migrated multi host connection pool from godropbox package

removing unneeded dependencies, which involved etcd versions.

weed/wdclient/resource_pool/multi_resource_pool.go

@@ -0,0 +1,200 @@
+package resource_pool
+
+import (
+	"fmt"
+	"sync"
+
+	"errors"
+)
+
+// A resource pool implementation that manages multiple resource location
+// entries.  The handles to each resource location entry acts independently.
+// For example "tcp localhost:11211" could act as memcache
+// shard 0 and "tcp localhost:11212" could act as memcache shard 1.
+type multiResourcePool struct {
+	options Options
+
+	createPool func(Options) ResourcePool
+
+	rwMutex    sync.RWMutex
+	isLameDuck bool // guarded by rwMutex
+	// NOTE: the locationPools is guarded by rwMutex, but the pool entries
+	// are not.
+	locationPools map[string]ResourcePool
+}
+
+// This returns a MultiResourcePool, which manages multiple
+// resource location entries.  The handles to each resource location
+// entry acts independently.
+//
+// When createPool is nil, NewSimpleResourcePool is used as default.
+func NewMultiResourcePool(
+	options Options,
+	createPool func(Options) ResourcePool) ResourcePool {
+
+	if createPool == nil {
+		createPool = NewSimpleResourcePool
+	}
+
+	return &multiResourcePool{
+		options:       options,
+		createPool:    createPool,
+		rwMutex:       sync.RWMutex{},
+		isLameDuck:    false,
+		locationPools: make(map[string]ResourcePool),
+	}
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) NumActive() int32 {
+	total := int32(0)
+
+	p.rwMutex.RLock()
+	defer p.rwMutex.RUnlock()
+
+	for _, pool := range p.locationPools {
+		total += pool.NumActive()
+	}
+	return total
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) ActiveHighWaterMark() int32 {
+	high := int32(0)
+
+	p.rwMutex.RLock()
+	defer p.rwMutex.RUnlock()
+
+	for _, pool := range p.locationPools {
+		val := pool.ActiveHighWaterMark()
+		if val > high {
+			high = val
+		}
+	}
+	return high
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) NumIdle() int {
+	total := 0
+
+	p.rwMutex.RLock()
+	defer p.rwMutex.RUnlock()
+
+	for _, pool := range p.locationPools {
+		total += pool.NumIdle()
+	}
+	return total
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) Register(resourceLocation string) error {
+	if resourceLocation == "" {
+		return errors.New("Registering invalid resource location")
+	}
+
+	p.rwMutex.Lock()
+	defer p.rwMutex.Unlock()
+
+	if p.isLameDuck {
+		return fmt.Errorf(
+			"Cannot register %s to lame duck resource pool",
+			resourceLocation)
+	}
+
+	if _, inMap := p.locationPools[resourceLocation]; inMap {
+		return nil
+	}
+
+	pool := p.createPool(p.options)
+	if err := pool.Register(resourceLocation); err != nil {
+		return err
+	}
+
+	p.locationPools[resourceLocation] = pool
+	return nil
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) Unregister(resourceLocation string) error {
+	p.rwMutex.Lock()
+	defer p.rwMutex.Unlock()
+
+	if pool, inMap := p.locationPools[resourceLocation]; inMap {
+		_ = pool.Unregister("")
+		pool.EnterLameDuckMode()
+		delete(p.locationPools, resourceLocation)
+	}
+	return nil
+}
+
+func (p *multiResourcePool) ListRegistered() []string {
+	p.rwMutex.RLock()
+	defer p.rwMutex.RUnlock()
+
+	result := make([]string, 0, len(p.locationPools))
+	for key, _ := range p.locationPools {
+		result = append(result, key)
+	}
+
+	return result
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) Get(
+	resourceLocation string) (ManagedHandle, error) {
+
+	pool := p.getPool(resourceLocation)
+	if pool == nil {
+		return nil, fmt.Errorf(
+			"%s is not registered in the resource pool",
+			resourceLocation)
+	}
+	return pool.Get(resourceLocation)
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) Release(handle ManagedHandle) error {
+	pool := p.getPool(handle.ResourceLocation())
+	if pool == nil {
+		return errors.New(
+			"Resource pool cannot take control of a handle owned " +
+				"by another resource pool")
+	}
+
+	return pool.Release(handle)
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) Discard(handle ManagedHandle) error {
+	pool := p.getPool(handle.ResourceLocation())
+	if pool == nil {
+		return errors.New(
+			"Resource pool cannot take control of a handle owned " +
+				"by another resource pool")
+	}
+
+	return pool.Discard(handle)
+}
+
+// See ResourcePool for documentation.
+func (p *multiResourcePool) EnterLameDuckMode() {
+	p.rwMutex.Lock()
+	defer p.rwMutex.Unlock()
+
+	p.isLameDuck = true
+
+	for _, pool := range p.locationPools {
+		pool.EnterLameDuckMode()
+	}
+}
+
+func (p *multiResourcePool) getPool(resourceLocation string) ResourcePool {
+	p.rwMutex.RLock()
+	defer p.rwMutex.RUnlock()
+
+	if pool, inMap := p.locationPools[resourceLocation]; inMap {
+		return pool
+	}
+	return nil
+}