Search:
wiki:export_ack
Last modified 17 months ago Last modified on 05/02/12 09:26:23

# Earthworm Module: export_ack

Contributed by:

## Function

Exports EARTHWORM messages over Internet (partner to import_generic).

## Details

Import-Export Overview

### EXAMPLE CONFIGURATION FILE

    #
    # export_ack configuration file
    #
    # Export_ack expects to receive an acknowledgment packet for every
    # packet that is writes to socket. It keeps a SendQueue of messages it has
    # sent and their status. The SocketSend thread will not re-use a slot in
    # its SendQueue until the SocketRecv thread has marked that slot as ACKed.
    #
    # Import/Export send heartbeats to each other, as well as into their
    # local earthworm systems. If the socket heartbeat from the distant partner
    # is not received whithin the expected time period (RcvAliveInt) the link is
    # terminated, and an attempt to reconnect is initiated. If things go
    # seriously wrong, the heartbeat into the local earthworm system in
    # stopped. The expectation is that "restartMe" has been set in the .desc
    # file, and we'll be killed and restarted.
    #
    # Socket heartbeats are not put in either the message stacking queue
    # or in the SendQueue, so they do not take up precious space when
    # the connection between import/export is down.
    #
    # All socket operations are performed with a timeout. This is noramlly
    # defaulted, but can be set in this file (SocketTimeout).
    #
    # Export maintains a circular FIFO buffer of messages to be shipped.
    # Let's call this the MessageStacking queue. The depth of this queue
    # (RingSize) controls the maximum latency of the data.
    #
    #
    # Configuration notes:
    #
    # "restartMe" should be uncommented in my .desc file.
    #
    # The period of our local heartbeat (HeartBeatInt) must be safely smaller
    # (faster) than our advertised period in our .desc file (tsec:).
    # Otherwise we'll get continually restarted for no good reason.
    # Note that tsec:0 implies no heartbeats expected, and so we'll never get
    # restarted.
    #
    # The rate at which we send socket heartbeats to our distant partner should
    # be considerably faster than the rate at which our partner expects them.
    # Otherwise, a heartbeat delayed in transmission will cause our partner to
    # conclude that the link is broken, and cause them to break the link and
    # reinitialize. Which will cause us to do the same.
    #
    # For export, the ServerIPAdr is the address of the port to be used in
    # the exporting machine.  This is to specify a network card case the
    # exporting machine has several network cards.
    # Using ServerIPAdr 0.0.0.0 will allow export to answer connections
    # on any valid address of the machine.
    #
    # If SocketTimeout is specified, it should be at least as large as the
    # expected period of heartbeats from our distant partner.

    # Basic Earthworm setup
    #----------------------
     MyModuleId     MOD_EXPORT_ACK      # module id for this program
     RingName       PICK_RING           # transport ring to use for input/output
     HeartBeatInt   30                  # EW internal heartbeat interval (sec)
                                        #   Should be >= RcvAliveInt
    # Logging Control
    #----------------
     LogFile        1      # If 0, don't write logfile
                           #    1, write to logfile and stdout
                           #    2, write to module log but not stderr/stdout
    #Verbose               # If uncommented, VERY LARGE logfiles will be
                           #   generated with info about queue status of
                           #   each msg, socket alive msgs sent & received.

    # Logos of messages to export to client systems
    #----------------------------------------------
    #              Installation       Module       Message Type
     GetMsgLogo    INST_UNKNOWN     MOD_WILDCARD     TYPE_PICK2K
     GetMsgLogo    INST_UNKNOWN     MOD_WILDCARD     TYPE_CODA2K

    # Set up Message Queues
    # Note: socket "alive" messages are not put in either queue
    #----------------------------------------------------------
     MaxMsgSize             4096   # maximum size (bytes) for input/output msgs
     RingSize                200   # number of msgs in MessageStacking queue.
                                   #  (msgs waiting to be sent to socket)
     SendQueueLength         100   # Optional command: #msgs in SendQueue
                                   #  (msgs sent, acknowledgments pending)
                                   #  Valid range: 1-254 (default 100)

    # Set up server/client communications
    #------------------------------------
     ServerIPAdr  aaa.bbb.ccc.dd   # Listen for connections on this IPaddress.
                                   #  0.0.0.0 will use any address on machine.
     ServerPort            16005   # Well-known port number to export msgs on

     SendAliveText      ExpAlive   # string sent to client as heartbeat
     SendAliveInt             30   # seconds between alive msgs sent to client.
                                   #  0 => no heartbeat
     RcvAliveText       ImpAlive   # text of client's heartbeat (we get this)
     RcvAliveInt              60   # seconds between client's heartbeats to us.
                                   #  0 => no heartbeat

    # Optional Socket commands:
    # SocketTimeout defaults to RcvAliveInt + 3
    #  If set to -1, all socket calls will block (no timeout).
    #  SocketTimeout has no effect in export, unless it is set to -1,
    #  because there is no code in export to handle socket timeouts.
    #  If set to -1, the program may run slightly more efficiently because
    #  timeout checking code will not execute.
    #----------------------------------------------------------------------
    #SocketTimeout 200000  # Timeout length in milliseconds for socket calls

     SocketDebug   0       # if 1, socket_ew debug statements are logged
                           # if 0, socket_ew debug is turned off (default)

## Helpful Hints

### Download in other formats:

- Plain Text