Class PingingPool (3.44.0)

PingingPool(
    size=10, default_timeout=10, ping_interval=3000, labels=None, database_role=None
)

Concrete session pool implementation:

Pre-allocates / creates a fixed number of sessions.
Sessions are used in "round-robin" order (LRU first).
"Pings" existing sessions in the background after a specified interval via an API call (session.ping()).
Blocks, with a timeout, when get is called on an empty pool. Raises after timing out.
Raises when put is called on a full pool. That error is never expected in normal practice, as users should be calling get followed by put whenever in need of a session.

The application is responsible for calling ping at appropriate times, e.g. from a background thread.

Parameters
Name	Description
`size`	`int` fixed pool size
`default_timeout`	`int` default timeout, in seconds, to wait for a returned session.
`ping_interval`	`int` interval at which to ping sessions.
`labels`	`dict (str -> str) or None` (Optional) user-assigned labels for sessions created by the pool.
`database_role`	`str` (Optional) user-assigned database_role for the session.

Methods

bind(database)

Associate the pool with a database.

Parameter
Name	Description
`database`	`Database` database used by the pool to create sessions when needed.

clear()

Delete all sessions in the pool.

get(timeout=None)

Check a session out from the pool.

Parameter
Name	Description
`timeout`	`int` seconds to block waiting for an available session

Exceptions
Type	Description
`queue.Empty	if the queue is empty.

Returns
Type	Description
`Session`	an existing session from the pool, or a newly-created session.

ping()

Refresh maybe-expired sessions in the pool.

This method is designed to be called from a background thread, or during the "idle" phase of an event loop.

put(session)

Return a session to the pool.

Never blocks: if the pool is full, raises.

Parameter
Name	Description
`session`	`Session` the session being returned.

Exceptions
Type	Description
`queue.Full	if the queue is full.