From 82cb5b781573bbdd314bae51694ffada3312b5da Mon Sep 17 00:00:00 2001
From: Gordon Sim <gsim@apache.org>
Date: Fri, 7 Nov 2008 14:08:29 +0000
Subject: * Added some doxygen comments for FailoverManager * Added means for
 application to alter the order in which urls are tried (or indeed the list of
 urls to try)

git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@712127 13f79535-47bb-0310-9956-ffa450edef68
---
 cpp/src/qpid/client/FailoverManager.cpp | 10 ++++--
 cpp/src/qpid/client/FailoverManager.h   | 59 +++++++++++++++++++++++++++++++--
 2 files changed, 64 insertions(+), 5 deletions(-)

(limited to 'cpp/src')

diff --git a/cpp/src/qpid/client/FailoverManager.cpp b/cpp/src/qpid/client/FailoverManager.cpp
index 73c6bfc2de..ab9dbca70f 100644
--- a/cpp/src/qpid/client/FailoverManager.cpp
+++ b/cpp/src/qpid/client/FailoverManager.cpp
@@ -28,7 +28,8 @@ namespace client {
 
 using qpid::sys::Monitor;
 
-FailoverManager::FailoverManager(const ConnectionSettings& s) : settings(s), state(IDLE) {}
+FailoverManager::FailoverManager(const ConnectionSettings& s, 
+                                 ReconnectionStrategy* rs) : settings(s), strategy(rs), state(IDLE) {}
 
 void FailoverManager::execute(Command& c)
 {
@@ -38,11 +39,11 @@ void FailoverManager::execute(Command& c)
         try {
             AsyncSession session = connect().newSession();
             c.execute(session, retry);
-            session.sync();//TODO: shouldn't be required, but seems there is a bug in session
+            session.sync();//TODO: shouldn't be required
             session.close();
             completed = true;
         } catch(const TransportFailure&) {
-            retry = true;
+            retry = true;            
         }            
     }
 }
@@ -86,6 +87,7 @@ Connection& FailoverManager::getConnection()
 void FailoverManager::attempt(Connection& c, ConnectionSettings s, std::vector<Url> urls)
 {
     Monitor::ScopedUnlock u(lock);
+    if (strategy) strategy->editUrlList(urls);
     if (urls.empty()) {
         attempt(c, s);
     } else {
@@ -105,7 +107,9 @@ void FailoverManager::attempt(Connection& c, ConnectionSettings s, std::vector<U
 void FailoverManager::attempt(Connection& c, ConnectionSettings s)
 {
     try {
+        QPID_LOG(info, "Attempting to connect to " << s.host << " on " << s.port << "..."); 
         c.open(s);
+        QPID_LOG(info, "Connected to " << s.host << " on " << s.port); 
     } catch (const Exception& e) {
         QPID_LOG(info, "Could not connect to " << s.host << " on " << s.port << ": " << e.what()); 
     }
diff --git a/cpp/src/qpid/client/FailoverManager.h b/cpp/src/qpid/client/FailoverManager.h
index d17b8371d0..5af2a8f994 100644
--- a/cpp/src/qpid/client/FailoverManager.h
+++ b/cpp/src/qpid/client/FailoverManager.h
@@ -38,21 +38,75 @@ struct CannotConnectException : qpid::Exception
 };
 
 /**
- * Utility to handle reconnection.
+ * Utility to manage failover.
  */
 class FailoverManager
 {
   public:
+    /**
+     * Interface to implement for doing work that can be resumed on
+     * failover
+     */
     struct Command
     {
+        /**
+         * This method will be called with isRetry=false when the
+         * command is first executed. The session to use for the work
+         * will be passed to the implementing class. If the connection
+         * fails while the execute call is in progress, the
+         * FailoverManager controlling the execution will re-establish
+         * a connection, open a new session and call back to the
+         * Command implementations execute method with the new session
+         * and isRetry=true.
+         */
         virtual void execute(AsyncSession& session, bool isRetry) = 0;
         virtual ~Command() {}
     };
 
-    FailoverManager(const ConnectionSettings& settings);
+    struct ReconnectionStrategy
+    {
+        /**
+         * This method is called by the FailoverManager prior to
+         * establishing a connection (or re-connection) and can be
+         * used if the application wishes to edit or re-order the list
+         * which will default to the list of known brokers for the
+         * last connection.
+         */
+        virtual void editUrlList(std::vector<Url>&  urls) = 0;
+        virtual ~ReconnectionStrategy() {}
+    };
+
+    /**
+     * Create a manager to control failover for a logical connection.
+     * 
+     * @param settings the initial connection settings
+     * @param strategy optional stratgey callback allowing application
+     * to edit or reorder the list of urls to which reconnection is
+     * attempted
+     */
+    FailoverManager(const ConnectionSettings& settings, ReconnectionStrategy* strategy = 0);
+    /**
+     * Return the current connection if open or attept to reconnect to
+     * the specified list of urls. If no list is specified the list of
+     * known brokers from the last connection will be used. If no list
+     * is specified and this is the first connect attempt, the host
+     * and port from the initial settings will be used.
+     */
     Connection& connect(std::vector<Url> brokers = std::vector<Url>());
+    /**
+     * Return the current connection whether open or not
+     */
     Connection& getConnection();
+    /**
+     * Close the current connection
+     */
     void close();
+    /**
+     * Reliably execute the specified command. This involves creating
+     * a session on which to carry out the work of the command,
+     * handling failover occuring while exeuting that command and
+     * re-starting the work.
+     */
     void execute(Command&);
   private:
     enum State {IDLE, CONNECTING, CANT_CONNECT};
@@ -60,6 +114,7 @@ class FailoverManager
     qpid::sys::Monitor lock;
     Connection connection;
     ConnectionSettings settings;
+    ReconnectionStrategy* strategy;
     State state;
 
     void attempt(Connection&, ConnectionSettings settings, std::vector<Url> urls);
-- 
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