| /* |
| * |
| * Copyright 2014, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| */ |
| |
| package grpc |
| |
| import ( |
| "container/list" |
| "fmt" |
| "sync" |
| |
| "golang.org/x/net/context" |
| "google.golang.org/grpc/grpclog" |
| "google.golang.org/grpc/naming" |
| "google.golang.org/grpc/transport" |
| ) |
| |
| // Picker picks a Conn for RPC requests. |
| // This is EXPERIMENTAL and please do not implement your own Picker for now. |
| type Picker interface { |
| // Init does initial processing for the Picker, e.g., initiate some connections. |
| Init(cc *ClientConn) error |
| // Pick blocks until either a transport.ClientTransport is ready for the upcoming RPC |
| // or some error happens. |
| Pick(ctx context.Context) (transport.ClientTransport, error) |
| // PickAddr picks a peer address for connecting. This will be called repeated for |
| // connecting/reconnecting. |
| PickAddr() (string, error) |
| // State returns the connectivity state of the underlying connections. |
| State() (ConnectivityState, error) |
| // WaitForStateChange blocks until the state changes to something other than |
| // the sourceState. It returns the new state or error. |
| WaitForStateChange(ctx context.Context, sourceState ConnectivityState) (ConnectivityState, error) |
| // Close closes all the Conn's owned by this Picker. |
| Close() error |
| } |
| |
| // unicastPicker is the default Picker which is used when there is no custom Picker |
| // specified by users. It always picks the same Conn. |
| type unicastPicker struct { |
| target string |
| conn *Conn |
| } |
| |
| func (p *unicastPicker) Init(cc *ClientConn) error { |
| c, err := NewConn(cc) |
| if err != nil { |
| return err |
| } |
| p.conn = c |
| return nil |
| } |
| |
| func (p *unicastPicker) Pick(ctx context.Context) (transport.ClientTransport, error) { |
| return p.conn.Wait(ctx) |
| } |
| |
| func (p *unicastPicker) PickAddr() (string, error) { |
| return p.target, nil |
| } |
| |
| func (p *unicastPicker) State() (ConnectivityState, error) { |
| return p.conn.State(), nil |
| } |
| |
| func (p *unicastPicker) WaitForStateChange(ctx context.Context, sourceState ConnectivityState) (ConnectivityState, error) { |
| return p.conn.WaitForStateChange(ctx, sourceState) |
| } |
| |
| func (p *unicastPicker) Close() error { |
| if p.conn != nil { |
| return p.conn.Close() |
| } |
| return nil |
| } |
| |
| // unicastNamingPicker picks an address from a name resolver to set up the connection. |
| type unicastNamingPicker struct { |
| cc *ClientConn |
| resolver naming.Resolver |
| watcher naming.Watcher |
| mu sync.Mutex |
| // The list of the addresses are obtained from watcher. |
| addrs *list.List |
| // It tracks the current picked addr by PickAddr(). The next PickAddr may |
| // push it forward on addrs. |
| pickedAddr *list.Element |
| conn *Conn |
| } |
| |
| // NewUnicastNamingPicker creates a Picker to pick addresses from a name resolver |
| // to connect. |
| func NewUnicastNamingPicker(r naming.Resolver) Picker { |
| return &unicastNamingPicker{ |
| resolver: r, |
| addrs: list.New(), |
| } |
| } |
| |
| type addrInfo struct { |
| addr string |
| // Set to true if this addrInfo needs to be deleted in the next PickAddrr() call. |
| deleting bool |
| } |
| |
| // processUpdates calls Watcher.Next() once and processes the obtained updates. |
| func (p *unicastNamingPicker) processUpdates() error { |
| updates, err := p.watcher.Next() |
| if err != nil { |
| return err |
| } |
| for _, update := range updates { |
| switch update.Op { |
| case naming.Add: |
| p.mu.Lock() |
| p.addrs.PushBack(&addrInfo{ |
| addr: update.Addr, |
| }) |
| p.mu.Unlock() |
| // Initial connection setup |
| if p.conn == nil { |
| conn, err := NewConn(p.cc) |
| if err != nil { |
| return err |
| } |
| p.conn = conn |
| } |
| case naming.Delete: |
| p.mu.Lock() |
| for e := p.addrs.Front(); e != nil; e = e.Next() { |
| if update.Addr == e.Value.(*addrInfo).addr { |
| if e == p.pickedAddr { |
| // Do not remove the element now if it is the current picked |
| // one. We leave the deletion to the next PickAddr() call. |
| e.Value.(*addrInfo).deleting = true |
| // Notify Conn to close it. All the live RPCs on this connection |
| // will be aborted. |
| p.conn.NotifyReset() |
| } else { |
| p.addrs.Remove(e) |
| } |
| } |
| } |
| p.mu.Unlock() |
| default: |
| grpclog.Println("Unknown update.Op %d", update.Op) |
| } |
| } |
| return nil |
| } |
| |
| // monitor runs in a standalone goroutine to keep watching name resolution updates until the watcher |
| // is closed. |
| func (p *unicastNamingPicker) monitor() { |
| for { |
| if err := p.processUpdates(); err != nil { |
| return |
| } |
| } |
| } |
| |
| func (p *unicastNamingPicker) Init(cc *ClientConn) error { |
| w, err := p.resolver.Resolve(cc.target) |
| if err != nil { |
| return err |
| } |
| p.watcher = w |
| p.cc = cc |
| // Get the initial name resolution. |
| if err := p.processUpdates(); err != nil { |
| return err |
| } |
| go p.monitor() |
| return nil |
| } |
| |
| func (p *unicastNamingPicker) Pick(ctx context.Context) (transport.ClientTransport, error) { |
| return p.conn.Wait(ctx) |
| } |
| |
| func (p *unicastNamingPicker) PickAddr() (string, error) { |
| p.mu.Lock() |
| defer p.mu.Unlock() |
| if p.pickedAddr == nil { |
| p.pickedAddr = p.addrs.Front() |
| } else { |
| pa := p.pickedAddr |
| p.pickedAddr = pa.Next() |
| if pa.Value.(*addrInfo).deleting { |
| p.addrs.Remove(pa) |
| } |
| if p.pickedAddr == nil { |
| p.pickedAddr = p.addrs.Front() |
| } |
| } |
| if p.pickedAddr == nil { |
| return "", fmt.Errorf("there is no address available to pick") |
| } |
| return p.pickedAddr.Value.(*addrInfo).addr, nil |
| } |
| |
| func (p *unicastNamingPicker) State() (ConnectivityState, error) { |
| return 0, fmt.Errorf("State() is not supported for unicastNamingPicker") |
| } |
| |
| func (p *unicastNamingPicker) WaitForStateChange(ctx context.Context, sourceState ConnectivityState) (ConnectivityState, error) { |
| return 0, fmt.Errorf("WaitForStateChange is not supported for unicastNamingPciker") |
| } |
| |
| func (p *unicastNamingPicker) Close() error { |
| p.watcher.Close() |
| p.conn.Close() |
| return nil |
| } |