Reading replication lag via _changelog_ table, also on control replicas #347
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Contributor
Author
jonahberquist
approved these changes
Jan 4, 2017
Contributor
jonahberquist
left a comment
There was a problem hiding this comment.
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
Outdated
| 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. | ||
|
|
||
| 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. |
Contributor
There was a problem hiding this comment.
s/and no longer needed/and is no longer needed/
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.