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Diffstat (limited to 'vendor/google.golang.org/grpc/balancer.go')
| -rw-r--r-- | vendor/google.golang.org/grpc/balancer.go | 400 |
1 files changed, 400 insertions, 0 deletions
diff --git a/vendor/google.golang.org/grpc/balancer.go b/vendor/google.golang.org/grpc/balancer.go new file mode 100644 index 000000000..9d943fbad --- /dev/null +++ b/vendor/google.golang.org/grpc/balancer.go @@ -0,0 +1,400 @@ +/* + * + * Copyright 2016, 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 ( + "fmt" + "sync" + + "golang.org/x/net/context" + "google.golang.org/grpc/codes" + "google.golang.org/grpc/credentials" + "google.golang.org/grpc/grpclog" + "google.golang.org/grpc/naming" +) + +// Address represents a server the client connects to. +// This is the EXPERIMENTAL API and may be changed or extended in the future. +type Address struct { + // Addr is the server address on which a connection will be established. + Addr string + // Metadata is the information associated with Addr, which may be used + // to make load balancing decision. + Metadata interface{} +} + +// BalancerConfig specifies the configurations for Balancer. +type BalancerConfig struct { + // DialCreds is the transport credential the Balancer implementation can + // use to dial to a remote load balancer server. The Balancer implementations + // can ignore this if it does not need to talk to another party securely. + DialCreds credentials.TransportCredentials +} + +// BalancerGetOptions configures a Get call. +// This is the EXPERIMENTAL API and may be changed or extended in the future. +type BalancerGetOptions struct { + // BlockingWait specifies whether Get should block when there is no + // connected address. + BlockingWait bool +} + +// Balancer chooses network addresses for RPCs. +// This is the EXPERIMENTAL API and may be changed or extended in the future. +type Balancer interface { + // Start does the initialization work to bootstrap a Balancer. For example, + // this function may start the name resolution and watch the updates. It will + // be called when dialing. + Start(target string, config BalancerConfig) error + // Up informs the Balancer that gRPC has a connection to the server at + // addr. It returns down which is called once the connection to addr gets + // lost or closed. + // TODO: It is not clear how to construct and take advantage of the meaningful error + // parameter for down. Need realistic demands to guide. + Up(addr Address) (down func(error)) + // Get gets the address of a server for the RPC corresponding to ctx. + // i) If it returns a connected address, gRPC internals issues the RPC on the + // connection to this address; + // ii) If it returns an address on which the connection is under construction + // (initiated by Notify(...)) but not connected, gRPC internals + // * fails RPC if the RPC is fail-fast and connection is in the TransientFailure or + // Shutdown state; + // or + // * issues RPC on the connection otherwise. + // iii) If it returns an address on which the connection does not exist, gRPC + // internals treats it as an error and will fail the corresponding RPC. + // + // Therefore, the following is the recommended rule when writing a custom Balancer. + // If opts.BlockingWait is true, it should return a connected address or + // block if there is no connected address. It should respect the timeout or + // cancellation of ctx when blocking. If opts.BlockingWait is false (for fail-fast + // RPCs), it should return an address it has notified via Notify(...) immediately + // instead of blocking. + // + // The function returns put which is called once the rpc has completed or failed. + // put can collect and report RPC stats to a remote load balancer. + // + // This function should only return the errors Balancer cannot recover by itself. + // gRPC internals will fail the RPC if an error is returned. + Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error) + // Notify returns a channel that is used by gRPC internals to watch the addresses + // gRPC needs to connect. The addresses might be from a name resolver or remote + // load balancer. gRPC internals will compare it with the existing connected + // addresses. If the address Balancer notified is not in the existing connected + // addresses, gRPC starts to connect the address. If an address in the existing + // connected addresses is not in the notification list, the corresponding connection + // is shutdown gracefully. Otherwise, there are no operations to take. Note that + // the Address slice must be the full list of the Addresses which should be connected. + // It is NOT delta. + Notify() <-chan []Address + // Close shuts down the balancer. + Close() error +} + +// downErr implements net.Error. It is constructed by gRPC internals and passed to the down +// call of Balancer. +type downErr struct { + timeout bool + temporary bool + desc string +} + +func (e downErr) Error() string { return e.desc } +func (e downErr) Timeout() bool { return e.timeout } +func (e downErr) Temporary() bool { return e.temporary } + +func downErrorf(timeout, temporary bool, format string, a ...interface{}) downErr { + return downErr{ + timeout: timeout, + temporary: temporary, + desc: fmt.Sprintf(format, a...), + } +} + +// RoundRobin returns a Balancer that selects addresses round-robin. It uses r to watch +// the name resolution updates and updates the addresses available correspondingly. +func RoundRobin(r naming.Resolver) Balancer { + return &roundRobin{r: r} +} + +type addrInfo struct { + addr Address + connected bool +} + +type roundRobin struct { + r naming.Resolver + w naming.Watcher + addrs []*addrInfo // all the addresses the client should potentially connect + mu sync.Mutex + addrCh chan []Address // the channel to notify gRPC internals the list of addresses the client should connect to. + next int // index of the next address to return for Get() + waitCh chan struct{} // the channel to block when there is no connected address available + done bool // The Balancer is closed. +} + +func (rr *roundRobin) watchAddrUpdates() error { + updates, err := rr.w.Next() + if err != nil { + grpclog.Printf("grpc: the naming watcher stops working due to %v.\n", err) + return err + } + rr.mu.Lock() + defer rr.mu.Unlock() + for _, update := range updates { + addr := Address{ + Addr: update.Addr, + Metadata: update.Metadata, + } + switch update.Op { + case naming.Add: + var exist bool + for _, v := range rr.addrs { + if addr == v.addr { + exist = true + grpclog.Println("grpc: The name resolver wanted to add an existing address: ", addr) + break + } + } + if exist { + continue + } + rr.addrs = append(rr.addrs, &addrInfo{addr: addr}) + case naming.Delete: + for i, v := range rr.addrs { + if addr == v.addr { + copy(rr.addrs[i:], rr.addrs[i+1:]) + rr.addrs = rr.addrs[:len(rr.addrs)-1] + break + } + } + default: + grpclog.Println("Unknown update.Op ", update.Op) + } + } + // Make a copy of rr.addrs and write it onto rr.addrCh so that gRPC internals gets notified. + open := make([]Address, len(rr.addrs)) + for i, v := range rr.addrs { + open[i] = v.addr + } + if rr.done { + return ErrClientConnClosing + } + rr.addrCh <- open + return nil +} + +func (rr *roundRobin) Start(target string, config BalancerConfig) error { + rr.mu.Lock() + defer rr.mu.Unlock() + if rr.done { + return ErrClientConnClosing + } + if rr.r == nil { + // If there is no name resolver installed, it is not needed to + // do name resolution. In this case, target is added into rr.addrs + // as the only address available and rr.addrCh stays nil. + rr.addrs = append(rr.addrs, &addrInfo{addr: Address{Addr: target}}) + return nil + } + w, err := rr.r.Resolve(target) + if err != nil { + return err + } + rr.w = w + rr.addrCh = make(chan []Address) + go func() { + for { + if err := rr.watchAddrUpdates(); err != nil { + return + } + } + }() + return nil +} + +// Up sets the connected state of addr and sends notification if there are pending +// Get() calls. +func (rr *roundRobin) Up(addr Address) func(error) { + rr.mu.Lock() + defer rr.mu.Unlock() + var cnt int + for _, a := range rr.addrs { + if a.addr == addr { + if a.connected { + return nil + } + a.connected = true + } + if a.connected { + cnt++ + } + } + // addr is only one which is connected. Notify the Get() callers who are blocking. + if cnt == 1 && rr.waitCh != nil { + close(rr.waitCh) + rr.waitCh = nil + } + return func(err error) { + rr.down(addr, err) + } +} + +// down unsets the connected state of addr. +func (rr *roundRobin) down(addr Address, err error) { + rr.mu.Lock() + defer rr.mu.Unlock() + for _, a := range rr.addrs { + if addr == a.addr { + a.connected = false + break + } + } +} + +// Get returns the next addr in the rotation. +func (rr *roundRobin) Get(ctx context.Context, opts BalancerGetOptions) (addr Address, put func(), err error) { + var ch chan struct{} + rr.mu.Lock() + if rr.done { + rr.mu.Unlock() + err = ErrClientConnClosing + return + } + + if len(rr.addrs) > 0 { + if rr.next >= len(rr.addrs) { + rr.next = 0 + } + next := rr.next + for { + a := rr.addrs[next] + next = (next + 1) % len(rr.addrs) + if a.connected { + addr = a.addr + rr.next = next + rr.mu.Unlock() + return + } + if next == rr.next { + // Has iterated all the possible address but none is connected. + break + } + } + } + if !opts.BlockingWait { + if len(rr.addrs) == 0 { + rr.mu.Unlock() + err = Errorf(codes.Unavailable, "there is no address available") + return + } + // Returns the next addr on rr.addrs for failfast RPCs. + addr = rr.addrs[rr.next].addr + rr.next++ + rr.mu.Unlock() + return + } + // Wait on rr.waitCh for non-failfast RPCs. + if rr.waitCh == nil { + ch = make(chan struct{}) + rr.waitCh = ch + } else { + ch = rr.waitCh + } + rr.mu.Unlock() + for { + select { + case <-ctx.Done(): + err = ctx.Err() + return + case <-ch: + rr.mu.Lock() + if rr.done { + rr.mu.Unlock() + err = ErrClientConnClosing + return + } + + if len(rr.addrs) > 0 { + if rr.next >= len(rr.addrs) { + rr.next = 0 + } + next := rr.next + for { + a := rr.addrs[next] + next = (next + 1) % len(rr.addrs) + if a.connected { + addr = a.addr + rr.next = next + rr.mu.Unlock() + return + } + if next == rr.next { + // Has iterated all the possible address but none is connected. + break + } + } + } + // The newly added addr got removed by Down() again. + if rr.waitCh == nil { + ch = make(chan struct{}) + rr.waitCh = ch + } else { + ch = rr.waitCh + } + rr.mu.Unlock() + } + } +} + +func (rr *roundRobin) Notify() <-chan []Address { + return rr.addrCh +} + +func (rr *roundRobin) Close() error { + rr.mu.Lock() + defer rr.mu.Unlock() + rr.done = true + if rr.w != nil { + rr.w.Close() + } + if rr.waitCh != nil { + close(rr.waitCh) + rr.waitCh = nil + } + if rr.addrCh != nil { + close(rr.addrCh) + } + return nil +} |