[5477] dhcpsrv/postgres and kea-dhcp4 now support db reconnect

kea-dhcp4
    added support for max-reconnect-tries and reconnect-wait-time
    to lease and host db parsers

    Added a callback for when DB backends detect loss of connectivity

    Added a self-rescheduling method to attempt to reconnect to the
    backends if retries are enabled

dhcpsrv
    Added a callback that DatabaseConnection derivations should invoke
    when they lose connectivity.

    Added an optional callback parameter from CfgDbAccess::createManagers()
    all the way down to DatabaseConnection ctor.

    pgsql_connection.cc
        PgSqlConnection::~PgSqlConnection() - Added logic to close the
        connection only when the connect state is still OK.
        Otherwise it likes to core dump.

        PgSqlConnection::checkStatementError() - Modified to invoke the
        connectivity lost callback on "fatal" errors

    pgsql_lease_mgr_unittest.cc
    pgsql_host_data_source_unittest.cc
        Added tests to verify that the lost callback is NOT invoked on an
        open failure

1 files changed, 8 insertions, 2 deletions

diff --git a/src/lib/dhcpsrv/cfg_db_access.h b/src/lib/dhcpsrv/cfg_db_access.h
index 2c87e4dafc..3459edf1e8 100644
--- a/src/lib/dhcpsrv/cfg_db_access.h
+++ b/src/lib/dhcpsrv/cfg_db_access.h
@@ -1,4 +1,4 @@
-// Copyright (C) 2016-2017 Internet Systems Consortium, Inc. ("ISC")
+// Copyright (C) 2016-2018 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
@@ -8,6 +8,8 @@
 #define CFG_DBACCESS_H
 
 #include <cc/cfg_to_element.h>
+#include <dhcpsrv/database_connection.h>
+
 #include <boost/shared_ptr.hpp>
 #include <string>
 
@@ -62,7 +64,11 @@ public:
 
     /// @brief Creates instance of lease manager and host data source
     /// according to the configuration specified.
-    void createManagers() const;
+    ///
+    /// @param db_lost_callback function to invoke if connectivity to
+    /// either the lease or host managers, once established, is subsequently
+    /// lost.
+    void createManagers(DatabaseConnection::Callback db_lost_callback = NULL) const;
 
     /// @brief Unparse an access string
     ///