From 371a0a82b669a8f4edf7449e1921a80ef2584a50 Mon Sep 17 00:00:00 2001
From: nicktrn <55853254+nicktrn@users.noreply.github.com>
Date: Mon, 24 Aug 2026 11:15:24 +0100
Subject: [PATCH] chore(hosting): trim clickhouse config comments

Rationale for the config belongs in the PR, not the artifact. The one claim kept was also inaccurate: processors_profile_log and asynchronous_insert_log already ship TTLs in the pinned image, so the tables are not all unbounded.

Drops the .server-changes entry: hosting-only changes are not covered by the webapp/supervisor areas, and a docker vs helm split is a separate discussion.
---
 .../hosting-clickhouse-system-logs.md           |  6 ------
 hosting/docker/clickhouse/override.xml          | 17 +++--------------
 hosting/docker/clickhouse/users-override.xml    |  8 +-------
 3 files changed, 4 insertions(+), 27 deletions(-)
 delete mode 100644 .server-changes/hosting-clickhouse-system-logs.md

diff --git a/.server-changes/hosting-clickhouse-system-logs.md b/.server-changes/hosting-clickhouse-system-logs.md
deleted file mode 100644
index dc6724232..000000000
--- a/.server-changes/hosting-clickhouse-system-logs.md
+++ /dev/null
@@ -1,6 +0,0 @@
----
-area: hosting
-type: fix
----
-
-Self-hosted ClickHouse now disables its unbounded internal telemetry tables and keeps query/error logs on a bounded retention, fixing runaway CPU and memory usage on the recommended machine size. Existing self-hosted deployments must drop the previously written disabled log tables separately to reclaim disk.
diff --git a/hosting/docker/clickhouse/override.xml b/hosting/docker/clickhouse/override.xml
index f9088054a..967426d47 100644
--- a/hosting/docker/clickhouse/override.xml
+++ b/hosting/docker/clickhouse/override.xml
@@ -10,14 +10,7 @@
     <mark_cache_size>524288000</mark_cache_size> <!-- 500MB -->
     <concurrent_threads_soft_limit_num>1</concurrent_threads_soft_limit_num>
 
-    <!-- ClickHouse's own telemetry tables have no TTL and grow without bound; on the
-         recommended webapp machine size their background merges eventually stop fitting
-         in memory and are retried forever (there is no backoff for failed merges),
-         pinning the CPU and ultimately failing the webapp's own inserts (#4343).
-         The ClickHouse low-RAM guide recommends disabling exactly these tables:
-         https://clickhouse.com/docs/operations/tips
-         Same list as the dev stack (docker/config/clickhouse-disable-system-logs.xml),
-         extended with the newer log tables. -->
+    <!-- ClickHouse's own telemetry, too heavy for the recommended machine size -->
     <metric_log remove="1"/>
     <asynchronous_metric_log remove="1"/>
     <part_log remove="1"/>
@@ -34,10 +27,7 @@
     <opentelemetry_span_log remove="1"/>
     <query_views_log remove="1"/>
 
-    <!-- Keep query_log and error_log (small and useful for debugging), but bounded.
-         A config-level TTL survives log-table recreation, unlike ALTER ... MODIFY TTL.
-         Note: ClickHouse renames the existing table to *_log_<N> when this changes;
-         drop those leftovers to reclaim disk. -->
+    <!-- A config-level ttl survives log-table recreation, unlike ALTER ... MODIFY TTL -->
     <query_log>
         <ttl>event_date + INTERVAL 7 DAY DELETE</ttl>
     </query_log>
@@ -45,6 +35,5 @@
         <ttl>event_date + INTERVAL 30 DAY DELETE</ttl>
     </error_log>
 
-    <!-- Profile settings do NOT live here: config.d is silently ignored for them.
-         See users-override.xml, mounted under users.d. -->
+    <!-- Profile settings only apply from users.d, see users-override.xml -->
 </clickhouse>
diff --git a/hosting/docker/clickhouse/users-override.xml b/hosting/docker/clickhouse/users-override.xml
index a3964125b..13bcb2aec 100644
--- a/hosting/docker/clickhouse/users-override.xml
+++ b/hosting/docker/clickhouse/users-override.xml
@@ -1,17 +1,11 @@
 <clickhouse>
     <profiles>
         <default>
-            <!-- Low-memory settings for the recommended webapp machine size. These were
-                 previously in config.d/override.xml where profile settings are silently
-                 ignored — they only take effect from the users config tree (#4343). -->
             <max_block_size>8192</max_block_size>
             <max_download_threads>1</max_download_threads>
             <input_format_parallel_parsing>0</input_format_parallel_parsing>
             <output_format_parallel_formatting>0</output_format_parallel_formatting>
-            <!-- The memory/query profilers sample stacks into system.trace_log
-                 (a Memory/MemoryPeak sample every 4 MB allocated, by default) — the main
-                 firehose that fills it. trace_log is disabled in override.xml; turn the
-                 samplers off too so they don't burn CPU producing discarded rows. -->
+            <!-- Samplers only feed trace_log, which is disabled -->
             <memory_profiler_step>0</memory_profiler_step>
             <memory_profiler_sample_probability>0</memory_profiler_sample_probability>
             <query_profiler_real_time_period_ns>0</query_profiler_real_time_period_ns>