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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 | 404 |
1 files changed, 404 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 000000000..09d61dd1b --- /dev/null +++ b/vendor/google.golang.org/grpc/balancer/balancer.go @@ -0,0 +1,404 @@ +/* + * + * 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 ( + "context" + "encoding/json" + "errors" + "net" + "strings" + + "google.golang.org/grpc/channelz" + "google.golang.org/grpc/connectivity" + "google.golang.org/grpc/credentials" + "google.golang.org/grpc/internal" + "google.golang.org/grpc/metadata" + "google.golang.org/grpc/resolver" + "google.golang.org/grpc/serviceconfig" +) + +var ( + // m is a map from name to balancer builder. + m = make(map[string]Builder) +) + +// Register registers the balancer builder to the balancer map. b.Name +// (lowercased) will be used as the name registered with this builder. If the +// Builder implements ConfigParser, ParseConfig will be called when new service +// configs are received by the resolver, and the result will be provided to the +// Balancer in UpdateClientConnState. +// +// NOTE: this function must only be called during initialization time (i.e. in +// an init() function), and is not thread-safe. If multiple Balancers are +// registered with the same name, the one registered last will take effect. +func Register(b Builder) { + m[strings.ToLower(b.Name())] = b +} + +// unregisterForTesting deletes the balancer with the given name from the +// balancer map. +// +// This function is not thread-safe. +func unregisterForTesting(name string) { + delete(m, name) +} + +func init() { + internal.BalancerUnregister = unregisterForTesting +} + +// Get returns the resolver builder registered with the given name. +// Note that the compare is done in a case-insensitive fashion. +// If no builder is register with the name, nil will be returned. +func Get(name string) Builder { + if b, ok := m[strings.ToLower(name)]; ok { + return b + } + return nil +} + +// A SubConn represents a single connection to a gRPC backend service. +// +// Each SubConn contains a list of addresses. +// +// All SubConns start in IDLE, and will not try to connect. To trigger the +// connecting, Balancers must call Connect. If a connection re-enters IDLE, +// Balancers must call Connect again to trigger a new connection attempt. +// +// gRPC will try to connect to the addresses in sequence, and stop trying the +// remainder once the first connection is successful. If an attempt to connect +// to all addresses encounters an error, the SubConn will enter +// TRANSIENT_FAILURE for a backoff period, and then transition to IDLE. +// +// Once established, if a connection is lost, the SubConn will transition +// directly to IDLE. +// +// This interface is to be implemented by gRPC. Users should not need their own +// implementation of this interface. For situations like testing, any +// implementations should embed this interface. This allows gRPC to add new +// methods to this interface. +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. + // + // Deprecated: This method is now part of the ClientConn interface and will + // eventually be removed from here. + UpdateAddresses([]resolver.Address) + // Connect starts the connecting for this SubConn. + Connect() + // GetOrBuildProducer returns a reference to the existing Producer for this + // ProducerBuilder in this SubConn, or, if one does not currently exist, + // creates a new one and returns it. Returns a close function which must + // be called when the Producer is no longer needed. + GetOrBuildProducer(ProducerBuilder) (p Producer, close func()) +} + +// NewSubConnOptions contains options to create new SubConn. +type NewSubConnOptions struct { + // CredsBundle is the credentials bundle that will be used in the created + // SubConn. If it's nil, the original creds from grpc DialOptions will be + // used. + // + // Deprecated: Use the Attributes field in resolver.Address to pass + // arbitrary data to the credential handshaker. + CredsBundle credentials.Bundle + // HealthCheckEnabled indicates whether health check service should be + // enabled on this SubConn + HealthCheckEnabled bool +} + +// State contains the balancer's state relevant to the gRPC ClientConn. +type State struct { + // State contains the connectivity state of the balancer, which is used to + // determine the state of the ClientConn. + ConnectivityState connectivity.State + // Picker is used to choose connections (SubConns) for RPCs. + Picker Picker +} + +// ClientConn represents a gRPC ClientConn. +// +// This interface is to be implemented by gRPC. Users should not need a +// brand new implementation of this interface. For the situations like +// testing, the new implementation should embed this interface. This allows +// gRPC to add new methods to this interface. +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) + // UpdateAddresses updates the addresses used in the passed in SubConn. + // gRPC checks if the currently connected address is still in the new list. + // If so, the connection will be kept. Else, the connection will be + // gracefully closed, and a new connection will be created. + // + // This will trigger a state transition for the SubConn. + UpdateAddresses(SubConn, []resolver.Address) + + // UpdateState notifies gRPC that the balancer's internal state has + // changed. + // + // gRPC will update the connectivity state of the ClientConn, and will call + // Pick on the new Picker to pick new SubConns. + UpdateState(State) + + // ResolveNow is called by balancer to notify gRPC to do a name resolving. + ResolveNow(resolver.ResolveNowOptions) + + // Target returns the dial target for this ClientConn. + // + // Deprecated: Use the Target field in the BuildOptions instead. + Target() string +} + +// BuildOptions contains additional information for Build. +type BuildOptions struct { + // DialCreds is the transport credentials to use when communicating with a + // remote load balancer server. Balancer implementations which do not + // communicate with a remote load balancer server can ignore this field. + DialCreds credentials.TransportCredentials + // CredsBundle is the credentials bundle to use when communicating with a + // remote load balancer server. Balancer implementations which do not + // communicate with a remote load balancer server can ignore this field. + CredsBundle credentials.Bundle + // Dialer is the custom dialer to use when communicating with a remote load + // balancer server. Balancer implementations which do not communicate with a + // remote load balancer server can ignore this field. + Dialer func(context.Context, string) (net.Conn, error) + // Authority is the server name to use as part of the authentication + // handshake when communicating with a remote load balancer server. Balancer + // implementations which do not communicate with a remote load balancer + // server can ignore this field. + Authority string + // ChannelzParentID is the parent ClientConn's channelz ID. + ChannelzParentID *channelz.Identifier + // CustomUserAgent is the custom user agent set on the parent ClientConn. + // The balancer should set the same custom user agent if it creates a + // ClientConn. + CustomUserAgent string + // Target contains the parsed address info of the dial target. It is the + // same resolver.Target as passed to the resolver. See the documentation for + // the resolver.Target type for details about what it contains. + Target resolver.Target +} + +// 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 +} + +// ConfigParser parses load balancer configs. +type ConfigParser interface { + // ParseConfig parses the JSON load balancer config provided into an + // internal form or returns an error if the config is invalid. For future + // compatibility reasons, unknown fields in the config should be ignored. + ParseConfig(LoadBalancingConfigJSON json.RawMessage) (serviceconfig.LoadBalancingConfig, error) +} + +// PickInfo contains additional information for the Pick operation. +type PickInfo struct { + // FullMethodName is the method name that NewClientStream() is called + // with. The canonical format is /service/Method. + FullMethodName string + // Ctx is the RPC's context, and may contain relevant RPC-level information + // like the outgoing header metadata. + Ctx context.Context +} + +// DoneInfo contains additional information for done. +type DoneInfo struct { + // Err is the rpc error the RPC finished with. It could be nil. + Err error + // Trailer contains the metadata from the RPC's trailer, if present. + Trailer metadata.MD + // BytesSent indicates if any bytes have been sent to the server. + BytesSent bool + // BytesReceived indicates if any byte has been received from the server. + BytesReceived bool + // ServerLoad is the load received from server. It's usually sent as part of + // trailing metadata. + // + // The only supported type now is *orca_v3.LoadReport. + ServerLoad interface{} +} + +var ( + // ErrNoSubConnAvailable indicates no SubConn is available for pick(). + // gRPC will block the RPC until a new picker is available via UpdateState(). + ErrNoSubConnAvailable = errors.New("no SubConn is available") + // ErrTransientFailure indicates all SubConns are in TransientFailure. + // WaitForReady RPCs will block, non-WaitForReady RPCs will fail. + // + // Deprecated: return an appropriate error based on the last resolution or + // connection attempt instead. The behavior is the same for any non-gRPC + // status error. + ErrTransientFailure = errors.New("all SubConns are in TransientFailure") +) + +// PickResult contains information related to a connection chosen for an RPC. +type PickResult struct { + // SubConn is the connection to use for this pick, if its state is Ready. + // If the state is not Ready, gRPC will block the RPC until a new Picker is + // provided by the balancer (using ClientConn.UpdateState). The SubConn + // must be one returned by ClientConn.NewSubConn. + SubConn SubConn + + // Done is called when the RPC is completed. If the SubConn is not ready, + // this will be called with a nil parameter. If the SubConn is not a valid + // type, Done may not be called. May be nil if the balancer does not wish + // to be notified when the RPC completes. + Done func(DoneInfo) + + // Metadata provides a way for LB policies to inject arbitrary per-call + // metadata. Any metadata returned here will be merged with existing + // metadata added by the client application. + // + // LB policies with child policies are responsible for propagating metadata + // injected by their children to the ClientConn, as part of Pick(). + Metatada metadata.MD +} + +// TransientFailureError returns e. It exists for backward compatibility and +// will be deleted soon. +// +// Deprecated: no longer necessary, picker errors are treated this way by +// default. +func TransientFailureError(e error) error { return e } + +// Picker is used by gRPC to pick a SubConn to send an RPC. +// Balancer is expected to generate a new picker from its snapshot every time its +// internal state has changed. +// +// The pickers used by gRPC can be updated by ClientConn.UpdateState(). +type Picker interface { + // Pick returns the connection to use for this RPC and related information. + // + // Pick should not block. If the balancer needs to do I/O or any blocking + // or time-consuming work to service this call, it should return + // ErrNoSubConnAvailable, and the Pick call will be repeated by gRPC when + // the Picker is updated (using ClientConn.UpdateState). + // + // If an error is returned: + // + // - If the error is ErrNoSubConnAvailable, gRPC will block until a new + // Picker is provided by the balancer (using ClientConn.UpdateState). + // + // - If the error is a status error (implemented by the grpc/status + // package), gRPC will terminate the RPC with the code and message + // provided. + // + // - For all other errors, wait for ready RPCs will wait, but non-wait for + // ready RPCs will be terminated with this error's Error() string and + // status code Unavailable. + Pick(info PickInfo) (PickResult, 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. +// +// UpdateClientConnState, ResolverError, UpdateSubConnState, 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 { + // UpdateClientConnState is called by gRPC when the state of the ClientConn + // changes. If the error returned is ErrBadResolverState, the ClientConn + // will begin calling ResolveNow on the active name resolver with + // exponential backoff until a subsequent call to UpdateClientConnState + // returns a nil error. Any other errors are currently ignored. + UpdateClientConnState(ClientConnState) error + // ResolverError is called by gRPC when the name resolver reports an error. + ResolverError(error) + // UpdateSubConnState is called by gRPC when the state of a SubConn + // changes. + UpdateSubConnState(SubConn, SubConnState) + // Close closes the balancer. The balancer is not required to call + // ClientConn.RemoveSubConn for its existing SubConns. + Close() +} + +// ExitIdler is an optional interface for balancers to implement. If +// implemented, ExitIdle will be called when ClientConn.Connect is called, if +// the ClientConn is idle. If unimplemented, ClientConn.Connect will cause +// all SubConns to connect. +// +// Notice: it will be required for all balancers to implement this in a future +// release. +type ExitIdler interface { + // ExitIdle instructs the LB policy to reconnect to backends / exit the + // IDLE state, if appropriate and possible. Note that SubConns that enter + // the IDLE state will not reconnect until SubConn.Connect is called. + ExitIdle() +} + +// SubConnState describes the state of a SubConn. +type SubConnState struct { + // ConnectivityState is the connectivity state of the SubConn. + ConnectivityState connectivity.State + // ConnectionError is set if the ConnectivityState is TransientFailure, + // describing the reason the SubConn failed. Otherwise, it is nil. + ConnectionError error +} + +// ClientConnState describes the state of a ClientConn relevant to the +// balancer. +type ClientConnState struct { + ResolverState resolver.State + // The parsed load balancing configuration returned by the builder's + // ParseConfig method, if implemented. + BalancerConfig serviceconfig.LoadBalancingConfig +} + +// ErrBadResolverState may be returned by UpdateClientConnState to indicate a +// problem with the provided name resolver data. +var ErrBadResolverState = errors.New("bad resolver state") + +// A ProducerBuilder is a simple constructor for a Producer. It is used by the +// SubConn to create producers when needed. +type ProducerBuilder interface { + // Build creates a Producer. The first parameter is always a + // grpc.ClientConnInterface (a type to allow creating RPCs/streams on the + // associated SubConn), but is declared as interface{} to avoid a + // dependency cycle. Should also return a close function that will be + // called when all references to the Producer have been given up. + Build(grpcClientConnInterface interface{}) (p Producer, close func()) +} + +// A Producer is a type shared among potentially many consumers. It is +// associated with a SubConn, and an implementation will typically contain +// other methods to provide additional functionality, e.g. configuration or +// subscription registration. +type Producer interface { +} |