setting config `broker.session_history_retain` allows EMQX to keep track of expired sessions for the retained period.
+
+API `GET /api/v5/sessions_count?since=1705682238` can be called to count the cluster-wide sessions which were alive (unexpired) since the provided timestamp (UNIX epoch at seconds precision).
+
+A new gauge `cluster_sessions` is added to the metrics collection. Exposed to prometheus as
+
+```
+# TYPE emqx_cluster_sessions_count gauge
+emqx_cluster_sessions_count 1234
+```
+
+The counter can only be used for an approximate estimation as the collection and calculations are async.