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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 callingget
followed byput
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
bind(database)
Associate the pool with a database.
Parameter | |
---|---|
Name | Description |
database |
Database
database used by the pool to create sessions when needed. |
clear
clear()
Delete all sessions in the pool.
get
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
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
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. |