$Id: README 94592 2011-10-05 13:58:05Z johnnyw $

This directory contains files that implement a server for the TAO
Naming Service.  In addition, it contains files that run the TAO
Naming Service as a Windows NT Service.  Both of these services are
described below.

How to Run the TAO Naming Service
=================================

The following describes how to run the TAO Naming Service.

1. Syntax

        % Naming_Service [-ORBNameServicePort nsport]
                         [-o ior_output_file]
                         [-p pid_file_name]
                         [-s context_size]
                         [-t time]
                         [-f persistence_file_name]
                         [-b base_address]
			 [-m (1=enable multicast responses,0=disable(default)]
			 [-z time]
                         [-d ]
                         [-u directory]
                         [-r directory]


2. Optional Command-line Arguments

        -ORBNameServicePort nsport
                Multicast port for listening for requests from clients
                trying to bootstrap to a Naming Service through the
                use of multicast.  This is only used when multicast
                responding is enabled via '-m 1'.

        -o ior_output_file
                The name of the file, in which to store the IOR of the
                root Naming Service context.

        -p pid_file_name
                The name of the file, in which to store the process id
                of the Naming Service server.

        -s context_size
                Size of the hash table allocated for the root Naming
                Context (if one is created).  All contexts created
                under the root will use the same size for their hash
                tables.  The default is 1024.

        -t time
                How long (in seconds) the server should listen for
                client requests before terminating.

        -f persistence_file_name
                The name of the file to use to store/retrieve
                persistent state of the Naming Service.  Without this
                option, Naming Service is started in non-persistent
                mode.

        -b base_address
                The address used for memory mapping the file specified
                with the "-f" option above.  The value supplied with
                this option is only used when the Naming Service runs
                in persistent mode, i.e., "-f" option is present.

	-m <0|1>
                TAO offers a simple, very non-standard method for
                clients to discover the initial reference for the
                Naming Service.  However, since it can be inadequate and cause
		unexpected results if, for example, there are multiple
		naming services running on the network, the DEFAULT
		behavior is for the Naming Service to NOT RESPOND to
		such multicast queries (use the Interoperable Naming
		Service bootstrap options instead).

        -z time
                A relative round trip timeout value (in seconds) that
                the service should wait for when trying to progress an
                operation through a federated naming context before
                timing out and throwing a 'Cannot proceed' exception
                to the client. If no value is set this will never occur.

        -d
               Provides Naming Service specific debug information. By default
               no diagnostics are given.

        -u directory
               Use a flat-file persistence implementation that stores object
               reference information in a file per context. Each context file
               is placed in the directory specified.

        -r directory
               Use redundant flat-file persistnece; same as the -u option,
               except more than one instance of the TAO Naming Service server
               can run, each using the same set of disk files, to achieve a
               degree of fault tolerence (as long as directory is accessible
               to both servers).


3. Environment Variables

        NameServicePort
                Multicast port for listening for requests from clients
                trying to bootstrap to a Naming Service through the
                use of multicast.  This is only used when multicast
                responding is enabled via '-m 1'.

4. Persistence

        TAO Naming Service has an optional persistence capability.  By
        default, the Naming Service is started in a non-persistent
        mode.  Supplying "-f" command-line option to the server causes
        a persistent version of the Naming Service to run.

        The file specified with the "-f" option is used to store the
        persistent state of the Naming Service, i.e., all Naming
        Contexts and their bindings.  When "-f" option is specified:

        1. If the specified file does not exist, it is created and
           used to store the state of the Naming Service.  An initial
           (root) Naming Context is also created.

        2. If the specified file exists, it is scanned and:

                a) If any inconsistency is detected in the stored
                state, or the file is not recognized by the Naming
                Service, the server exits.  (This may happen, for
                example, if a server or host crashed in the middle of
                writing a record to this file on a previous run).  A
                noncorrupted version of the file must be used instead.

                b) If the file is recognized and is ok, the state
                stored in the file becomes the current state of the
                Naming Service.

        Internally, TAO uses memory mapped file to implement
        persistence feature of the Naming Service.  A default memory
        address (ACE_DEFAULT_BASE_ADDR) is used for mapping the file.
        Alternate mapping address can be specified at compile-time by
        redefining TAO_NAMING_BASE_ADDR in tao/orbconf.h.  Alternate
        mapping address can also be specified at run-time
        with the "-b" command-line option, which takes precedence over
        TAO_NAMING_BASE_ADDR definition.
        NOTE: Naming Service stores absolute pointers in its
        memory-mapped file.  Therefore, it is important to use the
        same mapping address on each run for the same persistence file.


5. Implementation Policies

        a. Destroying Binding Iterators

                A binding iterator is destroyed when client invokes
                <destroy> operation either on the iterator itself or
                on the naming context it is iterating over.  In both
                cases, subsequent calls on the binding iterator object
                will cause OBJECT_NOT_EXIST exception.

        b. Dealing with orphaned contexts

                This implementation of the Naming Service does not
                include any form of 'garbage collection' for orphaned
                naming contexts.  It is solely the responsibility of
                clients to clean up after themselves and not leak
                server resources.  All the resources, including
                orphaned contexts, are released during the Naming
                Server shutdown.

6. Clients: ways to bootstrap to the Naming Service:

        There are several methods for a client to bootstrap to a
        Naming Service, i.e., there are several mechanisms
        <resolve_initial_references> can use when asked for
        "NameService".  In order of predictable behavior, they are:

        1. Command-line options

                The "-ORBInitRef NameService=IOR:..." or environment
                variable NameServiceIOR can be used on the client side
                to specify the object that the call to
                <resolve_initial_references> should return to the
                client.  (On the server side, -o option can be used to
                get the ior).

                Example (Unix, same host):

                        % $TAO_ROOT/orbsvcs/Naming_Service/Naming_Service -o ior_file
                        % my_client -ORBInitRef NameService=file://ior_file

                        On the first line, we start the Naming
                        Service, and output its ior to <ior_file>.  On
                        the second line, we start some client, and
                        specify the ior <resolve_initial_references>
                        should return for the Naming Service in a file
                        format.

        2. Interoperable Naming Service.

                TAO implements the standard CORBA Interoperable Naming
                Service (ING).  Therefore, most initialization options
                provided by INS can be used to bootstrap to the Naming
                Service (see TAO's release notes for the status of INS
                implementation).

        3. Multicast

                When started with the "respond to multicast queries"
                option turned on ('-m 1'), clients can use IP
                multicast to query for a Naming Service, and this
                instance will respond. TAO Naming Server is listening
                for client multicast requests on a specified port.  On
                the client side, <resolve_initial_references> sends
                out a multicast request on the network, trying to
                locate a Naming Service.  When a Naming Server
                receives a multicast request from a client, it replies
                to the sender with the ior of its root Naming Context.
                Note, the port used for this bootstrapping process,
                i.e., 'multicast port', has nothing to do with the ORB
                port used for CORBA communication.  Other points worth
                mentioning:

                - A client and a server will only click through this
                  multicast protocol if they are using the same
                  multicast port.  For both client and server
                  -ORBnameserviceport command-line option and
                  NameServicePort environment variable can be used to
                  specify the multicast port to use.  If none is
                  specified, the default port is used.  (The ability
                  to specify multicast ports can be used to match
                  certain clients with certain Naming Servers, when
                  there are more than one Naming Server running on the
                  network).

                - If there are several Naming Servers running on the
                  network, each listening on the same port for
                  multicast requests, each will send a reply to a
                  client's request.  The client's orb will use the
                  first response it receives, so the Naming Service
                  will, in fact, be selected at random.

                Since this mechanism is proprietary to TAO (i.e.,
                non-standard), it only works when both client and
                server are written using TAO.  There is no way to turn
                multicasting off on the client side, but it is used
                only as a last resort, i.e., any of the other options
                will override it.

                When OS platform doesn't support multicast, or client
                or server isn't written using TAO, or a more
                reliable/predictable location method is desired, etc.,
                one of the other options can be used to bootstrap to
                the Naming Service.


How to use the NT_Naming_Service
================================

To set the options for the TAO Naming Service, go to the Services icon
in the Settings group under the start menu (start menu -> settings ->
services).  There, highlight the NT_Naming_Service, which is the name
used by the Naming Service when it is registered.  After it's
highlighted, you should see at the bottom of the dialog box an area to
specify options.  Just enter the options you wish in that edit box and
everything should just work.  However, some options, such as
-ORBDebugLevel, won't work since an NT service can't write output to
standard out.

1. Syntax

        % NT_Naming_Server [-i value]
                           [-r]
                           [-s]
                           [-k]
                           [-t n]
                           [-d]

2. Optional Command-line Arguments

        -i value
                Install this program as an NT service, with specified startup

        -r
                Remove this program from the Service Manager
        -s
                Start the service

        -k
                Kill the service

        -t value
                Set startup for an existing service

        -d
                Debug; run as a regular application

3. Usage

        To see different stages of an NT service application, you have
        to run the program several times, with different options.
        Please note: run with only one option at a time.

        a. First, you must initialize the service in the NT SCM
           database.  Run NT_Naming_Service with -in, where n is one of
           the following startup options:

           // Start Type (from WinNT.h)
           //
           #define SERVICE_SYSTEM_START    0x00000001
           #define SERVICE_AUTO_START      0x00000002
           #define SERVICE_DEMAND_START    0x00000003
           #define SERVICE_DISABLED        0x00000004

           If only -i is specified, SERVICE_DEMAND_START is default option.

        b. Now you are ready to run the actual service. Run
           NT_Naming_Service again, this time with -s option. If the
           service starts successfully, it will ring the system
           bell every second or so until the service is stopped.

        c. To stop service execution, run NT_Naming_Service with the
           -k option.

        d. To remove the service from the Service Control Manager
           database, run NT_Naming_Service with -r.

        In addition, once you have initialized this service (by using
        the -i option) you can change its startup type to one of the
        other values above.  To do this, run NT_Naming_Service with
        -tn option. n is as explained above for -i.

        In order to debug the service's execution itself, use the -d
        option.

Troubleshooting
============================================

Q1. Error Message: "subscribe: no such device"

A1. On starting, the error message "subscribe: no such device" is a
rather cryptic message saying that basically either you don't support
multicasting or there is no route for multicasting on one of your
network interfaces( e.g. eth0 ).

---------------------------------------
(Step 1)
Check to see if you have multicasting enabled. In the case of Linux
you will need to check the configuration of your kernel. RedHat users
have multicasting enabled by default. Once you are sure that you have
multicast enabled then move to the next step. Alternative is to start
Naming_Service with multicast disabled.


---------------------------------------
(Step 2)
Check to see if you have the route for multicasting. Linux users can
do this by running:

	/sbin/route

You should see something like this:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.0.0.0        *               255.255.255.0   U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
224.0.0.0       *               240.0.0.0       U     0      0        0 eth0

If you don't see the line for multicast routing:

224.0.0.0       *               240.0.0.0       U     0      0        0 eth0

You will need to add in the next step. If you do see that line and the
problem is still there then contact the tao-users list by using
email. Please remember to use the problem form. It helps developers to
have a more educated guess at the exact problem you are having.


---------------------------------------
(Step 3)

You can do this manually in a script that start the Naming service:

(Linux/Unix):

	/sbin/route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0

Alternatively for RedHat users you can add this into a file
"/etc/sysconfig/static-routes". As of Redhat 7, you might have to
create this file, you can make an entry:

	eth0 net 240.0.0.0 netmask 240.0.0.0

On startup when the network interfaces that will be supporting
multicast routing are started the route will be added. In my case it
adds multicasting routing to eth0 (the first NIC).

----------------------------------------
(Step 4)

Double check that the route has been added correctly using /sbin/route.

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.0.0.0        *               255.255.255.0   U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
224.0.0.0       *               240.0.0.0       U     0      0        0 eth0

At this point you should be able to run Naming_Service. Have fun!
