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| -rw-r--r-- | src/bin/d2/d2_process.h | 324 |
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diff --git a/src/bin/d2/d2_process.h b/src/bin/d2/d2_process.h new file mode 100644 index 0000000..5ca3422 --- /dev/null +++ b/src/bin/d2/d2_process.h @@ -0,0 +1,324 @@ +// Copyright (C) 2013-2019 Internet Systems Consortium, Inc. ("ISC") +// +// This Source Code Form is subject to the terms of the Mozilla Public +// License, v. 2.0. If a copy of the MPL was not distributed with this +// file, You can obtain one at http://mozilla.org/MPL/2.0/. + +#ifndef D2_PROCESS_H +#define D2_PROCESS_H + +#include <d2/d2_queue_mgr.h> +#include <d2/d2_update_mgr.h> +#include <process/d_process.h> + +namespace isc { +namespace d2 { + +/// @brief DHCP-DDNS Application Process +/// +/// D2Process provides the top level application logic for DHCP-driven DDNS +/// update processing. It provides the asynchronous event processing required +/// to receive DNS mapping change requests and carry them out. +/// It implements the DProcessBase interface, which structures it such that it +/// is a managed "application", controlled by a management layer. +class D2Process : public process::DProcessBase { +public: + + /// @brief Defines the shutdown types supported by D2Process + /// + /// * SD_NORMAL - Stops the queue manager and finishes all current + /// transactions before exiting. This is the default. + /// + /// * SD_DRAIN_FIRST - Stops the queue manager but continues processing + /// requests from the queue until it is empty. + /// + /// * SD_NOW - Exits immediately. + enum ShutdownType { + SD_NORMAL, + SD_DRAIN_FIRST, + SD_NOW + }; + + /// @brief Defines the point at which to resume receiving requests. + /// If the receive queue has become full, D2Process will "pause" the + /// reception of requests by putting the queue manager in the stopped + /// state. Once the number of entries has decreased to this percentage + /// of the maximum allowed, D2Process will "resume" receiving requests + /// by restarting the queue manager. + static const unsigned int QUEUE_RESTART_PERCENT; + + /// @brief Constructor + /// + /// Construction creates the configuration manager, the queue + /// manager, and the update manager. + /// + /// @param name name is a text label for the process. Generally used + /// in log statements, but otherwise arbitrary. + /// @param io_service is the io_service used by the caller for + /// asynchronous event handling. + /// + /// @throw DProcessBaseError if io_service is NULL. + D2Process(const char* name, const asiolink::IOServicePtr& io_service); + + /// @brief Called after instantiation to perform initialization unique to + /// D2. + /// + /// This is invoked by the controller after command line arguments but + /// PRIOR to configuration reception. The base class provides this method + /// as a place to perform any derivation-specific initialization steps + /// that are inappropriate for the constructor but necessary prior to + /// configure. + /// For D2 it is used to initialize the command manager. + virtual void init(); + + /// @brief Implements the process's event loop. + /// + /// Once entered, the main control thread remains inside this method + /// until shutdown. The event loop logic is as follows: + /// @code + /// while should not shutdown { + /// process queue manager state change + /// process completed jobs + /// dequeue new jobs + /// wait for IO event(s) + /// + /// ON an exception, exit with fatal error + /// } + /// @endcode + /// + /// To summarize, each pass through the event loop first checks the state + /// of the received queue and takes any steps required to ensure it is + /// operating in the manner necessary. Next the update manager is given + /// a chance to clean up any completed transactions and start new + /// transactions by dequeuing jobs from the request queue. Lastly, it + /// allows IOService to process until one or more event handlers are + /// called. Note that this last step will block until at least one + /// ready handler is invoked. In other words, if no IO events have occurred + /// since it was last called, the event loop will block at this step until + /// an IO event occurs. At that time we return to the top of the loop. + /// + /// @throw DProcessBaseError if an error is encountered. Note that + /// exceptions thrown at this point are assumed to be FATAL exceptions. + /// This includes exceptions generated but not caught by IO callbacks. + /// Services which rely on callbacks are expected to be well behaved and + /// any errors they encounter handled internally. + virtual void run(); + + /// @brief Initiates the D2Process shutdown process. + /// + /// This is last step in the shutdown event callback chain. It is invoked + /// to notify D2Process that it needs to begin its shutdown procedure. + /// Note that shutting down may be neither instantaneous nor synchronous, + /// This method records the request for and the type of shutdown desired. + /// Generally it will require one or more subsequent events to complete, + /// dependent on the type of shutdown requested. The type of shutdown is + /// specified as an optional argument of the shutdown command. The types + /// of shutdown supported are: + /// + /// * "normal" - Stops the queue manager and finishes all current + /// transactions before exiting. This is the default. + /// + /// * "drain_first" - Stops the queue manager but continues processing + /// requests from the queue until it is empty. + /// + /// * "now" - Exits immediately. + /// + /// @param args Specifies the shutdown "type" as "normal", "drain_first", + /// or "now" + /// + /// @return an Element that contains the results of argument processing, + /// consisting of an integer status value (0 means successful, + /// non-zero means failure), and a string explanation of the outcome. + virtual isc::data::ConstElementPtr + shutdown(isc::data::ConstElementPtr args); + + /// @brief Processes the given configuration. + /// + /// This method may be called multiple times during the process lifetime. + /// Certainly once during process startup, and possibly later if the user + /// alters the configuration. This method must not throw, it should catch any + /// processing errors and return a success or failure answer as described + /// below. + /// + /// This method passes the newly received configuration to the configuration + /// manager instance for parsing. The configuration manager parses the + /// configuration and updates the necessary values within the context, + /// assuming it parses correctly. If that's the case this method sets the + /// flag to reconfigure the queue manager and returns a successful response + /// as described below. + /// + /// If the new configuration fails to parse, then the current configuration + /// is retained and a failure response is returned as described below. + /// + /// @param config_set a new configuration (JSON) for the process + /// @param check_only true if configuration is to be verified only, not applied + /// @return an Element that contains the results of configuration composed + /// of an integer status value (0 means successful, non-zero means failure), + /// and a string explanation of the outcome. + virtual isc::data::ConstElementPtr + configure(isc::data::ConstElementPtr config_set, + bool check_only = false); + + /// @brief Destructor + virtual ~D2Process(); + +protected: + /// @brief Monitors current queue manager state, takes action accordingly + /// + /// This method ensures that the queue manager transitions to the state + /// most appropriate to the operational state of the D2Process and any + /// events that may have occurred since it was last called. It is called + /// once for each iteration of the event loop. It is essentially a + /// switch statement based on the D2QueueMgr's current state. The logic + /// is as follows: + /// + /// If the state is D2QueueMgr::RUNNING, and the queue manager needs to be + /// reconfigured or we have been told to shutdown, then instruct the queue + /// manager to stop listening. Exit the method. + /// + /// If the state is D2QueueMgr::STOPPED_QUEUE_FULL, then check if the + /// number of entries in the queue has fallen below the "resume threshold". + /// If it has, then instruct the queue manager to start listening. Exit + /// the method. + /// + /// If the state is D2QueueMgr::STOPPED_RECV_ERROR, then attempt to recover + /// by calling reconfigureQueueMgr(). Exit the method. + /// + /// If the state is D2QueueMgr::STOPPING, simply exit the method. This is + /// a NOP condition as we are waiting for the IO cancel event + /// + /// For any other state, (NOT_INITTED,INITTED,STOPPED), if the reconfigure + /// queue flag is set, call reconfigureQueueMgr(). Exit the method. + /// + /// This method is exception safe. + virtual void checkQueueStatus(); + + /// @brief Initializes then starts the queue manager. + /// + /// This method initializes the queue manager with the current + /// configuration parameters and instructs it to start listening. + /// Note the existing listener instance (if it exists) is destroyed, + /// and that a new listener is created during initialization. + /// + /// This method is exception safe. + virtual void reconfigureQueueMgr(); + + /// @brief Allows IO processing to run until at least callback is invoked. + /// + /// This method is called from within the D2Process main event loop and is + /// the point at which the D2Process blocks, waiting for IO events to + /// cause IO event callbacks to be invoked. + /// + /// If callbacks are ready to be executed upon entry, the method will + /// return as soon as these callbacks have completed. If no callbacks + /// are ready, then it will wait (indefinitely) until at least one callback + /// is executed. + /// + /// @note: Should become desirable to periodically force an + /// event, an interval timer could be used to do so. + /// + /// @return The number of callback handlers executed, or 0 if the IO + /// service has been stopped. + /// + /// @throw This method does not throw directly, but the execution of + /// callbacks invoked in response to IO events might. If so, these + /// will propagate upward out of this method. + virtual size_t runIO(); + + /// @brief Indicates whether or not the process can perform a shutdown. + /// + /// Determines if the process has been instructed to shutdown and if + /// the criteria for performing the type of shutdown requested has been + /// met. + /// + /// @return Returns true if the criteria has been met, false otherwise. + virtual bool canShutdown() const; + + /// @brief Sets queue reconfigure indicator to the given value. + /// + /// @param value is the new value to assign to the indicator + /// + /// @note this method is really only intended for testing purposes. + void setReconfQueueFlag(const bool value) { + reconf_queue_flag_ = value; + } + + /// @brief Sets the shutdown type to the given value. + /// + /// @param value is the new value to assign to shutdown type. + /// + /// @note this method is really only intended for testing purposes. + void setShutdownType(const ShutdownType& value) { + shutdown_type_ = value; + } + + /// @brief (Re-)Configure the command channel. + /// + /// Only close the current channel, if the new channel configuration is + /// different. This avoids disconnecting a client and hence not sending + /// them a command result, unless they specifically alter the channel + /// configuration. In that case the user simply has to accept they'll + /// be disconnected. + void reconfigureCommandChannel(); + +public: + /// @brief Returns a pointer to the configuration manager. + /// Note, this method cannot return a reference as it uses dynamic + /// pointer casting of the base class configuration manager. + D2CfgMgrPtr getD2CfgMgr(); + + /// @brief Returns a reference to the queue manager. + const D2QueueMgrPtr& getD2QueueMgr() const { + return (queue_mgr_); + } + + /// @brief Returns a reference to the update manager. + const D2UpdateMgrPtr& getD2UpdateMgr() const { + return (update_mgr_); + } + + /// @brief Returns true if the queue manager should be reconfigured. + bool getReconfQueueFlag() const { + return (reconf_queue_flag_); + } + + /// @brief Returns the type of shutdown requested. + /// + /// Note, this value is meaningless unless shouldShutdown() returns true. + ShutdownType getShutdownType() const { + return (shutdown_type_); + } + + /// @brief Returns a text label for the given shutdown type. + /// + /// @param type the numerical shutdown type for which the label is desired. + /// + /// @return A text label corresponding the value or "invalid" if the + /// value is not a valid value. + static const char* getShutdownTypeStr(const ShutdownType& type); + +private: + /// @brief Pointer to our queue manager instance. + D2QueueMgrPtr queue_mgr_; + + /// @brief Pointer to our update manager instance. + D2UpdateMgrPtr update_mgr_; + + /// @brief Indicates if the queue manager should be reconfigured. + bool reconf_queue_flag_; + + /// @brief Indicates the type of shutdown requested. + ShutdownType shutdown_type_; + + /// @brief Current socket control configuration. + isc::data::ConstElementPtr current_control_socket_; + +}; + +/// @brief Defines a shared pointer to D2Process. +typedef boost::shared_ptr<D2Process> D2ProcessPtr; + +}; // namespace isc::d2 +}; // namespace isc + +#endif |