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MXS_WORKER is an abstraction of a worker aka worker thread. It has a pipe whose read descriptor is added to the worker/thread specific poll set and a write descriptor used for sending messages to the worker. The worker exposes a function mxs_worker_post_message using which messages can be sent to the worker. These messages can be sent from any thread but will be delivered on the thread dedicated for the worker. To illustrate how it works, maxadmin has been provided with a new command "ping workers" that sends a message to every worker, which then logs a message to the log. Additional refactoring are needed, since there currently are overlaps and undesirable interactions between the poll mechanism, the thread mechanism and the worker mechanism. This is visible currently, for instance, by it not being possible to shut down MaxScale. The reason is that the workers should be shut down first, then the poll mechanism and finally the threads. The shutdown need to be arranged so that a shutdown message is sent to the workers who then cause the polling loop to exit, which will cause the threads to exit. That can be arranged cleanly by making poll_waitevents() a "method" of the worker, which implies that the poll set becomes a "member variable" of the worker. To be continued.
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.
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.