v.21.4New Features

Add slowdowns_count column to system.clusters for hedged requests

Official CH changelog text
Add new column slowdowns_count to system.clusters. When using hedged requests, it shows how many times we switched to another replica because this replica was responding slowly. Also show actual value of errors_count in system.clusters. #21480 (Kruglov Pavel).
Added a new column slowdowns_count to the system.clusters table to track the number of times ClickHouse switched to another replica due to slow responses when using hedged requests. Additionally, the errors_count column now shows the actual number of errors in system.clusters.

Why it matters

This feature provides better visibility into replica performance and error occurrences during hedged requests, helping users diagnose and monitor cluster behavior related to slow replicas and failures.

How to use it

Users can query the system.clusters table to view the new slowdowns_count and updated errors_count columns. No additional configuration is required; the data is available when hedged requests are enabled.

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