Reading replication lag via _changelog_ table, also on control replicas#347
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shlomi-noach merged 8 commits intomasterfrom Jan 4, 2017
Merged
Reading replication lag via _changelog_ table, also on control replicas#347shlomi-noach merged 8 commits intomasterfrom
shlomi-noach merged 8 commits intomasterfrom
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jonahberquist
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Jan 4, 2017
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Nice work! I like that this will allow folks to use subsecond replication delay throttling without having to have a third-party subsecond heartbeat mechanism.
I noticed a missing is in one of the docs file changes, but I'm hitting approve here anyway 👍
doc/subsecond-lag.md
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| You can explicitly define how frequently will `gh-ost` inject heartbeat events, via `heartbeat-interval-millis`. You should set `heartbeat-interval-millis <= max-lag-millis`. It still works if not, but loses granularity and effect. | ||
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| On the `throttle-control-replicas`, `gh-ost` only issues SQL queries, and does not attempt to read the binary log stream. Perhaps those other replicas don't have binary logs in the first place. | ||
| In earlier versions, the `--throttle-control-replicas` list was subjected to `1` second resolution or to 3rd party heartbeat injections such as `pt-heartbeat`. This is no longer the case. The argument `--replication-lag-query` has been deprecated and no longer needed. |
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s/and no longer needed/and is no longer needed/
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Storyline: #346
This PR removes the use of
--replication-lag-queryand uniformly reads replication lag via changelog table, base ongh-ost's internal heartbeat mechanism -- also on the throttle control replicas.