JUG Master DB Module

The master uses a MySQL database to keep track of the state of everything. InnoDB tables are used for high concurrency and robust transactional support. This module is used to run queries and make updates to the database.

For documentation on how to use the cursor object, see Python Database API 2.0.

The database schema describes the tables and columns in the database.

For multi-threaded applications, such as JugMasterRPC, the DB module manages a pool of connection objects. Each thread should lock/unlock a connection by calling AllocateConnectionForThread() and ReleaseConnection(). Otherwise, when a thread finishes, the automatically allocated connection will remain open and consume a slot in the connection pool, which may fill up and block creation of additional database connections.

Functions

Query(SQL="")

Return a cursor object suitable for reading from the database. If SQL is provided, call cursor.execute(SQL).

Update(SQL="")

Return a cursor object suitable for writing to the database. If SQL is provided, call cursor.execute(SQL).

Update_AutoRetryOnDeadlock(SQL)

Execute given SQL and retry until the operation succeeds whenever a deadlock condition happens, which is a case that should be expected whenever using InnoDB tables. Do not use this in the middle of a multi-step transaction. In that case, you need to catch DB.DeadlockError yourself and retry the whole transaction.

Quote(str)

Return a quoted SQL string value, with any special characters escaped.

AllocateConnectionForThread()

In a multi-threaded application with threads that are dynamically allocated and deallocated, each thread that uses the database should call this before accessing the database and then ReleaseConnection() to release its lock on the connection and allow another thread to use it.

ReleaseConnection(c)

Release this thread's claim to a connection returned by AllocateConnectionForThread().

Example 1

Example 2

Example 3