hcq/MaxScale
hcq/MaxScale
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Change strict_multi_stmt default value

Browse Source 
The default value for strict_multi_stmt prevents compound statements and
atomic multi-statement commands from being executed without completely
disabling load balancing. As the new default value will have no practical
effect on all correct uses of readwritesplit, this is a relatively safe
thing to change.
This commit is contained in:
Markus Mäkelä 2017-12-20 23:50:07 +02:00
parent 9062c31865
commit d4aeca0d24
3 changed files with 29 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
Documentation/Release-Notes/MaxScale-2.2.1-Release-Notes.md
View File

@ -50,6 +50,21 @@ root@host:~# maxscale --user=root ...
The default value of the configuration parameter `detect_standalone_master` has
been changed from `false` to `true`.
### ReadWritesplit
The default value of `strict_multi_stmt` was changed to `false` to make
usage of atomic compound statements and multi-statement queries less
restrictive and to align it with the default value of `strict_sp_calls`.
Most cases where the functionality of `strict_multi_stmt` was triggered
were cases where the added safety of locking a session to the master did
more harm than it did good.
The only case where `strict_multi_stmt` should be enabled is when a
multi-statement or a compound statement modifies the state of the
session. This is not a good practice and a change in the client side
behavior is advised.
## Dropped Features
## New Features

24
Documentation/Routers/ReadWriteSplit.md
View File

@ -220,21 +220,23 @@ router_options=master_accept_reads=true
### `strict_multi_stmt`
When a client executes a multi-statement query, all queries after that will be
routed to the master to guarantee a consistent session state. This behavior can
be controlled with the **`strict_multi_stmt`** router option. This option is
enabled by default.
This option is disabled by default since MaxScale 2.2.1. In older versions, this
option was enabled by default.
If set to false, queries are routed normally after a multi-statement query.
When a client executes a multi-statement query, it will be treated as if it were
a DML statement and routed to the master. If the option is enabled, all queries
after a multi-statement query will be routed to the master to guarantee a
consistent session state.
**Warning:** this can cause false data to be read from the slaves if the
multi-statement query modifies the session state. Only disable the strict mode
if you know that no changes to the session state will be made inside the
multi-statement queries.
If the feature is disabled, queries are routed normally after a multi-statement
query.
**Warning:** Enable the strict mode only if you know that the clients will send
statements that cause inconsistencies in the session state.
```
# Disable strict multi-statement mode
router_options=strict_multi_stmt=false
# Enable strict multi-statement mode
router_options=strict_multi_stmt=true
```
### `strict_sp_calls`

2
server/modules/routing/readwritesplit/readwritesplit.cc
View File

@ -1432,7 +1432,7 @@ MXS_MODULE *MXS_CREATE_MODULE()
{"retry_failed_reads", MXS_MODULE_PARAM_BOOL, "true"},
{"disable_sescmd_history", MXS_MODULE_PARAM_BOOL, "true"},
{"max_sescmd_history", MXS_MODULE_PARAM_COUNT, "0"},
{"strict_multi_stmt", MXS_MODULE_PARAM_BOOL, "true"},
{"strict_multi_stmt", MXS_MODULE_PARAM_BOOL, "false"},
{"strict_sp_calls", MXS_MODULE_PARAM_BOOL, "false"},
{"master_accept_reads", MXS_MODULE_PARAM_BOOL, "false"},
{"connection_keepalive", MXS_MODULE_PARAM_COUNT, "0"},