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The mapping from a canonical statement to the query classification result is maintained by the class QCInfoCache of which there exist an instance per thread. That way no locking is needed but the information will be cached multiple times (but that is a smaller price to pay). Currently the information is stored in a regular std::unordered_map, which means that the consumed amount of memory will just keep on growing unless the number of canonical statements used by clients happens to have an upper bound. The LRU cache (that provides means for putting a bound on the amount of memory used and number of items) used in the cache filter will be generalized and be taken into use here as well. The key is now the canonical statement itself, which means that a fair amount of memory will be used. To preserve memory it might make sense to use a hashed value instead, although that at least in principle opens up the possibility for unintended collisions. This feature will also be made configurable.
MaxScale by MariaDB Corporation
The MariaDB Corporation MaxScale is an intelligent proxy that allows forwarding of database statements to one or more database servers using complex rules, a semantic understanding of the database statements and the roles of the various servers within the backend cluster of databases.
MaxScale is designed to provide load balancing and high availability functionality transparently to the applications. In addition it provides a highly scalable and flexible architecture, with plugin components to support different protocols and routing decisions.
MaxScale is implemented in C and makes extensive use of the asynchronous I/O capabilities of the Linux operating system. The epoll system is used to provide the event driven framework for the input and output via sockets.
The protocols are implemented as external shared object modules which can be loaded at runtime. These modules support a fixed interface, communicating the entries points via a structure consisting of a set of function pointers. This structure is called the "module object".
The code that routes the queries to the database servers is also loaded as external shared objects and are referred to as routing modules.
An Google Group exists for MaxScale that can be used to discuss ideas, issues and communicate with the MaxScale community.
We're also on the #maria and #maxscale channels on FreeNode.
Please report all feature requests, improvements and bugs in the MariaDB Jira.
Documentation
For information about installing and using MaxScale, please refer to the documentation. The official documentation can be found on the MariaDB Knowledge Base.
- MariaDB MaxScale 2.1 Documentation
- MariaDB MaxScale 2.0 Documentation
- MariaDB MaxScale 1.4 Documentation
The module and configuration documentation can be found in the Documentation directory of the source tree.
Contributing Code
Read the Contributing page on the wiki for more information on how to do pull request and where to do them.