From 09fd27b106533a4bc8ce295d1576a30ef85203d0 Mon Sep 17 00:00:00 2001
From: randomdan <randomdan@localhost>
Date: Thu, 15 Jul 2010 22:51:10 +0000
Subject: Cache that a DSN is unavailable for 60sec

---
 project2/cgiAppEngine.cpp    |  1 -
 project2/rdbmsDataSource.cpp | 52 ++++++++++++++++++++++++++++++--------------
 project2/rdbmsDataSource.h   |  2 ++
 3 files changed, 38 insertions(+), 17 deletions(-)

diff --git a/project2/cgiAppEngine.cpp b/project2/cgiAppEngine.cpp
index 4f04b7e..363bcb7 100644
--- a/project2/cgiAppEngine.cpp
+++ b/project2/cgiAppEngine.cpp
@@ -5,7 +5,6 @@
 #include "cgiEnvironment.h"
 #include <libxml/xinclude.h>
 #include "xmlObjectLoader.h"
-#include "rdbmsDataSource.h"
 #include "iterate.h"
 #include <boost/bind.hpp>
 #include <boost/lexical_cast.hpp>
diff --git a/project2/rdbmsDataSource.cpp b/project2/rdbmsDataSource.cpp
index e9c0089..6f3fc92 100644
--- a/project2/rdbmsDataSource.cpp
+++ b/project2/rdbmsDataSource.cpp
@@ -7,6 +7,7 @@
 #include <sqlext.h>
 
 _RdbmsDataSource::DBHosts _RdbmsDataSource::dbhosts;
+_RdbmsDataSource::FailedHosts _RdbmsDataSource::failedhosts;
 
 _RdbmsDataSource::_RdbmsDataSource(const xmlpp::Element * p) :
 	_SourceObject(p),
@@ -53,23 +54,26 @@ _RdbmsDataSource::getReadonly() const
 	}
 	if (preferLocal) {
 		ReadonlyDSNs::const_iterator ro = roDSNs.find(localhost);
-		if (ro == roDSNs.end()) {
-			syslog(LOG_WARNING, "%s: No database host makes local host name (%s) Will use master DSN",
-					__FUNCTION__, localhost.c_str());
-			return *connectTo(masterDsn);
+		try {
+			if (ro == roDSNs.end()) {
+				syslog(LOG_WARNING, "%s: No database host makes local host name (%s) Will use master DSN",
+						__FUNCTION__, localhost.c_str());
+				return *connectTo(masterDsn);
+			}
+			return *connectTo(ro->second);
+		}
+		catch (...) {
+			// Failed to connect to a preferred DB... carry on and try the others...
 		}
-		return *connectTo(ro->second);
 	}
-	else {
-		BOOST_FOREACH(ReadonlyDSNs::value_type db, roDSNs) {
-			try {
-				return *connectTo(db.second);
-			}
-			catch (...) {
-			}
+	BOOST_FOREACH(ReadonlyDSNs::value_type db, roDSNs) {
+		try {
+			return *connectTo(db.second);
+		}
+		catch (...) {
 		}
-		return *connectTo(masterDsn);
 	}
+	return *connectTo(masterDsn);
 }
 
 void
@@ -94,6 +98,15 @@ _RdbmsDataSource::rollback()
 _RdbmsDataSource::ConnectionPtr
 _RdbmsDataSource::connectTo(const std::string & dsn)
 {
+	FailedHosts::iterator dbf = failedhosts.find(dsn);
+	if (dbf != failedhosts.end()) {
+		if (time(NULL) - 20 > dbf->second.FailureTime) {
+			failedhosts.erase(dbf);
+		}
+		else {
+			throw dbf->second;
+		}
+	}
 	DBHosts::const_iterator dbi = dbhosts.find(dsn);
 	if (dbi != dbhosts.end()) {
 		try {
@@ -107,8 +120,15 @@ _RdbmsDataSource::connectTo(const std::string & dsn)
 			syslog(LOG_WARNING, "%s: Cached connection failed", __FUNCTION__);
 		}
 	}
-	ConnectionPtr db = ConnectionPtr(new ODBC::Connection(dsn));
-	dbhosts[dsn] = db;
-	return db;
+	
+	try {
+		ConnectionPtr db = ConnectionPtr(new ODBC::Connection(dsn));
+		dbhosts[dsn] = db;
+		return db;
+	}
+	catch (const ODBC::ConnectionError & e) {
+		failedhosts.insert(FailedHosts::value_type(dsn, e));
+		throw;
+	}
 }
 
diff --git a/project2/rdbmsDataSource.h b/project2/rdbmsDataSource.h
index 57a607f..a9dad6c 100644
--- a/project2/rdbmsDataSource.h
+++ b/project2/rdbmsDataSource.h
@@ -12,6 +12,7 @@ class _RdbmsDataSource : public _DataSource {
 		typedef boost::shared_ptr<ODBC::Connection> ConnectionPtr;
 		typedef std::map<std::string, std::string> ReadonlyDSNs; // Map hostname to DSN string
 		typedef std::map<std::string, ConnectionPtr> DBHosts; // Map DSN strings to connections
+		typedef std::map<std::string, const ODBC::ConnectionError> FailedHosts; // Map DSN strings to failures
 		_RdbmsDataSource(const xmlpp::Element * p);
 		ODBC::Connection & getReadonly() const;
 		ODBC::Connection & getWritable() const;
@@ -28,6 +29,7 @@ class _RdbmsDataSource : public _DataSource {
 	private:
 		mutable std::string localhost;
 		static DBHosts dbhosts;
+		static FailedHosts failedhosts;
 };
 typedef boost::shared_ptr<_RdbmsDataSource> RdbmsDataSource;
 typedef std::map<std::string, RdbmsDataSource> RdbmsDataSources;
-- 
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