X-Git-Url: http://jsfdemo.indexdata.com/?a=blobdiff_plain;f=src%2Ffilter_virt_db.cpp;h=db26acd37561d1ebc4210db6f8ca9404cb711451;hb=df8db6d8a539fa6d793aeb541f7c64d625c91d42;hp=9b614651bcdf0c11b90d33dc5ffa96ac03ab2c72;hpb=b3a5a3535ff97f71581c9b496f95e0820120f743;p=metaproxy-moved-to-github.git

diff --git a/src/filter_virt_db.cpp b/src/filter_virt_db.cpp
index 9b61465..db26acd 100644
--- a/src/filter_virt_db.cpp
+++ b/src/filter_virt_db.cpp
@@ -1,4 +1,4 @@
-/* $Id: filter_virt_db.cpp,v 1.6 2005-10-25 21:32:01 adam Exp $
+/* $Id: filter_virt_db.cpp,v 1.23 2006-01-13 15:09:35 adam Exp $
    Copyright (c) 2005, Index Data.
 
 %LICENSE%
@@ -7,19 +7,19 @@
 #include "config.hpp"
 
 #include "filter.hpp"
-#include "router.hpp"
 #include "package.hpp"
 
 #include <boost/thread/mutex.hpp>
+#include <boost/thread/condition.hpp>
+#include <boost/shared_ptr.hpp>
 
+#include "util.hpp"
 #include "filter_virt_db.hpp"
 
 #include <yaz/zgdu.h>
-#include <yaz/log.h>
 #include <yaz/otherinfo.h>
 #include <yaz/diagbib1.h>
 
-#include <list>
 #include <map>
 #include <iostream>
 
@@ -27,410 +27,681 @@ namespace yf = yp2::filter;
 
 namespace yp2 {
     namespace filter {
-        struct Virt_db_set {
-            Virt_db_set(yp2::Session &id, std::string setname,
-                        std::string vhost);
-            Virt_db_set();
-            ~Virt_db_set();
 
-            yp2::Session m_session;
+        struct Virt_db::Set {
+            Set(BackendPtr b, std::string setname);
+            Set();
+            ~Set();
+
+            BackendPtr m_backend;
             std::string m_setname;
-            std::string m_vhost;
         };
-        struct Virt_db_session {
-            Virt_db_session(yp2::Session &id, bool use_vhost);
-            Virt_db_session();
-            yp2::Session m_session;
-            bool m_use_vhost;
-            std::map<std::string,Virt_db_set> m_sets;
+        struct Virt_db::Map {
+            Map(std::string vhost, std::string route);
+            Map();
+            std::string m_vhost;
+            std::string m_route;
         };
-        struct Virt_db_map {
-            Virt_db_map(std::string vhost);
-            Virt_db_map();
+        struct Virt_db::Backend {
+            yp2::Session m_backend_session;
+            std::string m_backend_database;
+            std::string m_frontend_database;
             std::string m_vhost;
+            std::string m_route;
+            bool m_named_result_sets;
+            int m_number_of_sets;
         };
+        struct Virt_db::Frontend {
+            Frontend(Rep *rep);
+            ~Frontend();
+            yp2::Session m_session;
+            bool m_is_virtual;
+            bool m_in_use;
+            std::list<BackendPtr> m_backend_list;
+            std::map<std::string,Virt_db::Set> m_sets;
+
+            void search(Package &package, Z_APDU *apdu);
+            void present(Package &package, Z_APDU *apdu);
+            void scan(Package &package, Z_APDU *apdu);
+
+            void close(Package &package);
+            typedef std::map<std::string,Virt_db::Set>::iterator Sets_it;
+
+            BackendPtr lookup_backend_from_database(std::string database);
+            BackendPtr create_backend_from_database(std::string database);
+            
+            BackendPtr init_backend(std::string database, Package &package,
+                                    int &error_code, std::string &addinfo);
+            Rep *m_p;
+        };            
         class Virt_db::Rep {
             friend class Virt_db;
+            friend class Frontend;
             
-            void release_session(Package &package);
-            void init(Package &package, Z_APDU *apdu, bool &move_later);
-            void search(Package &package, Z_APDU *apdu, bool &move_later);
-            void present(Package &package, Z_APDU *apdu, bool &move_later);
+            Frontend *get_frontend(Package &package);
+            void release_frontend(Package &package);
         private:
             boost::mutex m_sessions_mutex;
-            std::map<yp2::Session,Virt_db_session>m_sessions;
-            std::map<std::string, Virt_db_map>m_maps;
+            std::map<std::string, Virt_db::Map>m_maps;
+
+            typedef std::map<std::string,Virt_db::Set>::iterator Sets_it;
 
-            typedef std::map<yp2::Session,Virt_db_session>::iterator Ses_it;
-            typedef std::map<std::string,Virt_db_set>::iterator Sets_it;
+            boost::mutex m_mutex;
+            boost::condition m_cond_session_ready;
+            std::map<yp2::Session,Frontend *> m_clients;
         };
     }
 }
 
-yf::Virt_db_set::Virt_db_set(yp2::Session &id, std::string setname,
-                             std::string vhost)
-    :   m_session(id), m_setname(setname), m_vhost(vhost)
+using namespace yp2;
+
+yf::Virt_db::BackendPtr yf::Virt_db::Frontend::lookup_backend_from_database(
+    std::string database)
+{
+    std::list<BackendPtr>::const_iterator map_it;
+    map_it = m_backend_list.begin();
+    for (; map_it != m_backend_list.end(); map_it++)
+        if ((*map_it)->m_frontend_database == database)
+            return *map_it;
+    BackendPtr null;
+    return null;
+}
+
+yf::Virt_db::BackendPtr yf::Virt_db::Frontend::create_backend_from_database(
+    std::string database)
+{
+    std::map<std::string, Virt_db::Map>::iterator map_it;
+    map_it = m_p->m_maps.find(database);
+    if (map_it == m_p->m_maps.end())
+    {
+        BackendPtr ptr;
+        return ptr;
+    }
+    BackendPtr b(new Backend);
+
+    b->m_number_of_sets = 0;
+    b->m_frontend_database = database;
+    b->m_named_result_sets = false;
+    b->m_route = map_it->second.m_route;
+    b->m_vhost = map_it->second.m_vhost;
+    const char *sep = strchr(b->m_vhost.c_str(), '/');
+    std::string backend_database;
+    if (sep)
+        b->m_backend_database = std::string(sep+1);
+    else
+        b->m_backend_database = database;
+
+    return b;
+}
+
+yf::Virt_db::BackendPtr yf::Virt_db::Frontend::init_backend(
+    std::string database, Package &package,
+    int &error_code, std::string &addinfo)
 {
+    BackendPtr b = create_backend_from_database(database);
+    if (!b)
+    {
+        error_code = YAZ_BIB1_DATABASE_UNAVAILABLE;
+        addinfo = database;
+        return b;
+    }
+    Package init_package(b->m_backend_session, package.origin());
+    init_package.copy_filter(package);
+
+    yp2::odr odr;
+
+    Z_APDU *init_apdu = zget_APDU(odr, Z_APDU_initRequest);
+    
+    yaz_oi_set_string_oidval(&init_apdu->u.initRequest->otherInfo, odr,
+                             VAL_PROXY, 1, b->m_vhost.c_str());
+    
+    Z_InitRequest *req = init_apdu->u.initRequest;
+
+    ODR_MASK_SET(req->options, Z_Options_search);
+    ODR_MASK_SET(req->options, Z_Options_present);
+    ODR_MASK_SET(req->options, Z_Options_namedResultSets);
+    ODR_MASK_SET(req->options, Z_Options_scan);
+
+    ODR_MASK_SET(req->protocolVersion, Z_ProtocolVersion_1);
+    ODR_MASK_SET(req->protocolVersion, Z_ProtocolVersion_2);
+    ODR_MASK_SET(req->protocolVersion, Z_ProtocolVersion_3);
+
+    init_package.request() = init_apdu;
+    
+    init_package.move(b->m_route);  // sending init 
+    
+    if (init_package.session().is_closed())
+    {
+        error_code = YAZ_BIB1_DATABASE_UNAVAILABLE;
+        addinfo = database;
+        BackendPtr null;
+        return null;
+    }
+    Z_GDU *gdu = init_package.response().get();
+    // we hope to get an init response
+    if (gdu && gdu->which == Z_GDU_Z3950 && gdu->u.z3950->which ==
+        Z_APDU_initResponse)
+    {
+        if (ODR_MASK_GET(gdu->u.z3950->u.initResponse->options,
+                         Z_Options_namedResultSets))
+        {
+            b->m_named_result_sets = true;
+        }
+    }
+    else
+    {
+        error_code = YAZ_BIB1_DATABASE_UNAVAILABLE;
+        addinfo = database;
+        BackendPtr null;
+        return null;
+    }        
+    m_backend_list.push_back(b);
+    return b;
+}
+
+void yf::Virt_db::Frontend::search(Package &package, Z_APDU *apdu_req)
+{
+    Z_SearchRequest *req = apdu_req->u.searchRequest;
+    std::string vhost;
+    std::string resultSetId = req->resultSetName;
+    yp2::odr odr;
+
+    // only one datatabase for now
+    if (req->num_databaseNames != 1)
+    {   // exactly one database must be specified
+        Z_APDU *apdu =
+            odr.create_searchResponse(
+                apdu_req, YAZ_BIB1_TOO_MANY_DATABASES_SPECIFIED, 0);
+        package.response() = apdu;
+        
+        return;
+    }
+    std::string database = std::string(req->databaseNames[0]);
+
+    BackendPtr b; // null for now
+    Sets_it sets_it = m_sets.find(req->resultSetName);
+    if (sets_it != m_sets.end())
+    {
+        // result set already exist 
+        // if replace indicator is off: we return diagnostic if
+        // result set already exist.
+        if (*req->replaceIndicator == 0)
+        {
+            Z_APDU *apdu = 
+                odr.create_searchResponse(
+                    apdu_req,
+                    YAZ_BIB1_RESULT_SET_EXISTS_AND_REPLACE_INDICATOR_OFF,
+                    0);
+            package.response() = apdu;
+            
+            return;
+        } 
+        sets_it->second.m_backend->m_number_of_sets--;
+
+        // pick up any existing backend with a database match
+        std::list<BackendPtr>::const_iterator map_it;
+        map_it = m_backend_list.begin();
+        for (; map_it != m_backend_list.end(); map_it++)
+        {
+            BackendPtr tmp = *map_it;
+            if (tmp->m_frontend_database == database)
+                break;
+        }
+        if (map_it != m_backend_list.end()) 
+            b = *map_it;
+    }
+    else
+    {
+        // new result set.
+
+        // pick up any existing database with named result sets ..
+        // or one which has no result sets.. yet.
+        std::list<BackendPtr>::const_iterator map_it;
+        map_it = m_backend_list.begin();
+        for (; map_it != m_backend_list.end(); map_it++)
+        {
+            BackendPtr tmp = *map_it;
+            if (tmp->m_frontend_database == database &&
+                (tmp->m_named_result_sets ||
+                 tmp->m_number_of_sets == 0))
+                break;
+        }
+        if (map_it != m_backend_list.end()) 
+            b = *map_it;
+    }
+    if (!b)  // no backend yet. Must create a new one
+    {
+        int error_code;
+        std::string addinfo;
+        b = init_backend(database, package, error_code, addinfo);
+        if (!b)
+        {
+            // did not get a backend (unavailable somehow?)
+            
+            Z_APDU *apdu = 
+                odr.create_searchResponse(
+                    apdu_req, error_code, addinfo.c_str());
+            package.response() = apdu;
+            return;
+        }
+    }
+    m_sets.erase(req->resultSetName);
+    // sending search to backend
+    Package search_package(b->m_backend_session, package.origin());
+
+    search_package.copy_filter(package);
+
+    std::string backend_setname;
+    if (b->m_named_result_sets)
+    {
+        std::cout << "named_result_sets TRUE\n";
+        backend_setname = std::string(req->resultSetName);
+    }
+    else
+    {
+        std::cout << "named_result_sets FALSE\n";
+        backend_setname = "default";
+        req->resultSetName = odr_strdup(odr, backend_setname.c_str());
+    }
+
+    const char *backend_database = b->m_backend_database.c_str();
+    req->databaseNames[0] = odr_strdup(odr, backend_database);
+
+    *req->replaceIndicator = 1;
+
+    search_package.request() = yazpp_1::GDU(apdu_req);
+    
+    search_package.move(b->m_route);
+
+    if (search_package.session().is_closed())
+    {
+        Z_APDU *apdu = 
+            odr.create_searchResponse(
+                apdu_req,
+                YAZ_BIB1_DATABASE_UNAVAILABLE, database.c_str());
+        package.response() = apdu;
+        return;
+    }
+    package.response() = search_package.response();
+
+    b->m_number_of_sets++;
+
+    m_sets[resultSetId] = Virt_db::Set(b, backend_setname);
 }
 
+yf::Virt_db::Frontend::Frontend(Rep *rep)
+{
+    m_p = rep;
+    m_is_virtual = false;
+}
 
-yf::Virt_db_set::Virt_db_set()
+void yf::Virt_db::Frontend::close(Package &package)
 {
+    std::list<BackendPtr>::const_iterator b_it;
+    
+    for (b_it = m_backend_list.begin(); b_it != m_backend_list.end(); b_it++)
+    {
+        (*b_it)->m_backend_session.close();
+        Package close_package((*b_it)->m_backend_session, package.origin());
+        close_package.copy_filter(package);
+        close_package.move((*b_it)->m_route);
+    }
+    m_backend_list.clear();
 }
 
+yf::Virt_db::Frontend::~Frontend()
+{
+}
 
-yf::Virt_db_set::~Virt_db_set()
+yf::Virt_db::Frontend *yf::Virt_db::Rep::get_frontend(Package &package)
 {
+    boost::mutex::scoped_lock lock(m_mutex);
+
+    std::map<yp2::Session,yf::Virt_db::Frontend *>::iterator it;
+    
+    while(true)
+    {
+        it = m_clients.find(package.session());
+        if (it == m_clients.end())
+            break;
+        
+        if (!it->second->m_in_use)
+        {
+            it->second->m_in_use = true;
+            return it->second;
+        }
+        m_cond_session_ready.wait(lock);
+    }
+    Frontend *f = new Frontend(this);
+    m_clients[package.session()] = f;
+    f->m_in_use = true;
+    return f;
 }
 
-yf::Virt_db_map::Virt_db_map(std::string vhost)
-    : m_vhost(vhost) 
+
+void yf::Virt_db::Rep::release_frontend(Package &package)
 {
+    boost::mutex::scoped_lock lock(m_mutex);
+    std::map<yp2::Session,yf::Virt_db::Frontend *>::iterator it;
+    
+    it = m_clients.find(package.session());
+    if (it != m_clients.end())
+    {
+        if (package.session().is_closed())
+        {
+            it->second->close(package);
+            delete it->second;
+            m_clients.erase(it);
+        }
+        else
+        {
+            it->second->m_in_use = false;
+        }
+        m_cond_session_ready.notify_all();
+    }
 }
 
-yf::Virt_db_map::Virt_db_map()
+yf::Virt_db::Set::Set(BackendPtr b, std::string setname)
+    :  m_backend(b), m_setname(setname)
 {
 }
 
-yf::Virt_db_session::Virt_db_session()
-    : m_use_vhost(false)
+
+yf::Virt_db::Set::Set()
 {
+}
+
 
+yf::Virt_db::Set::~Set()
+{
 }
 
-yf::Virt_db_session::Virt_db_session(yp2::Session &id,
-                                     bool use_vhost) :
-    m_session(id) , m_use_vhost(use_vhost)
+yf::Virt_db::Map::Map(std::string vhost, std::string route)
+    : m_vhost(vhost), m_route(route) 
 {
+}
 
+yf::Virt_db::Map::Map()
+{
 }
 
-yf::Virt_db::Virt_db() {
-    m_p = new Virt_db::Rep;
+yf::Virt_db::Virt_db() : m_p(new Virt_db::Rep)
+{
 }
 
 yf::Virt_db::~Virt_db() {
-    delete m_p;
 }
 
-void yf::Virt_db::Rep::release_session(Package &package)
+void yf::Virt_db::Frontend::present(Package &package, Z_APDU *apdu_req)
 {
-    boost::mutex::scoped_lock lock(m_sessions_mutex);
-    
-    m_sessions.erase(package.session());
-}
+    Z_PresentRequest *req = apdu_req->u.presentRequest;
+    std::string resultSetId = req->resultSetId;
+    yp2::odr odr;
 
-void yf::Virt_db::Rep::present(Package &package, Z_APDU *apdu, bool &move_later){
-    Session *id = 0;
-    Z_PresentRequest *req = apdu->u.presentRequest;
+    Sets_it sets_it = m_sets.find(resultSetId);
+    if (sets_it == m_sets.end())
     {
-        boost::mutex::scoped_lock lock(m_sessions_mutex);
+        Z_APDU *apdu = 
+            odr.create_presentResponse(
+                apdu_req,
+                YAZ_BIB1_SPECIFIED_RESULT_SET_DOES_NOT_EXIST,
+                resultSetId.c_str());
+        package.response() = apdu;
         
-        Ses_it it = m_sessions.find(package.session());
-        if (it == m_sessions.end())
-        {
-            ODR odr = odr_createmem(ODR_ENCODE);
-            
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_close);
-            
-            *apdu->u.close->closeReason = Z_Close_protocolError;
-            apdu->u.close->diagnosticInformation =
-                odr_strdup(odr, "no session for present request");
-            
-            package.response() = apdu;
-            package.session().close();
-            odr_destroy(odr);
-            assert(false);
-            return;
-        }
-        if (it->second.m_use_vhost)
-        {
-            move_later = true;
-            return;
-        }
-        Sets_it sets_it = it->second.m_sets.find(req->resultSetId);
-        if (sets_it == it->second.m_sets.end())
-        {
-            ODR odr = odr_createmem(ODR_ENCODE);
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_presentResponse);
-            
-            Z_Records *rec = (Z_Records *) odr_malloc(odr, sizeof(Z_Records));
-            apdu->u.presentResponse->records = rec;
-            rec->which = Z_Records_NSD;
-            rec->u.nonSurrogateDiagnostic =
-                zget_DefaultDiagFormat(
-                    odr,
-                    YAZ_BIB1_SPECIFIED_RESULT_SET_DOES_NOT_EXIST,
-                    req->resultSetId);
-            package.response() = apdu;
-            odr_destroy(odr);
-            return;
-        }
-        id = new yp2::Session(sets_it->second.m_session);
+        return;
     }
-    ODR odr = odr_createmem(ODR_ENCODE);
+    Session *id =
+        new yp2::Session(sets_it->second.m_backend->m_backend_session);
     
     // sending present to backend
     Package present_package(*id, package.origin());
     present_package.copy_filter(package);
     
     req->resultSetId = odr_strdup(odr, "default");
-    present_package.request() = yazpp_1::GDU(apdu);
-    
-    odr_destroy(odr);
-    
+    present_package.request() = yazpp_1::GDU(apdu_req);
+
     present_package.move();
 
-    package.response() = present_package.response();
-    // must check for a closed present session..
+    if (present_package.session().is_closed())
+    {
+        Z_APDU *apdu = 
+            odr.create_presentResponse(
+                apdu_req,
+                YAZ_BIB1_RESULT_SET_NO_LONGER_EXISTS_UNILATERALLY_DELETED_BY_,
+                resultSetId.c_str());
+        package.response() = apdu;
+        m_sets.erase(resultSetId);
+    }
+    else
+    {
+        package.response() = present_package.response();
+    }
     delete id;
 }
 
-void yf::Virt_db::Rep::search(Package &package, Z_APDU *apdu, bool &move_later)
+void yf::Virt_db::Frontend::scan(Package &package, Z_APDU *apdu_req)
 {
-    Z_SearchRequest *req = apdu->u.searchRequest;
+    Z_ScanRequest *req = apdu_req->u.scanRequest;
     std::string vhost;
-    std::string database;
-    Session *id = 0;
+    yp2::odr odr;
+
+    // only one datatabase for now
+    if (req->num_databaseNames != 1)
+    {   // exactly one database must be specified
+        Z_APDU *apdu =
+            odr.create_scanResponse(
+                apdu_req,
+                YAZ_BIB1_TOO_MANY_DATABASES_SPECIFIED, 0);
+        package.response() = apdu;
+        return;
+    }
+    std::string database = std::string(req->databaseNames[0]);
+    
+    BackendPtr b;
+    // pick up any existing backend with a database match
+    std::list<BackendPtr>::const_iterator map_it;
+    map_it = m_backend_list.begin();
+    for (; map_it != m_backend_list.end(); map_it++)
     {
-        boost::mutex::scoped_lock lock(m_sessions_mutex);
-
-        Ses_it it = m_sessions.find(package.session());
-        if (it == m_sessions.end())
-        {
-            ODR odr = odr_createmem(ODR_ENCODE);
-            
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_close);
-            
-            *apdu->u.close->closeReason = Z_Close_protocolError;
-            apdu->u.close->diagnosticInformation =
-                odr_strdup(odr, "no session for search request");
-            
-            package.response() = apdu;
-            package.session().close();
-            odr_destroy(odr);
-            return;
-        }
-        if (it->second.m_use_vhost)
-        {
-            move_later = true;
-            return;
-        }
-        if (req->num_databaseNames != 1)
-        {   // exactly one database must be specified
-            ODR odr = odr_createmem(ODR_ENCODE);
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_searchResponse);
-            
-            Z_Records *rec = (Z_Records *) odr_malloc(odr, sizeof(Z_Records));
-            apdu->u.searchResponse->records = rec;
-            rec->which = Z_Records_NSD;
-            rec->u.nonSurrogateDiagnostic =
-                zget_DefaultDiagFormat(
-                    odr, YAZ_BIB1_TOO_MANY_DATABASES_SPECIFIED, 0);
-            package.response() = apdu;
-            
-            odr_destroy(odr);
-            return;
-        }
-        database = req->databaseNames[0];
-        std::map<std::string, Virt_db_map>::iterator map_it;
-        map_it = m_maps.find(database);
-        if (map_it == m_maps.end()) 
-        {   // no map for database: return diagnostic
-            ODR odr = odr_createmem(ODR_ENCODE);
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_searchResponse);
-            
-            Z_Records *rec = (Z_Records *) odr_malloc(odr, sizeof(Z_Records));
-            apdu->u.searchResponse->records = rec;
-            rec->which = Z_Records_NSD;
-            rec->u.nonSurrogateDiagnostic =
-                zget_DefaultDiagFormat(
-                    odr, YAZ_BIB1_DATABASE_UNAVAILABLE, database.c_str());
-            package.response() = apdu;
-            
-            odr_destroy(odr);
-            return;
-        }
-        if (*req->replaceIndicator == 0)
-        {
-            Sets_it sets_it = it->second.m_sets.find(req->resultSetName);
-            if (sets_it != it->second.m_sets.end())
-            {
-                ODR odr = odr_createmem(ODR_ENCODE);
-                Z_APDU *apdu = zget_APDU(odr, Z_APDU_searchResponse);
-                
-                Z_Records *rec = (Z_Records *) odr_malloc(odr, sizeof(Z_Records));
-                apdu->u.searchResponse->records = rec;
-                rec->which = Z_Records_NSD;
-                rec->u.nonSurrogateDiagnostic =
-                    zget_DefaultDiagFormat(
-                        odr,
-                        YAZ_BIB1_RESULT_SET_EXISTS_AND_REPLACE_INDICATOR_OFF,
-                        0);
-                package.response() = apdu;
-                
-                odr_destroy(odr);
-                return;
-            }
-        }
-        vhost = map_it->second.m_vhost;
-        id = new Session;
-
-        it->second.m_sets[req->resultSetName] =
-            Virt_db_set(*id, req->resultSetName, vhost);
+        BackendPtr tmp = *map_it;
+        if (tmp->m_frontend_database == database)
+            break;
     }
-    const char *vhost_cstr = vhost.c_str();
-    if (true)
-    {  // sending init to backend
-        Package init_package(*id, package.origin());
-        init_package.copy_filter(package);
-        
-        ODR odr = odr_createmem(ODR_ENCODE);
-        Z_APDU *init_apdu = zget_APDU(odr, Z_APDU_initRequest);
-        
-        yaz_oi_set_string_oidval(&init_apdu->u.initRequest->otherInfo, odr,
-                                 VAL_PROXY, 1, vhost_cstr);
-        
-        init_package.request() = init_apdu;
-        odr_destroy(odr);
-
-        init_package.move();  // sending init 
-
-        if (init_package.session().is_closed())
+    if (map_it != m_backend_list.end()) 
+        b = *map_it;
+    if (!b)  // no backend yet. Must create a new one
+    {
+        int error_code;
+        std::string addinfo;
+        b = init_backend(database, package, error_code, addinfo);
+        if (!b)
         {
-            ODR odr = odr_createmem(ODR_ENCODE);
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_searchResponse);
-            
-            Z_Records *rec = (Z_Records *) odr_malloc(odr, sizeof(Z_Records));
-            apdu->u.searchResponse->records = rec;
-            rec->which = Z_Records_NSD;
-            rec->u.nonSurrogateDiagnostic =
-                zget_DefaultDiagFormat(
-                    odr, YAZ_BIB1_DATABASE_UNAVAILABLE, database.c_str());
+            // did not get a backend (unavailable somehow?)
+            Z_APDU *apdu =
+                odr.create_scanResponse(
+                    apdu_req, error_code, addinfo.c_str());
             package.response() = apdu;
             
-            odr_destroy(odr);
             return;
         }
     }
-    // sending search to backend
-    Package search_package(*id, package.origin());
+    // sending scan to backend
+    Package scan_package(b->m_backend_session, package.origin());
 
-    search_package.copy_filter(package);
-    const char *sep = strchr(vhost_cstr, '/');
-    ODR odr = odr_createmem(ODR_ENCODE);
-    if (sep)
-        req->databaseNames[0] = odr_strdup(odr, sep+1);
+    scan_package.copy_filter(package);
 
-    *req->replaceIndicator = 1;
-    req->resultSetName = odr_strdup(odr, "default");
-    search_package.request() = yazpp_1::GDU(apdu);
-    
-    odr_destroy(odr);
-    
-    search_package.move();
+    const char *backend_database = b->m_backend_database.c_str();
+    req->databaseNames[0] = odr_strdup(odr, backend_database);
 
-    package.response() = search_package.response();
-    // must check for a closed search session..
-    delete id;
-}
-
-void yf::Virt_db::Rep::init(Package &package, Z_APDU *apdu, bool &move_later)
-{
-    release_session(package);
-    boost::mutex::scoped_lock lock(m_sessions_mutex);
-
-    Z_InitRequest *req = apdu->u.initRequest;
+    scan_package.request() = yazpp_1::GDU(apdu_req);
     
-    const char *vhost =
-        yaz_oi_get_string_oidval(&req->otherInfo, VAL_PROXY, 1, 0);
-    if (!vhost)
-    {
-        ODR odr = odr_createmem(ODR_ENCODE);
-        
-        Z_APDU *apdu = zget_APDU(odr, Z_APDU_initResponse);
-        Z_InitResponse *resp = apdu->u.initResponse;
-        
-        int i;
-        static const int masks[] = {
-            Z_Options_search, Z_Options_present, Z_Options_namedResultSets, -1 
-        };
-        for (i = 0; masks[i] != -1; i++)
-            if (ODR_MASK_GET(req->options, masks[i]))
-                ODR_MASK_SET(resp->options, masks[i]);
-        
-        static const int versions[] = {
-            Z_ProtocolVersion_1,
-            Z_ProtocolVersion_2,
-            Z_ProtocolVersion_3,
-            -1
-        };
-        for (i = 0; versions[i] != -1; i++)
-            if (ODR_MASK_GET(req->protocolVersion, versions[i]))
-                ODR_MASK_SET(resp->protocolVersion, versions[i]);
-            else
-                break;
-
-        package.response() = apdu;
-        
-        odr_destroy(odr);
+    scan_package.move(b->m_route);
 
-        m_sessions[package.session()] = Virt_db_session(package.session(), false);
-    }
-    else
+    if (scan_package.session().is_closed())
     {
-        m_sessions[package.session()] = Virt_db_session(package.session(), true);
-        move_later = true;
+        Z_APDU *apdu =
+            odr.create_scanResponse(
+                apdu_req, YAZ_BIB1_DATABASE_UNAVAILABLE, database.c_str());
+        package.response() = apdu;
+        return;
     }
+    package.response() = scan_package.response();
 }
 
-void yf::Virt_db::add_map_db2vhost(std::string db, std::string vhost)
+
+void yf::Virt_db::add_map_db2vhost(std::string db, std::string vhost,
+                                   std::string route)
 {
-    m_p->m_maps[db] = Virt_db_map(vhost);
+    m_p->m_maps[db] = Virt_db::Map(vhost, route);
 }
 
 void yf::Virt_db::process(Package &package) const
 {
-    Z_GDU *gdu = package.request().get();
-
-    if (!gdu || gdu->which != Z_GDU_Z3950)
-        package.move();
-    else
+    yf::Virt_db::Frontend *f = m_p->get_frontend(package);
+    if (f)
     {
-        bool move_later = false;
-        Z_APDU *apdu = gdu->u.z3950;
-        if (apdu->which == Z_APDU_initRequest)
+        Z_GDU *gdu = package.request().get();
+        
+        if (gdu && gdu->which == Z_GDU_Z3950 && gdu->u.z3950->which ==
+            Z_APDU_initRequest && !f->m_is_virtual)
         {
-            m_p->init(package, apdu, move_later);
+            Z_InitRequest *req = gdu->u.z3950->u.initRequest;
+
+            const char *vhost =
+                yaz_oi_get_string_oidval(&req->otherInfo, VAL_PROXY, 1, 0);
+            if (!vhost)
+            {
+                yp2::odr odr;
+                Z_APDU *apdu = odr.create_initResponse(gdu->u.z3950, 0, 0);
+                Z_InitResponse *resp = apdu->u.initResponse;
+                
+                int i;
+                static const int masks[] = {
+                    Z_Options_search,
+                    Z_Options_present,
+                    Z_Options_namedResultSets,
+                    Z_Options_scan,
+                    -1 
+                };
+                for (i = 0; masks[i] != -1; i++)
+                    if (ODR_MASK_GET(req->options, masks[i]))
+                        ODR_MASK_SET(resp->options, masks[i]);
+                
+                static const int versions[] = {
+                    Z_ProtocolVersion_1,
+                    Z_ProtocolVersion_2,
+                    Z_ProtocolVersion_3,
+                    -1
+                };
+                for (i = 0; versions[i] != -1; i++)
+                    if (ODR_MASK_GET(req->protocolVersion, versions[i]))
+                        ODR_MASK_SET(resp->protocolVersion, versions[i]);
+                    else
+                        break;
+                
+                package.response() = apdu;
+                f->m_is_virtual = true;
+            }
+            else
+                package.move();
         }
-        else if (apdu->which == Z_APDU_searchRequest)
+        else if (!f->m_is_virtual)
+            package.move();
+        else if (gdu && gdu->which == Z_GDU_Z3950)
         {
-            m_p->search(package, apdu, move_later);
+            Z_APDU *apdu = gdu->u.z3950;
+            if (apdu->which == Z_APDU_initRequest)
+            {
+                yp2::odr odr;
+                
+                package.response() = odr.create_close(
+                    apdu,
+                    Z_Close_protocolError,
+                    "double init");
+                
+                package.session().close();
+            }
+            else if (apdu->which == Z_APDU_searchRequest)
+            {
+                f->search(package, apdu);
+            }
+            else if (apdu->which == Z_APDU_presentRequest)
+            {
+                f->present(package, apdu);
+            }
+            else if (apdu->which == Z_APDU_scanRequest)
+            {
+                f->scan(package, apdu);
+            }
+            else
+            {
+                yp2::odr odr;
+                
+                package.response() = odr.create_close(
+                    apdu, Z_Close_protocolError,
+                    "unsupported APDU in filter_virt_db");
+                
+                package.session().close();
+            }
         }
-        else if (apdu->which == Z_APDU_presentRequest)
+    }
+    m_p->release_frontend(package);
+}
+
+
+void yp2::filter::Virt_db::configure(const xmlNode * ptr)
+{
+    for (ptr = ptr->children; ptr; ptr = ptr->next)
+    {
+        if (ptr->type != XML_ELEMENT_NODE)
+            continue;
+        if (!strcmp((const char *) ptr->name, "virtual"))
         {
-            m_p->present(package, apdu, move_later);
+            std::string database;
+            std::string target;
+            xmlNode *v_node = ptr->children;
+            for (; v_node; v_node = v_node->next)
+            {
+                if (v_node->type != XML_ELEMENT_NODE)
+                    continue;
+                
+                if (yp2::xml::is_element_yp2(v_node, "database"))
+                    database = yp2::xml::get_text(v_node);
+                else if (yp2::xml::is_element_yp2(v_node, "target"))
+                    target = yp2::xml::get_text(v_node);
+                else
+                    throw yp2::filter::FilterException
+                        ("Bad element " 
+                         + std::string((const char *) v_node->name)
+                         + " in virtual section"
+                            );
+            }
+            std::string route = yp2::xml::get_route(ptr);
+            add_map_db2vhost(database, target, route);
+            std::cout << "Add " << database << "->" << target
+                      << "," << route << "\n";
         }
         else
         {
-            ODR odr = odr_createmem(ODR_ENCODE);
-            
-            Z_APDU *apdu = zget_APDU(odr, Z_APDU_close);
-            
-            *apdu->u.close->closeReason = Z_Close_protocolError;
-
-            apdu->u.close->diagnosticInformation =
-                odr_strdup(odr, "unsupported APDU in filter_virt_db");
-            
-            package.response() = apdu;
-            package.session().close();
-            odr_destroy(odr);
+            throw yp2::filter::FilterException
+                ("Bad element " 
+                 + std::string((const char *) ptr->name)
+                 + " in virt_db filter");
         }
-        if (move_later)
-            package.move();
     }
-    if (package.session().is_closed())
-        m_p->release_session(package);
+}
+
+static yp2::filter::Base* filter_creator()
+{
+    return new yp2::filter::Virt_db;
+}
+
+extern "C" {
+    struct yp2_filter_struct yp2_filter_virt_db = {
+        0,
+        "virt_db",
+        filter_creator
+    };
 }