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MXS-2273 Update release notes regarding draining

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TODO: This much explanation in the release notes is a bit too
much, the beef should be moved somewhere else and the release
notes simply refer to that.
This commit is contained in:
Johan Wikman 2019-01-28 11:38:59 +02:00
parent 8e59f4efbd
commit 05b650ed91
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1
Documentation/Changelog.md
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@ -4,6 +4,7 @@
* Names starting with `@@` are reserved for use by MaxScale.
* Names can no longer contain whitespace.
* Servers can now be drained.
For more details, please refer to:

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Documentation/Release-Notes/MaxScale-2.4.0-Release-Notes.md
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@ -23,6 +23,46 @@ rejected and cause the startup of MaxScale to fail.
## New Features
### Servers can be drained
It is now possible to drain a server, which means that existing
connections to the server can continue to be used but new connections
are no longer created to the server.
In the output of `maxctrl`, the fact that a server is being drained
is visible in the `State` column as the value `Being Drained`.
```
┌─────────┬─────────────────┬──────┬─────────────┬───────────────────────────────┬───────┐
│ Server │ Address │ Port │ Connections │ State │ GTID │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server1 │ 192.168.121.159 │ 3306 │ 2 │ Master, Running │ 0-1-6 │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server2 │ 192.168.121.80 │ 3306 │ 1 │ Being Drained, Slave, Running │ 0-1-6 │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server3 │ 192.168.121.122 │ 3306 │ 2 │ Slave, Running │ 0-1-6 │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server4 │ 192.168.121.144 │ 3306 │ 2 │ Slave, Running │ 0-1-6 │
└─────────┴─────────────────┴──────┴─────────────┴───────────────────────────────┴───────┘
```
A server is set in the _being drained_ state the same way as it is
set in the _maintenance_ state:
```
$ maxctrl set server Server2 drain
```
Note that although the state is displayed as `Being Drained`, when setting
and clearing the state, the word `drain` is used.
Note that the full implication of draining a server depends upon
both on the role of the server and on the router being used, and its
configuration.
For instance, if readwritesplit is used and the server being drained
is a slave, then from a client's perspective there will be no difference;
readwritesplit will simply not use that server. However, if the server
being drained is the master, then it will not be possible to connect
unless `master_failure_mode` has been set to something else but the
default `fail_instantly`.
## Bug fixes
[Here is a list of bugs fixed in MaxScale 2.4.0.](https://jira.mariadb.org/issues/?jql=project%20%3D%20MXS%20AND%20issuetype%20%3D%20Bug%20AND%20status%20%3D%20Closed%20AND%20fixVersion%20%3D%202.4.0)