| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you 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. |
| #ifndef KUDU_RPC_RPC_CONTROLLER_H |
| #define KUDU_RPC_RPC_CONTROLLER_H |
| |
| #include <functional> |
| #include <glog/logging.h> |
| #include <memory> |
| #include <unordered_set> |
| |
| #include "kudu/gutil/macros.h" |
| #include "kudu/util/locks.h" |
| #include "kudu/util/monotime.h" |
| #include "kudu/util/status.h" |
| namespace kudu { |
| |
| namespace rpc { |
| |
| class ErrorStatusPB; |
| class OutboundCall; |
| class RequestIdPB; |
| |
| // Controller for managing properties of a single RPC call, on the client side. |
| // |
| // An RpcController maps to exactly one call and is not thread-safe. The client |
| // may use this class prior to sending an RPC in order to set properties such |
| // as the call's timeout. |
| // |
| // After the call has been sent (e.g using Proxy::AsyncRequest()) the user |
| // may invoke methods on the RpcController object in order to probe the status |
| // of the call. |
| class RpcController { |
| public: |
| RpcController(); |
| ~RpcController(); |
| |
| // Swap the state of the controller (including ownership of sidecars, buffers, |
| // etc) with another one. |
| void Swap(RpcController* other); |
| |
| // Reset this controller so it may be used with another call. |
| void Reset(); |
| |
| // Return true if the call has finished. |
| // A call is finished if the server has responded, or if the call |
| // has timed out. |
| bool finished() const; |
| |
| // Return the current status of a call. |
| // |
| // A call is "OK" status until it finishes, at which point it may |
| // either remain in "OK" status (if the call was successful), or |
| // change to an error status. Error status indicates that there was |
| // some RPC-layer issue with making the call, for example, one of: |
| // |
| // * failed to establish a connection to the server |
| // * the server was too busy to handle the request |
| // * the server was unable to interpret the request (eg due to a version |
| // mismatch) |
| // * a network error occurred which caused the connection to be torn |
| // down |
| // * the call timed out |
| Status status() const; |
| |
| // If status() returns a RemoteError object, then this function returns |
| // the error response provided by the server. Service implementors may |
| // use protobuf Extensions to add application-specific data to this PB. |
| // |
| // If Status was not a RemoteError, this returns NULL. |
| // The returned pointer is only valid as long as the controller object. |
| const ErrorStatusPB* error_response() const; |
| |
| // Set the timeout for the call to be made with this RPC controller. |
| // |
| // The configured timeout applies to the entire time period between |
| // the AsyncRequest() method call and getting a response. For example, |
| // if it takes too long to establish a connection to the remote host, |
| // or to DNS-resolve the remote host, those will be accounted as part |
| // of the timeout period. |
| // |
| // Timeouts must be set prior to making the request -- the timeout may |
| // not currently be adjusted for an already-sent call. |
| // |
| // Using an uninitialized timeout will result in a call which never |
| // times out (not recommended!) |
| void set_timeout(const MonoDelta& timeout); |
| |
| // Like a timeout, but based on a fixed point in time instead of a delta. |
| // |
| // Using an uninitialized deadline means the call won't time out. |
| void set_deadline(const MonoTime& deadline); |
| |
| // Allows settting the request id for the next request sent to the server. |
| // A request id allows the server to identify each request sent by the client uniquely, |
| // in some cases even when sent to multiple servers, enabling exactly once semantics. |
| void SetRequestIdPB(std::unique_ptr<RequestIdPB> request_id); |
| |
| // Returns whether a request id has been set on RPC header. |
| bool has_request_id() const; |
| |
| // Returns the currently set request id. |
| // When the request is sent to the server, it gets "moved" from RpcController |
| // so an absence of a request after send doesn't mean one wasn't sent. |
| // REQUIRES: the controller has a request ID set. |
| const RequestIdPB& request_id() const; |
| |
| // Add a requirement that the server side must support a feature with the |
| // given identifier. The set of required features is sent to the server |
| // with the RPC call, and if any required feature is not supported, the |
| // call will fail with a NotSupported() status. |
| // |
| // This can be used when an RPC call changes in a way that is protobuf-compatible, |
| // but for which it would not be appropriate for the server to simply ignore |
| // an added field. For example, consider an API call like: |
| // |
| // message DeleteAccount { |
| // optional string username = 1; |
| // optional bool dry_run = 2; // ADDED LATER! |
| // } |
| // |
| // In this case, if a new client which supports the 'dry_run' flag sends the RPC |
| // to an old server, the old server will simply ignore the unrecognized parameter, |
| // with highly problematic results. To solve this problem, the new version can |
| // add a feature flag: |
| // |
| // In .proto file |
| // ---------------- |
| // enum MyFeatureFlags { |
| // UNKNOWN = 0; |
| // DELETE_ACCOUNT_SUPPORTS_DRY_RUN = 1; |
| // } |
| // |
| // In client code: |
| // --------------- |
| // if (dry_run) { |
| // rpc.RequireServerFeature(DELETE_ACCOUNT_SUPPORTS_DRY_RUN); |
| // req.set_dry_run(true); |
| // } |
| // |
| // This has the effect of (a) maintaining compatibility when dry_run is not specified |
| // and (b) rejecting the RPC with a "NotSupported" error when it is. |
| // |
| // NOTE: 'feature' is an int rather than an enum type because each service |
| // must define its own enum of supported features, and protobuf doesn't support |
| // any ability to 'extend' enum types. Implementers should define an enum in the |
| // service's protobuf definition as shown above. |
| void RequireServerFeature(uint32_t feature); |
| |
| // Executes the provided function with a reference to the required server |
| // features. |
| const std::unordered_set<uint32_t>& required_server_features() const { |
| return required_server_features_; |
| } |
| |
| // Return the configured timeout. |
| MonoDelta timeout() const; |
| |
| // Fills the 'sidecar' parameter with the slice pointing to the i-th |
| // sidecar upon success. |
| // |
| // Should only be called if the call's finished, but the controller has not |
| // been Reset(). |
| // |
| // May fail if index is invalid. |
| Status GetSidecar(int idx, Slice* sidecar) const; |
| |
| private: |
| friend class OutboundCall; |
| friend class Proxy; |
| |
| MonoDelta timeout_; |
| std::unordered_set<uint32_t> required_server_features_; |
| |
| mutable simple_spinlock lock_; |
| |
| // The id of this request. |
| // Ownership is transfered to OutboundCall once the call is sent. |
| std::unique_ptr<RequestIdPB> request_id_; |
| |
| // Once the call is sent, it is tracked here. |
| std::shared_ptr<OutboundCall> call_; |
| |
| DISALLOW_COPY_AND_ASSIGN(RpcController); |
| }; |
| |
| } // namespace rpc |
| } // namespace kudu |
| #endif |