Adding upstream version 2.4.1.upstream/2.4.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 344 insertions, 0 deletions

diff --git a/src/lib/http/client.h b/src/lib/http/client.h
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+++ b/src/lib/http/client.h
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+// Copyright (C) 2018-2023 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 HTTP_CLIENT_H
+#define HTTP_CLIENT_H
+
+#include <asiolink/io_service.h>
+#include <asiolink/tls_socket.h>
+#include <exceptions/exceptions.h>
+#include <http/url.h>
+#include <http/request.h>
+#include <http/response.h>
+#include <boost/shared_ptr.hpp>
+#include <functional>
+#include <string>
+#include <thread>
+#include <vector>
+
+namespace isc {
+namespace http {
+
+/// @brief A generic error raised by the @ref HttpClient class.
+class HttpClientError : public Exception {
+public:
+    HttpClientError(const char* file, size_t line, const char* what) :
+        isc::Exception(file, line, what) { };
+};
+
+class HttpClientImpl;
+
+/// @brief HTTP client class.
+///
+/// This class implements an asynchronous HTTP client. The caller can schedule
+/// transmission of the HTTP request using @ref HttpClient::asyncSendRequest
+/// method. The caller specifies target URL for each request. The caller also
+/// specifies a pointer to the @ref HttpRequest or derived class, holding a
+/// request that should be transmitted to the destination. Such request must
+/// be finalized, i.e. @ref HttpRequest::finalize method must be called prior
+/// to sending it. The caller must also provide a pointer to the
+/// @ref HttpResponse object or an object derived from it. The type of the
+/// response object must match the expected content type to be returned in the
+/// server's response. The last argument specified in this call is the pointer
+/// to the callback function, which should be launched when the response is
+/// received, an error occurs or when a timeout in the transmission is
+/// signaled.
+///
+/// The HTTP client supports multiple simultaneous and persistent connections
+/// with different destinations. The client determines if the connection is
+/// persistent by looking into the Connection header and HTTP version of the
+/// request. If the connection should be persistent the client doesn't
+/// close the connection after sending a request and receiving a response from
+/// the server. If the client is provided with the request to be sent to the
+/// particular destination, but there is an ongoing communication with this
+/// destination, e.g. as a result of sending previous request, the new
+/// request is queued in the FIFO queue. When the previous request completes,
+/// the next request in the queue for the particular URL will be initiated.
+///
+/// Furthermore, the class supports two modes of operation: single-threaded
+/// and multi-threaded mode. In single-threaded mode, all IO is driven by
+/// an external IOService passed into the class constructor, and ultimately
+/// only a single connection per URL can be open at any given time.
+///
+/// In multi-threaded mode an internal thread pool driven by a private
+/// IOService instance is used to support multiple concurrent connections
+/// per URL. Currently, the number of connections per URL is set to the
+/// number of threads in the thread pool.
+///
+/// The client tests the persistent connection for usability before sending
+/// a request by trying to read from the socket (with message peeking). If
+/// the socket is usable the client uses it to transmit the request.
+///
+/// This classes exposes the underlying transport socket's descriptor for
+/// each connection via connect, handshake and close callbacks.
+/// This is done to permit the sockets to be monitored for IO readiness
+/// by external code that's something other than boost::asio
+/// (e.g.select() or epoll()), and would thus otherwise starve the
+/// client's IOService and cause a backlog of ready event handlers.
+///
+/// All errors are reported to the caller via the callback function supplied
+/// to the @ref HttpClient::asyncSendRequest. The IO errors are communicated
+/// via the @c boost::system::error code value. The response parsing errors
+/// are returned via the 3rd parameter of the callback.
+class HttpClient {
+public:
+    /// @brief HTTP request/response timeout value.
+    struct RequestTimeout {
+        /// @brief Constructor.
+        ///
+        /// @param value Request/response timeout value in milliseconds.
+        explicit RequestTimeout(long value)
+            : value_(value) {
+        }
+        long value_; ///< Timeout value specified.
+    };
+
+    /// @brief Callback type used in call to @ref HttpClient::asyncSendRequest.
+    typedef std::function<void(const boost::system::error_code&,
+                               const HttpResponsePtr&,
+                               const std::string&)> RequestHandler;
+
+    /// @brief Optional handler invoked when client connects to the server.
+    ///
+    /// Returned boolean value indicates whether the client should continue
+    /// connecting to the server (if true) or not (false).
+    /// It is passed the IO error code along with the native socket handle of
+    /// the connection's TCP socket.  The passed socket descriptor may be used
+    /// to monitor the readiness of the events via select() or epoll().
+    ///
+    /// @note Beware that the IO error code can be set to "in progress"
+    /// so a not null error code does not always mean the connect failed.
+    typedef std::function<bool(const boost::system::error_code&, const int)> ConnectHandler;
+
+    /// @brief Optional handler invoked when client performs the TLS handshake
+    /// with the server.
+    ///
+    /// It is called when the TLS handshake completes:
+    /// - if the handshake succeeds it is called with error code 0
+    /// - if the handshake fails it is called with error code != 0
+    /// - if TLS is not enabled, it is not called at all
+    ///
+    /// Returned boolean value indicates whether the client should continue
+    /// connecting to the server (if true) or not (false).
+    /// @note The second argument is not used.
+    typedef std::function<bool(const boost::system::error_code&, const int)> HandshakeHandler;
+
+    /// @brief Optional handler invoked when client closes the connection to the server.
+    ///
+    /// It is passed the native socket handler of the connection's TCP socket.
+    typedef std::function<void(const int)> CloseHandler;
+
+    /// @brief Constructor.
+    ///
+    /// @param io_service IO service to be used by the HTTP client.
+    /// @param multi_threading_enabled The flag which indicates if MT is enabled.
+    /// @param thread_pool_size maximum number of threads in the thread pool.
+    /// A value greater than zero enables multi-threaded mode and sets the
+    /// maximum number of concurrent connections per URL.  A value of zero
+    /// (default) enables single-threaded mode with one connection per URL.
+    /// @param defer_thread_start When true, starting of the pool threads is
+    /// deferred until a subsequent call to @ref start(). In this case the
+    /// pool's operational state after construction is STOPPED.  Otherwise,
+    /// the thread pool threads will be created and started, with the
+    /// operational state being RUNNING.  Applicable only when thread-pool size
+    /// is greater than zero.
+    explicit HttpClient(asiolink::IOService& io_service,
+                        bool multi_threading_enabled,
+                        size_t thread_pool_size = 0,
+                        bool defer_thread_start = false);
+
+    /// @brief Destructor.
+    ~HttpClient();
+
+    /// @brief Queues new asynchronous HTTP request for a given URL.
+    ///
+    /// The client maintains an internal connection pool which manages lists
+    /// of connections per URL. In single-threaded mode, each URL is limited
+    /// to a single connection.  In multi-threaded mode, each URL may have
+    /// more than one open connection per URL, enabling the client to carry
+    /// on multiple concurrent requests per URL.
+    ///
+    /// The client will search the pool for an open, idle connection for the
+    /// given URL.  If there are no idle connections, the client will open
+    /// a new connection up to the maximum number of connections allowed by the
+    /// thread mode.  If all possible connections are busy, the request is
+    /// pushed on to back of a URL-specific FIFO queue of pending requests.
+    ///
+    /// If however, there is an idle connection available than a new transaction
+    /// for the request will be initiated immediately upon that connection.
+    ///
+    /// Note that when a connection completes a transaction, and its URL
+    /// queue is not empty, it will pop a pending request from the front of
+    /// the queue and begin a new transaction for that request. The net effect
+    /// is that requests are always pulled from the front of the queue unless
+    /// the queue is empty.
+    ///
+    /// The existing connection is tested before it is used for the new
+    /// transaction by attempting to read (with message peeking) from
+    /// the open transport socket. If the read attempt is successful,
+    /// the client will transmit the HTTP request to the server using
+    /// this connection. It is possible that the server closes the
+    /// connection between the connection test and sending the request.
+    /// In such case, an error will be returned and the caller will
+    /// need to try re-sending the request.
+    ///
+    /// If the connection test fails, the client will close the socket and
+    /// reconnect to the server prior to sending the request.
+    ///
+    /// Pointers to the request and response objects are provided as arguments
+    /// of this method. These pointers should have appropriate types derived
+    /// from the @ref HttpRequest and @ref HttpResponse classes. For example,
+    /// if the request has content type "application/json", a pointer to the
+    /// @ref HttpResponseJson should be passed. In this case, the response type
+    /// should be @ref HttpResponseJson. These types are used to validate both
+    /// the request provided by the caller and the response received from the
+    /// server.
+    ///
+    /// The callback function provided by the caller is invoked when the
+    /// transaction terminates, i.e. when the server has responded or when an
+    /// error occurred. The callback is expected to be exception safe, but the
+    /// client internally guards against exceptions thrown by the callback.
+    ///
+    /// The first argument of the callback indicates an IO error during
+    /// communication with the server. If the communication is successful the
+    /// error code of 0 is returned. However, in this case it is still possible
+    /// that the transaction is unsuccessful due to HTTP response parsing error,
+    /// e.g. invalid content type, malformed response etc. Such errors are
+    /// indicated via third argument.
+    ///
+    /// If message parsing was successful the second argument of the callback
+    /// contains a pointer to the parsed response (the same pointer as provided
+    /// by the caller as the argument). If parsing was unsuccessful, the null
+    /// pointer is returned.
+    ///
+    /// The default timeout for the transaction is set to 10 seconds
+    /// (10 000 ms). If the timeout occurs, the callback is invoked with the
+    /// error code of @c boost::asio::error::timed_out.
+    /// The timeout covers both the connect and the transaction phases
+    /// so when connecting to the server takes too long (e.g. with a
+    /// misconfigured firewall) the timeout is triggered. The connect
+    /// callback can be used to recognize this condition.
+    ///
+    /// @param url URL where the request should be send.
+    /// @param tls_context TLS context.
+    /// @param request Pointer to the object holding a request.
+    /// @param response Pointer to the object where response should be stored.
+    /// @param request_callback Pointer to the user callback function invoked
+    /// when transaction ends.
+    /// @param request_timeout Timeout for the transaction in milliseconds.
+    /// @param connect_callback Optional callback invoked when the client
+    /// connects to the server.
+    /// @param handshake_callback Optional callback invoked when the client
+    /// performs the TLS handshake with the server.
+    /// @param close_callback Optional callback invoked when the client
+    /// closes the connection to the server.
+    ///
+    /// @throw HttpClientError If invalid arguments were provided.
+    void asyncSendRequest(const Url& url,
+                          const asiolink::TlsContextPtr& tls_context,
+                          const HttpRequestPtr& request,
+                          const HttpResponsePtr& response,
+                          const RequestHandler& request_callback,
+                          const RequestTimeout& request_timeout =
+                          RequestTimeout(10000),
+                          const ConnectHandler& connect_callback =
+                          ConnectHandler(),
+                          const HandshakeHandler& handshake_callback =
+                          HandshakeHandler(),
+                          const CloseHandler& close_callback =
+                          CloseHandler());
+
+    /// @brief Check if the current thread can perform thread pool state
+    /// transition.
+    ///
+    /// @throw MultiThreadingInvalidOperation if the state transition is done on
+    /// any of the worker threads.
+    void checkPermissions();
+
+    /// @brief Starts running the client's thread pool, if multi-threaded.
+    void start();
+
+    /// @brief Pauses the client's thread pool.
+    ///
+    /// Suspends thread pool event processing.
+    /// @throw InvalidOperation if the thread pool does not exist.
+    void pause();
+
+    /// @brief Resumes running the client's thread pool.
+    ///
+    /// Resumes thread pool event processing.
+    /// @throw InvalidOperation if the thread pool does not exist.
+    void resume();
+
+    /// @brief Halts client-side IO activity.
+    ///
+    /// Closes all connections, discards any queued requests, and in
+    /// multi-threaded mode discards the thread-pool and the internal
+    /// IOService.
+    void stop();
+
+    /// @brief Closes a connection if it has an out-of-band socket event
+    ///
+    /// If the  client owns a connection using the given socket and that
+    /// connection is currently in a transaction the method returns as this
+    /// indicates a normal ready event.  If the connection is not in an
+    /// ongoing transaction, then the connection is closed.
+    ///
+    /// This is method is intended to be used to detect and clean up then
+    /// sockets that are marked ready outside of transactions. The most common
+    /// case is the other end of the socket being closed.
+    ///
+    /// @param socket_fd socket descriptor to check
+    void closeIfOutOfBand(int socket_fd);
+
+    /// @brief Fetches a pointer to the internal IOService used to
+    /// drive the thread-pool in multi-threaded mode.
+    ///
+    /// @return pointer to the IOService instance, or an empty pointer
+    /// in single-threaded mode.
+    const asiolink::IOServicePtr getThreadIOService() const;
+
+    /// @brief Fetches the maximum size of the thread pool.
+    ///
+    /// @return the maximum size of the thread pool.
+    uint16_t getThreadPoolSize() const;
+
+    /// @brief Fetches the number of threads in the pool.
+    ///
+    /// @return the number of running threads.
+    uint16_t getThreadCount() const;
+
+    /// @brief Indicates if the thread pool is running.
+    ///
+    /// @return True if the thread pool exists and it is in the RUNNING state,
+    /// false otherwise.
+    bool isRunning();
+
+    /// @brief Indicates if the thread pool is stopped.
+    ///
+    /// @return True if the thread pool exists and it is in the STOPPED state,
+    /// false otherwise.
+    bool isStopped();
+
+    /// @brief Indicates if the thread pool is paused.
+    ///
+    /// @return True if the thread pool exists and it is in the PAUSED state,
+    /// false otherwise.
+    bool isPaused();
+
+private:
+
+    /// @brief Pointer to the HTTP client implementation.
+    boost::shared_ptr<HttpClientImpl> impl_;
+};
+
+/// @brief Defines a pointer to an HttpClient instance.
+typedef boost::shared_ptr<HttpClient> HttpClientPtr;
+
+} // end of namespace isc::http
+} // end of namespace isc
+
+#endif