sync: take 2 at aborting active HTTP requests.

chrome/browser/sync/engine/net/server_connection_manager.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SYNC_ENGINE_NET_SERVER_CONNECTION_MANAGER_H_
 #define CHROME_BROWSER_SYNC_ENGINE_NET_SERVER_CONNECTION_MANAGER_H_
 #pragma once
 
 #include <iosfwd>
 #include <string>
 
 #include "base/atomicops.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/string_util.h"
 #include "base/threading/non_thread_safe.h"
+#include "base/threading/thread_checker.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/sync/syncable/syncable_id.h"
 #include "chrome/common/net/http_return.h"
 
 namespace syncable {
 class WriteTransaction;
 class DirectoryManager;
 }
 
 namespace sync_pb {
@@ skipping 105 matching lines @@
  private:
   ServerConnectionManager* const conn_mgr_;
   HttpResponse* const response_;
   bool server_reachable_;
   DISALLOW_COPY_AND_ASSIGN(ScopedServerStatusWatcher);
 };
 
 // Use this class to interact with the sync server.
 // The ServerConnectionManager currently supports POSTing protocol buffers.
 //
-class ServerConnectionManager : public base::NonThreadSafe {
+class ServerConnectionManager {
  public:
   // buffer_in - will be POSTed
   // buffer_out - string will be overwritten with response
   struct PostBufferParams {
     std::string buffer_in;
     std::string buffer_out;
     HttpResponse response;
   };
 
   // Abstract class providing network-layer functionality to the
   // ServerConnectionManager. Subclasses implement this using an HTTP stack of
   // their choice.
-  class Post {
+  class Connection {
    public:
-    explicit Post(ServerConnectionManager* scm) : scm_(scm) {
-    }
-    virtual ~Post() { }
+    explicit Connection(ServerConnectionManager* scm);
+    virtual ~Connection();
 
     // Called to initialize and perform an HTTP POST.
     virtual bool Init(const char* path,
                       const std::string& auth_token,
                       const std::string& payload,
                       HttpResponse* response) = 0;
 
+    // Immediately abandons a pending HTTP POST request and unblocks caller
+    // in Init.
+    virtual void Abort() = 0;
+
     bool ReadBufferResponse(std::string* buffer_out, HttpResponse* response,
                             bool require_response);
     bool ReadDownloadResponse(HttpResponse* response, std::string* buffer_out);
 
    protected:
     std::string MakeConnectionURL(const std::string& sync_server,
                                   const std::string& path,
                                   bool use_ssl) const;
 
     void GetServerParams(std::string* server,
@@ skipping 39 matching lines @@
 
   // Updates status and broadcasts events on change.
   bool CheckServerReachable();
 
   void AddListener(ServerConnectionEventListener* listener);
   void RemoveListener(ServerConnectionEventListener* listener);
 
   inline std::string user_agent() const { return user_agent_; }
 
   inline HttpResponse::ServerConnectionCode server_status() const {
-    DCHECK(CalledOnValidThread());
+    DCHECK(thread_checker_.CalledOnValidThread());
     return server_status_;
   }
 
   inline bool server_reachable() const { return server_reachable_; }
 
   const std::string client_id() const { return client_id_; }
 
   // This changes the server info used by the connection manager. This allows
   // a single client instance to talk to different backing servers. This is
   // typically called during / after authentication so that the server url
   // can be a function of the user's login id.
   void SetServerParameters(const std::string& server_url,
                            int port,
                            bool use_ssl);
 
   // Returns the current server parameters in server_url, port and use_ssl.
   void GetServerParameters(std::string* server_url,
                            int* port,
                            bool* use_ssl) const;
 
   std::string GetServerHost() const;
 
-  // Factory method to create a Post object we can use for communication with
-  // the server.
-  virtual Post* MakePost();
+  // Factory method to create an Connection object we can use for
+  // communication with the server.
+  virtual Connection* MakeConnection();
+
+  // Aborts any active HTTP POST request.
+  // We expect this to get called on a different thread than the valid
+  // ThreadChecker thread, as we want to kill any pending http traffic without
+  // having to wait for the request to complete.
+  void TerminateAllIO();
 
   void set_client_id(const std::string& client_id) {
-    DCHECK(CalledOnValidThread());
+    DCHECK(thread_checker_.CalledOnValidThread());
     DCHECK(client_id_.empty());
     client_id_.assign(client_id);
   }
 
   // Returns true if the auth token is succesfully set and false otherwise.
   bool set_auth_token(const std::string& auth_token) {
-    DCHECK(CalledOnValidThread());
+    DCHECK(thread_checker_.CalledOnValidThread());
     if (previously_invalidated_token != auth_token) {
       auth_token_.assign(auth_token);
       previously_invalidated_token = std::string();
       return true;
     }
     return false;
   }
 
   void InvalidateAndClearAuthToken() {
-    DCHECK(CalledOnValidThread());
+    DCHECK(thread_checker_.CalledOnValidThread());
     // Copy over the token to previous invalid token.
     if (!auth_token_.empty()) {
       previously_invalidated_token.assign(auth_token_);
       auth_token_ = std::string();
     }
   }
 
   const std::string auth_token() const {
-    DCHECK(CalledOnValidThread());
+    DCHECK(thread_checker_.CalledOnValidThread());
     return auth_token_;
   }
 
  protected:
   inline std::string proto_sync_path() const {
     return proto_sync_path_;
   }
 
   std::string get_time_path() const {
     return get_time_path_;
   }
 
   // Called wherever a failure should be taken as an indication that we may
   // be experiencing connection difficulties.
   virtual bool IncrementErrorCount();
 
   // NOTE: Tests rely on this protected function being virtual.
   //
   // Internal PostBuffer base function.
   virtual bool PostBufferToPath(PostBufferParams*,
                                 const std::string& path,
                                 const std::string& auth_token,
                                 ScopedServerStatusWatcher* watcher);
 
+  // Helper to check terminated flags and build a Connection object, installing
+  // it as the |active_connection_|.  If this ServerConnectionManager has been
+  // terminated, this will return NULL.
+  Connection* MakeActiveConnection();
+
+  // Called by Connection objects as they are destroyed to allow the
+  // ServerConnectionManager to cleanup active connections.
+  void OnConnectionDestroyed(Connection* connection);
+
   // The sync_server_ is the server that requests will be made to.
   std::string sync_server_;
 
   // The sync_server_port_ is the port that HTTP requests will be made on.
   int sync_server_port_;
 
   // The unique id of the user's client.
   std::string client_id_;
 
   // The user-agent string for HTTP.
@@ skipping 12 matching lines @@
   // The previous auth token that is invalid now.
   std::string previously_invalidated_token;
 
   int error_count_;  // Tracks the number of connection errors.
 
   ObserverList<ServerConnectionEventListener> listeners_;
 
   HttpResponse::ServerConnectionCode server_status_;
   bool server_reachable_;
 
+  base::ThreadChecker thread_checker_;
+
+  // Protects all variables below to allow bailing out of active connections.
+  base::Lock terminate_connection_lock_;
+
+  // If true, we've been told to terminate IO and expect to be destroyed
+  // shortly.  No future network requests will be made.
+  bool terminated_;
+
+  // A non-owning pointer to any active http connection, so that we can abort
+  // it if necessary.
+  Connection* active_connection_;
+
  private:
-  friend class Post;
+  friend class Connection;
   friend class ScopedServerStatusWatcher;
 
+  // A class to help deal with cleaning up active Connection objects when (for
+  // ex) multiple early-exits are present in some scope. ScopedConnectionHelper
+  // informs the ServerConnectionManager before the Connection object it takes
+  // ownership of is destroyed.
+  class ScopedConnectionHelper {
+   public:
+    // |manager| must outlive this. Takes ownership of |connection|.
+    ScopedConnectionHelper(ServerConnectionManager* manager,
+                           Connection* connection);
+    ~ScopedConnectionHelper();
+    Connection* get();
+   private:
+    ServerConnectionManager* manager_;
+    scoped_ptr<Connection> connection_;
+    DISALLOW_COPY_AND_ASSIGN(ScopedConnectionHelper);
+  };
+
   void NotifyStatusChanged();
 
   DISALLOW_COPY_AND_ASSIGN(ServerConnectionManager);
 };
 
 // Fills a ClientToServerMessage with the appropriate share and birthday
 // settings.
 bool FillMessageWithShareDetails(sync_pb::ClientToServerMessage* csm,
                                  syncable::DirectoryManager* manager,
                                  const std::string& share);
 
 std::ostream& operator<<(std::ostream& s, const struct HttpResponse& hr);
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_ENGINE_NET_SERVER_CONNECTION_MANAGER_H_