migrated multi host connection pool from godropbox package

removing unneeded dependencies, which involved etcd versions.

weed/wdclient/net2/connection_pool.go

@@ -0,0 +1,97 @@
+package net2
+
+import (
+	"net"
+	"time"
+)
+
+type ConnectionOptions struct {
+	// The maximum number of connections that can be active per host at any
+	// given time (A non-positive value indicates the number of connections
+	// is unbounded).
+	MaxActiveConnections int32
+
+	// The maximum number of idle connections per host that are kept alive by
+	// the connection pool.
+	MaxIdleConnections uint32
+
+	// The maximum amount of time an idle connection can alive (if specified).
+	MaxIdleTime *time.Duration
+
+	// This limits the number of concurrent Dial calls (there's no limit when
+	// DialMaxConcurrency is non-positive).
+	DialMaxConcurrency int
+
+	// Dial specifies the dial function for creating network connections.
+	// If Dial is nil, net.DialTimeout is used, with timeout set to 1 second.
+	Dial func(network string, address string) (net.Conn, error)
+
+	// This specifies the now time function.  When the function is non-nil, the
+	// connection pool will use the specified function instead of time.Now to
+	// generate the current time.
+	NowFunc func() time.Time
+
+	// This specifies the timeout for any Read() operation.
+	// Note that setting this to 0 (i.e. not setting it) will make
+	// read operations block indefinitely.
+	ReadTimeout time.Duration
+
+	// This specifies the timeout for any Write() operation.
+	// Note that setting this to 0 (i.e. not setting it) will make
+	// write operations block indefinitely.
+	WriteTimeout time.Duration
+}
+
+func (o ConnectionOptions) getCurrentTime() time.Time {
+	if o.NowFunc == nil {
+		return time.Now()
+	} else {
+		return o.NowFunc()
+	}
+}
+
+// A generic interface for managed connection pool.  All connection pool
+// implementations must be threadsafe.
+type ConnectionPool interface {
+	// This returns the number of active connections that are on loan.
+	NumActive() int32
+
+	// This returns the highest number of active connections for the entire
+	// lifetime of the pool.
+	ActiveHighWaterMark() int32
+
+	// This returns the number of idle connections that are in the pool.
+	NumIdle() int
+
+	// This associates (network, address) to the connection pool; afterwhich,
+	// the user can get connections to (network, address).
+	Register(network string, address string) error
+
+	// This dissociate (network, address) from the connection pool;
+	// afterwhich, the user can no longer get connections to
+	// (network, address).
+	Unregister(network string, address string) error
+
+	// This returns the list of registered (network, address) entries.
+	ListRegistered() []NetworkAddress
+
+	// This gets an active connection from the connection pool.  The connection
+	// will remain active until one of the following is called:
+	//  1. conn.ReleaseConnection()
+	//  2. conn.DiscardConnection()
+	//  3. pool.Release(conn)
+	//  4. pool.Discard(conn)
+	Get(network string, address string) (ManagedConn, error)
+
+	// This releases an active connection back to the connection pool.
+	Release(conn ManagedConn) error
+
+	// This discards an active connection from the connection pool.
+	Discard(conn ManagedConn) error
+
+	// Enter the connection pool into lame duck mode.  The connection pool
+	// will no longer return connections, and all idle connections are closed
+	// immediately (including active connections that are released back to the
+	// pool afterward).
+	EnterLameDuckMode()
+}