8.12
Resource Pool
| (require data/pool) | package: resource-pool-lib |
This module provides a generic blocking resource pool implementation. Useful for managing things such as database and HTTP connections.
procedure
v : any/c
procedure
(make-pool make-resource [ destroy-resource #:max-size max-size #:idle-ttl idle-ttl]) → pool? make-resource : (-> any/c) destroy-resource : (-> any/c void?) = void max-size : exact-positive-integer? = 8
idle-ttl : (or/c +inf.0 exact-positive-integer?) = (* 3600 1000)
The make-pool function returns a new resource pool
that lazily creates new resources using make-resource. The
resulting pool can contain up to #:max-size resources.
The #:idle-ttl argument controls how long a resource can remain idle before destroy-resource is applied to it and it is removed from the pool.
procedure
(call-with-pool-resource p f #:timeout timeout) → any/c p : pool? f : (-> any/c any) timeout : (or/c #f exact-nonnegative-integer?)
Leases a resource from p and applies f to it,
returning the leased value back into the pool once f
finishes executing.
The #:timeout behaves the same as in pool-take!, except that if the timeout is hit, an exn:fail:pool? is raised and #f is not executed.
procedure
(pool-take! p [timeout]) → (or/c #f any/c)
p : pool? timeout : (or/c #f exact-nonnegative-integer?) = #f
Waits for a resource to become available and then leases it from
p. If the timeout argument is provided, the function
will block for at most timeout milliseconds before returning.
On timeout, #f is returned.
procedure
(pool-release! p v) → void?
p : pool? v : any/c
procedure
(pool-close! p) → void?
p : pool?
Closes p. If pool-close is called before
all of the leased resources have been returned to the pool, an
exn:fail:pool? error is raised and the pool remains open.
Raises an error if p has already been closed.
procedure
(exn:fail:pool? v) → boolean?
v : any/c