resourcepool

Documentation

Overview

Package resourcepool provides for managing shared resource pools.

Package resourcepool may be used by other packages to manage shared resources (e.g. the lib/connpool package uses this package to help manage connection pools). A typical programming pattern is:

pool := New(...)
cr0 := pool.Create(...)
cr1 := pool.Create(...)
go func() {
	for ... {
		c := cr0.Get(...)
		defer c.Put()
		if err { c.Release() }
	}
}()
go func() {
	for ... {
		c := cr1.Get(...)
		defer c.Put()
		if err { c.Release() }
	}
}()

This pattern ensures Get and Put are always matched, and if there is an error, Release releases the underlying resource so that a subsequent Get creates a new underlying resource.

It is resonable to create one goroutine for each resource, since the Get methods will block, waiting for available resources.

Index

• Variables
• func MakeImmediateCanceler() <-chan struct{}
• type AllocateReleaser
• type Pool
  • func New(max uint, metricsSubDirname string) *Pool
  • func (pool *Pool) Create(allocateReleaser AllocateReleaser) *Resource
• type Resource
  • func (resource *Resource) Get(cancelChannel <-chan struct{}) error
  • func (resource *Resource) Put()
  • func (resource *Resource) Release() error
  • func (resource *Resource) ScheduleRelease() error

Variables

var (
	ErrorPutTimeout            = errors.New("timed out waiting for put")
	ErrorResourceLimitExceeded = errors.New("resource limit exceeded")
)

Functions

func MakeImmediateCanceler

func MakeImmediateCanceler() <-chan struct{}

MakeImmediateCanceler returns a channel that may be passed to the Resource.Get method for callers that do not want to wait for a resource.

Types

type AllocateReleaser

type AllocateReleaser interface {
	Allocate() error
	Release() error
}

AllocateReleaser defines a type that can be used to allocate and release resources.

type Pool

type Pool struct {
	// contains filtered or unexported fields
}

Pool groups and manages a set of resources.

func New

func New(max uint, metricsSubDirname string) *Pool

New returns a new resource Pool. The maximum number of resources that can be allocated concurrently is specified by max.

func (*Pool) Create

func (pool *Pool) Create(allocateReleaser AllocateReleaser) *Resource

Create returns a new Resource for the pool. An unlimted number of resources may be created. The mechanism to specify how to allocate and release underlying resources is given by allocateReleaser. Create does not allocate resources.

type Resource

type Resource struct {
	// contains filtered or unexported fields
}

Resource is a container for an underlying resource.

func (*Resource) Get

func (resource *Resource) Get(cancelChannel <-chan struct{}) error

Get attempts to allocate an underlying resource. It calls the Allocate method of the AllocateReleaser passed to the Create method. Get will wait until a resource is available or a message is received on cancelChannel. If cancelChannel is nil then Get will wait indefinitely until a resource is available. If the wait is cancelled then Get will return ErrorResourceLimitExceeded. The resource is considered in use until a later call to Put or Release.

func (*Resource) Put

func (resource *Resource) Put()

Put will free the resource, indicating that it is not currently needed. It may be internally released later if required to free limited resources. If Put is called after Release, no action is taken (this is a safe operation and is commonly used in some programming patterns).

func (*Resource) Release

func (resource *Resource) Release() error

Release will release the resource, immediately calling the Release method of the AllocateReleaser and returning its return value.

func (*Resource) ScheduleRelease

func (resource *Resource) ScheduleRelease() error

ScheduleRelease will immediately release the resource if it is not currently in use, otherwise it will schedule the resource to be released after the next Put.