18. API: AsyncConnectionPool Objects

18.1. AsyncConnectionPool Class

class oracledb.AsyncConnectionPool(dsn: str | None = None, *, params: PoolParams | None = None, cache_name: str | None = None, **kwargs)

Constructor for creating a connection pool.

An AsyncConnectionPool object should be created with oracledb.create_pool_async().

This object is an extension to the DB API definition.

Added in version 2.0.0.

Note

AsyncConnectionPool objects are only supported in python-oracledb Thin mode.

18.2. AsyncConnectionPool Methods

AsyncConnectionPool.acquire(user: str | None = None, password: str | None = None, cclass: str | None = None, purity: int = oracledb.PURITY_DEFAULT, tag: str | None = None, matchanytag: bool = False, shardingkey: list | None = None, supershardingkey: list | None = None) → AsyncConnection

Acquires a connection from the pool and returns an asynchronous connection object.

If the pool is homogeneous, the user and password parameters cannot be specified. If they are, an exception will be raised.

The cclass parameter, if specified, should be a string corresponding to the connection class for Database Resident Connection Pooling (DRCP).

The purity parameter is expected to be one of PURITY_NEW, PURITY_SELF, or PURITY_DEFAULT.

The tag, matchanytag, shardingkey, and supershardingkey parameters are ignored in python-oracledb Thin mode.

async AsyncConnectionPool.close(force: bool = False) → None

Closes the pool now, rather than when the last reference to it is released, which makes it unusable for further work.

If any connections have been acquired and not released back to the pool, this method will fail unless the force parameter is set to True.

async AsyncConnectionPool.drop(connection: Connection) → None: Drops the connection from the pool which is useful if the connection is no longer usable (such as when the session is killed).

async AsyncConnectionPool.release(connection: AsyncConnection, tag: str | None = None) → None

Releases the connection back to the pool now. The connection will be unusable from this point forward. An Error exception will be raised if any operation is attempted with the connection. Any cursors or LOBs created by the connection will also be marked unusable and an Error exception will be raised if any operation is attempted with them.

The tag parameter is ignored in python-oracledb Thin mode.

Note

Asynchronous connections are not automatically closed at the end of scope. This is different to synchronous connection behavior. Asynchronous connections should either be explicitly released, or have been initially created via a context manager with statement.

18.3. AsyncConnectionPool Attributes

property AsyncConnectionPool.busy: int: This read-only attribute returns the number of connections currently acquired.

property AsyncConnectionPool.dsn: str: This read-only attribute returns the TNS entry of the database to which a connection has been established.

property AsyncConnectionPool.getmode: PoolGetMode: This read-write attribute determines how connections are returned from the pool. If POOL_GETMODE_FORCEGET is specified, a new connection will be returned even if there are no free connections in the pool. POOL_GETMODE_NOWAIT will raise an exception if there are no free connections are available in the pool. If POOL_GETMODE_WAIT is specified and there are no free connections in the pool, the caller will wait until a free connection is available. POOL_GETMODE_TIMEDWAIT uses the value of wait_timeout to determine how long the caller should wait for a connection to become available before returning an error.

property AsyncConnectionPool.homogeneous: bool: This read-only boolean attribute indicates whether the pool is considered homogeneous or not. If the pool is not homogeneous, different authentication can be used for each connection acquired from the pool.

property AsyncConnectionPool.increment: int: This read-only attribute returns the number of connections that will be established when additional connections need to be created.

property AsyncConnectionPool.max: int: This read-only attribute returns the maximum number of connections that the pool can control.

property AsyncConnectionPool.max_lifetime_session: int: This read-write attribute is the maximum length of time (in seconds) that a pooled connection may exist since first being created. A value of 0 means there is no limit. Connections become candidates for termination when they are acquired or released back to the pool, and have existed for longer than max_lifetime_session seconds. Connections that are in active use will not be closed. In python-oracledb Thick mode, Oracle Client libraries 12.1 or later must be used and, prior to Oracle Client 21, cleanup only occurs when the pool is accessed.

property AsyncConnectionPool.max_sessions_per_shard: int: This read-write attribute returns the number of sessions that can be created per shard in the pool. Setting this attribute greater than zero specifies the maximum number of sessions in the pool that can be used for any given shard in a sharded database. This lets connections in the pool be balanced across the shards. A value of 0 will not set any maximum number of sessions for each shard. This attribute is only available in Oracle Client 18.3 and higher.

property AsyncConnectionPool.min: int: This read-only attribute returns the number of connections with which the connection pool was created and the minimum number of connections that will be controlled by the connection pool.

property AsyncConnectionPool.name: str: This read-only attribute returns the name assigned to the pool by Oracle.

property AsyncConnectionPool.opened: int: This read-only attribute returns the number of connections currently opened by the pool.

property AsyncConnectionPool.ping_interval: int: This read-write integer attribute specifies the pool ping interval in seconds. When a connection is acquired from the pool, a check is first made to see how long it has been since the connection was put into the pool. If this idle time exceeds ping_interval, then a round-trip ping to the database is performed. If the connection is unusable, it is discarded and a different connection is selected to be returned by acquire(). Setting ping_interval to a negative value disables pinging. Setting it to 0 forces a ping for every acquire() and is not recommended.

property AsyncConnectionPool.soda_metadata_cache: bool: This read-write boolean attribute returns whether the SODA metadata cache is enabled or not. Enabling the cache significantly improves the performance of methods SodaDatabase.createCollection() (when not specifying a value for the metadata parameter) and SodaDatabase.openCollection(). Note that the cache can become out of date if changes to the metadata of cached collections are made externally.

property AsyncConnectionPool.stmtcachesize: int

This read-write attribute specifies the size of the statement cache that will be used for connections obtained from the pool. Once a connection is created, that connection’s statement cache size can only be changed by setting the stmtcachesize attribute on the connection itself.

See Statement Caching for more information.

property AsyncConnectionPool.thin: bool: This read-only attribute returns a boolean indicating if python-oracledb is in Thin mode (True) or Thick mode (False).

property AsyncConnectionPool.timeout: int: This read-write attribute specifies the time (in seconds) after which idle connections will be terminated in order to maintain an optimum number of open connections. A value of 0 means that no idle connections are terminated. Note that in python-oracledb Thick mode with older Oracle Client Libraries, the termination only occurs when the pool is accessed.

property AsyncConnectionPool.username: str: This read-only attribute returns the name of the user which established the connection to the database.

property AsyncConnectionPool.wait_timeout: int: This read-write attribute specifies the time (in milliseconds) that the caller should wait for a connection to become available in the pool before returning with an error. This value is only used if the getmode parameter to oracledb.create_pool() was the value oracledb.POOL_GETMODE_TIMEDWAIT.