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Add changes to persistent connections to documentation

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The documentation now states that, starting with 2.1, the persistent
connections will reset the MySQL session state when they are taken into
use.
This commit is contained in:
Markus Makela
2016-11-01 11:20:34 +02:00
parent 57eb599769
commit d69025bfa6
2 changed files with 28 additions and 7 deletions
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23
Documentation/Tutorials/Administration-Tutorial.md
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@ -106,13 +106,22 @@ than `persistmaxtime` seconds. It was also be discarded if it has been disconne
by the back end server. Connections will be selected that match the user name and
protocol for the new request.
**Please note** that because persistent connections have previously been in use, they
may give a different environment from a fresh connection. For example, if the
previous use of the connection issued "use mydatabase" then this setting will be
carried over into the reuse of the same connection. For many applications this will
not be noticeable, since each request will assume that nothing has been set and
will issue fresh requests such as "use" to establish the desired configuration. In
exceptional cases this feature could be a problem.
Starting with the 2.1 version of MaxScale, when a MySQL protocol connection is
taken from the pool the backend protocol module resets the session state. This
allows persistent connections to be used with no functional limitations.
The session state is reset when the first outgoing network transmission is
done. This _lazy initialization_ of the persistent connections allows
MaxScale to take multiple new connections into use but only initialize the
ones that it actually needs.
**Please note** that in versions before 2.1 the persistent connections may give
a different environment when compared to a fresh connection. For example, if the
previous use of the connection issued a "USE mydatabase;" statement then this
setting will be carried over into the reuse of the same connection. For many
applications this will not be noticeable, since each request will assume that
nothing has been set and will issue fresh requests such as "USE" to establish
the desired configuration. In exceptional cases this feature could be a problem.
It is possible to have pools for as many servers as you wish, with configuration
values in each server section.