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Published: May 22, 2017 License: BSD-3-Clause Imports: 6 Imported by: 0



Package pools provides functionality to manage and reuse resources like connections.



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var (
	// ErrClosed is returned if ResourcePool is used when it's closed.
	ErrClosed = errors.New("resource pool is closed")

	// ErrTimeout is returned if a resource get times out.
	ErrTimeout = errors.New("resource pool timed out")


This section is empty.


type Factory

type Factory func() (Resource, error)

Factory is a function that can be used to create a resource.

type IDPool

type IDPool struct {
	// contains filtered or unexported fields

IDPool is used to ensure that the set of IDs in use concurrently never contains any duplicates. The IDs start at 1 and increase without bound, but will never be larger than the peak number of concurrent uses.

IDPool's Get() and Set() methods can be used concurrently.

func NewIDPool

func NewIDPool() *IDPool

NewIDPool creates and initializes an IDPool.

func (*IDPool) Get

func (pool *IDPool) Get() (id uint32)

Get returns an ID that is unique among currently active users of this pool.

func (*IDPool) Put

func (pool *IDPool) Put(id uint32)

Put recycles an ID back into the pool for others to use. Putting back a value or 0, or a value that is not currently "checked out", will result in a panic because that should never happen except in the case of a programming error.

type Numbered

type Numbered struct {
	// contains filtered or unexported fields

Numbered allows you to manage resources by tracking them with numbers. There are no interface restrictions on what you can track.

func NewNumbered

func NewNumbered() *Numbered

func (*Numbered) Get

func (nu *Numbered) Get(id int64, purpose string) (val interface{}, err error)

Get locks the resource for use. It accepts a purpose as a string. If it cannot be found, it returns a "not found" error. If in use, it returns a "in use: purpose" error.

func (*Numbered) GetAll

func (nu *Numbered) GetAll() (vals []interface{})

GetAll returns the list of all resources in the pool.

func (*Numbered) GetIdle

func (nu *Numbered) GetIdle(timeout time.Duration, purpose string) (vals []interface{})

GetIdle returns a list of resurces that have been idle for longer than timeout, and locks them. It does not return any resources that are already locked.

func (*Numbered) GetOutdated

func (nu *Numbered) GetOutdated(age time.Duration, purpose string) (vals []interface{})

GetOutdated returns a list of resources that are older than age, and locks them. It does not return any resources that are already locked.

func (*Numbered) Put

func (nu *Numbered) Put(id int64)

Put unlocks a resource for someone else to use.

func (*Numbered) Register

func (nu *Numbered) Register(id int64, val interface{}) error

Register starts tracking a resource by the supplied id. It does not lock the object. It returns an error if the id already exists.

func (*Numbered) Size

func (nu *Numbered) Size() (size int64)

func (*Numbered) StatsJSON

func (nu *Numbered) StatsJSON() string

func (*Numbered) Unregister

func (nu *Numbered) Unregister(id int64)

Unregiester forgets the specified resource. If the resource is not present, it's ignored.

func (*Numbered) WaitForEmpty

func (nu *Numbered) WaitForEmpty()

WaitForEmpty returns as soon as the pool becomes empty

type Resource

type Resource interface {

Resource defines the interface that every resource must provide. Thread synchronization between Close() and IsClosed() is the responsibility of the caller.

type ResourcePool

type ResourcePool struct {
	// contains filtered or unexported fields

ResourcePool allows you to use a pool of resources.

func NewResourcePool

func NewResourcePool(factory Factory, capacity, maxCap int, idleTimeout time.Duration) *ResourcePool

NewResourcePool creates a new ResourcePool pool. capacity is the number of active resources in the pool: there can be up to 'capacity' of these at a given time. maxCap specifies the extent to which the pool can be resized in the future through the SetCapacity function. You cannot resize the pool beyond maxCap. If a resource is unused beyond idleTimeout, it's discarded. An idleTimeout of 0 means that there is no timeout.

func (*ResourcePool) Available

func (rp *ResourcePool) Available() int64

Available returns the number of currently unused resources.

func (*ResourcePool) Capacity

func (rp *ResourcePool) Capacity() int64

Capacity returns the capacity.

func (*ResourcePool) Close

func (rp *ResourcePool) Close()

Close empties the pool calling Close on all its resources. You can call Close while there are outstanding resources. It waits for all resources to be returned (Put). After a Close, Get is not allowed.

func (*ResourcePool) Get

func (rp *ResourcePool) Get(ctx context.Context) (resource Resource, err error)

Get will return the next available resource. If capacity has not been reached, it will create a new one using the factory. Otherwise, it will wait till the next resource becomes available or a timeout. A timeout of 0 is an indefinite wait.

func (*ResourcePool) IdleTimeout

func (rp *ResourcePool) IdleTimeout() time.Duration

IdleTimeout returns the idle timeout.

func (*ResourcePool) IsClosed

func (rp *ResourcePool) IsClosed() (closed bool)

IsClosed returns true if the resource pool is closed.

func (*ResourcePool) MaxCap

func (rp *ResourcePool) MaxCap() int64

MaxCap returns the max capacity.

func (*ResourcePool) Put

func (rp *ResourcePool) Put(resource Resource)

Put will return a resource to the pool. For every successful Get, a corresponding Put is required. If you no longer need a resource, you will need to call Put(nil) instead of returning the closed resource. The will eventually cause a new resource to be created in its place.

func (*ResourcePool) SetCapacity

func (rp *ResourcePool) SetCapacity(capacity int) error

SetCapacity changes the capacity of the pool. You can use it to shrink or expand, but not beyond the max capacity. If the change requires the pool to be shrunk, SetCapacity waits till the necessary number of resources are returned to the pool. A SetCapacity of 0 is equivalent to closing the ResourcePool.

func (*ResourcePool) SetIdleTimeout

func (rp *ResourcePool) SetIdleTimeout(idleTimeout time.Duration)

SetIdleTimeout sets the idle timeout.

func (*ResourcePool) Stats

func (rp *ResourcePool) Stats() (capacity, available, maxCap, waitCount int64, waitTime, idleTimeout time.Duration)

Stats returns the stats.

func (*ResourcePool) StatsJSON

func (rp *ResourcePool) StatsJSON() string

StatsJSON returns the stats in JSON format.

func (*ResourcePool) WaitCount

func (rp *ResourcePool) WaitCount() int64

WaitCount returns the total number of waits.

func (*ResourcePool) WaitTime

func (rp *ResourcePool) WaitTime() time.Duration

WaitTime returns the total wait time.

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