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ericyan merged 4 commits into from
Aug 3, 2026
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docs: clarify replica selection requirements for --throttle-control-replicas #1745

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`docs: clarify replica selection requirements for --throttle-control-…
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docs: condense throttle-control-replicas note per review feedback
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3 changes: 3 additions & 0 deletions doc/throttle.md
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Expand Up @@ -24,12 +24,15 @@ Otherwise you may specify your own list of replica servers you wish it to observ

- `--throttle-control-replicas`: list of replicas you explicitly wish `gh-ost` to check for replication lag.

- _Note:_ these hosts should be actual replicas within the migrated table's replication chain — pointing this at unrelated hosts can report healthy lag while leaving your real downstream replicas unmonitored.

Example: `--throttle-control-replicas=myhost1.com:3306,myhost2.com,myhost3.com:3307`
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- `--max-lag-millis`: maximum allowed lag; any controlled replica lagging more than this value will cause throttling to kick in. When all control replicas have smaller lag than indicated, operation resumes.

Note that you may dynamically change both `--max-lag-millis` and the `throttle-control-replicas` list via [interactive commands](interactive-commands.md)


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#### Status thresholds

- `--max-load`: list of metrics and threshold values; topping the threshold of any will cause throttler to kick in.
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