Using the Object Gateway in a Production

This chapter describes how to use the Object Gateway within a production.

There are different ways to invoke the basic Object Gateway Start, Connect, Import, Disconnect, and Stop commands. Practical approaches to this functionality include:

This chapter describes each approach and explains how to work with it. Related topics include:

Creating a Business Service

While it is possible to start the Object Gateway server from the command prompt, the simplest way to use the Object Gateway with a production is to configure the EnsLib.DotNetGateway.Service class as a business service within the production. You can only do this if the Object Gateway server is on the local machine where you are running the production.

Otherwise, you need to start the Object Gateway server from the command prompt. For details, see the Using the Command Prompt section.

To configure the EnsLib.DotNetGateway.Service class as a business service:

From the Management Portal main menu, choose Productions.
Find your production in the list and click Configure beside its name.
Click Add Service to start the Business Service Wizard.
Click Other and in the ServiceClass list, click EnsLib.DotNetGateway.Service.
Click OK to display the updated production diagram that now contains the Object Gateway business service. Click the EnsLib.DotNetGateway.Service box to configure it.

The wizard fills in the associated Object Gateway adapter class. The Business Service Settings for the Object Gateway section lists the configurable settings.

Business Service Settings for the Object Gateway

Dot Net Server

IP address or name of the machine where the Object Gateway server executable is located.

Port

TCP port number for communication between the Object Gateway server and the proxy classes in the production. The default is 55000.

File Path

Location of the Object Gateway server executable. It is used to find the target executable and assemble the command to start the Object Gateway on a local server. If you do not specify this setting, the service uses the default directory ...\Dev\dotnet\bin\ under the installation directory.

Allowed IP Addresses

IP addresses allowed to connect to the Object Gateway server. If this setting is 0.0.0.0 (default) or "", any system (local or remote) may connect; otherwise any listed IP addresses are allowed to connect.

Exec64

If you select this check box, the business service uses the 64–bit version of the Object Gateway executable. Otherwise, it uses the 32–bit version of the executable. This setting is available only on Windows 64-bit platforms.

.NET Version

Select the .NET version to use: 2.0 or 4.0.

Log File

Full pathname of the file where the Object Gateway logs messages. These messages include acknowledgment of opening and closing connections to the server, and any difficulties encountered in mapping .NET classes to proxy classes.

Heartbeat Interval

Number of seconds between each communication with the Object Gateway to check whether it is active. When enabled, the minimum value is 5 seconds and the maximum value is 3600 seconds (1 hour). The default is 10 seconds. A value of 0 disables this feature.

Heartbeat Failure Timeout

Number of seconds without responding to the heartbeat, to consider that the Object Gateway is in failure state. If this value is smaller than the HeartbeatInterval property, the gateway is in failure state every time the Object Gateway communication check fails. The maximum value is 86400 seconds (1 day). The default is 30 seconds.

Heartbeat Failure Action

Action to take if the Object Gateway goes into a failure state. Setting it to Restart (default) causes the Object Gateway to restart. Setting it to Alert generates an alert entry in the Event Log. This is independent of the Alert on Error setting.

Heartbeat Failure Retry

Time to wait before retrying the HeartbeatFailureAction if the Object Gateway server goes into failure state, and stays in failure state. The default is 300 seconds (5 minutes). A value of 0 disables this feature, meaning that once there is a failure that cannot be immediately recovered, there are no attempts at automatic recovery.

Once you have added and configured the Object Gateway business service, it automatically manages the Object Gateway as follows:

When the production starts, the Object Gateway business service starts an instance of the Object Gateway server, using the settings that you specify on the configuration page.
When the production receives a signal to stop, the Object Gateway business service attaches to the Object Gateway server and instructs it to stop, as well.

For more information, see the EnsLib.DotNetGateway.Service entry in the Class Reference.

Calling Business Service Methods

The Object Gateway business service provides methods that you can use to start, connect to, and stop the Object Gateway engine. You can call the following methods from the production code after you have configured the Object Gateway business service as a member of the production:

See the EnsLib.DotNetGateway.Service entry in the Class Reference for details on these methods.

StartGateway() Method

EnsLib.DotNetGateway.Service:StartGateway(pFilePath As %String,
     pPort As %String,
     pAllowedIPAddresses As %String,
     pLogfile As %String = "",
     ByRef pDevice As %String = "",
     pServer As %String = "127.0.0.1",
     pCmdLine As %String = "")

This class method starts the Object Gateway server using the specified arguments. If pLogFile specifies a valid file name, then messages regarding gateway activities are written to this file. These messages include acknowledgment of opening and closing connections to the server, and difficulties encountered (if any) in mapping .NET classes to the production proxy classes.

ConnectGateway() Method

EnsLib.DotNetGateway.Service:ConnectGateway(pEndpoint As %String,
     ByRef pGateway As %Net.Remote.Gateway,
     pTimeout As %Integer = 5,
     pAdditionalPaths As %String = "")

This class method connects to the Object Gateway server at the specified pEndpoint (hostname:port:namespace).

StopGateway() Method

EnsLib.DotNetGateway.Service:StopGateway(pPort As %String,
     pServer As %String = "127.0.0.1",
     pTimeout As %Integer = 5)

This class method connects to the Object Gateway server and shuts it down.

Creating a Business Operation

An abstract business operation is available as a base for building Object Gateway oriented business operations for productions. You can simply subclass the abstract class EnsLib.DotNetGateway.AbstractOperation and implement the appropriate message handlers.

Call the GetConnection() method to verify there is a valid Object Gateway connection. For example:

 Set tSC = ..GetConnection(.tGateway)
     If $$$ISOK(tSC) { 
        // Start using the Object Gateway connection object tGateway 
      ... 
     }

This method returns a private gateway connection object to be used with the proxy classes.

You can configure the Object Gateway IP address and port in the business operation settings when you add the business operation to the production. Note that the connection to the Object Gateway instance is made during OnInit() and closed in OnTearDown(). You must override these methods in the business operation class to implement your own setup and tear down procedures.

See the EnsLib.DotNetGateway.AbstractOperation entry in the Class Reference for details on these methods and also the AdditionalPaths, ConnectTimeout, DotNetServer, and Port properties.

Calling API Methods

In addition to using connect, disconnect, and stop from the business service, the following methods are also available in the %Net.Remote.Gateway class. You can use them when the business service model is not appropriate for your situation:

The %Net.Remote.Gateway class provides the following types of methods:

API methods that let you %Connect to the Object Gateway server, %Disconnect from it, and %Shutdown the Object Gateway server.
The %Import method, which imports .NET classes or assemblies from the .NET and generates all the necessary proxy classes for the InterSystems IRIS® side.
The %ExpressImport method, which combines calls to %Connect, %Import, and %Disconnect.
The utility method %GetAllClasses.

%Connect() Method

Method %Connect(host As %String,
                port As %Integer,
                namespace As %String,
                timeout As %Numeric = 5,
                additionalClassPaths As %ListOfDataTypes = "")
    As %Status [ Final ]

The %Connect() method establishes a connection with the Object Gateway engine. It accepts the following arguments:

Argument	Description
host	Identifies the machine on which the Object Gateway server is running.
port	Port number over which the proxy classes communicate with the .NET classes.
namespace	interoperability-enabled namespace.
timeout	Number of seconds to wait before timing out, the default is 5.
additionalClassPaths	Optional — use this argument to supply additional class paths, such as the names of additional assembly DLLs that contain the classes you are importing via the Object Gateway. See the Import Arguments section for details using this argument.

%Disconnect() Method

Method %Disconnect() As %Status [ Final ]

The %Disconnect() method closes a connection to the Object Gateway engine.

%Shutdown() Method

Method %Shutdown() As %Status [ Final ]

The %Shutdown() method shuts down the Object Gateway engine.

%Import() Method

Method %Import(class As %String,
               ByRef imported As %ListOfDataTypes,
               additionalClassPaths As %ListOfDataTypes = "",
               exclusions As %ListOfDataTypes = "")
    As %Status [ Final ]

The %Import() method imports the given class and all its dependencies by creating and compiling all the necessary proxy classes. The %Import() method returns, by reference, a list (in imported) of generated proxy classes. For details of how .NET class definitions are mapped to proxy classes, see the “Mapping Specification” chapter.

%Import() is a onetime, startup operation. It only needs to be called the first time you wish to generate the proxy classes. It is necessary again only if you recompile your .NET code and wish to regenerate the proxies. The following sections provide further details about the %Import() method:

Import Arguments

Before you invoke %Import(), prepare the additionalClassPaths and exclusions arguments. That is, for each argument, create a new %ListOfDataTypes object and call its Insert() method to fill the list. The optional additionalClassPaths argument can be used to supply additional path arguments, such as the names of additional assembly DLLs that contain the classes you are importing via the Object Gateway. List elements should correspond to individual additional assembly DLL entries, which require the following format:

" rootdir\...\mydll.dll "

You can try to load an assembly from a directory outside of where DotNetGatewaySS.exe is running, but you might experience a load error for your assembly when you try to use a class in the assembly. InterSystems recommends that you put all local assemblies in the same directory as DotNetGatewaySS.exe. You can also specify assemblies in the GAC by using partial names for them, System.Data, for example.

Import Dependencies and Exclusions

While mapping a .NET class into a proxy class and importing it into InterSystems IRIS, the Object Gateway loops over all class dependencies discovered in the given .NET class, including all classes referenced as properties and in argument lists. In other words, the Object Gateway collects a list of all class dependencies needed for a successful import of the given class, then walks that dependency list and generates all necessary proxy classes.

You can control this process by specifying a list of assembly and class name prefixes to exclude from this process. While this situation would be rare, it does give you some flexibility to control what classes get imported. The Object Gateway automatically excludes a small subset of assemblies such as Microsoft.* assemblies.

%ExpressImport() Method

ClassMethod %ExpressImport(name As %String,
                           port As %Integer,
                           host As %String = "127.0.0.1",
                           silent As %Boolean = 0,
                           additionalClassPaths As %ListOfDataTypes = "",
                           exclusions As %ListOfDataTypes = "")
    As %Status [ Final ]

%ExpressImport() is a one-step convenience class method that combines calls to %Connect(), %Import(), and %Disconnect(). It returns a list of generated proxies. It also logs that list, if the silent argument is set to 0. The name argument is a semicolon-delimited list of classes or assembly DLLs.

%GetAllClasses()Method

 %GetAllClasses(jarFileOrDirectoryName As %String,
                ByRef allClasses As %ListOfDataTypes)
     As %Status

This method returns, in the ByRef argument allClasses, a list of all public classes available in the assembly DLL specified by the first argument, jarFileOrDirectoryName.

Using the Command Prompt

Usually you start and stop the Object Gateway server automatically, by configuring the EnsLib.DotNetGateway.Service business service as a member of the production. Once this is done, the Object Gateway server starts and stops automatically with the production. The StartGateway() class method is also available to manually start the Object Gateway server.

However, during development or debugging, or when InterSystems IRIS and the Object Gateway server run on different machines, you may find it useful to start the gateway server from a command prompt. Copy the file DotNetGatewaySS.exe to the directory where you load an assembly. By default, DotNetGatewaySS.exe is shipped in the directory install-dir\dev\dotnet\bin. Run DotNetGatewaySS.exe from install-dir\dev\dotnet\bin as follows:

DotNetGatewaySS port listener logfile

Argument	Description
port	Port number on which to listen for the incoming requests.
listener	Optional — Contains the local IP address on the local machine where the gateway listens. Specify null, "", or 0.0.0.0 (the default) to listen on all IP addresses local to the machine (127.0.0.1, VPN address, etc.) You can restrict the listener to one existing local IP address or listen on all of them; you cannot enter a list of acceptable addresses. You must provide a value for this argument if you are specifying a logfile.
logfile	Optional — If specified, the command procedure creates a log file of this name; you must specify the full pathname in the string. The listener argument is required if you enter a value for logfile.

For example:

DotNetGatewaySS 55000 "" ./gatewaySS.log

Note:

When using classes in local side-by-side assemblies (assemblies are not installed into the GAC), run DotNetGatewaySS.exe from the same directory as those assemblies to resolve their dependencies.

Using the .NET Object Gateway Wizard

You can import a DLL assembly file from .NET and create a set of corresponding classes using the .NET Object Gateway wizard built into Studio. To start the wizard:

Start Studio.
From the Tools menu, point to and click Add-Ins.
Click .NET Gateway Wizard to start the .NET Object Gateway Wizard dialog.
Enter the path and name of a DLL assembly file; or click Browse to help navigate to one.
Enter the .NET Gateway server name / IP address and .NET Gateway server port for the Object Gateway server.
You can also enter Additional paths\assemblies to be used in finding dependent classes and Exclude dependent classes matching the following prefixes as instructed in the dialog.
Click Next to generate proxy classes. The wizard displays the class name as it generates each proxy class.
When the import operation is complete, click Finish to exit the wizard.

Error Checking

The Object Gateway provides error checking as follows:

When an error occurs while executing proxy methods, the error is, in most cases, a .NET exception, coming either from the original .NET method itself, or from the Object Gateway engine. When this happens, an error is trapped.
The Object Gateway API methods like %Import() or %Connect() return a typical %Status variable.

In both cases, InterSystems IRIS records the last error value returned from a .NET class (which in many cases is the actual .NET exception thrown) in the local variable %objlasterror.

You can retrieve the complete text of the error message by calling $system.OBJ.DisplayError(), as follows:

 Do $system.OBJ.DisplayError(%objlasterror)

Troubleshooting

Should you encounter problems while using the Object Gateway it is always a good idea to turn logging on. That might be necessary for InterSystems staff to help you troubleshoot problems. To activate logging, simply identify a log file when you start the Object Gateway. You can do this whether you start from the command line or use the StartGateway() API method.

Sometimes, while using the Object Gateway in a debugging or test situation, you may encounter problems with a Terminal session becoming unusable, or with write errors in the Terminal window. It is possible that a Object Gateway connection terminated without properly disconnecting. In this case, the port used for that connection may be left open.

If you suspect this is the case, to close the port, type the following command at the Terminal prompt:

 Close "|TCP|port"

Where port is the port number to close.