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Diffstat (limited to 'vendor/google.golang.org/grpc/balancer/balancer.go')
| -rw-r--r-- | vendor/google.golang.org/grpc/balancer/balancer.go | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/vendor/google.golang.org/grpc/balancer/balancer.go b/vendor/google.golang.org/grpc/balancer/balancer.go new file mode 100644 index 0000000..84e10b6 --- /dev/null +++ b/vendor/google.golang.org/grpc/balancer/balancer.go @@ -0,0 +1,206 @@ +/* + * + * Copyright 2017 gRPC authors. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + * + */ + +// Package balancer defines APIs for load balancing in gRPC. +// All APIs in this package are experimental. +package balancer + +import ( + "errors" + "net" + + "golang.org/x/net/context" + "google.golang.org/grpc/connectivity" + "google.golang.org/grpc/credentials" + "google.golang.org/grpc/resolver" +) + +var ( + // m is a map from name to balancer builder. + m = make(map[string]Builder) + // defaultBuilder is the default balancer to use. + defaultBuilder Builder // TODO(bar) install pickfirst as default. +) + +// Register registers the balancer builder to the balancer map. +// b.Name will be used as the name registered with this builder. +func Register(b Builder) { + m[b.Name()] = b +} + +// Get returns the resolver builder registered with the given name. +// If no builder is register with the name, the default pickfirst will +// be used. +func Get(name string) Builder { + if b, ok := m[name]; ok { + return b + } + return defaultBuilder +} + +// SubConn represents a gRPC sub connection. +// Each sub connection contains a list of addresses. gRPC will +// try to connect to them (in sequence), and stop trying the +// remainder once one connection is successful. +// +// The reconnect backoff will be applied on the list, not a single address. +// For example, try_on_all_addresses -> backoff -> try_on_all_addresses. +// +// All SubConns start in IDLE, and will not try to connect. To trigger +// the connecting, Balancers must call Connect. +// When the connection encounters an error, it will reconnect immediately. +// When the connection becomes IDLE, it will not reconnect unless Connect is +// called. +type SubConn interface { + // UpdateAddresses updates the addresses used in this SubConn. + // gRPC checks if currently-connected address is still in the new list. + // If it's in the list, the connection will be kept. + // If it's not in the list, the connection will gracefully closed, and + // a new connection will be created. + // + // This will trigger a state transition for the SubConn. + UpdateAddresses([]resolver.Address) + // Connect starts the connecting for this SubConn. + Connect() +} + +// NewSubConnOptions contains options to create new SubConn. +type NewSubConnOptions struct{} + +// ClientConn represents a gRPC ClientConn. +type ClientConn interface { + // NewSubConn is called by balancer to create a new SubConn. + // It doesn't block and wait for the connections to be established. + // Behaviors of the SubConn can be controlled by options. + NewSubConn([]resolver.Address, NewSubConnOptions) (SubConn, error) + // RemoveSubConn removes the SubConn from ClientConn. + // The SubConn will be shutdown. + RemoveSubConn(SubConn) + + // UpdateBalancerState is called by balancer to nofity gRPC that some internal + // state in balancer has changed. + // + // gRPC will update the connectivity state of the ClientConn, and will call pick + // on the new picker to pick new SubConn. + UpdateBalancerState(s connectivity.State, p Picker) + + // Target returns the dial target for this ClientConn. + Target() string +} + +// BuildOptions contains additional information for Build. +type BuildOptions 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 + // Dialer is the custom dialer the Balancer implementation can use to dial + // to a remote load balancer server. The Balancer implementations + // can ignore this if it doesn't need to talk to remote balancer. + Dialer func(context.Context, string) (net.Conn, error) +} + +// Builder creates a balancer. +type Builder interface { + // Build creates a new balancer with the ClientConn. + Build(cc ClientConn, opts BuildOptions) Balancer + // Name returns the name of balancers built by this builder. + // It will be used to pick balancers (for example in service config). + Name() string +} + +// PickOptions contains addition information for the Pick operation. +type PickOptions struct{} + +// DoneInfo contains additional information for done. +type DoneInfo struct { + // Err is the rpc error the RPC finished with. It could be nil. + Err error +} + +var ( + // ErrNoSubConnAvailable indicates no SubConn is available for pick(). + // gRPC will block the RPC until a new picker is available via UpdateBalancerState(). + ErrNoSubConnAvailable = errors.New("no SubConn is available") + // ErrTransientFailure indicates all SubConns are in TransientFailure. + // WaitForReady RPCs will block, non-WaitForReady RPCs will fail. + ErrTransientFailure = errors.New("all SubConns are in TransientFailure") +) + +// Picker is used by gRPC to pick a SubConn to send an RPC. +// Balancer is expected to generate a new picker from its snapshot everytime its +// internal state has changed. +// +// The pickers used by gRPC can be updated by ClientConn.UpdateBalancerState(). +type Picker interface { + // Pick returns the SubConn to be used to send the RPC. + // The returned SubConn must be one returned by NewSubConn(). + // + // This functions is expected to return: + // - a SubConn that is known to be READY; + // - ErrNoSubConnAvailable if no SubConn is available, but progress is being + // made (for example, some SubConn is in CONNECTING mode); + // - other errors if no active connecting is happening (for example, all SubConn + // are in TRANSIENT_FAILURE mode). + // + // If a SubConn is returned: + // - If it is READY, gRPC will send the RPC on it; + // - If it is not ready, or becomes not ready after it's returned, gRPC will block + // this call until a new picker is updated and will call pick on the new picker. + // + // If the returned error is not nil: + // - If the error is ErrNoSubConnAvailable, gRPC will block until UpdateBalancerState() + // - If the error is ErrTransientFailure: + // - If the RPC is wait-for-ready, gRPC will block until UpdateBalancerState() + // is called to pick again; + // - Otherwise, RPC will fail with unavailable error. + // - Else (error is other non-nil error): + // - The RPC will fail with unavailable error. + // + // The returned done() function will be called once the rpc has finished, with the + // final status of that RPC. + // done may be nil if balancer doesn't care about the RPC status. + Pick(ctx context.Context, opts PickOptions) (conn SubConn, done func(DoneInfo), err error) +} + +// Balancer takes input from gRPC, manages SubConns, and collects and aggregates +// the connectivity states. +// +// It also generates and updates the Picker used by gRPC to pick SubConns for RPCs. +// +// HandleSubConnectionStateChange, HandleResolvedAddrs and Close are guaranteed +// to be called synchronously from the same goroutine. +// There's no guarantee on picker.Pick, it may be called anytime. +type Balancer interface { + // HandleSubConnStateChange is called by gRPC when the connectivity state + // of sc has changed. + // Balancer is expected to aggregate all the state of SubConn and report + // that back to gRPC. + // Balancer should also generate and update Pickers when its internal state has + // been changed by the new state. + HandleSubConnStateChange(sc SubConn, state connectivity.State) + // HandleResolvedAddrs is called by gRPC to send updated resolved addresses to + // balancers. + // Balancer can create new SubConn or remove SubConn with the addresses. + // An empty address slice and a non-nil error will be passed if the resolver returns + // non-nil error to gRPC. + HandleResolvedAddrs([]resolver.Address, error) + // Close closes the balancer. The balancer is not required to call + // ClientConn.RemoveSubConn for its existing SubConns. + Close() +} |