khenaidoo | 5fc5cea | 2021-08-11 17:39:16 -0400 | [diff] [blame] | 1 | /* |
| 2 | * |
| 3 | * Copyright 2020 gRPC authors. |
| 4 | * |
| 5 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 6 | * you may not use this file except in compliance with the License. |
| 7 | * You may obtain a copy of the License at |
| 8 | * |
| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | * |
| 11 | * Unless required by applicable law or agreed to in writing, software |
| 12 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | * See the License for the specific language governing permissions and |
| 15 | * limitations under the License. |
| 16 | * |
| 17 | */ |
| 18 | |
| 19 | // Package resolver provides internal resolver-related functionality. |
| 20 | package resolver |
| 21 | |
| 22 | import ( |
| 23 | "context" |
| 24 | "sync" |
| 25 | |
| 26 | "google.golang.org/grpc/internal/serviceconfig" |
| 27 | "google.golang.org/grpc/metadata" |
| 28 | "google.golang.org/grpc/resolver" |
| 29 | ) |
| 30 | |
| 31 | // ConfigSelector controls what configuration to use for every RPC. |
| 32 | type ConfigSelector interface { |
| 33 | // Selects the configuration for the RPC, or terminates it using the error. |
| 34 | // This error will be converted by the gRPC library to a status error with |
| 35 | // code UNKNOWN if it is not returned as a status error. |
| 36 | SelectConfig(RPCInfo) (*RPCConfig, error) |
| 37 | } |
| 38 | |
| 39 | // RPCInfo contains RPC information needed by a ConfigSelector. |
| 40 | type RPCInfo struct { |
| 41 | // Context is the user's context for the RPC and contains headers and |
| 42 | // application timeout. It is passed for interception purposes and for |
| 43 | // efficiency reasons. SelectConfig should not be blocking. |
| 44 | Context context.Context |
| 45 | Method string // i.e. "/Service/Method" |
| 46 | } |
| 47 | |
| 48 | // RPCConfig describes the configuration to use for each RPC. |
| 49 | type RPCConfig struct { |
| 50 | // The context to use for the remainder of the RPC; can pass info to LB |
| 51 | // policy or affect timeout or metadata. |
| 52 | Context context.Context |
| 53 | MethodConfig serviceconfig.MethodConfig // configuration to use for this RPC |
| 54 | OnCommitted func() // Called when the RPC has been committed (retries no longer possible) |
| 55 | Interceptor ClientInterceptor |
| 56 | } |
| 57 | |
| 58 | // ClientStream is the same as grpc.ClientStream, but defined here for circular |
| 59 | // dependency reasons. |
| 60 | type ClientStream interface { |
| 61 | // Header returns the header metadata received from the server if there |
| 62 | // is any. It blocks if the metadata is not ready to read. |
| 63 | Header() (metadata.MD, error) |
| 64 | // Trailer returns the trailer metadata from the server, if there is any. |
| 65 | // It must only be called after stream.CloseAndRecv has returned, or |
| 66 | // stream.Recv has returned a non-nil error (including io.EOF). |
| 67 | Trailer() metadata.MD |
| 68 | // CloseSend closes the send direction of the stream. It closes the stream |
| 69 | // when non-nil error is met. It is also not safe to call CloseSend |
| 70 | // concurrently with SendMsg. |
| 71 | CloseSend() error |
| 72 | // Context returns the context for this stream. |
| 73 | // |
| 74 | // It should not be called until after Header or RecvMsg has returned. Once |
| 75 | // called, subsequent client-side retries are disabled. |
| 76 | Context() context.Context |
| 77 | // SendMsg is generally called by generated code. On error, SendMsg aborts |
| 78 | // the stream. If the error was generated by the client, the status is |
| 79 | // returned directly; otherwise, io.EOF is returned and the status of |
| 80 | // the stream may be discovered using RecvMsg. |
| 81 | // |
| 82 | // SendMsg blocks until: |
| 83 | // - There is sufficient flow control to schedule m with the transport, or |
| 84 | // - The stream is done, or |
| 85 | // - The stream breaks. |
| 86 | // |
| 87 | // SendMsg does not wait until the message is received by the server. An |
| 88 | // untimely stream closure may result in lost messages. To ensure delivery, |
| 89 | // users should ensure the RPC completed successfully using RecvMsg. |
| 90 | // |
| 91 | // It is safe to have a goroutine calling SendMsg and another goroutine |
| 92 | // calling RecvMsg on the same stream at the same time, but it is not safe |
| 93 | // to call SendMsg on the same stream in different goroutines. It is also |
| 94 | // not safe to call CloseSend concurrently with SendMsg. |
| 95 | SendMsg(m interface{}) error |
| 96 | // RecvMsg blocks until it receives a message into m or the stream is |
| 97 | // done. It returns io.EOF when the stream completes successfully. On |
| 98 | // any other error, the stream is aborted and the error contains the RPC |
| 99 | // status. |
| 100 | // |
| 101 | // It is safe to have a goroutine calling SendMsg and another goroutine |
| 102 | // calling RecvMsg on the same stream at the same time, but it is not |
| 103 | // safe to call RecvMsg on the same stream in different goroutines. |
| 104 | RecvMsg(m interface{}) error |
| 105 | } |
| 106 | |
| 107 | // ClientInterceptor is an interceptor for gRPC client streams. |
| 108 | type ClientInterceptor interface { |
| 109 | // NewStream produces a ClientStream for an RPC which may optionally use |
| 110 | // the provided function to produce a stream for delegation. Note: |
| 111 | // RPCInfo.Context should not be used (will be nil). |
| 112 | // |
| 113 | // done is invoked when the RPC is finished using its connection, or could |
| 114 | // not be assigned a connection. RPC operations may still occur on |
| 115 | // ClientStream after done is called, since the interceptor is invoked by |
| 116 | // application-layer operations. done must never be nil when called. |
| 117 | NewStream(ctx context.Context, ri RPCInfo, done func(), newStream func(ctx context.Context, done func()) (ClientStream, error)) (ClientStream, error) |
| 118 | } |
| 119 | |
| 120 | // ServerInterceptor is an interceptor for incoming RPC's on gRPC server side. |
| 121 | type ServerInterceptor interface { |
| 122 | // AllowRPC checks if an incoming RPC is allowed to proceed based on |
| 123 | // information about connection RPC was received on, and HTTP Headers. This |
| 124 | // information will be piped into context. |
| 125 | AllowRPC(ctx context.Context) error // TODO: Make this a real interceptor for filters such as rate limiting. |
| 126 | } |
| 127 | |
| 128 | type csKeyType string |
| 129 | |
| 130 | const csKey = csKeyType("grpc.internal.resolver.configSelector") |
| 131 | |
| 132 | // SetConfigSelector sets the config selector in state and returns the new |
| 133 | // state. |
| 134 | func SetConfigSelector(state resolver.State, cs ConfigSelector) resolver.State { |
khenaidoo | 5cb0d40 | 2021-12-08 14:09:16 -0500 | [diff] [blame] | 135 | state.Attributes = state.Attributes.WithValue(csKey, cs) |
khenaidoo | 5fc5cea | 2021-08-11 17:39:16 -0400 | [diff] [blame] | 136 | return state |
| 137 | } |
| 138 | |
| 139 | // GetConfigSelector retrieves the config selector from state, if present, and |
| 140 | // returns it or nil if absent. |
| 141 | func GetConfigSelector(state resolver.State) ConfigSelector { |
| 142 | cs, _ := state.Attributes.Value(csKey).(ConfigSelector) |
| 143 | return cs |
| 144 | } |
| 145 | |
| 146 | // SafeConfigSelector allows for safe switching of ConfigSelector |
| 147 | // implementations such that previous values are guaranteed to not be in use |
| 148 | // when UpdateConfigSelector returns. |
| 149 | type SafeConfigSelector struct { |
| 150 | mu sync.RWMutex |
| 151 | cs ConfigSelector |
| 152 | } |
| 153 | |
| 154 | // UpdateConfigSelector swaps to the provided ConfigSelector and blocks until |
| 155 | // all uses of the previous ConfigSelector have completed. |
| 156 | func (scs *SafeConfigSelector) UpdateConfigSelector(cs ConfigSelector) { |
| 157 | scs.mu.Lock() |
| 158 | defer scs.mu.Unlock() |
| 159 | scs.cs = cs |
| 160 | } |
| 161 | |
| 162 | // SelectConfig defers to the current ConfigSelector in scs. |
| 163 | func (scs *SafeConfigSelector) SelectConfig(r RPCInfo) (*RPCConfig, error) { |
| 164 | scs.mu.RLock() |
| 165 | defer scs.mu.RUnlock() |
| 166 | return scs.cs.SelectConfig(r) |
| 167 | } |